bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular structure of 1,7‐dichlorotetradecaphenylheptasilane as a model of poly(diphenylsilane)
Authors: Ovchinnikov Yuri E. , Dement'ev Vyacheslav V. , Shklover Valery E. , Frunze Tat'yana M. , Struchkov Yuri T. , Antipova Bella A. , Igonin Vladimir A.
Published: April 2003

The molecular and crystal of 1,7‐dichlorotetradecaphenylheptasilane Cl(SiPh2)7Cl

Dedicated to Prof. Dr. H. Sinn on the occasion of his 60th birthday

(I) was determined. The molecule has a helical conformation with the torsion angles SiSiSiSi in the range of 154°–162°. Crystal I is built of infinite polysilane chains extended along the [111] direction and separated by solvating benzene and toluene molecules.
Synthèse de polysiloxanes acyloxyméthylés par réaction des acides acétique, benzoïque et méthacrylique, en présence de triéthylamine, sur des polysiloxanes chlorométhylés, 1. Synthèse et identification de trisiloxanes et tétrasiloxanes modèles
Authors: Jazouli Talha , Reyx Danièle , Thomas Michel
Published: April 2003

3‐(Acyloxymethyl)‐1,1,1,3,5,5,5‐heptamethyltrisiloxanes 7b1, 7c1, 7d1 and 3,5‐bis(acyloxymethyl)‐1,1,1,3,5,7,7,7‐octamethyltetrasiloxanes 7b2, 7c2, 7d2 (7b: acetoxymethyl, 7c: benzoyloxymethyl and 7d: methacryloyloxyméthyl derivatives) were synthesized from 3‐(chloromethyl)‐1,1,1,3,5,5,5‐heptamethyltrisiloxane (7a1) or from 3,5‐bis(chloromethyl)‐1,1,1,3,5,7,7,7‐octamethyltetrasiloxane (7a2), respectively. Spectroscopic (1H NMR) and chromatographic (GPC and CG) characteristics of the isolated products were defined in order to standardize the analytical tools used for the study of the carboxylic acid reaction with chloromethylated polysiloxanes in the presence of triethylamine.
Synthèse de polysiloxanes acyloxyméthylés par réaction des acides acétique, benzoïque et méthacrylique, en présence de triéthylamine, sur des polysiloxanes chlorométhylés, 2. Etude de la réaction sur trisiloxane et tétrasiloxane modèles
Authors: Jazouli Talha , Reyx Danièle , Thomas Michel
Published: April 2003

The reaction of acetic, benzoic and methacrylic acids with 3‐chloromethylheptamethyltrisiloxane and 3,5‐bis(chloromethyl)octamethyltetrasiloxane in toluene in the presence of triethylamine was studied. Beside the expected transformation of oxy(chloromethyl)methylsilanediyle (A) units into oxy(acyloxymethyl)methylsilanediyle (C) units, redistributions of A, C and trimethylsilyl/oxytrimethylsilyl (M) were observed. The conversion versus time curves of distribution of the former oligomers (mole fractions of trisiloxanes: F1 = mM‐X‐M = mM‐A‐M + mM‐C‐M and tetrasiloxanes: F2 = mM‐X‐X‐M = mM‐A‐A‐M + mM‐A‐C‐M + mM‐C‐C‐M) were followed. The reaction rates were not only controlled by the acid used but also by the starting oligosiloxane (trisiloxane or tetrasiloxane). The distributions of the homogeneous and heterogeneous oligomers seem to result from controlled combinations of A, C and M according to orientations of cleavages and to relative affinities of RCOOH/NEt3 towards various siloxanes. For the total conversions the mole fractions F1 and F2 fit with those calculated by a law based on a hazard combination of C and M. This result may be explained by the compensation of electronic and steric factors.
On the distribution of the degree of polymerization occurring in the third kinetic stage of dilute‐acid‐catalyzed degradation of cellulose
Authors: Soubelet Oscar , Presta Mario A. , Marx‐Figini Marianne
Published: April 2003

The distributions of the degree of polymerization (DP) of cellulose degraded in the third kinetic stage, i.e. in the second stage of decreasing reaction rate, obey throughout the most probable (Schulz‐Flory) type, and consequently cellulose specimens degraded at different conditions but with coinciding average DP coincide also with their DP distributions.
Liquid‐crystalline polyethers and copolyethers based on conformational isomerism, 5. Thermotropic copolyethers based on 1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyphenyl)ethane and flexible spacers containing odd and even numbers of methylene units
Authors: Percec Virgil , Yourd Raymond
Published: April 2003

The synthesis and characterization of thermotropic main‐chain liquid‐crystalline copolyethers based on 3‐methyl‐4,4′‐ethylenediphenol [1‐(4‐hydroxyphenyl)‐2‐(2‐methyl‐4‐hydroxyhenyl)‐ethane (MBPE)], which is a flexible rod‐like mesogenic unit or a rod‐like mesogenic unit based on conformational isomerism, and pairs of flexible spacers containing odd and even numbers of methylene units, X, Y, i.e., MBPE‐X/Y, where X/Y = 5/12, 5/10, 5/8, 6/11, 6/9, 4/11 and 4/9, are described. Copolymerization decreases the rate of crystallization and subsequently transforms virtual or monotropic mesophases of homopolymers into monotropic or even enantiotropic mesophases. Both liquid‐crystalline transition temperatures and enthalpy changes of the identical mesophases displayed by copolymers represent weight‐averaged values of the similar parameters of the parent homopolymers. Their extrapolation leads to the determination of the virtual mesomorphic transition temperatures and enthalpy changes of the parent homopolymers.
Functionalized polyacetals, 1. Copolymerization of trioxane with 1,3‐dioxep‐5‐ene and properties of the resulting copolymer
Authors: Pesce‐Rodriguez Rose Ann , Wang Shiang , Yang Nan‐Loh , Auerbach Andrew , Paul James
Published: April 2003

1,3,5‐Trioxane (1) and 1,3‐dioxep‐5‐ene (2) were copolymerized with BF3OEt2 at 65°C. The products, after base hydrolysis, were characterized by 13C and 1H NMR and were found to assume the chemical structure 4 of a copolymer containing oxymethylene and oxy‐2‐butenylene units with 4‐hydroxy‐2‐butenyl and methoxy end groups, with the ratio of hydroxy‐2‐butenylene to methoxy end groups varying with experimental conditions. The copolymer demonstrates crystallinity and thermal stability comparable to poly(trioxane‐co‐ethylene oxide)s. Copolymer melting point was observed to decrease with increasing comonomer incorporation. The upper limit for incorporation of the comonomer 2 was found to be ca. 4 mol per cent. Viscosity and end group analysis (by 1H NMR) indicate molecular weights in the range of 104 to 105. The comonomeric unit demonstrates the ability to act as both a stopper against unzipping and as a trap for certain degrading agents.
Studies on elementary reactions in the polymerization of 1,2‐epoxycyclohexane with organozinc compounds as initiators
Authors: Hasebe Yoshihiro , Izumitani Keiko , Torii Masao , Tsuruta Teiji
Published: April 2003

1,2‐Epoxycyclohexane (1) was found to behave differently from propylene oxide (PO) in polymerization reactions with organozinc compounds as initiators. A chair‐type complex, [Zn‐MP]2,2, is the only compound that shows high catalytic activity for both polymerization of 1 and PO, following an anionic coordination mechanism. On the other hand, the polymerization of 1 with ZnEt2 or (EtZnOMe)4 as initiator proceeds according to a cationic mechanism. Cationic polymerization of 1 with ZnEt2 has two modes of termination reaction resulting in the formation of terminal units containing vinyl ether and allyl ether moieties. The initiation and propagation mechanism of 1 by [Zn‐MP]2;2 is similar to that of PO, but chain transfer reaction takes place in the polymerization of 1 owing to the low stability of the growing chain end. By using [Zn‐MP]2,2 as initiator, it was possible to prepare a block copolymer consisting of an isotactic sequence of monomeric units of PO and a syndiotactic sequence of monomeric units of 1.
Synthèse de polymères α,ω‐bifonctionnels par réaction de métathèse. Méthodologie d'approche des différences de réactivité des sites carbéniques en présence
Authors: Reyx Danièle , Campistron Irène
Published: April 2003

The results of studies of co‐metathesis reactions of 1,5‐cyclooctadiene (1) with dimethyl 3‐hexenedioate (2a) and for comparison, with 4‐octene (2b) and 1,5‐hexadiene (2c) are analyzed in order to approximate the relative reactivities of the carbene species and of the different types of double bonds. To this end, the experimental distributions of the first telomers are compared with theoretical ones calculated on the one hand allowing equal probability of arrangement of alkylidene groups and on the other hand allowing a kinetic control of propagation and transfer reactions. In other respects, the possibilities of mass control of the products obtained by the same co‐metathesis or by degradation of 1,4‐polybutadiene are studied. The results show that the reactivity of the 1,5‐cyclooctadiene double bonds is higher than that of the other types of double bonds, this being in agreement with the hypothesis of stabilization of the β‐carbomethoxycarbene species by carbene/ester complexation. This stabilization allows us to explain the distribution of α,β‐difunctional oligomers in agreement with the hypothesis of kinetic control. The distribution of non‐functional oligomers agrees with a random combination of alkylidene groups. This stabilization is compatible with the controlling method of molecular weights in the products obtained by polymerization of cyclooctadiene and also by degradation of 1,4‐polybutadiene in the presence of 2a.
Simulation of coupled modification reactions of polymers, 4. Mono‐ and disubstitution of 1,4‐polybutadiene, coupled with partial double‐bond shift
Authors: Martl Michael G. , Hummel Klaus
Published: April 2003

Monte Carlo calculations for a modification reaction of 1,4‐polybutadiene were carried out. The simulated process consisted in the substitution in α‐position to the double bond, partially coupled with double‐bond shift. The reaction model included mono‐ and disubstitution (one or two substituents at a carbon atom) and the formation of substituted double bonds in shift reactions. The number of molecules, the degree of polymerization and the degree of substitution were varied. The resulting multicomponent copolymers were evaluated with respect to different units (considered from one double bond to the next) and to their mole fractions. For example, more than 800 different units resulted for a mean of two substituents per unit. Units with up to 10 carbon atoms of the chain were found. Small molecule collectives gave representative results if only units above a minimum mole fraction were considered. The constitution of the products depended on the molecular size in the oligomer range. The distribution of the length of the units and of the number of substituents in a unit were determined.
The key to successful acyclic diene metathesis polymerization chemistry
Authors: Wagener Kenneth B. , Boncella James M. , Nel Jan G. , Duttweiler Robert P. , Hillmyer Marc A.
Published: April 2003

This paper describes the key to successful metathesis polycondensation chemistry. Model compound reactions with styrene and styrene derivatives show that metathesis chemistry can occur exclusively if carbocation formation can be obviated through the proper choice of a Lewis acid free catalyst. Vinyl terminated oligo(octenylene)s were synthesized in this manner, which in turn were converted to polymers of high molecular weight.
Intramolecular charge transfer complexes, 28. Poly[ω‐(N‐carbazolyl)alkyl methacrylate‐co‐2‐(methacryloyloxy)ethyl 3,5‐dinitrobenzoate]s
Authors: Simionescu Cristofor I. , David Geta , Grigoras Mircea
Published: April 2003

Copolymers with intramolecular charge transfer interactions were synthesized by radical copolymerization of ω‐(N‐carbazolyl)alkyl methacrylates (where alkyl is propyl and butyl) with 2‐(methacryloyloxy)ethyl 3,5‐dinitrobenzoate. These copolymers are characterized by a dependence of the electronic absorption, the solubility and the density on the composition. The intramolecular degree of complexation depends on spacer length and exerts a maximum for the spacer with three methylene groups.
Determination of substituent distribution in cellulose ethers by means of a 13C NMR study on their acetylated derivatives, 4. O‐methyl‐O‐hydroxyalkylcelluloses
Authors: Tezuka Yasuyuki , Imai Kiyokazu , Oshima Mitsuyoshi , Chiba Tohru
Published: April 2003

A structural study on O‐methyl‐O‐hydroxypropylcellulose (MHPC) and on O‐methyl‐O‐hydroxyethylcellulose (MHEC) was performed by means of a 13C NMR analysis after acetylation of the unsubstituted hydroxyl groups at the anhydroglucose ring and those at the end of the substituents. The carbonyl signal of the acetyl group in acetylated MHPC and MHPC samples was found to be resolved into four peaks according to the location of the acetyl function either at the 2‐, 3‐ and 6‐position of an anhydroglucose unit or at the end of an oligo(oxyalkylene) substituent, allowing to determine the distribution of methyl and oligo(oxyalkylene) substituent groups. The methyl signal of the methoxy group in MHPC was also found to be sensitive to its position either at the anhydroglucose unit or at the end of the oligo(oxypropylene) substituent.
Reversible immobilization of drugs on a hydrogel matrix, 3. Hydrolysis of chloramphenicol precursors
Authors: Yean Leanirith , Meslard Jean‐Claude , Subira Franck , Bunel Claude , Vairon Jean‐Pierre
Published: April 2003

Kinetics of hydrolytic release of chloramphenicol (1) chemically immobilized on HEMA‐based ophthalmic hydrogels were examined. The rate constants of hydrolysis of the phenolic ester and acetal bonds of the spacer immobilizing the drug were determined at 37°C, and essentially at neutral pH, for the monomeric drug, the soluble copolymers and the cross‐linked hydrogels, respectively. A drastic decrease in reactivity of the ester bond was observed from the small monomeric molecule to the soluble chains and then to the swollen network (relative reactivities ≈ 1300/25/1), whereas the acetal bond is less reactive, with a rate constant apparently independent of the size of the carrier. It is suggested that in all cases the ester bond is cleaved at first, liberating a drug bearing acetal intermediate which is then slowly hydrolysed to free chloramphenicol. All reactions were observed to be first order with respect to the hydrolysable precursor. When the rate constants are low enough, which is the case when considering the hydrogels, a pseudo‐zero order is obtained and the release rate of chloramphenicol is constant over a long period of time and depends only on the initial concentration of immobilized, drug. Nevertheless, the too slow acetal hydrolysis in neutral physiological conditions limits the daily delivery to a few micrograms for a standard corneal lens with a 5 mol‐% drug loading.
Synthesis and characterization of new halogen‐containing poly(azomethine‐urethane)s
Authors: Tamareselvy Krishnan , Venkatarao Krishnan , Kothandaraman Harimurthi
Published: April 2003

A series of fluorine‐ and chlorine‐containing bisphenols and their non‐halogenated analogues were synthesized from various hydroxyaldehydes (1) and diamines (2). The structures of the corresponding bisphenols (3) were confirmed by 1H NMR, 19F NMR and IR spectra. Poly(azomethine‐urethane)s were prepared by reacting these monomeric bisphenols (3) with diisocyanates such as 4,4′‐methylenedi(phenyl isocyanate) (4), 2,4‐toluylene diisocyanate (6) and hexamethylene diisocyanate (8). Poly(azomethine‐urethane)s (5, 7 and 9) thus obtained were characterized by IR, UV, solubility, viscosity and thermal analysis (TG).
A novel rearrangement in the syntheses of poly(3,3′‐phthalidylidene‐4,4′‐biphenylylene)s
Authors: Zolotukhin Mikhail G. , Sedova Elvira A. , Sorokina Yulia L. , Salazkin Sergei N. , Sangalov Yuri A. , Sultanova Venera S. , Panasenko Anatoly A. , Khalilov Leonard M. , Muslukhov Rinat M.
Published: April 2003

Studies were made on the synthesis of halide‐substituted poly(phthalidylidenearylene)s by Friedel‐Crafts polycondensations of 3‐aryl‐3‐chlorophthalides containing substituents in 4‐position of the phthalide cycle. As follows from the C13 NMR spectra, those monomers can afford polymers containing two types of isomeric units substituted in 4‐ or 7‐position. The possible routes of formation of the isomeric units are analyzed and a scheme is suggested for the monomer rearrangement in the synthetic course. The polymers containing those two types of units were shown to be highly thermostable and to contain about 30% of a crystalline phase.
Methyl labeling as a tool for investigating the regiochemistry of the electrochemical oxidative polymerization of 1H,8H‐pyrrolo[3,2‐g]indole
Authors: Berlin Anna , Pagani Giorgio , Schiavon Gilberto , Zotti Gianni
Published: April 2003

The preparation of the three isomeric dimethyl derivatives 4–6 of 1 H,8H‐pyrrolo[3,2‐g]indole (1), substituted at the nitrogen atoms or in the positions α and β to them, respectively, is described. These products were synthesized for investigating the regiochemistry of the electrochemical oxidative polymerization of the parent compound 1. Anodic coupling in acetonitrile of the dimethyl derivatives 4–6 produces polymeric films which are reversibly oxidized with a charge exchange of 0,5 electrons per repeating unit. For 5 and 6, coupling occurs in the free positions of the pyrrole rings, yielding a non‐conjugated and poorly conducting (5 · 10−6 Ω−1 · cm−1) polymer and a conjugated and conducting (1 Ω−1 · cm−1) polymer, respectively. The N‐substituted isomer 4 couples in the α‐positions and the resulting polymer shows a decrease in conductivity (10−2 Ω−1 · cm−1) relative to poly(1), analogous to that of poly(N‐methylpyrrole) relative to polypyrrole. Further comparisons of conductivity data and behaviour of the methyl substituted derivatives of 1 allow to conclude that the unsubstituted polymer couples in the position α to the nitrogen atom.
Synthesis and rheological study of some maleic acid and fumaric acid stereoregular polyesters, 4. Synthesis of random, multi‐block and alternating unsaturated copolyesters from fumaric, maleic and phthalic acid potassium salts and 1,4‐dibromobutane
Authors: Djonlagić Jasna , Sepulchre Marie‐Odile , Sepulchre Maurice , Spassky Nicolas , Dunjić Branco , Jaćović Mihailo S.
Published: April 2003

The reaction of dicarboxylic acid potassium salts with dibromo derivatives in 1‐methyl‐2‐pyrrolidone at moderate temperature was applied to the synthesis of high‐molecular‐weight co‐ and terpolyesters containing fumaric, maleic, phthalic and succinic ester residues and tetramethylene groups. Co‐ and terpolyesters with a random structure were obtained from the reaction of binary or ternary mixtures of salts with 1,4‐dibromobutane. While the composition in ester residues of the organic phase varies continuously during the first 6 h of the polycondensation reaction, that of the copolyesters obtained after 24 h is determined by the composition of the initial mixture of salts. The relative amounts of cyclic n‐mers produced in the course of the reaction and those of the different possible dimers were evaluated from GPC analyses of the reaction products. Multi‐block copolyesters were prepared either by the reaction of a potassium salt with a mixture of 1,4‐dibromobutane and a low‐molecular‐weight α‐ω‐dibromopolyester or by the coupling reaction of two low‐molecular‐weight α,ω‐dibromopolyesters with succinic acid potassium salt. The reaction of bis(4‐bromobutyl) phthalate and fumaric or maleic acid potassium salt produced the corresponding alternating copolyesters. Physico‐chemical and compositional data of the prepared unsaturated copolyesters are given.
Studies of the characteristics in the synthesis of polystyrene‐block‐poly(ethylene‐co‐propylene) through a transformation of an anionic to a Ziegler‐Natta mechanism
Authors: Zhang Xuequan , Li Weidong , Huang Baotong
Published: April 2003

Restriction of β‐elimination in polystyrene‐lithium (PSLi) in the block copolymerization of polystyrene with poly(ethylene‐co‐propene) catalyzed with PSLi/TiCl4 (resulting in sample A‐2) by adding a spacer of a few monomeric units of isoprene (I) (PS‐InLi/TiCl4 (n ≤ 3)); resulting in sample A‐3), was evidenced by a M̄w/M̄n‐value of 2,67 lower than that of sample A‐2, and a crystallinity (χ) of 7,4% in the poly(ethylene‐co‐propene) (EPR) block in sample A‐3. These, together with shorter ethylene (E)‐sequences EEEn≥1, 27,6%) and a higher content of inverted propylene units (P) make the EPR‐block in A‐3 look like a polymer obtained with a soluble vanadium catalyst. This is due to the solubilization of the active centers by the PS chains. Higher M̄w/M̄n‐values (4,23) and crystallinity of the EPR block (18,3%) and longer EEEn≥1 sequences (55,4%) in the case of sample A‐2 make it to look like a typical polymer as obtained with a heterogeneous Ti‐catalyst. Comparison of sample A‐3 with that obtained by E‐P copolymerization with BuLi/TiCl4 (sample A‐1) corroborates the solubilization effect of PS in A‐3 and the effects of the typical heterogeneous catalyst used for the preparation of A‐1, showing up in EEEn≥1 (A‐1: 63,4% A‐3: 27,6%), M̄w/M̄n (A‐1: 35,7; A‐3: 2,67) and P̄ (A‐1: nil; A‐3: 4%).
Analysis of the linear methods of determining copolymerization reactivity ratios, 10. Estimation of errors and planning of experiments in penultimate systems
Authors: Kelen Tibor , Tüdős Ferenc , Braun Dietrich , Czerwinski Wojciech K.
Published: April 2003

For a recently proposed new linearization method of the two‐parameter penultimate model (monomer M2 does not homopolymerize, i.e. r2 = 0), an estimation of confidence intervals for both parameters r1 and r1′ is presented. A procedure of minimizing the experimental error in both parameters was developed according to statistical planning of experiments. In analogy to the already existing procedure of planning (classical model) an “efficiency factor” of planning, Q, was introduced, which makes it possible to estimate the quality of planning for a given series of copolymerization experiments.
New polymer syntheses, 45. Soluble and meltable poly(benzobisthiazole)s derived from substituted terephthalic acids
Authors: Kricheldorf Hans R. , Engelhardt Jürgen
Published: April 2003

A not perfectly pure 1,4‐bis(trimethylsilylamino)‐2,5‐bis(trimethylsilylthio)benzene was prepared as starting material for all condensations. Condensations with 4‐chlorobenzoyl chloride under a variety of reaction conditions revealed formation of benzobisthiazoles at temperatures ≥250°C. Condensation with various aryloxy or bisalkoxyterephthaloyl chlorides in an one‐pot procedure yielded substituted poly(benzobisthiazole)s. All poly(benzobisthiazole)s were soluble in mixtures of dichloromethane or chloroform and trifluoroacetic acid (TFA). Inherent viscosities up to 2,0 dl/g were found in this solvent system. Neither homo‐ nor copoly(benzobisthiazole)s formed a freely flowing melt up to 450°C, where thermal degradation beings to affect the properties. Thermogravimetric analyses in air proved that aryloxy‐substituted polymers possess a significantly greater thermostability than alkoxy‐substituted ones.
Photosensitive multilayer films of tetraolefinic compounds: preparation and polymerization‐depolymerization behaviour
Authors: Nakanishi Fusae
Published: April 2003

A novel photosensitive multilayer film was prepared using a solid‐state photoreactive compound having four double bonds, dihexyl 5,5′‐(1,4‐phenylene)bis(2‐cyano‐2,4‐pentadienoate) (PCPAC6). PCPAC6, which forms a stable mixed monolayer on the water surface when mixed with arachidic acid, was transferred onto a substrate, thereby forming an Y‐type multilayer film. The multilayer film has an absorption maximum at 356 nm, showing a blue shift with respect to that of crystals. This indicates that the molecular arrangement of PCPAC6 in the multilayer film is different from that in the crystals. The multilayer film is very sensitive to visible light and was converted into the oligomer or polymer film on irradiation. The polymer film shows a photoreversible transition between polymers and oligomers, depending on the wavelength of the irradiating light. This phenomenon is caused by the cleavage and formation of cyclobutane rings.
Cyclopropanation of poly[(methylphenylsilanediyl)‐(Z)‐butenylene]. Synthesis and characterization of poly[(methylphenylsilanediyl)methylenecyclopropylenemethylene]
Authors: Liao Xiugao , Lee Howard Shih‐Jen , Weber Williams P.
Published: April 2003

Poly[(methylphenylsilanediyl)methylenecyclopropylenemethylene] (3a) was prepared by cyclopropanation of the CC double bonds of poly[(methylphenylsilanediyl)‐(Z)‐butenylene] (2a) by a Simmons‐Smith reaction. Alternatively, 3a was prepared by a Birch reduction of the dichlorocarbene adduct poly[(methylphenylsilanediyl)methylene(2,2‐dichloro‐1,3‐cyclopropanediyl)‐methylene] (4a). Both 3a and 4a show the characteristic absorptions in the 1H, 13C, and 29Si NMR, IR and UV spectra. Their molecular weight distributions, determined by GPC, are rather broad and their thermal stabilities (by TG) are relatively high.
Thermally irreversible photoresponsive polymers: Synthesis and preliminary characterization of copolymers containing side‐chain trans‐cinnamamide chromophores
Authors: Shen Sunny , Torkelson John M. , Elbert Jeffrey E. , Lewis Frederick D.
Published: April 2003

A novel photoresponsive polymer containing organic chromophores which possess thermal stability as well as substantial and reversible responsiveness upon external photostimulus has been developed. trans‐2{4‐[2‐(Dimethylcarbamoyl)vinyl]phenoxy}ethyl methacrylate (1) was synthesized and copolymerized by free‐radical methods with methyl methacrylate giving a copolymer poly[(methyl methacrylate)‐co‐1] (poly(MMA‐co‐1)) (2) with cinnamamide moiety chromophores randomly attached as side groups. Photoisomerization and ultraviolet absorbance were used to examine the photostationary states and solubility changes upon photoirradiation. Poly[(methyl methacrylate)‐co‐1] (90,7 : 9,3 mol%) with 9,3 mol‐% cinnamamide content has better solubility in a polar solvent such as acetonitrile (theta temperature ΘPMMA = 30°C) than in a nonpolar solvent such as carbon tetrachloride (ΘPMMA = 27°C). Photoisomerization of the trans‐cinnamamide to cis‐cinnamamide units significantly shifts the cloud point of poly[(methyl methacrylate)‐co‐1] (90,7 :9,3 mol‐%) in carbon tetrachloride; this cloud point shift is reversible by photoisomerization back to the trans state. However, in a hydrogen‐bonding solvent such as tert‐butyl alcohol, while photoirradiation of poly[(methyl methacrylate)‐co‐1] (90,7 :9,3 mol%) yields a significant shift in cloud point, this is not reversible by photoirradiation as hydrogen‐bond formation between the tertiary amide and the hydroxylic solvent reduces the isomerization efficiency. Fatigue of the photoreversibility of the copolymer, which is not present in dilute solutions of the cinnamamide chromophore, is noted.
Graft copolymers, 1. Anionic grafting reactions
Authors: Jenkins Aubrey D. , Tsartolia Eugenia , Walton David R. M. , Horská‐Jenkins Jitka , Kratochvíl Pavel , Stejskal Jaroslav
Published: April 2003

Two different units have been incorporated into polymer backbones to provide sites for potential anionic grafting reactions. In the first case, the sites were provided by p‐vinylacetophenone residues, and the technique attempted involved the addition of polystyryl anions. In the second case, the functional sites were p‐isopropenylstyrene residues, and these were used as initiating centres, from which grafts of poly(methyl methacrylate) were grown by means of anionic polymerisation initiated by butyllithium. Only the second method was met with success.
Influence of coagulation process on solid‐phase structure of poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,4‐phenylene): non‐solvent induced crystallization
Authors: Calandrelli Luigi , Immirzi Barbara , Malinconico Mario , Martuscelli Ezio , Riva Fernando
Published: April 2003

A preliminary investigation on the influence of the coagulation process on the solid‐phase structure of poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,4‐phenylene) (1) is reported. Interesting correlations between the method of coagulation of the polymer from sulfuric acid solution and the structure which develops, as observed by thermal analysis, X‐ray diffraction, infrared spectroscopy, and optical microscopy are found. A new method for the preparation of highly crystalline spherulites of 1 is described. This method allows to grow a relatively large number of “single spherulites”, because coagulation and crystallization induced by a non‐solvent may be stopped before impingements occur.
Emulsion polymerization of butadiene, 2. Polymerizations with sodium dodecyl sulfate
Authors: Weerts Pierre A. , van der Loos J. L. M. , German Anton L.
Published: April 2003

The emulsion polymerization of butadiene was investigated with sodium dodecyl sulfate as emulsifier, and the results were compared with those obtained with the industrial‐grade emulsifier Dresinate 214. Limited coagulation was observed in both cases, caused by the high ionic strength of the aqueous phase. Sodium dodecyl sulfate was found to be a better stabilizer than Dresinate 214. The average rate per particle in interval II (corresponding to the linear portion of the conversion vs. time curve) depends strongly on particle size, but not on recipe parameters used to vary the final particle diameter, such as the type and amount of emulsifier and ionic strength. The dependence of particle number per volume of water N on initiator ([I]) and emulsifier concentration ([E]) is usually expressed as the exponent in the empirical relationship N ∼ [I]x · [E]y. Promoting coagulation by increasing the ionic strength decreases x towards zero, while y increases sharply. Increasing [I] at constant [E] and constant ionic strength induces limited coagulation, presumably because the rate of emulsifier adsorption becomes insufficient.
Doping effects on electrical conductivity and infrared spectra of thianthrenic polymers
Authors: Bertinelli Franco , Bizzarri Paolo Costa , Casa Carlo Della , Fiorini Maurizio
Published: April 2003

The electrical conductivity, σ, of different samples of SbCl5‐doped thianthrenic polymers is found to vary from 10−6 to 10−3 S · cm−1. The relationship between conductivity and dopant concentration is examined for one representative sample and a transition from an insulator to a semiconductive regime is observed near a dopant/repeating unit mole ratio of 0.06, above which σ tends to saturate. A detailed infrared analysis of the doped polymers, essentially based on a comparison with the pristine (undoped) polymers and the thianthrene‐SbCl5 (1:1) complex as a model compound, is reported. A first tentative assignment of the IR spectrum of this complex is made. Additional absorptions are observed near 1120 and 1080 cm−1 and are common features of all the doped thianthrenic polymers. The new peaks, which increase with dopant concentration, seem to be intrinsic vibrations of the polymer chains in the doped material and are referred to stretching modes of CSC groups enhanced by complexation. Another characteristic absorption around 340–325 cm−1, due to SbCl stretching modes of the dopant species, is discussed.
Kinetics of 1,3‐cyclohexadiene polymerization initiated by organolithium compounds in a non‐polar medium, 2. Secondary reactions in the propagation step
Authors: François Bernard , Zhong Xing Fu
Published: April 2003

It is confirmed that during the polymerization of 1,3‐cyclohexadiene initiated by polystyryllithium in cyclohexane a tranfer to the monomer takes place, as previously reported. It is shown that a part of the metallated monomer reinitiates the polymerization and another part decomposes to inert lithium hydride. The formation of 1,4‐cyclohexadiene is observed and interpreted. The transfer constant is deduced from measured molecular weights. The propagation constants were reported in a previous paper of this series. Knowing these values, the ratio between reinitiation and decomposition constants is deduced from a comparison between experimental kinetics and a numerical resolution of kinetic equations. This study allows a prediction of the best conditions for the synthesis of block copolymers including poly(1,3‐cyclohexadiene) sequences in 1–4 addition.
Complexation of poly(monobenzyl itaconate) and poly(N‐vinyl‐2‐pyrrolidone) in dilute solution, 2. Influence of variables involved in sample preparation
Authors: Pérez‐Dorado Angel , Piérola Inés F. , Baselga Juan , Gargallo Ligia , Radic Deodato
Published: April 2003

Upon mixing dilute solutions of poly(monobenzyl itaconate)(c) (PMBI) and poly(N‐vinyl‐2‐pyrrolidone) (PVP) in methanol, a soluble interpolymer complex is formed whose properties depend on the method employed to prepare the sample. It was found that the local concentration of the polyacid is the controlling factor. Depending on that concentration, a metastable polymer complex is formed which turns to equilibrium upon sonication. Cooling or heating and aging time have a minor effect. The turbidity of the polymer complex depends on the polyacid concentration to the power ν (at constant polybase/polyacid ratio). For the metastable complex, ν ≈ 2, typical of week polymer complexes. Changes in turbidity are accompanied by a decrease in ν. In the equilibrium state, ν ≈ 1,5, a value being more typical of strong complexes.
The synthesis of symmetrical α,ω‐difunctional polymers
Authors: Al‐Takrity Emad Taha Bakir , Jenkins Aubrey D. , Walton David R. M.
Published: April 2003

Anionic polymerisation of methyl methacrylate initiated by allyllithium and terminated by allyl iodide affords polymer molecules with allyl units at both ends. The method is shown to be efficient for the introduction of such other terminal moieties as hydroxyl and certain fluorescent (or fluorescence‐quenching) groups, such as 1‐pyrenyl.
Preparation of polystyrene particles with poly[(acylimino)ethylene] chains on the surface
Authors: Kobayashi Shiro , Uyama Hiroshi , Yamamoto Ikuo
Published: April 2003

Polymer particles with poly[(acylimino)ethylene] chains on the surface were prepared by soap‐free emulsion copolymerization of styrene with a styryl‐type poly[(acylimino)ethylene] macromonomer. The macromonomer used was highly hydrophilic and soluble in water. The contour of the particles was examined by scanning electron microscopy. The copolymer particles were spherical and monodisperse. The average diameter of the particles was in the sub‐micron range and smaller than that of pure polystyrene particles prepared in a similar way. The surface composition of the particles was analyzed by ESCA (electron spectroscopy for chemical application). It was found that poly[(acylimino)ethylene] chains are enriched on the particle surface.
Studies of structure and properties of photocrosslinked polyurethane acrylates
Authors: Dai Jie , Gao Xuemin , Jiang Guoji
Published: April 2003

A series of ultraviolet‐induced photocrosslinkable polyurethane acrylates was synthesized. They are composed of a polyether [poly(propylene oxide) or poly(tetramethylene oxide)] soft segment and two terminal hard segments derived from 2‐hydroxyethyl methacrylate and a diisocyanate. Based on stress‐strain and DSC measurements of their UV‐cured materials, relations between their structure and physical properties were investigated systematically. The results show that parameters which increase the content of hard segments and the crosslinking density of UV‐cured materials lead to an increase in Young's modulus and stress at break accompanied by a decrease in elongation at break. The glass transition temperature of the polyether soft segment is determined mainly by the type and molecular weight of the polyether, due to a two‐phase morphology.
Dispersion of trans‐polyoctenylene in isotactic poly(propylene), 2. Crystallization behaviour
Authors: Wenig Werner , Fiedel Heinz‐Werner
Published: April 2003

The crystallization kinetics of thin films of isotactic poly(propylene) (iPP) and transpolyoctenylene rubber (TOR) was investigated by optical microscopy. Nucleation densities, Avrami exponents and spherulitic growth rates show specific dependencies on the concentration of TOR in the blend. From the results it is concluded, that at a mass fraction of TOR wTOR = 0,10 the TOR is more finely dispersed in the blend than for other compositions. Due to the subsequent formation of interfaces, the nucleation is found to be predominantly heterogeneous at wTOR = 0,10, while it is preferentially homogeneous at all other compositions.
Novel synthesis of poly(benzoin) and poly(benzil). Characterization and application as photosensitizer materials
Authors: Abd‐Alla Mohamed A.
Published: April 2003

New photoactive polymers containing benzoin or benzil groups have been prepared by condensation of terephthalaldehyde. The influence of the alkali metal ions and solvents used upon the progress of polycondensation and yield of poly(benzoin)

Systematic name: Poly(1,4‐phenylene‐1‐hydroxy‐2‐oxoethylene).

were studied. Oxidation of this polymer by nitric acid or ammonium nitrate in acetic acid afforded the corresponding poly(benzil)

Systematic name: Poly(1,4‐phenylene‐1,2‐dioxoethylene).

in quantitative yield. The resulting polymers were confirmed by elemental analysis, IR, 1H NMR and UV/visible spectral data, and characterized using viscometry, DTA measurements, thermogravimetric and X‐ray analysis. The photosensitizing property of the prepared polymers was detected by fluorescence. It was found that irradiation of poly(benzoin) in DMSO solution at 285 nm causes yellow fluorescence whereas poly(benzil) does not display fluorescence at the same excitation wavelength. Moreover, the use of poly(benzil) as photosensitizer material in the photochemical cleavage of thiourea and its derivatives was also studied.
Computerized theoretical study of local structural properties of polyene and polymethylene chains in solutions. The continuum model
Authors: Rabinovich Alexander L.
Published: April 2003

In different solutions, the chains of cis‐1,4‐ and trans‐1,4‐polybutadiene, poly(cis‐ and trans‐propenylene), and poly(methylene) of 60 CC bonds were studied by Monte Carlo calculations. The developed computer simulation model takes into account the continuous spectrum of conformations of the chain molecule, the interdependence (in pairs) of internal rotations, hindrances to rotation and the excluded volume. The coordinate system is fixed to the molecule with the origin in the centre of mass and the axes along the principal axes of the inertia tensor. The tensors of the order parameter of each CC bond were calculated. The totality of the bond order parameters and the sequences of the bond directors were studied in this system. In “good” solvents the order parameters of bonds of the same type increase with a change of the position from the terminals towards the centre of the chain differently for single, cis‐ and trans‐double bonds.
Solution properties of poly(octadecyl methacrylate) in butyl acetate, 2. Semidilute solution
Authors: Ricker Mathias , Schmidt Manfred
Published: April 2003

Semidilute solutions of a fraction of poly(octadecyl methacrylate) (PODMA) obtained by radical‐initiated polymerization were investigated in the theta‐solvent butyl acetate (BuAc) with static and dynamic light scattering (SLS, DLS, resp.) at four different temperatures between 13°C (near theta‐temperature Θ) and 70°C. The molar mass of the investigated sample (PODMA 4) was 3,2 · 106 g · mol−1. A concentration region from dilute to 8 c* was covered, where c* = 1/[η] was taken as the coil overlap concentration, [η] denoting intrinsic viscosity. Above c = 3c* the DLS correlation function exhibited bimodal behaviour at all temperatures. At these concentrations one finds two “apparent” molar masses, radii of gyration and diffusion coefficients for each concentration. The smaller apparent molar masses, smaller radii of gyration and larger diffusion coefficients correspond to characteristics of the transient network. The larger apparent molar masses, larger radii of gyration and smaller diffusion coefficients may be attributed to the formation of inhomogeneities in the semidilute solution.
Carbonyl‐olefin exchange reaction. A new route to conjugated polymers, 5. Effect of different catalytic systems
Authors: Jossifov Christo , Schopov Ivan
Published: April 2003

The influence of experimental conditions and the nature of the catalytic system on the yield of products insoluble in methanol from the carbonyl‐olefin exchange reaction (COER) was investigated. It was established that the COER of some α, β‐unsaturated carbonyl compounds can be catalyzed by transition metal halides (WCl6, MoCl5), by oxo compounds (WOCl4), and by binary systems (WCl6 + AlCl3, MoCl5 + AlCl3). Under the influence of these catalysts, some α,β‐unsaturated ketones can be transformed into conjugated polymers via different pathways. That is why the yield of the polymer product can be higher than calculated on the basis of the simple COER.
Chain‐sphere models for complexes of biological interest. Monte Carlo simulation and hydrodynamic properties
Authors: Bernal J. M. García , García M. M. Tirado , de La Torre José García
Published: April 2003

Many complexes of biological interest, like nucleosomes or v bodies and DNA‐protein complexes, can be modelled like a structure composed by a sphere joined to a rigid rod or to a flexible chain of identical beads. In this work we present a theoretical study using these models for the evaluation of some reduced conformational and hydrodynamic properties: end‐to‐end distance, radius of gyration and translational friction coefficient. Two kinds of models were employed: a sphere joined to one of the two ends of a rod or chain and a sphere joined to the halfpoint of a rod or chain, i. e. the models show one or two arms, respectively. Several cases were studied, varying the number of chain beads N = 10, 20, 30, … 60 (with radius σ ⩽ 1/2 and bond length b = 1) and the radius of the sphere R = 1, 2, 4, 8 (in units of b). For the flexible models the position of the chain beads have been obtained randomly from Monte Carlo simulations. For these models we have made also a statistical treatment in order to obtain averaged values of the conformational and hydrodynamic properties. Finally, we conducted a comparison of our theoretical results with the experimental data for nucleosomes. The overall agreement is good and gives confidence in the applicability of our results to similar macromolecular complexes.
The environmentally controlled photoisomerization of probe molecules containing azobenzene moieties in solid poly(methyl methacrylate)
Authors: Shen Yu‐Quan , Rau Hermann
Published: April 2003

Upon n → π* (436 nm) excitation of azobenzene probes 1, 2 and 3 in a solid film of poly(methyl methacrylate) we observe cis‐trans isomerization and a monoexponential approach towards the photostationary state; upon π → π* (313 nm) irradiation this approach is bi‐exponential. The latter is not due to the loss of concentration homogeneity during the reaction. By transferring the concept of dual isomerization mechanisms (rotation and inversion) from former work we reinterpret the “fast” component of isomerization at 313 nm excitation as being due to rigidly held molecules unable to isomerize via the rotation mechanism, but undergoing internal conversion and subsequent inversion, and the “slow” component as being due to molecules isomerizing by rotation. On 436 nm irradiation only one isomerization mechanism is active, viz. inversion.
Reactivity ratios for grafting of vinyl acetate and methyl acrylate mixtures onto cellulose at high conversions
Authors: Casinos Ismael
Published: April 2003

The heterogeneous graft copolymerization of a mixture of vinyl acetate (VAc) and methyl acrylate (MA) onto cellulose was carried out in an aqueous medium through a radical mechanism. Copolymerization led, as usual, to the simultaneous formation of grafted and non‐grafted poly(vinyl acetate‐co‐methyl acrylate). The reactivity ratios of VAc and MA were determined from high‐conversion data by using an integrated form of the copolymerization equation. Values of the reactivity ratios for VAc (r1 = 0,020) and MA (r2 = 6,750) were calculated. The capacity of the methods for determining reactivity ratios based on the differential copolymerization equation is discussed for the present copolymerization system. Some significant characteristics of the copolymer and the copolymerization reaction are deduced from the copolymerization parameters. It is concluded that the polymerization sites of the grafting and homopolymerization reactions are identical. Also, the present aqueous dispersion technique yields similar results as bulk polymerizations.
A new selective agent for poly(tetrahydrofuran) degradation as a tool for the determination of the crystallite core size
Authors: Ishikawa Satoshi , Ishizu Koji , Fukutomi Takashi
Published: April 2003

The method formerly used to determine the crystallite core size of polyethylene was applied to poly(tetrahydrofuran) (PTHF). This method is based on the different diffusivity of a chaincleaving agent in crystalline and amorphous parts of the polymer. Butyllithium was used as a cleaving agent of PTHF. The degree of polymerization of the undecomposed part of the polymer (PTHF crystallites) was determined by gel permeation chromatography. This value agrees well with the value to be expected from the size of the crystallites determined small‐angle X‐ray scattering.
Thermotropic polyesters, 7.. Liquid‐crystalline polymers with meta‐phenylene units in the mesogenic moiety
Authors: Tenkovtsev Andrey V. , Piraner Olga N. , Bilibin Alexander Yu.
Published: April 2003

Polyesters containing 3,3′‐substituted azobenzene and benzanilide moieties as a part of conformationally mobile aromatic blocks were synthesized. Polymers based on 3,3′‐substituted azobenzene residues exhibit liquid‐crystalline properties and unusual thermal properties such as opposite odd‐even effect and unexpected cis‐trans isomeric ratio of azo group. Similar polymers with an amide group between the 1,3‐substituted benzene rings cannot form liquid crystals.
Polymères photoréticulables à unités cinnamiques, 2. Synthèse par modification chimique et par polycondensation
Authors: Brosse Jean‐Claude , Remmas Miloud , Soutif Jean‐Claude
Published: April 2003

Polymers containing cinnamic acid units were obtained by chemical modification of poly(vinyl alcohol) by cinnamic acid derivatives with a carbon‐carbon double bond in para position. The reactivity of the acid chloride is lowered by the inductive effect of the double bond. Polycondensation of these derivatives, when difunctional, leads to low‐molecular‐weight polyamides and polyesters with good yields. The introduction of acrylic or methacrylic groups on photosensitizers has also been studied, leading to monomers which can be polymerized by a radical process, or copolymerized with the previous monomers, the polymer bearing then the photosensitizer and the cinnamic double bond on the same chain.
The influence of the H‐bonded association of COOH groups on the copolymerization of unsaturated carboxylic acids
Authors: Hrabák František , Bezděk Milan
Published: April 2003

The monomer reactivity ratios of styrene with unsaturated acids—4‐(acryloyloxy)phenylacetic acid, α‐(methacryloyloxy)phenylacetic acid and 4‐(methacryloyloxy)phenylacetic acid—and their alkyl esters were determined in acetone and acetic acid solutions. Due to the isolation of the COOH and COOR groups from the benzene ring owing of the CH2 group the electron densities on the polymerizable CC double bonds of these acids, their H‐dimers, the H‐associates with the solvent and their alkyl esters are identical. In spite of this, however, in the copolymerization of styrene with unsaturated acids the rate of addition to the polymeric radical was fastest for the H‐dimers of the acids, less fast for a mixture of H‐dimers and H‐associates “unsaturated acid‐acetic acid”, and slowest for the acid esters. The preferential enrichment of the copolymer with the acid is explained through a bimolecular addition of the first CC of the H‐dimer to the polymeric radical and a faster “monomolecular” addition of the CC of the second dimer acid unit associated with the polymeric radical. If however, there is some steric hindrance to an immediate radical propagation between the CC of two acid units joined by H‐bonds between the carboxyl groups, several elementary acts of bimolecular addition of the other comonomer molecules may take place between the addition of the first and the second dimer acid unit.