Record 1 of 50
Author(s): YILDIZ E; GUNGOR A; YILDIRIM H; BAYSAL BM
Title: SYNTHESIS AND CHARACTERIZATION OF UV CURABLE ACRYLATED URETHANE PREPOLYMERS .2. EFFECTS OF VARIOUS DIACRYLATES AS DILUENTS AND RELATIVE-HUMIDITY ON MECHANICAL-PROPERTIES OF TDI/PEG/HEMA-BASED POLYMERIC FILMS
Source: ANGEWANDTE MAKROMOLEKULARE CHEMIE 1995, Vol 233, pp 33-45
Publisher: HUTHIG & WEPF VERLAG
Addresses: TURKISH SCI & TECH RES COUNCIL,MARMARA RES CTR,DEPT CHEM ENGN,GEBZE 41470,TURKEY
YILDIZ UNIV,DEPT CHEM,SISLI 80270,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,BEBECK 80815,TURKEY
Abstract: Various UV-curable acrylated urethane prepolymers based on tolylene-2,4-diisocyanate (TDI), poly(ethylene glycol) (PEG 400), and 2-hydroxyethyl methacrylate (HEMA) were synthesized. The effects of reactive diluent types, the composition of the products and of different humidity conditions on mechanical properties of cured films were investigated. Effects of diethylene glycol diacrylate (DEGDA) and thiodiethylene glycol diacrylate (TDGDA) as reactive diluents on tensile strength, elongation and Young's modulus values of the UV cured films were examined systematically. The results show that the increase of relative humidity from 50 to 95% leads to a decrease in tensile strength and Young's modulus values of polymeric films. The decrease of these mechanical properties in high relative humidity is due to the formation of hydrogen bonding in the polymer chain caused by water molecules.
Times Cited: 1
Source item page count: 13
Publication Date: NOV
IDS No.: TJ271
29-char source abbrev: ANGEW MAKROMOL CHEM
Publisher address: AUF DEM WOLF 4 FX#001-41-61-317-94-11, CH-4052 BASEL, SWITZERLAND


Record 2 of 50
Author(s): KONUKMAN AES; AKMAN U; CAMURDAN MC
Title: OPTIMAL-DESIGN OF CONTROLLABLE HEAT-EXCHANGER NETWORKS UNDER MULTIDIRECTIONAL RESILIENCY-TARGET CONSTRAINTS
Source: COMPUTERS & CHEMICAL ENGINEERING 1995, Vol 19, pp S149-S154
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: KONUKMAN AES, BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
Author Keywords: HEAT EXCHANGER NETWORKS; FLEXIBILITY; RESILIENCY; CONTROLLABLE RETROFIT DESIGN; OPTIMIZATION
KeywordsPlus: INDEX
Abstract: Controllable design of heat exchanger networks is formulated as constrained nonlinear optimization problem. The objective of this new method is to find the individual exchanger areas and bypass fractions which minimize the total annualized cost (or the total area) of the given heat exchanger network structure and, at the same time, to satisfy all the target temperature constraints (hard or soft) for a set of disturbances predefined in all possible directions. This is achieved by solving only one constrained optimization problem which considers the exchanger model equations (heat transfer and mixing) and constraints (resiliency index, heat load and the minimum approach temperature) simultaneously for all possible predefined disturbance directions. With the proposed method, a retrofit design satisfying given set of resiliency-target constraints of a heat exchanger network at minimum cost is accomplished.
Times Cited: 4
Source item page count: 6
Supplement: S
IDS No.: RM179
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 3 of 50
Author(s): OZYURT B; SUNOL AK; CAMURDAN MC; MOGILI P; HALL LO
Title: CHEMICAL-PLANT FAULT-DIAGNOSIS THROUGH A HYBRID SYMBOLIC-CONNECTIONIST APPROACH AND COMPARISON WITH NEURAL NETWORKS
Source: COMPUTERS & CHEMICAL ENGINEERING 1995, Vol 19, pp S753-S758
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: OZYURT B, UNIV S FLORIDA,COLL ENGN,TAMPA,FL 33620
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
Author Keywords: FAULT DIAGNOSIS; SYMBOLIC CONNECTIONIST SYSTEMS; NEURAL NETWORKS; EXPERT SYSTEMS; INDUCTIVE LEARNING
Abstract: A novel hybrid symbolic-connectionist approach to machine learning is illustrated for fault diagnosis of a hydrocarbon chlorination plant. The learning algorithm addressed the knowledge acquisition problem by developing and maintaining the knowledge base through inductive learning. The performance ofthe learning system is discussed in terms ofthe knowledge extracted from example cases and its classification accuracy on the test cases. Results indicate that the introduced system is a promising alternative to neural networks for fault diagnosis and a complement to expert systems.
Times Cited: 0
Source item page count: 6
Supplement: S
IDS No.: RM179
29-char source abbrev: COMPUT CHEM ENG
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 4 of 50
Author(s): ENSARI S; OZKAN P; HORTACSU A
Title: EFFECTS OF TEMPERATURE, TOC OF A COMPLEX MEDIUM ON THE GROWTH OF THERMUS-THERMOPHILUS AND INDUCTION TIME ON D-GLUCOSE ISOMERASE ACTIVITY
Source: TURKISH JOURNAL OF CHEMISTRY 1995, Vol 19, Iss 2, pp 108-113
Publisher: SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
Author Keywords: THERMUS THERMOPHILUS; D-GLUCOSE ISOMERASE; FED-BATCH FERMENTATION
Abstract: The effect of temperature and substrate concentration (TOC) on the growth of Thermus thermophilus cells in batch fermentation were investigated, and the data were correlated using unstructured specific growth rate equations. The batch fermentations showed low substrate utilization at about 35% of the initial total organic carbon content (TOC) of the substrate. Intermittent substrate feeding strategies were adopted at two low substrate concentrations The fed-batch fermentations which were conducted to maintain relatively low constant substrate concentrations in the medium did not improve substrate utilization, but led to biomass production comparable to that obtained in simple batch fermentations with the same total amount of substrates. The optimal induction time for D-glucose isomerase activity by D-xylose was found to he at the end of the exponential phase.
Times Cited: 2
Source item page count: 6
IDS No.: RL905
29-char source abbrev: TURK J CHEM
Publisher address: PO BOX 5 KIZILAY, 06420 ANKARA, TURKEY


Record 5 of 50
Author(s): HAMURCU EE; BAYSAL BM
Title: INTERPENETRATING POLYMERIC NETWORKS OF POLY(DIMETHYLSILOXANE) ELASTOMERS
Source: KAUTSCHUK GUMMI KUNSTSTOFFE 1995, Vol 48, Iss 5, pp 345-348
Publisher: DR ALFRED HUTHIG VERLAG GMBH
Addresses: HAMURCU EE, BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
TUBITAK,MARMARA RES CTR,BASIC SCI RES INST,MARMARA,TURKEY
KeywordsPlus: POLYDIMETHYLSILOXANE
Abstract: Semi and full interpenetrating polymer networks of polydimethyl siloxane/polystyrene (PDMS/PS) and polydimethyl siloxane/polyurethane (PDMS/PU) were prepared sequentially. Characterization of the networks was made with swelling, differential scanning, calorimetry, stress-strain tests, dynamic mechanical thermal analyser, and scanning electron microscopy. The polymeric components are incompatible. However, considerable improvement in mechanical properties is observed by adding PS or PU to the PDMS host network.
Times Cited: 0
Source item page count: 4
Publication Date: MAY
IDS No.: RB912
29-char source abbrev: KAUT GUMMI KUNSTST
Publisher address: POSTFACH 102869, W-69018 HEIDELBERG 1, GERMANY


Record 6 of 50
Author(s): KAZAN D; CAMURDAN A; HORTACSU A
Title: THE EFFECT OF GLUCOSE-CONCENTRATION ON THE GROWTH-RATE AND SOME INTRACELLULAR COMPONENTS OF A RECOMBINANT ESCHERICHIA-COLI CULTURE
Source: PROCESS BIOCHEMISTRY 1995, Vol 30, Iss 3, pp 269-273
Publisher: ELSEVIER SCI LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
BOGAZICI UNIV,DEPT BIOL,ISTANBUL 80815,TURKEY
KeywordsPlus: ESCHERICHIA-COLI; MODEL
Abstract: The effect of the concentration of a limiting substrate on growth and the concentrations of several intracellular components of recombinant E. coli JM 109 containing the plasmid pUC13 were investigated. The limiting substrate was glucose and the intracellular components measured were plasmid content, RNA content, and beta-lactamase activity.

The specific growth rate increased with increase in substrate concentration up to 16 g/litre. A further increase in glucose concentration inhibited growth. The RNA content increased with increasing specific growth rate while the plasmid content and beta-lactamase activity decreased.

An unstructured model for the effect of substrate concentration on the specific growth rate was found to fit the experimental data. The equation simulates substrate inhibition during growth at high glucose concentrations.

Times Cited: 4
Source item page count: 5
IDS No.: QX204
29-char source abbrev: PROCESS BIOCHEM
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 7 of 50
Author(s): GONENC ZS; AKMAN U; SUNOL AK
Title: SOLUBILITY RETENTION RELATIONSHIPS IN SUPERCRITICAL-FLUID CHROMATOGRAPHY
Source: CANADIAN JOURNAL OF CHEMICAL ENGINEERING 1995, Vol 73, Iss 2, pp 267-271
Publisher: CANADIAN SOC CHEMICAL ENGINEERING
Addresses: GONENC ZS, UNIV S FLORIDA,DEPT CHEM ENGN,TAMPA,FL 33620
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
Author Keywords: SUPERCRITICAL PARTITION CHROMATOGRAPHY; SOLUBILITY SORPTION RETENTION RELATIONSHIPS
KeywordsPlus: PARTIAL MOLAR VOLUME; CARBON-DIOXIDE; STATIONARY PHASE; SOLUTE; STATE
Abstract: The effects of temperature, pressure and supercritical fluid density on solubility-retention relationship of solutes in supercritical fluid partition chromatography are investigated. New retention data for naphthalene and phenanthrene are obtained as a function of pressure at different temperatures. The mobile-phase partial molar volumes of the solutes are determined from infinite-dilution fugacity coefficients and used to model the pressure dependence of solute retention that reveals the nature of interactions between the stationary phase and the solute. Relationships between pressure and temperature dependence of solubility and retention of solutes are also illustrated.
Times Cited: 8
Source item page count: 5
Publication Date: APR
IDS No.: QU901
29-char source abbrev: CAN J CHEM ENG
Publisher address: 130 SLATER ST, STE 550, OTTAWA ON K1P 6E2, CANADA


Record 8 of 50
Author(s): HAMURCU EE; BAYSAL BM
Title: INTERPENETRATING POLYMER NETWORKS OF POLY(DIMETHYLSILOXANE) WITH POLYSTYRENE, POLYBUTADIENE AND POLY(GLYCERYLPROPOXYTRIACRYLATE)
Source: MACROMOLECULAR CHEMISTRY AND PHYSICS 1995, Vol 196, Iss 4, pp 1261-1276
Publisher: HUTHIG & WEPF VERLAG
Addresses: HAMURCU EE, BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
MARMARA RES CTR,BASIC SCI RES INST,GEBZE 41470,TURKEY
KeywordsPlus: LINKED POLYDIMETHYLSILOXANE CHAINS; BIMODAL NETWORKS; CURED POLY(DIMETHYLSILOXANE); VOLUME DEPENDENCE; ELASTIC EQUATION; MODEL NETWORKS; STATE; SYSTEM; SEMI
Abstract: The synthesis of full and semi interpenetrating networks (IPNs) based on poly(dimethylsiloxane) (PDMS)/polystyrene, PDMS/polybutadiene and PDMS/poly(glycerylpropoxytriacrylate)(a)) is described. PDMS was used as host polymer in most cases. PDMS networks were prepared with two prepolymers having different number-average molecular weights between junctions, ($) over bar M(c) = 15 . 10(3) and ($) over bar M(c) = 75 . 10(3). Physical properties of IPN samples such as stress-strain behaviour, swelling and glass transition temperature (T-g) were examined. IPNs of both PDMS/polystyrene and PDMS/poly(glycerylpropoxytriacrylate) exhibit superior mechanical and elastomeric properties with respect to pure PDMS network. Most of the IPN systems studied in this work display two T(g)s and indicate phase separation.
Times Cited: 6
Source item page count: 16
Publication Date: APR
IDS No.: QU125
29-char source abbrev: MACROMOL CHEM PHYSICS
Publisher address: AUF DEM WOLF 4 FX#001-41-61-317-94-11, CH-4052 BASEL, SWITZERLAND


Record 9 of 50
Author(s): ROY BC; GOTO M; HIROSE T; NAVARO O; HORTACSU O
Title: EXTRACTION RATES OF OIL FROM TOMATO SEEDS WITH SUPERCRITICAL CARBON-DIOXIDE
Source: JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 1994, Vol 27, Iss 6, pp 768-772
Publisher: SOC CHEMICAL ENG JAPAN
Addresses: KUMAMOTO UNIV,DEPT APPL CHEM,KUMAMOTO 860,JAPAN
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
Author Keywords: EXTRACTION; SUPERCRITICAL FLUID; CARBON DIOXIDE; TOMATO SEED; OIL; MODELING; MASS TRANSFER
Abstract: Tomato seed oil was extracted with supercritical carbon dioxide in a semibatch-flow extraction apparatus. The effect of milling of seeds and solvent flow rate on the extraction behavior was studied. The extraction rate increased as solvent flow rate increased. Milling the seeds,prior to extraction enhanced the extraction rate. During extraction from milled seeds, the solute from the cells opened by milling was extracted fast, and the solute inside the cell walls was extracted slowly. Mathematical models based on two distinct extraction periods with different extraction rate were applied to analyze the experimental data. The models simulated the extraction behavior satisfactorily.
Times Cited: 18
Source item page count: 5
Publication Date: DEC
IDS No.: PZ068
29-char source abbrev: J CHEM ENG JPN
Publisher address: KYORITSU BUILDING 4-16-19 KOHINATA, BUNKYO KU TOKYO 112, JAPAN


Record 10 of 50
Author(s): BAYSAL BM; STOCKMAYER WH
Title: DIRECTION OF THE DIPOLE-MOMENT IN THE ESTER GROUP OF POLY(EPSILON-CAPROLACTONE)
Source: MACROMOLECULES 1994, Vol 27, Iss 25, pp 7429-7432
Publisher: AMER CHEMICAL SOC
Addresses: DARTMOUTH COLL,DEPT CHEM,HANOVER,NH 03755
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
TUBITAK,MARMARA RES CTR,INST BASIC SCI,DEPT CHEM,GEBZE 41470,TURKEY
KeywordsPlus: METHYL-ACRYLATE; RELAXATION; POLYMERS; ACETATE
Abstract: The low-frequency dielectric permittivity of a dioxane solution of poly(epsilon-caprolactone) was reinvestigated at a lower concentration than in earlier work. The recalculated magnitude of the dipole-moment component parallel to the virtual bond in an ester group is 0.64 D.
Times Cited: 3
Source item page count: 4
Publication Date: DEC 5
IDS No.: PW059
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 11 of 50
Author(s): APOSTOLOV AA; FAKIROV S; SEZEN B; BAHAR I; KLOCZKOWSKI A
Title: STRUCTURAL AND MECHANICAL STUDIES OF A BLEND OF POLY(BUTYLENE TEREPHTHALATE) AND POLY(ETHER ESTER) BASED ON POLY(BUTYLENE TEREPHTHALATE) AND POLY(ETHYLENE GLYCOL)
Source: POLYMER 1994, Vol 35, Iss 24, pp 5247-5255
Publisher: ELSEVIER SCI LTD
Addresses: UNIV SOFIA,STRUCT & PROPERTIES POLYMERS LAB,BU-1126 SOFIA,BULGARIA
BOGAZICI UNIV,CTR POLICY RES,DEPT CHEM ENGN,BEBEK 80815,TURKEY
TUBITAK ADV POLYMER MAT RES CTR,BEBEK 80815,TURKEY
UNIV CINCINNATI,DEPT CHEM,CINCINNATI,OH 45221
UNIV CINCINNATI,POLYMER RES CTR,CINCINNATI,OH 45221
Author Keywords: POLY(BUTYLENE TEREPHTHALATE); POLY(ETHER ESTER); BLEND
KeywordsPlus: NYLON-6
Abstract: Poly(butylene terephthalate) (PBT), poly(ether ester) (PEE) based on PBT and poly(ethylene glycol) (PEG) (PBT/PEG=49/51 wt%) and their blend are extruded with quenching, drawn x 5 and annealed together with undrawn samples at 170, 180, 190 and 200 degrees C for 6 h in vacuum. All samples are characterized by differential scanning calorimetry (d.s.c.), small-angle and wide-angle X-ray scattering, dynamic mechanical thermal analysis and static mechanical measurements. D.s.c. and X-ray results show the absence of complete cocrystallization of homo-PBT and PBT from PEE in the blend in accordance with other reports. The drawn blend annealed at 200 degrees C reveals much higher (by 30 degrees C) T-m than the PEE component (49/51). Also the mechanical properties of the blend are in between those of the components (homo-PBT and PEE 49/51) but improved compared to those of PEE with the same chemical composition (PEE 75/25). Both observations are explained by partial cocrystallization, i.e. formation of crystallites consisting of two populations of crystallites differing in their size, perfection, origin and time of appearance. The lack of complete cocrystallization and miscibility in this particular blend as well as in other cases with PEE containing less than 75 wt% PBT is explained by the insufficient length of PBT hard segments in PEE necessary for the formation of lamellar thickness typical of the crystallites of homo-PBT.
Times Cited: 6
Source item page count: 9
IDS No.: PV756
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 12 of 50
Author(s): PLATIN S; OZER EO; AKMAN U; HORTACSU O
Title: EQUILIBRIUM DISTRIBUTIONS OF KEY COMPONENTS OF SPEARMINT OIL IN SUB/SUPERCRITICAL CARBON-DIOXIDE
Source: JOURNAL OF THE AMERICAN OIL CHEMISTS SOCIETY 1994, Vol 71, Iss 8, pp 833-837
Publisher: AMER OIL CHEMISTS SOC
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
Author Keywords: SOLUBILITY; SPEARMINT OIL; SUB/SUPERCRITICAL CO2
Abstract: Effects of temperature (at 35, 45 or 55 degrees C) and pressure (10-110 atm) on the relative distribution coefficients of the twelve key components of spearmint oil (essential oil of Mentha cardiaca; Scotch spearmint) at equilibrium in dense CO2 were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO2 are discussed. At 35 degrees C, all key components of spearmint oil are equally soluble in dense CO2 within the 12-102 atm pressure region. At 45 and 55 degrees C, the key components are equally soluble for pressures greater than about 60 atm. However, around either 45 degrees C/27 atm or 55 degrees C/35 atm conditions, the relative distribution coefficients of all monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher vapor pressures of these components and significantly lower solvating power of the dense gas solvent at these particular temperatures and pressures. Vapor-pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and molecular mass of the key components. Deterpenation of spearmint oil with dense CO2 is possible around either 45 degrees C/27 atm or 55 degrees C/35 atm, where the monoterpene hychocarbons tend to concentrate in the CO2-rich phase.
Times Cited: 7
Source item page count: 5
Publication Date: AUG
IDS No.: PC644
29-char source abbrev: J AMER OIL CHEM SOC
Publisher address: 1608 BROADMOOR DRIVE, CHAMPAIGN, IL 61821-0489


Record 13 of 50
Author(s): KUNTMAN A; UYANIK N; BAYSAL BM
Title: A NOVEL METHOD TO ESTIMATE VARIOUS EQUATION-OF-STATE PARAMETERS
Source: POLYMER 1994, Vol 35, Iss 15, pp 3356-3358
Publisher: ELSEVIER SCI LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
TECH UNIV ISTANBUL,FAC ELECT & ELECTR ENGN,MASLAK 80626,TURKEY
MARMARA RES CTR,BASIC SCI RES INST,GEBZE 41470,TURKEY
Author Keywords: EQUATION-OF-STATE PARAMETERS; POLYMER SOLVENT INTERACTION; THETA TEMPERATURE
KeywordsPlus: TEMPERATURE-DEPENDENCE; POLYSTYRENE SOLUTIONS; INTRINSIC-VISCOSITY; HYDRODYNAMIC RADIUS; FLEXIBLE COILS; TRANSITION; THERMODYNAMICS; CYCLOHEXANE; THETA; NETWORKS
Abstract: In the estimation of thermodynamic equation-of-state parameters, the ratio of contact sites of polymer segment and solvent molecule (s2/s1) is an important quantity to be determined. In this work we have evaluated this ratio by using a novel method of approximation. For this purpose, we have arbitrarily changed the value of s2/s1 and obtained the most suitable value yielding chi2 = 0.303 by interpolation.
Times Cited: 6
Source item page count: 3
IDS No.: NZ515
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 14 of 50
Author(s): YILDIZ E; GUNGOR A; YILDIRIM H; BAYSAL BM
Title: SYNTHESIS AND CHARACTERIZATION OF UV-CURABLE ACRYLATED URETHANE PREPOLYMERS .1. EFFECTS OF REACTIVE DILUENTS AND RELATIVE-HUMIDITY ON PHYSICAL-PROPERTIES
Source: ANGEWANDTE MAKROMOLEKULARE CHEMIE 1994, Vol 219, pp 55-66
Publisher: HUTHIG & WEPF VERLAG
Addresses: YILDIZ E, TURKISH SCI & TECH RES COUNCIL,MARMARA RES CTR,DEPT CHEM ENGN,41470 GEBZE,TURKEY
YILDIZ UNIV,DEPT CHEM,80270 SISLI,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,80815 BEBEK,TURKEY
Abstract: A UV-curable acrylated urethane prepolymer was synthesized from tolylene-2,4-diisocyanate (TDI), a polyether polyol (Arcol 1131) and endcapped with 2-hydroxyethyl methacrylate (HEMA) by addition reaction in the presence of dibutyltin dilaurate as catalyst. UV curing was performed with either diethylene glycol diacrylate or thiodiethylene glycol diacrylate as reactive diluent.

The effects of reactive diluent types, their concentrations and the humidity of environment on mechanical properties of cured films were investigated. Changes in the tensile strength, elongation and Young's modulus values of the cured films upon addition of reactive diluents with different concentrations were related to the effect of the diluent on the crosslinking density of cured films.

The increase of relative humidity from 50 to 95% caused a decrease of tensile strength and Young's modulus values of cured films. It is proposed that the decrease of these physical properties in high relative humidity is due to the formation of hydrogen bonding in polymer chains caused by water molecules.

Times Cited: 5
Source item page count: 12
Publication Date: JUN
IDS No.: NX083
29-char source abbrev: ANGEW MAKROMOL CHEM
Publisher address: AUF DEM WOLF 4 FX#001-41-61-317-94-11, CH-4052 BASEL, SWITZERLAND


Record 15 of 50
Author(s): JERNIGAN R; RAGHUNATHAN G; BAHAR I
Title: CHARACTERIZATION OF INTERACTIONS AND METAL-ION BINDING-SITES IN PROTEINS
Source: CURRENT OPINION IN STRUCTURAL BIOLOGY 1994, Vol 4, Iss 2, pp 256-263
Publisher: CURRENT BIOLOGY LTD
Addresses: JERNIGAN R, NCI,DCBDC,MATH BIOL LAB,BETHESDA,MD 20892
BOGAZICI UNIV,POLYMER RES CTR,DEPT CHEM ENGN,BEBEK 80815,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,BEBEK 80815,TURKEY
KeywordsPlus: BACKBONE DYNAMICS; NMR-SPECTROSCOPY; CALMODULIN; THERMODYNAMICS; RECOGNITION; PEPTIDE
Abstract: Recent investigations show that as a class of interactions for designing proteins, hydrophobic interactions are not specific enough, hydrophilic interactions are typically too weak, and water interactions are always on the exterior. In terms of overall protein stability, there is a substantial advantage to a nucleus with strong, directional interactions. Metal ion sites in proteins exhibit strong directional preferences for their coordinate ligands, and the specificities manifested by ions have been demonstrated to be useful in reducing molecular fluctuations. The engineered introduction of zinc binding sites has been shown to improve the stabilities of designed proteins. Metal binding sites can therefore provide important structural building blocks for protein design.
Times Cited: 25
Source item page count: 8
Publication Date: APR
IDS No.: NG689
29-char source abbrev: CURR OPIN STRUCT BIOL
Publisher address: 34-42 CLEVELAND STREET, LONDON, ENGLAND W1P 6LB


Record 16 of 50
Author(s): BAHAR I; JERNIGAN RL
Title: STABILIZATION OF INTERMEDIATE DENSITY STATES IN GLOBULAR-PROTEINS BY HOMOGENEOUS INTRAMOLECULAR ATTRACTIVE INTERACTIONS
Source: BIOPHYSICAL JOURNAL 1994, Vol 66, Iss 2, pp 454-466
Publisher: BIOPHYSICAL SOCIETY
Addresses: NCI,DIV CANC BIOL & DIAG & CTR,MATH BIOL LAB,BETHESDA,MD 20892
BOGAZICI UNIV,DEPT CHEM ENGN,POLYMER RES CTR,BEBEK 80815,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,BEBEK 80815,TURKEY
KeywordsPlus: ALPHA-LACTALBUMIN; SOLVATION THERMODYNAMICS; COOPERATIVE TRANSITIONS; COMPUTER-SIMULATION; RANGE INTERACTIONS; FOLDING REACTIONS; BIO-POLYMERS; DENATURATION; MOLECULES; CONFORMATIONS
Abstract: On-lattice simulations of two-dimensional self-avoiding chains subject to homogeneous intramolecular attractive interactions were performed as a model for studying various density regimes in globular proteins. For short chains of less than 15 units, all conformations were generated and classified by density. The range of intramolecular interactions was found to increase uniformly with density, and the average number of topological contacts is directly proportional to density. The uniform interaction energy increases the probability of high density states but does not necessarily lead to dominance of the highest density state. Typically, several large peaks appear in the probability distribution of packing densities, their location and amplitude being determined by the balance between entropic effects enhancing more expanded conformations and attractive interactions favoring compact forms. Also, the homogeneous interaction energy affects the distribution of most probable interacting points in favor of the longer range interactions over the short range ones, but in addition it introduces some more detailed preferences even among short range interactions. There are some implications about the characteristics of the intermediate density states and also for the likelihood that the native state does not correspond completely to the lowest energy conformation.
Times Cited: 5
Source item page count: 13
Publication Date: FEB
IDS No.: MU275
29-char source abbrev: BIOPHYS J
Publisher address: 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998


Record 17 of 50
Author(s): BAHAR I; JERNIGAN RL
Title: COOPERATIVE STRUCTURAL TRANSITIONS INDUCED BY NONHOMOGENEOUS INTRAMOLECULAR INTERACTIONS IN COMPACT GLOBULAR-PROTEINS
Source: BIOPHYSICAL JOURNAL 1994, Vol 66, Iss 2, pp 467-481
Publisher: BIOPHYSICAL SOCIETY
Addresses: NCI,DIV CANC BIOL & DIAG & CTR,MATH BIOL LAB,BETHESDA,MD 20892
BOGAZICI UNIV,DEPT CHEM ENGN,POLYMER RES CTR,BEBEK 80815,TURKEY
TUBITAK,ADV POLYMER MAT RES CTR,BEBEK 80815,TURKEY
KeywordsPlus: COMPUTER-SIMULATION; RANGE INTERACTIONS; LATTICE MODEL; FLUCTUATIONS; SEQUENCES; POLYMERS; CHAINS; WALKS
Abstract: The role played by non-homogeneous interactions in stabilizing cooperative structural changes in proteins was investigated by exhaustive simulations of all compact conformations compatible with several well-defined globule-like shapes in three dimensions. Conformational free energies corresponding to the association of residues i and j were computed both for the unperturbed system, all subject to identical intramolecular interactions, and for the perturbed system in which a single pair of residues is probed by changing its interactions with an attractive or repulsive interaction. The high packing density leads to strong coupling between residues so that specific interactions between a given pair of residues are accompanied by considerable enthalpy changes. Relatively weak, about 1-2 kcal/mol, attractive interactions can exert a dramatic effect on the free energy distribution. Usually, central positions in the sequence most affect the conformational characteristics. Some of these interaction pairs appear to be capable of effecting major conformation transitions because of the high level of cooperativity in the dense state. Effects of repulsive interactions, however, do not depend so strongly on residue pair and cause more localized structural changes. This approach can suggest more, or less, sensitive loci for amino acid substitution.
Times Cited: 6
Source item page count: 15
Publication Date: FEB
IDS No.: MU275
29-char source abbrev: BIOPHYS J
Publisher address: 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998


Record 18 of 50
Author(s): HAMURCU EE; BAYSAL BM
Title: SOLUBILITY PARAMETER OF A POLY(DIMETHYLSILOXANE) NETWORK
Source: JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 1994, Vol 32, Iss 3, pp 591-594
Publisher: JOHN WILEY & SONS INC
Addresses: HAMURCU EE, BOGAZICI UNIV,DEPT CHEM ENGN,80815 BEBEK,TURKEY
MARMARA RES CTR,41470 GEBZE,TURKEY
Author Keywords: SOLUBILITY PARAMETER; MODEL NETWORK; POLY(DIMETHYLSILOXANE); SWELLING
Times Cited: 6
Source item page count: 4
Publication Date: FEB
IDS No.: MR784
29-char source abbrev: J POLYM SCI B-POLYM PHYS
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 19 of 50
Author(s): HAMURCU EE; BAYSAL BM
Title: INTERPENETRATING POLYMER NETWORKS OF POLY(DIMETHYLSILOXANE) .1. PREPARATION AND CHARACTERIZATION
Source: POLYMER 1993, Vol 34, Iss 24, pp 5163-5167
Publisher: ELSEVIER SCI LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,BEBEK 80815,TURKEY
Author Keywords: POLY(DIMETHYLSILOXANE); INTERPENETRATING NETWORKS; PHYSICAL PROPERTIES
KeywordsPlus: POLYDIMETHYLSILOXANE; STATE; SEMI
Abstract: Model networks of alpha,omega-dihydroxy-poly(dimethylsiloxane) (PDMS) were prepared by tetrafunctional crosslinking agent tetraethyl orthosilicate (TEOS) and the catalyst stannous 2-ethylhexanoate. Hydroxyl-terminated chains of PDMS having molecular weights 15 x 10(3) and 75 x 10(3) mol-1 were used in the crosslinking reaction. Bimodal networks were obtained from a 50% (w/w) mixture of PDMS chains with M(n) = 15 x 10(3) and 75 x 10(3) g mol-1. A sequential interpenetrating network of these PDMS chains was also prepared. Physical properties of the elastomers were determined by stress-strain tests, swelling and extraction experiments, and differential scanning calorimetry measurements.
Times Cited: 23
Source item page count: 5
IDS No.: MN348
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 20 of 50
Author(s): GONENC ZS; YILDIRIM R; BELERBAYKAL AB; ONSAN ZI
Title: ADSORPTION PARAMETERS OF SOME C5-C-8 PARAFFINIC HYDROCARBONS ON PLATINUM ALUMINA BY GAS-CHROMATOGRAPHIC PULSE TECHNIQUES
Source: APPLIED CATALYSIS A-GENERAL 1993, Vol 103, Iss 1, pp 35-42
Publisher: ELSEVIER SCIENCE BV
Addresses: GONENC ZS, BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
Author Keywords: CHROMATOGRAPHIC TECHNIQUES; HYDROCARBON ADSORPTION; PLATINUM ALUMINA; PULSE TECHNIQUES
Abstract: Adsorption isotherms of six C5-C-8 paraffinic hydrocarbons (n-pentane, n-hexane, n-heptane, iso-octane, cyclohexane and methylcyclohexane) on the commercial 0.3 wt.-% Pt/Al2O3 reforming catalyst were investigated under isothermal chromatographic conditions using the elution technique in the temperature range 458-510 K. Average enthalpies of adsorption were determined by using the isosteres obtained from experimental adsorption isotherms and compared with those calculated on the basis of pulse retention data at infinite dilution for eleven C5-C-8 alkanes including the six mentioned above. The isotherms were also fitted to the Langmuir equation for the evaluation of adsorption equilibrium coefficients, Gibbs free energies, average adsorption enthalpies and entropies.
Times Cited: 3
Source item page count: 8
Publication Date: SEP 13
IDS No.: LX126
29-char source abbrev: APPL CATAL A-GEN
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 21 of 50
Author(s): KUNTMAN A; BAYSAL BM
Title: ESTIMATION OF THERMODYNAMIC PARAMETERS FOR POLY(ETHYL METHACRYLATE) ISOPROPYL-ALCOHOL SYSTEM FROM INTRINSIC-VISCOSITY MEASUREMENTS
Source: POLYMER 1993, Vol 34, Iss 17, pp 3723-3726
Publisher: ELSEVIER SCI LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
TECH UNIV ISTANBUL,FAC ELECT & ELECTR ENGN,ISTANBUL 80626,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL 80815,TURKEY
Author Keywords: THERMODYNAMIC PARAMETERS; INTRINSIC VISCOSITY; POLY(ETHYL METHACRYLATE); ISOPROPYL ALCOHOL
KeywordsPlus: UNPERTURBED DIMENSIONS; POLYSTYRENE SOLUTIONS; POLYMERS
Abstract: Intrinsic viscosities of poly(ethyl methacrylate) (PEMA) solutions in isopropyl alcohol (IPA) above and below the theta (theta) temperature (36.9-degrees-C) have been measured by using a capillary viscometer. The equation-of-state exchange energy (X12) and entropy (Q12) parameters were estimated as 62.82 J cm-3 and 0.03 J cm-3 K-1, respectively. The unperturbed dimension constant (K(theta)) and characteristic ratio (C(infinity)) were determined as 5.91 x 10(-4) dl Mol1/2 g-3/2 and 9.3 using the intrinsic viscosity data obtained at the theta temperature for PEMA in IPA. The polymer-solvent interaction parameters (chi1, chi2) were calculated from equation-of-state theory as a function of temperature. The value of the ratio of contact sites (s2/s1) is found to be 0.73 for this PEMA-IPA pair.
Times Cited: 7
Source item page count: 4
IDS No.: LW710
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 22 of 50
Author(s): BAYSAL B; STOCKMAYER WH
Title: TERMINAL-MODE DIELECTRIC-RELAXATION IN THE TERNARY-SYSTEM POLY(EPSILON-CAPROLACTONE)/POLY(4-CHLOROSTYRENE) DIOXANE
Source: JOURNAL OF MOLECULAR LIQUIDS 1993, Vol 56, pp 175-181
Publisher: ELSEVIER SCIENCE BV
Addresses: BAYSAL B, BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
BOGAZICI UNIV,POL MER RES CTR,BEBEK 80815,TURKEY
DARTMOUTH COLL,DEPT CHEM,HANOVER,NH 03755
KeywordsPlus: DILUTE-SOLUTIONS; CIS-POLYISOPRENE; POLYMERS; BLENDS; TIMES
Abstract: Dielectric permittivity has been measured for some ternary mixtures of poly(epsilon-caprolactone), poly(4-chlorostyrene) and dioxane at 25-degrees-C. The relaxation time due to the longitudinal component of the ester-group dipole in the polylactone chain increases roughly linearly with increasing total polymer concentration at a rate in rough agreement with earlier dielectric data for binary systems.
Times Cited: 3
Source item page count: 7
Publication Date: JUL
IDS No.: LW564
29-char source abbrev: J MOL LIQ
Publisher address: PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS


Record 23 of 50
Author(s): BAHAR I; JERNIGAN RL
Title: CONFORMATIONAL CHARACTERISTICS OF MODEL PROTEINS WITH HOMOGENEOUS AND NONHOMOGENEOUS INTERACTIONS
Source: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 1993, Vol 206, pp 79-PHYS
Publisher: AMER CHEMICAL SOC
Addresses: NCI,MATH BIOL LAB,BETHESDA,MD 20892
BOGAZICI UNIV,POLYMER RES CTR,DEPT CHEM ENGN,ISTANBUL,TURKEY
Times Cited: 0
Source item page count: 0
Publication Date: AUG 22
Part number: 2
IDS No.: LP322
29-char source abbrev: ABSTR PAP AMER CHEM SOC
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 24 of 50
Author(s): BAHAR I; BADUR B; DORUKER P
Title: SOLVENT EFFECT ON TRANSLATIONAL DIFFUSIVITY AND ORIENTATIONAL MOBILITY OF POLYMERS IN SOLUTION - A MOLECULAR-DYNAMICS STUDY
Source: JOURNAL OF CHEMICAL PHYSICS 1993, Vol 99, Iss 3, pp 2235-2246
Publisher: AMER INST PHYSICS
Addresses: BAHAR I, BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
TUBITAK ADV POLYMER MAT RES CTR,BEBEK 80815,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
KeywordsPlus: BULK AMORPHOUS POLYMERS; LOCAL CHAIN MOTION; STATISTICAL-MECHANICS; GLASS-TRANSITION; KINETIC-THEORY; NORMAL-BUTANE; SIMULATION; SINGLE; STATE; POLY(PARA-CHLOROSTYRENE)
Abstract: Molecular dynamics simulations have been performed for a bead-spring model chain of 30 beads immersed in 738 solvent molecules. The solvent-solute interaction energy epsilon(bs) has been varied in the range 0.1 less-than-or-equal-to epsilon(bs) less-than-or-equal-to 0.8 kcal/mol to assess the role and importance of solvent type on the dynamic and equilibrium properties of the chain. Radial distribution functions for polymer bead-solvent and bead-bead pairs indicate the enhancement of more expanded chain configurations with increasing quality of the solvent. The translational diffusivity D of the chain exhibits an inverse linear dependence on epsilon(bs), thus decreasing in the presence of more favorable polymer-solvent interactions. Molecular dimensions of the chain such as the mean-square end-to-end distance [r2] and the radius of gyration R(g) are examined in various solvent environment. The ratio [r2]/R(g)2 approximates the limiting value of 6 corresponding to infinitely long freely jointed chains. A linear dependence of D on 1/R(g) is observed, in conformity with the Zimm theory of dilute polymer solutions subject to hydrodynamic interactions. The orientational motion of internal chain vectors is also found to slow down with increasing strength of intermolecular interactions, in parallel with the translational diffusivity. Characteristic orientational relaxation times tau are calculated for chain segments of various sizes n, using the initial decay rates of the corresponding orientational autocorrelations functions. These are found to obey a scaling law of the form tau is similar to n(a) for a given epsilon(bs). The exponent a therein decreases with the quality of the solvent, assuming values in the interval 1.0 less-than-or-equal-to a less-than-or-equal-to 1.5 throughout the investigated range of polymer-solvent interactions.
Times Cited: 1
Source item page count: 12
Publication Date: AUG 1
IDS No.: LN782
29-char source abbrev: J CHEM PHYS
Publisher address: CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999


Record 25 of 50
Author(s): DINCBAS V; HORTACSU A; CAMURDAN A
Title: PLASMID STABILITY IN IMMOBILIZED MIXED CULTURES OF RECOMBINANT ESCHERICHIA-COLI
Source: BIOTECHNOLOGY PROGRESS 1993, Vol 9, Iss 2, pp 218-220
Publisher: AMER CHEMICAL SOC
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
BOGAZICI UNIV,DEPT BIOL,ISTANBUL 80815,TURKEY
KeywordsPlus: GENE-EXPRESSION; CELLS
Abstract: The growth behavior of a mixed culture of plasmid-free and plasmid-containing (YEp352) Escherichia coli HB101 cells in free suspension and immobilized conditions was studied experimentally. It was found that immobilization in calcium alginate beads delayed the reduction of the plasmid-containing fraction for a period of time inversely related to the total number of cells initially immobilized. A simple unstructured model that assumes compartmentalization of cells in the immobilization matrix at the beginning of growth gave a fit which was in good agreement with the data.
Times Cited: 7
Source item page count: 3
Publication Date: MAR-APR
IDS No.: KW540
29-char source abbrev: BIOTECHNOL PROGR
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 26 of 50
Author(s): YILMAZ F; BAYSAL BM
Title: ESTIMATION OF THE EQUATION OF STATE EXCHANGE ENERGY AND ENTROPY PARAMETERS OF A POLYMER SOLVENT PAIR BY INTRINSIC-VISCOSITY MEASUREMENTS
Source: POLYMER INTERNATIONAL 1993, Vol 31, Iss 1, pp 107-111
Publisher: JOHN WILEY & SONS LTD
Addresses: YILMAZ F, YILDIZ UNIV,DEPT CHEM,SISLI ISTANBUL 80270,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,BEBEK 80815,TURKEY
Author Keywords: POLY(4-CHLOROSTYRENE); INTRINSIC VISCOSITY; POLYMER SOLVENT INTERACTIONS; EQUATION OF STATE PARAMETERS
KeywordsPlus: POLYSTYRENE SOLUTIONS; THERMODYNAMICS
Abstract: The intrinsic viscosity data of linear poly(4-chlorostyrene) in n-propylbenzene and isopropylbenzene were used to estimate the equation of state exchange energy (X12) and entropy (Q12) parameters. The quantities estimated for X12 were 6.7 and 8.1 J cm-3 and those of Q12 were -0.069 and -0.063 J cm-3 deg-1 in n-propylbenzene and isopropylbenzene, respectively. The average values of the chain unperturbed dimension constant (K0) and the characteristic ratio (C(infinity)) were found to be 0.55 x 10(-3) dl mol1/2 g-3/2 and 10.54, respectively, from the intrinsic viscosities measured at the corresponding theta-temperatures.
Times Cited: 4
Source item page count: 5
IDS No.: KN261
29-char source abbrev: POLYM INT
Publisher address: BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD


Record 27 of 50
Author(s): BAYSAL BM; UYANIK N
Title: STUDIES OF LINEAR POLYMER DIMENSIONS OF POLYSTYRENE IN CYCLOHEXANE OVER A WIDE-RANGE OF TEMPERATURE BY INTRINSIC-VISCOSITY
Source: POLYMER 1992, Vol 33, Iss 22, pp 4798-4804
Publisher: ELSEVIER SCI LTD
Addresses: BAYSAL BM, BOGAZICI UNIV,DEPT CHEM ENGN,80815 BEBEK,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,80815 BEBEK,TURKEY
TECH UNIV ISTANBUL,DEPT CHEM,80626 MASLAK,TURKEY
Author Keywords: POLYSTYRENE; CYCLOHEXANE; INTRINSIC VISCOSITY; POLYMER DIMENSION
KeywordsPlus: COIL-GLOBULE TRANSITION; PHASE-TRANSITION; HYDRODYNAMIC RADIUS; THETA-TEMPERATURE; COLLAPSED REGIME; MOLECULAR-WEIGHT; DNA CONDENSATION; FLEXIBLE COILS; DEPENDENCE; GELS
Abstract: Intrinsic viscosities ([eta]) of polystyrene solutions in cyclohexane above and below the theta temperature have been measured using a capillary viscometer. The viscosity measurements were performed on five polystyrene samples with molecular weights of 6.3 x 10(4), 9.0 x 10(4), 6.0 x 10(5), 2.8 x 10(6) and 10 x 10(6). A smooth and continuous contraction was observed below the theta temperature (34.5-degrees-C). The temperature dependence of [eta] can be represented by a master curve in a alpha(eta)3\tau\M1/2 (g1/2 mol-1/2) versus \tau\M1/2 (g1/2 mol-1/2) plot, where alpha(eta) = [eta(T)]/[eta(theta)]1/3 is a viscosity expansion factor and tau = (T - theta)/T is the reduced temperature. A universal plot of reduced viscosity (alpha(eta)) versus reduced blob parameter (N/N(c)) shows the achievement of the collapsed state for the T < 0 region. The prediction of the temperature blob theory is also verified for the T > theta region.
Times Cited: 9
Source item page count: 7
IDS No.: JY848
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 28 of 50
Author(s): YILMAZ F; CANKURTARAN OG; BAYSAL BM
Title: THERMODYNAMIC INTERACTIONS AND CHARACTERIZATION OF POLY(P-CHLOROSTYRENE) WITH SOME ALIPHATIC AND AROMATIC PROBES BY INVERSE GAS-CHROMATOGRAPHY
Source: POLYMER 1992, Vol 33, Iss 21, pp 4563-4568
Publisher: ELSEVIER SCI LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,80815 BEBEK,TURKEY
YILDIZ UNIV,DEPT CHEM,80270 SISLI,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,80815 BEBEK,TURKEY
Author Keywords: POLY(P-CHLOROSTYRENE); INVERSE GAS CHROMATOGRAPHY; POLYMER SOLVENT INTERACTIONS; EQUATION OF STATE PARAMETERS
KeywordsPlus: POLYSTYRENE SOLUTIONS; POLYMERS
Abstract: Some thermodynamic quantities were obtained for the interactions of poly (p-chlorostyrene) with n-pentane, n-hexane, n-heptane, benzene, toluene, isopropylbenzene and n-propylbenzene by the inverse gas chromatography method in the temperature range 150-170-degrees-C. The specific retention volumes (V(g)0), weight fraction activity coefficients of solute probes at infinite dilution (OMEGA1infinity), Flory-Huggins thermodynamic interaction parameters (chi12infinity), interaction parameters based on hard-core volumes (chi12*), effective exchange interaction parameters (X12BAR) of the equation of state theory, between polymer and solutes are given. The molar enthalpy of sorption (DELTAH(s)BAR), the partial molar heat of mixing at infinite dilution (DELTAH-1infinityBAR) and the solubility parameter of polymer (delta2) were also calculated.
Times Cited: 9
Source item page count: 6
IDS No.: JX127
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 29 of 50
Author(s): MENCELOGLU YZ; BAYSAL BM
Title: SYNTHESIS AND CHARACTERIZATION OF MULTIFUNCTIONAL INITIATORS FOR PREPARATION OF 4-BRANCH POLYMERS
Source: ANGEWANDTE MAKROMOLEKULARE CHEMIE 1992, Vol 200, pp 37-47
Publisher: HUTHIG & WEPF VERLAG
Addresses: TECH UNIV ISTANBUL,DEPT CHEM,80626 MASLAK,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,80815 BEBEK,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
KeywordsPlus: ACRYLONITRILE
Abstract: Tetrafunctional initiators T4-AZO4, T4-TCE1 and T4-IPDI4 have been synthesized by using insertion reaction of tetrakis(dimethylamino)-titanium (T4) with 2,2'-azoiso-butyronitrile (AIBN), tetracyanoethylene (TCE) or isophorone diisocyanate (IPDI), respectively, in dry benzene under nitrogen at 35-degrees-C. T4-AZO4 is useful for preparing four-branch polymers from radically polymerizable monomers by decompositon of the azo groups incorporated in the related initiator. Four-branch polyacrylonitrile can be synthesized by using the initiator T4-TCE1. This initiator possesses titanium-amino functionalities which are capable of initiating acrylonitrile polymerizations. The tetrafunctional isocyanate compound T4-IPDI4 is found to be useful to prepare a model network of dihydroxy-terminated polymers.
Times Cited: 1
Source item page count: 11
Publication Date: SEP
IDS No.: JR935
29-char source abbrev: ANGEW MAKROMOL CHEM
Publisher address: AUF DEM WOLF 4, CH-4052 BASEL, SWITZERLAND


Record 30 of 50
Author(s): BAHAR I; NEUBURGER N; MATTICE WL
Title: MECHANISM OF LOCAL CONFORMATIONAL TRANSITIONS IN POLY(DIALKYLSILOXANES) - MOLECULAR-DYNAMICS SIMULATIONS AND DYNAMIC ROTATIONAL ISOMERIC STATE APPROACH
Source: MACROMOLECULES 1992, Vol 25, Iss 18, pp 4619-4625
Publisher: AMER CHEMICAL SOC
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,BEBEK 80815,TURKEY
UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
KeywordsPlus: POLYMERS; MOTIONS; CHAINS; MODEL
Abstract: Results from molecular dynamics simulations of isolated poly(dialkylsiloxane) chains are analyzed with emphasis on the conformational dynamics of a fragment of five repeat units, in which the alkyl group is tert-butyl. This fragment furnishes a typical example of a chain in which the bulky substituents restrict to a considerable extent the rotational motions of the backbone, which otherwise enjoys a high degree of flexibility. The rotational motions of the bonds flanking the oxygen atom are observed to be strongly correlated: the main mechanism of relaxation in the time range of picoseconds is the coupled counterrotations of those adjacent bonds. Examination of the molecular dynamics trajectories over much longer time scales, such as tenths of nanoseconds, reveals correlations between the rotational motions of neighboring repeat units, causing a relatively long-range coupling of backbone bonds along the chains, mainly between bonds i and i + 3. The orientational motion of the pair of bonds flanking the oxygen atom is analyzed within the framework of the dynamic rotational isomeric state formalism.
Times Cited: 6
Source item page count: 7
Publication Date: AUG 31
IDS No.: JL964
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 31 of 50
Author(s): OZ B; DERVISOGLU S; DERVISOGLU M; OZ O
Title: SILVER BINDING NUCLEOLAR ORGANIZER REGIONS IN ADRENOCORTICAL NEOPLASIA
Source: CYTOPATHOLOGY 1992, Vol 3, Iss 2, pp 93-99
Publisher: BLACKWELL SCIENCE LTD
Addresses: OZ B, ISTANBUL UNIV,CERRHPASA MED SCH,DEPT PATHOL,ISTANBUL,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
ISTANBUL UNIV,CERRAHPASA MED SCH,DEPT BIOMED STAT,ISTANBUL,TURKEY
Author Keywords: NUCLEOLAR ORGANIZER REGION; SILVER STAINING; ADRENOCORTICAL NEOPLASIA
KeywordsPlus: NON-HODGKINS LYMPHOMAS; DNA; AGNORS; TUMORS
Abstract: The possible contribution of the silver colloid technique for staining nucleolar organizer regions in the distinction between benign and malignant adrenocortical neoplasms was investigated. Nine cases of adenoma, eight cases of carcinoma, nine cases of hyperplasia and four normal adrenal cortex specimens were examined. The mean silver binding nucleolar organizer region (Ag-NOR) value in adenoma was 4.29, and in carcinoma 7.16 (P < 0.001). Adenomas with diameters > 3 cm had significantly higher Ag-NOR counts than smaller adenomas. For normal cortex, the mean Ag-NOR value was 2.05 and in hyperplasia, 3.62. The results indicate that the Ag-NOR technique can help in differential diagnosis between benign and malignant adrenocortical lesions and thus may have a prognostic value.
Times Cited: 2
Source item page count: 7
IDS No.: JA361
29-char source abbrev: CYTOPATHOLOGY
Publisher address: OSNEY MEAD, OXFORD, OXON, ENGLAND OX2 0EL


Record 32 of 50
Author(s): NEUBURGER N; BAHAR I; MATTICE WL
Title: MOLECULAR-DYNAMICS SIMULATIONS OF POLY(DIALKYLSILOXANES) - CONFORMATIONAL STATISTICS AND UNPERTURBED CHAIN DIMENSIONS
Source: MACROMOLECULES 1992, Vol 25, Iss 9, pp 2447-2454
Publisher: AMER CHEMICAL SOC
Addresses: UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
Abstract: Molecular dynamics trajectories have been computed for isolated poly(dialkylsiloxane) chains in which the alkyl groups are methyl, ethyl, propyl, butyl, isopropyl, isobutyl, or tert-butyl. The joint probability profiles for the pair of Si-O bonds flanking a silicon atom are insensitive to the changes in the alkyl substituents. In contrast, the joint probability profiles for the pair of bonds flanking an oxygen atom change systematically as the size of the alkyl group increases. There is a strong correlation in the dihedral angles at these two bonds when the alkyl groups are large. The features in these probability profiles are incorporated into a rotational isomeric state analysis that permits predictions of the characteristic ratio, C infinity in the limit as n --> infinity. If the alkyl groups are not branched, the values of C infinity increase with the size of the alkyl group and reach a limit of about 8.3. Branching of the side chain reduces the characteristic ratio.
Times Cited: 6
Source item page count: 8
Publication Date: APR 27
IDS No.: HR586
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 33 of 50
Author(s): BAYSAL BM; YILMAZ F
Title: STUDIES OF LINEAR POLYMER DIMENSIONS OF POLY(4-CHLOROSTYRENE) IN VARIOUS SOLVENTS AROUND THE THETA-TEMPERATURES BY INTRINSIC-VISCOSITY
Source: POLYMER INTERNATIONAL 1992, Vol 27, Iss 4, pp 339-345
Publisher: JOHN WILEY & SONS LTD
Addresses: BAYSAL BM, BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,BEBEK 80815,TURKEY
YILDIZ UNIV,DEPT CHEM,SISLI ISTANBUL 80270,TURKEY
Author Keywords: POLYMER; COIL-GLOBULE; TRANSITION; COLLAPSE; THETA-TEMPERATURE; INTRINSIC VISCOSITY
KeywordsPlus: PHASE-TRANSITION; HYDRODYNAMIC RADIUS; COLLAPSED REGIME; MOLECULAR-WEIGHT; DNA CONDENSATION; FLEXIBLE COILS; POLYSTYRENE; GELS; CYCLOHEXANE; DEPENDENCE
Abstract: Intrinsic viscosities of poly(4-chlorostyrene) solutions in isopropyl-benzene and n-propylbenzene at temperatures above and below the theta (theta) temperatures of these solvents were measured using a capillary viscometer. The viscosity measurements were performed on three poly(4-chlorostyrene) samples having molecular weights (M(v)BAR) 1.75 x 10(6), 6.5 x 10(5) and 2.7 x 10(5). A smooth and continuous contraction below the theta-temperatures was observed for both solvents. The temperature dependence of [eta] can be represented by a master curve in a plot of alpha(eta)3\tau\M1/2 (g1/2 mol-1/2) versus \tau\M1/2 (g1/2 mol-1/2), where alpha(eta) = [eta(T)]/[eta(theta)]1/3 is the expansion factor and tau = (T - theta)/T is the reduced temperature. A universal plot of reduced viscosity size (alpha(eta)) versus reduced blob parameter (N/N(c)) shows the achievement of collapsed state for T < theta. The prediction of thermal blob theory is also verified for T > theta. The temperature dependence of intrinsic viscosity, both below and above the theta-temperature, exhibits similar behaviour to the temperature dependence of dipole moments for both of these solvents.
Times Cited: 7
Source item page count: 7
IDS No.: HR166
29-char source abbrev: POLYM INT
Publisher address: BAFFINS LANE CHICHESTER, W SUSSEX, ENGLAND PO19 1UD


Record 34 of 50
Author(s): ARICAN TF; HORTACSU O
Title: ENERGY-CONSERVATION IN GLASS MANUFACTURE
Source: ENERGY 1992, Vol 17, Iss 6, pp 617-624
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
Abstract: Regenerative glass furnaces have continuous glass production but are cyclic in thermal operation. The length of the thermal cycle affects the thermal efficiency of the furnace. We summarize the results of 11 experiments performed on a 33 ton/day end-port type regenerative glass furnace. Six flame-direction reversal times, ranging from 15 to 40 min, were used. The furnace thermal efficiencies were determined to be in the range 41.8-43.8%, with longer flame direction reversal times yielding higher efficiencies. Two alternative methods were used to determine the optimum flame-direction reversal time and both resulted in an optimum cycle time of 40-45 min.
Times Cited: 0
Source item page count: 8
Publication Date: JUN
IDS No.: HL136
29-char source abbrev: ENERGY
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB


Record 35 of 50
Author(s): NEUBURGER NA; MATTICE WL; BAHAR I
Title: CORRELATIONS OF NEAREST-NEIGHBOR BONDS IN CERTAIN POLY(DIALKYLSILOXANES)
Source: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 1992, Vol 203, pp 35-IEC
Publisher: AMER CHEMICAL SOC
Addresses: UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
Times Cited: 0
Source item page count: 0
Publication Date: APR 5
Part number: 2
IDS No.: HK162
29-char source abbrev: ABSTR PAP AMER CHEM SOC
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 36 of 50
Author(s): BAHAR I; LEE KJ; MATTICE WL
Title: RELAXATION OF RUNS OF TRANSROTATIONAL ISOMERS IN SINGLE RACEMIC POLY(VINYL CHLORIDE) CHAINS
Source: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY 1991, Vol 202, pp 69-POLY
Publisher: AMER CHEMICAL SOC
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,BEBEK 80815,TURKEY
UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
Times Cited: 0
Source item page count: 0
Publication Date: AUG 25
Part number: 2
IDS No.: HG081
29-char source abbrev: ABSTR PAP AMER CHEM SOC
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 37 of 50
Author(s): YILMAZ F; BAYSAL BM
Title: DIPOLE-MOMENTS OF POLY(PARA-CHLOROSTYRENE) CHAINS DETERMINED IN BENZENE, ISOPROPYL BENZENE AND NORMAL-PROPYL BENZENE
Source: JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS 1992, Vol 30, Iss 2, pp 197-202
Publisher: JOHN WILEY & SONS INC
Addresses: YILMAZ F, YILDIZ UNIV,DEPT CHEM,ISTANBUL 80270,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL 80815,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL 80815,TURKEY
Author Keywords: DIPOLE MOMENTS OF POLY(PARA-CHLOROSTYRENE) IN BENZENE; ISOPROPYL BENZENE AND NORMAL-PROPYL BENZENE; POLY(PARA-CHLOROSTYRENE) DIPOLE MOMENTS IN BENZENE; ISOPROPYL BENZENE AND NORMAL-PROPYL BENZENE
KeywordsPlus: CONFORMATIONAL CHARACTERISTICS; TEMPERATURE-COEFFICIENT; POLY(METHYL ACRYLATE); SOLVENT
Abstract: Dipole moments of poly (p-chlorostyrene) were determined from dielectric and refractive index measurements performed on their dilute benzene, isopropyl benzene and n-propyl benzene solutions over a wide range of temperatures. Experimental results are expressed in terms of the dimensionless dipole moment ratios, D(x) = [mu-2]/x-mu-0(2). The temperature coefficients of dipole moments, d ln[mu-2]/dT were calculated. The presence and importance of the specific solvent-segment interactions are demonstrated by considering the temperature dependence of the dipole moment ratio in the vicinity of the theta temperature. These results are compared with dipole moments and temperature coefficients which were calculated by Bahar et al. using the appropriate rotational isomeric state model to study the local solvent effect for the poly (p-chlorostyrene)-benzene system.
Times Cited: 4
Source item page count: 6
Publication Date: FEB
IDS No.: HA097
29-char source abbrev: J POLYM SCI B-POLYM PHYS
Publisher address: 605 THIRD AVE, NEW YORK, NY 10158-0012


Record 38 of 50
Author(s): KUCUKYAVUZ Z; BAYSAL BM
Title: DIPOLE-MOMENTS OF COPOLYMERS IN RELATION TO THE DISTRIBUTION OF POLAR MONOMER UNIT SEQUENCES
Source: POLYMER 1991, Vol 32, Iss 18, pp 3418-3421
Publisher: ELSEVIER SCI LTD
Addresses: KUCUKYAVUZ Z, MIDDLE E TECH UNIV,DEPT CHEM,ANKARA 06531,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,BEBEK 80815,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
Author Keywords: DIPOLE MOMENT; POLY(STYRENE-CO-PARA-CHLOROSTYRENE); POLY(STYRENE-CO-PARA-METHOXYSTYRENE); SEQUENCE DISTRIBUTION; NEAREST NEIGHBOR INTERACTION; MICROSTRUCTURE
KeywordsPlus: RANDOM-COIL DIMENSIONS; CHAINS
Abstract: A method for evaluating the dipole moments of copolymers in relation to the distribution of polar unit sequences is proposed. Experimental data on the synthesis and dipole moments of styrene-p-chlorostyrene and styrene-p-methoxystyrene copolymers were used to calculate the effective dipole moment of a polar unit in a copolymer. For this purpose, we assumed the following effective moment values for the corresponding polar unit sequences along the copolymer chains: when both of the nearest neighbours are polar, mu(PP), when one of the nearest neighbours is polar and the other is non-polar, mu(PS), and when both of the nearest neighbours are non-polar, mu(SS). The relative magnitudes of mu(SS), mu(PS) and mu(PP) calculated for both copolymers reflect the influence of dipole-dipole interactions on the effective dipole moment of a polar unit in a copolymer molecule.
Times Cited: 1
Source item page count: 4
IDS No.: GX980
29-char source abbrev: POLYMER
Publisher address: THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, OXON, ENGLAND OX5 1GB


Record 39 of 50
Author(s): ZUNIGA I; BAHAR I; DODGE R; MATTICE WL
Title: MOLECULAR-DYNAMICS ANALYSIS OF TRANSITIONS BETWEEN ROTATIONAL ISOMERS IN POLYMETHYLENE
Source: JOURNAL OF CHEMICAL PHYSICS 1991, Vol 95, Iss 7, pp 5348-5354
Publisher: AMER INST PHYSICS
Addresses: ZUNIGA I, UNIV NACL EDUC DISTANCIA,DEPT FIS FUNDAMENTAL,APARTADO 60141,E-28080 MADRID,SPAIN
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
KeywordsPlus: POLYMER CONFORMATIONAL TRANSITIONS; BROWNIAN DYNAMICS; ALKANES; SIMULATIONS; MODEL; CHAINS; BUTANE
Abstract: Molecular dynamics trajectories have been computed and analyzed for linear chains, with sizes ranging from C10H22 to C100H202, and for cyclic C100H200. All hydrogen atoms are included discretely. All bond lengths, bond angles, and torsion angles are variable. Hazard plots show a tendency, at very short times, for correlations between rotational isomeric transitions at bond i and i +/- 2, in much the same manner as in the Brownian dynamics simulations reported by Helfand and co-workers. This correlation of next nearest neighbor bonds in isolated polyethylene chains is much weaker than the correlation found for next nearest neighbor CHCH2 bonds in poly(1,4-trans-butadiene) confined to the channel formed by crystalline perhydrotriphenylene [Dodge and Mattice, Macromolecules 24, 2709 (1991)]. Less than half of the rotational isomeric transitions observed in the entire trajectory for C50H102 can be described as strongly coupled next nearest neighbor transitions. If correlated motions are identified with successive transitions, which occur within a time interval of DELTA-t less-than-or-equal-to 1 ps, only 18% of the transitions occur through cooperative motion of bonds i and i +/- 2. An analysis of the entire data set of 2482 rotational isomeric state transitions, observed in a 3.7 ns trajectory for C50H102 at 400 K, was performed using a formalism that treats the transitions at different bonds as being independent. On time scales of 0.1 ns or longer, the analysis based on independent bonds accounts reasonably well for the results from the molecular dynamics simulations. At shorter times the molecular dynamics simulation reveals a higher mobility than implied by the analysis assuming independent bonds, presumably due to the influence of correlations that are important at shorter times.
Times Cited: 33
Source item page count: 7
Publication Date: OCT 1
IDS No.: GH356
29-char source abbrev: J CHEM PHYS
Publisher address: CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999


Record 40 of 50
Author(s): BAHAR I; ZUNIGA I; DODGE R; MATTICE WL
Title: CONFORMATIONAL STATISTICS OF POLY(DIMETHYLSILOXANE) .1. PROBABILITY-DISTRIBUTION OF ROTATIONAL ISOMERS FROM MOLECULAR-DYNAMICS SIMULATIONS
Source: MACROMOLECULES 1991, Vol 24, Iss 10, pp 2986-2992
Publisher: AMER CHEMICAL SOC
Addresses: UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
UNIV NACL EDUC DISTANCIA,DEPT FIS FUNDAMENTAL,E-28080 MADRID,SPAIN
Abstract: The probability distribution of isomeric conformations in poly(dimethylsiloxane) has been investigated both by conformational energy considerations and by molecular dynamics simulations. A comparatively smooth distribution of isomeric states is obtained from both approaches. The molecular dynamics trajectory of a simulated dimethylsiloxane oligomer of eight units is used as a reliable and realistic tool to estimate the probability of occurrence for various rotational isomeric states. Conformations involving bonds in the gauche state produce attractive intramolecular potentials through suitable spatial arrangement of close neighbors, which is contradictory to the unfavorable interactions attributed to them in the model described by Flory, Crescenzi, and Mark. The relative potential energies of the various conformational states are obtained from the probability of those conformations occurring in a molecular dynamics simulation.
Times Cited: 26
Source item page count: 7
Publication Date: MAY 13
IDS No.: FL697
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 41 of 50
Author(s): BAHAR I; ZUNIGA I; DODGE R; MATTICE WL
Title: CONFIGURATIONAL STATISTICS OF POLY(DIMETHYLSILOXANE) .2. A NEW ROTATIONAL ISOMERIC STATE APPROACH
Source: MACROMOLECULES 1991, Vol 24, Iss 10, pp 2993-2998
Publisher: AMER CHEMICAL SOC
Addresses: UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
UNIV NACL EDUC DISTANCIA,DEPT FIS FUNDAMENTAL,E-28080 MADRID,SPAIN
Abstract: A new rotational isomeric state treatment, compatible with the molecular mechanics and dynamics considerations of the preceding paper, is introduced for describing the conformational statistics of poly(dimethylsiloxane). In view of the smooth distribution of rotamers deduced from molecular dynamics simulations, softer potentials are assigned to bonds in gauche states compared to the model of Flory, Crescenzi, and Mark. Second-order interactions prevailing in states involving trans bonds are included in the theory. The model yields satisfactory agreement with experiments on the mean-square unperturbed end-to-end separations, the mean-square dipole moment and its temperature dependence, and the molar cyclization equilibrium constants for dimethylsiloxane oligomers. It cannot account for the positive temperature coefficient of the unperturbed chain dimensions. Intramolecular interactions extending beyond first and second neighbors along the chan are investigated as a possible origin of the discrepancy.
Times Cited: 20
Source item page count: 6
Publication Date: MAY 13
IDS No.: FL697
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036


Record 42 of 50
Author(s): MENCELOGLU YZ; GUNGOR A; BAYSAL BM
Title: GRAFTING OF ACRYLONITRILE TO POLY(STYRENE-CO-ACRYLONITRILE) BY TRANSFORMATION WITH A TITANIUM CATALYST
Source: MAKROMOLEKULARE CHEMIE-MACROMOLECULAR CHEMISTRY AND PHYSICS 1991, Vol 192, Iss 4, pp 847-855
Publisher: HUTHIG & WEPF VERLAG
Addresses: TECH UNIV ISTANBUL,DEPT CHEM,MASLAK 80626,TURKEY
TUBITAK,BASIC SCI RES INST,GEBZE 41470,TURKEY
BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,BEBEK 80815,TURKEY
Abstract: Poly(styrene-co-acrylonitrile)-graft-polyacrylonitrile graft copolymers were prepared using a mixed (free-radical/anionic) mechanism technique. For this purpose, poly(styrene-co-acrylonitrile) random copolymers which contain different amounts of acrylonitrile segments were regarded as saturated high-molecular-weight nitrile compounds and were allowed to react with tetrakis(dimethylamino)titanium. By this treatment pendant nitrile groups were transformed to organometallic active sites. These active groups lead to the polymerization of acrylonitrile via an anionic insertion process. Polyacrylonitrile grafts were grown on the poly(styrene-co-acrylonitrile) backbone.
Times Cited: 1
Source item page count: 9
Publication Date: APR
IDS No.: FK982
29-char source abbrev: MAKROMOL CHEM-MACRO CHEM PHYS
Publisher address: AUF DEM WOLF 4 FX#001-41-61-317-94-11, CH-4052 BASEL, SWITZERLAND


Record 43 of 50
Author(s): YILDIRIM H; BAYSAL BM
Title: SYNTHESIS, CHARACTERIZATION AND KINETICS OF THERMAL-DECOMPOSITION OF VARIOUS PEROXYCARBAMATES AND THEIR INITIATION OF METHYL-METHACRYLATE POLYMERIZATION
Source: ANGEWANDTE MAKROMOLEKULARE CHEMIE 1990, Vol 181, pp 103-117
Publisher: HUTHIG & WEPF VERLAG
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,ISTANBUL,TURKEY
UNIV YILDIZ,DEPT CHEM,SISLI ISTANBUL,TURKEY
KeywordsPlus: BLOCK COPOLYMERS; STYRENE
Abstract: Several dimeric and polymeric peroxycarbamates were synthesized using various aliphatic diisocyanates and hydroperoxides. The products were characterized by IR spectroscopy, molecular weight measurements, isocyanate and peroxide analyses. Thermal decomposition kinetics of these peroxycarbamates were studied in 1,4-dioxane or toluene solutions at 80, 90, and 100-degrees-C. All reactions were found to proceed according to a first-order kinetics with activation energies in the range of 126-144 kJ/mol, depending on the structure of the peroxycarbamate. One of the polymeric products was used to initiate methyl methacrylate polymerization at 80-degrees-C in bulk. The initiating activity of this peroxycarbamate was found to be better than that of some hydroperoxides.
Times Cited: 0
Source item page count: 15
Publication Date: OCT
IDS No.: FA606
29-char source abbrev: ANGEW MAKROMOL CHEM
Publisher address: AUF DEM WOLF 4 FX#001-41-61-317-94-11, CH-4052 BASEL, SWITZERLAND


Record 44 of 50
Author(s): BAHAR I; MATTICE WL
Title: BIMODAL DISTRIBUTION OF RELAXATIONAL MODES FOR THE HELIX COIL TRANSITION IN POLY(OXYMETHYLENE)
Source: MACROMOLECULES 1991, Vol 24, Iss 4, pp 877-882
Publisher: AMER CHEMICAL SOC
Addresses: BOGAZICI UNIV,DEPT CHEM ENGN,BEBEK 80815,ISTANBUL,TURKEY
BOGAZICI UNIV,POLYMER RES CTR,ISTANBUL,TURKEY
UNIV AKRON,INST POLYMER SCI,AKRON,OH 44325
KeywordsPlus: POLYMERS; CHAINS
Abstract: The helix-coil transition in poly(oxymethylene) has been investigated by using the recently developed dynamic rotational isomeric state (DRIS) model and the related matrix multiplication technique. The conditional probability P-tau-(h/h) that a chain originally in the perfect helical form will preserve its state unchanged at a later time tau is evaluated for various chain lengths and temperatures.The transition to the coiled structure in an originally fully ordered helix is found to exhibit a bimodal relaxation, indicated by a plateau in the time decay curves of the conditional probabilities, before restoration of equilibrium distribution. This intermediate quasi-steady state preceding full relaxation is attributed to an equilibrium between perfect helices and chains possessing a single defect in the form of a trans bond, interrupting sequences of gauche bonds of the same sign.
Times Cited: 4
Source item page count: 6
Publication Date: FEB 18
IDS No.: EY303
29-char source abbrev: MACROMOLECULES
Publisher address: 1155 16TH ST, NW, WASHINGTON, DC 20036