bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of conversion in free radical copolymerization from dilatometric data
Authors: Braun Dietrich , Cei Gustavo
Published: April 2003

In order to evaluate copolymerization rates from dilatometric measurements, the relationship between volume contraction and conversion (dilatometric constant) must be investigated. This can be done gravimetrically or by means of density measurements. In cases where one of the monomers is not able to homopolymerize, both methods lead to different values. Equations necessary for this evaluation were derived and verified in the systems diethyl maleate‐methyl methacrylate and diethyl maleate‐styrene. In some cases, the dependence of the dilatometric constant on feed composition may be predicted taking into account the contributions to volume contraction of the different bond types present in the copolymer. An expression was derived for describing this dependence in cases where one of the monomers does not homopolymerize. Its validity for the system diethyl maleate‐styrene was experimentally verified.
Polymeric phospholipid analogues, 20. Synthesis and polymerization of 20‐(methacryloyloxy)icosyl 2‐(trimethylammonio)ethyl phosphate and 32‐(methacryloyloxy)dotriacontyl 2‐(trimethylammonio)ethyl phosphate
Authors: Furukawa Akio , Shoji Hajime , Nakaya Tadao , Imoto Minoru
Published: April 2003

20‐(Methacryloyloxy)icosyl 2‐(trimethylammonio)ethyl phosphate (4a) and 32‐(methacryloyloxy)dotriacontyl 2‐(trimethylammonio)ethyl phosphate (4b) were prepared and characterized. These monomers were polymerized and the properties of the resultant polymers are described.
Cyclopolymerization, 13. Cyclocopolymerizations of maleic anhydride with 1,5‐hexadiene and 2,5‐dimethyl‐1,5‐hexadiene
Authors: Kodaira Toshiyuki , Nishioka Kohji
Published: April 2003

Cyclocopolymerizations of maleic anhydride (1) with 1,5‐hexadiene (2a) and 2,5‐dimethyl‐1,5‐hexadiene (2b) were compared with those of 1 with 1,4‐dienes which have been reported to yield highly cyclized polymers following a bimolecular alternating inter‐intramolecular mechanism. The mole ratio of monomeric units of 1 to those of the dienes in the copolymers was almost 2:1, though it changed slightly with the monomer composition in the feeds. Although the fundamental aspect of the copolymerization of 1 with 1,5‐dienes was found to be similar to that with 1,4‐dienes, the structures of the copolymers are different from those obtained with 1,4‐dienes in that not only pendant double bonds, but also other unsaturations were detected. The unsaturations were formed by combination of propagating radicals with the allyl radical, which is considered to be formed by hydrogen abstraction from the penultimate hexenyl group. A mechanism is proposed to explain the degree of cyclization and the copolymer composition.
X‐ray studies on phospholipid bilayers, 7. Structure determination of oriented films of L‐α‐dimyristoylphosphatidylethanolamine (DMPE)
Authors: Suwalsky Mario , Duk Leonora
Published: April 2003

The bilayer structure of the phospholipid L‐α‐dimyristoylphosphatidylethanolamine (DMPE) was determined by X‐ray diffraction fiber methods. This study was carried out on oriented films at different degrees of hydration at room temperature (about 19°C). DMPE molecules pack very closely with their two hydrocarbon chains almost fully extended and coplanar with their polar group, which lies perpendicular to the chains. It was found that the unit cell dimensions of DMPE did not vary appreciably between 0 and 86% relative humidity nor did its longest axis with an excess of water. The methods and techniques used to prepare the specimens and to solve the structure are described.
Effect of poly(ethylene glycol) on the photochemical immobilization of an enzyme in photocrosslinkable poly(vinyl alcohol)
Authors: Ichimura Kunihiro
Published: April 2003

A novel method was applied to improve the activity of enzymes immobilized in photocrosslinked poly(vinyl alcohol). Whereas the addition of glycerol to photosensitive poly(vinyl alcohol), bearing a styrylpyridinium group, diminishes the rate of photocrosslinking as well as the mechanical strength of the insolubilized gel, no considerable decrease in the rate of photoreaction was observed when poly(vinyl alcohol) was mixed with poly(ethylene glycol). This difference is based on the phase separation of the two water‐soluble polymers, resulting in the formation of a porous structure of the photocrosslinked gel. Immobilization of invertase in the photocrosslinked gel in the presence of poly(ethylene glycol) changes the activity, because of the case of diffusion of the substrate into the porous matrix.
Liquid crystalline polymers containing heterocycloalkanediyl groups as mesogens, 1. Liquid crystalline polymethacrylates and polyacrylates containing 1,3‐dioxane‐2,5‐diyl groups as mesogens in the side chain
Authors: Hsu Chain Shu , Rodriguez‐Parada José M. , Percec Virgil
Published: April 2003

Polymethacrylates and polyacrylates containing 4‐[5‐(4‐methoxyphenyl)‐1,3‐dioxan‐2‐yl]‐phenol moieties as mesogenic units and an aliphatic spacer containing eleven methylene units were synthesized. Their phase behavior was studied by differential scanning calorimetry and optical polarizing microscopy, and compared with the phase behavior of the corresponding polymethacrylates and polyacrylates containing 4′‐methoxy‐4‐biphenylol as mesogens. All polymers present smectic mesomorphism. The substituted 2,5‐diphenyl‐1,3‐dioxane mesogen resembles a terphenyl mesogen in which the internal phenyl ring is hydrogenated. Even so, when compared with polymers containing biphenyl moieties, the glass transition temperatures of the polymers containing 1,3‐dioxane moieties are lower, although their isotropization occurs at higher temperatures.
Preparation of polyamides having 1,2,4‐triazine rings in the main chain
Authors: Akutsu Fumihiko , Suzuki Atushi , Saitoh Futoshi , Naruchi Kiyoshi , Miura Masatoshi , Nagakubo Kuniharu
Published: April 2003

Polyamides having 1,2,4‐triazine rings in the main chain (6 and 7) were prepared from 3‐substituted 4,4′‐(1,2,4‐triazine‐5,6‐diyl)dibenzoic acids (5) and aromatic diamines. The thermal stability and the solubility of polyamides 6 and 7 were compared with those of structurally identical polyamides (polymers 3 and 4) obtained by polymer homologous reaction of polyamides having α‐diketone moieties with amidrazones. The effects of introduction of 1,2,4‐triazine‐5,6‐diyl unit in the main chain on the thermal stability and solubility of the polymers are discussed.
Solution properties of drug carriers based on poly[N‐(2‐hydroxypropyl)methacrylamide] containing biodegradable bonds
Authors: Ulbrich Karel , Koňák Čestmír , Tuzar Zdeněk , Kopeček Jindřich
Published: April 2003

The solution properties of water‐soluble drug carriers based on copolymers of N‐(2‐hydroxypropyl)methacrylamide containing p‐nitroaniline (drug model) attached to the copolymer by enzymatically degradable oligopeptide chains, were studied using light scattering, GPC and sedimentation methods. It was found that these polymers associate in water forming micelles with p‐nitroaniline being inside and hydrophilic polymer chains outside. The association number and compactness of micelles both depend on the content of hydrophobic side chains, polymer concentration and temperature. Micellar shells hinder the penetration of enzymes into the micellar core, thus reducing the rate of enzyme‐catalyzed release of p‐nitroaniline.
New polymer syntheses, 17. Cis/trans isomerism of 1,4‐cyclohexanedicarboxylic acid in crystalline, liquid‐crystalline and amorphous polyesters
Authors: Kricheldorf Hans. R. , Schwarz Gert
Published: April 2003

Dimethyl 1,4‐cyclohexanedicarboxylate was treated with various potential isomerization catalysts under reflux (ca. 280°C). Lithium cloride and sulfonic acids caused rapid isomerization. Also the diphenyl ester and 1,4‐cyclohexandicarbonyl dichloride were isomerized, and in all cases a thermodynamically controlled equilibrium with 66 ± 2% trans‐isomer was obtained. The same cis/trans ratio was found for the molten polyesters prepared from 1,4‐butanediole, 1,6‐hexanediole or phenylhydroquinone and 1,4‐cyclohexanedicarboxylic acid. The polyester, prepared at 20°C from phenylhydroquinone and trans‐1,4‐cyclohexanedicarbonyl dichlorid, exhibits a mesogenic phase above 250°C; yet, this LC‐phase is thermodynamically unstable and isomerizes to an isotropic melt containing 66 ± 2% trans‐isomer. However, when the free diacid or the crystalline polyester from hydroquinone and 1,4‐cyclohexanedicarboxylic acid are heated or synthesized at ca. 300°C, a content of 100% trans‐isomer is the thermodynamical optimum. This is also true for the LC‐phase of polyesters prepared from methyl‐ or chlorophydroquinone. The trans content of LC‐copolyesters, containing variable mole ratios of monomeric units of hydroquinone and phenylhydroquinone, varies with these mole ratios between 66 and 100%. Obviously, the coexistence of LC‐domains containing 100% trans‐isomer and isotropic domains containing 66% trans‐isomer are responsible for this result.
Structural study of compounds modelling elementary polymer units, 3. Molecular and crystal structure of 1,3,5‐tris[4′‐(C‐o‐carboranyl)biphenyl‐4‐yl]benzene
Authors: Lindeman Sergey V. , Struchkov Yurii T. , Shklover Valerii E. , Khotina Irina A. , Teplyakov Mikhail M. , Korshak Vasilii V.
Published: April 2003

Following the studies on elucidating the main structural features of elementary units of polyphenylene‐type polymers prepared by condensation of di‐ and monoacetylaromatic compounds, an X‐ray structural analysis of 1,3,5‐tris[4′‐(C‐o‐carboranyl)biphenyl‐4‐yl]benzene (2) (systematic name: 1,3,5‐tris[)1,2‐dicarba‐closo‐dodecarborane(12)‐1‐yl(biphenyl‐4‐yl]benzene), which is the low‐molecular‐weight analog of one of the polymers in the given series, was performed. Compound 2 crystallizes as unstable solvate 1:1:1 with chloroform and benzene. The crystals are monoclinic, a = 17,060 Å, b = 20,220 Å, c = 18,448 Å, β = 102,79°, space group P21/n, Z = 4. Molecule 2 exhibits asymmetric conformation with substantial distortions of the linear geometry of polyphenylene units. The crystal is built of layers of molecules 2, the solvate molecules being situated between these molecules in the channels and cavities with a population of 2/3. The benzene molecules participate in stacking‐interaction with one of the carboranyl‐substituted (i.e., the strongest electron‐acceptor) benzene rings of the host molecule 2; chloroform molecules pack the channels without a specific interaction with the host molecules.
Thermotropic poly[oxy(2,6‐dimethyl‐1,4‐phenylene)]‐block‐poly(oxyterephthaloyloxy‐1,4‐phenylenealkylene‐1,4‐phenylene)
Authors: Fradet Alain , Heitz Walter
Published: April 2003

Block copolymers containing a rigid [oxy(2,6‐dimethyl‐1,4‐phenylene)] block and thermotropic poly[oxyterephthaloyloxy‐1,4‐phenylene‐hexamethylene (or/and decamethylene)‐1,4‐phenylene] blocks were synthesized. Their structures were examined by means of 1H and 13C NMR and X‐ray diffraction, and their liquid crystalline properties investigated by polarizing microscopy.
Relative affinities of mono and difunctional sulfoxides for lithium picrate in toluene. Effects of structure and stereochemistry
Authors: Buese Mark A. , Hogen‐Esch Thieo E. , Xu Wen‐Ying , Smid Johannes
Published: April 2003

The relative affinity of various mono and difunctional sulfoxides for lithium picrate in toluene was investigated by a competition method utilizing immobilized linear polyethers (glymes). In general, the difunctional sulfoxides were found to bind more strongly than the monofunctional sulfoxides. However, difunctional ligands which would result in eight‐membered ring chelated structures bound lithium ion more strongly than those which would result in six‐membered ring chelated structures.
Cellulose and chitosan hydrogen phthalates
Authors: Levesque Guy , Chiron Gérard , Roux Odette
Published: April 2003

Cellulose and chitosan hydrogen phthalates of various degrees of substitution were readily prepared from polysaccharides when reacted with phthalic, nitrophthalic and trimellitic anhydrides in presence of 4‐dimethylaminopyridine in dimethyl sulfoxide/triethylamine as reaction medium. Cellulose requires at least one equivalent of phthalic anhydride to dissolve entirely.
Adsorption of propylene and allene on TiCl3·1/3 AlCl3 and polymerization of allene with the system TiCl3·1/3 AlCl3/AlEt2Cl
Authors: Kratochvíla Jan , Mejzlík Jiří
Published: April 2003

Adsorption of propylene and allene from the gas phase on TiCl3·1/3 AlCl3 and TiCl3·1/3 AlCl3/AlEt2Cl catalyst was measured volumetrically. In the ranges of 296–334 K and 1–100 kPa, the adsorbed amounts of both gases was found to be approximately proportional to the gas pressure. The adsorbed amount of allene is about twice as high as that of propylene under the same conditions. Low heats of adsorption of both propylene and allene support the assumption of the physical nature of the adsorption. Addition of AlEt2Cl to the TiCl3·1/3 AlCl3 catalyst did not change substantially the sorption properties of the catalyst. Polymerization of allene with the system TiCl3·1/3 AlCl3/AlEt2Cl in heptane was found to be first order in monomer and the rate decreases with increasing yield. A mechanism of retardation by the polymer formed is probably operative. Both heptane‐soluble and heptane‐insoluble polyallenes are produced. The soluble polymer has M̄n ≈ 103 and a very narrow molecular weight distribution (M̄w/M̄n = 1,2 ± 0,2). Polyallene comprises mainly vinylidene units.
Polymerization beyond the gel point, 2. A study of the soluble fraction as a function of the extent of reaction
Authors: Argyropoulos Dimitris S. , Berry Richard M. , Bolker Henry I.
Published: April 2003

Theoretical expressions that relate the amount of soluble material coexisting with the gel as a function of the extent of reaction beyond the gel point are tested experimentally. Three chemically different monomer combinations are examined for their yield of soluble material at various degrees of polymerization. It is concluded that, for the copolymerization of 1,3,5‐benzenetriacetic acid with 1,10‐decanediol, both modern and classical expressions adequately describe the experimental results beyond the gel point. The validity of the available equations is thus substantiated.
Polymere Aminoschutzgruppen. Synthese von neuen poly[2‐(N‐vinylpyridinio)ethoxycarbonyl]‐,2‐(N‐pyridinio)ethoxycarbonyl‐ und 2‐(N‐4‐picolinio)ethoxycarbonyl‐geschützten Aminoderivaten und kinetische Untersuchungen zur basisch induzierten Aminosäurefreisetzung
Authors: Ritter Helmut , Thöne Jochen
Published: April 2003

2‐Bromoethoxycarbonyl modified amino acids were reacted with pyridine, 4‐picoline and poly(4‐vinylpyridine) to yield the corresponding 2‐(N‐pyridinio)ethoxycarbonyl derivatives as water‐soluble amino‐protecting groups. The kinetics and activation energies of basicly induced cleavage of the amino acids were investigated by 1H NMR spectroscopy in a D2O/NaOD medium. The polymeric salts were found to be more reactive than the low molecular weight pyridinium bromides because of electrostatic polymeric effects. Additionally, the kinetic measurements confirmed a E1cB mechanism for the cleavage of the urethane function. The formation of peptide bonds was performed in the case of poly[2‐(N‐4‐vinylpyridinioethoxycarbonyl)]‐protected amino acids in aqueous medium by water‐soluble carbodiimides.
Photochemical reaction of a polymer containing vinyl ether moieties with thiol compounds
Authors: Nishikubo Tadatomi , Shimokawa Tsutomu , Arita Hiroki
Published: April 2003

The photochemical addition reaction of poly(oxy‐1‐methyleneethylene‐co‐oxy‐1‐chloromethylethylene) (1), a polymer containing vinyl ether groups and synthesized by partial elimination reaction of poly(epichlorohydrin)

Poly(oxy‐1‐chloromethylethylene).

, with methyl 3‐mercaptopropionate was carried out using benzophenone (BP) as a photosensitizer. The addition reaction proceeds with high conversion in benzene, toluene and tetrahydrofuran (THF). However, the degree of addition in both 1,4‐dioxane and N‐methyl‐2‐pyrrolidone (NMP) is relatively low, and the reaction does not proceed in dimethyl sulfoxide (DMSO) under the same reaction conditions. An optically active polymer containing pendant amino acid moieties was also synthesized by the photochemical reaction of polymer 1 with N‐acetyl‐L‐cysteine using BP as a photosensitizer in THF. It was found that the specific angle of rotation of the obtained polymer increases with increasing degree of conversion.
Synthesis and polymerization of poly(ethylene glycol) fumarates
Authors: Berlinova Iliyana V. , Panayotov Ivan M.
Published: April 2003

Fumaric esters of poly(ethylene glycol) (1a–d) were prepared as macromonomers. The halfesters 1a and 1c were obtained by interaction of maleic anhydride with the monoethers of poly(ethylene glycol) (2a and 2b) in the presence of 4‐dimethylaminopyridine, and the diesters 1b and 1d by esterification of methyl hydrogen fumarate (13) with the monoethers of poly(ethylene glycol) (2a and 2b). The macromonomers were found to homopolymerize and to copolymerize with styrene and methyl methacrylate following a radical polymerization mechanism.
Comparison of molecular weight distributions of polymers determined by dynamic light scattering
Authors: Witkowski Konrad , Woliński Leszek
Published: April 2003

Several methods for the treatment of experimental data (including 3 different parameter‐fitting procedures, histograms, and Provencher's constrained regularization) are considered which allow to obtain molecular weight distributions w(M) from quasielastic light scattering measurements. As a result of the introduction of a few improvements to these methods described in the literature, we were able to use more severe criteria for the quality of the distribution functions obtained, based on the mean‐square deviation rather than on the coincidence of a few first moments. The quality of five investigated inversion methods was compared on the basis of simulated and experimental data for flexible chain polymers (polystyrene standards) in dilute solution.
Polymerization of tetrahydrofuran, 2. Equilibrium monomer concentration
Authors: Hirota Masahiro , Fukuda Hiroyuki
Published: April 2003

The equilibrium polymerization of tetrahydrofuran was studied at relatively low initial monomer concentrations with 1‐methyltetrahydrofurylium hexachloroantimonate as initiator. The equilibrium concentrations of monomer, [M]e, and initiator, [I]e, as well as the equilibrium number‐average degree of polymerization, Pn, were determined by means of 1H NMR spectroscopy, and found to follow simplified relations, which were derived from Tobolsky's equations.
Kinetik der startreaktion der radikalischen homo‐ und copolymerisation von styrol, N‐vinyl‐2‐pyrrolidon und methylmethacrylat
Authors: Braun Dietrich , Czerwinski Wojciech K.
Published: April 2003

In one, two and three component polymerizations of the monomer system styrene (St = M1), N‐vinyl‐2‐pyrrolidone (NVP = M2) and methyl methacrylate (MMA = M3) the rate constants of the initiation step 2kdf were measured in bulk at 60°C by means of the inhibition method with the stable Banfield radical as inhibitor and AIBN as initiator. The obtained 2kdf‐values depend non‐linearly on the monomer feed. It results from the evaluation of initiator decomposition constant kd that the chain initiation step is mainly determined by the rate of initiator decomposition. In all polymerizations the efficiency factor f was almost equal to 0,5.
Evidence of crosslinks in a butadiene‐divinylbenzene‐ethylvinylbenzene copolymer by metathesis degradation
Authors: Hubmann Ewald , Loy Walter A. , Pongratz Thomas , Hummel Klaus
Published: April 2003

1,3‐Butadiene was copolymerized with a mixture of divinylbenzene isomers containing ethyl‐vinylbenzene isomers. The crosslinked copolymers were degraded in a cross metathesis reaction with (Z)‐2‐butene or (E)‐3‐hexene using the catalyst WCl6/Sn(CH3)4. The low‐molecular‐weight products were investigated by gas chromatography/mass spectrometry coupling. Products containing the crosslinks were found. Others were attributable to copolymer units resulting from butadiene and ethylvinylbenzene. Characteristic mass spectra of the products are discussed.
Synthesis and properties of star shaped block copolymers of styrene and ethylene oxide
Authors: Xie Hongquan , Xia Jun
Published: April 2003

Star shaped block copolymers with two arms of polystyrene (PS) blocks and two arms of poly(oxyethylene) (PEO) blocks were synthesized by coupling living PS anions first and then living PEO anions, using SiCl4 as the coupling agent, while the star shaped block copolymers with two arms of PS blocks and one arm of PEO block were prepared by using CH3SiCl3 as the coupling agent. The products were purified by extractions, and the purified copolymers were characterized by GPC, IR, 1H NMR and torsional braid analysis. The crystalline, emulsifying and complexing properties and also the phase transfer catalytic effect of the star shaped block copolymers were studied.
Linear polymerization of endo‐dicyclopentadiene initiated by metathesis catalysts
Authors: Pacreau Annie , Fontanille Michel
Published: April 2003

The polymerization of endo‐dicyclopentadiene

Systematic name of endo‐dicyclopentadiene is: tricyclo[5.2.1.02,6]deca‐3,8‐diene.

(endo‐DCP) by the metathesis catalyst ReCl5/(CH3)4 Sn gave a substantial yield of a linear polymer with high molecular weight and high content of cis double bonds. The kinetics of the early stage of the reaction was studied by calorimetry. The polymerization proceeds via an oligomerization reaction followed by the formation of polymers. A mechanistic scheme is proposed to explain the generation of the primary active species and the two‐step polymerization process.
Properties of membranes from polyelectrolyte complexes consisting of methyl glycol chitosan, [2‐(diethylamino)ethyl]dextran, and poly(potassium vinyl sulfate)
Authors: Kikuchi Yasuo , Kubota Naoji , Maruo Kazushi , Goto Yasuo
Published: April 2003

Water‐insoluble polyelectrolyte complexes (PEC) were prepared by mixing methyl glycol chitosan (MGC, 1) and [2‐(diethylamino)ethyl]dextran (EA, 2) with poly(potassium vinyl sulfate) (PVSK, 3) in aqueous solution at various hydrogen ion concentrations. Elemental analyses, IR spectroscopy, and solubilities of PEC reveal that PEC differ in molecular structure and properties according to pH. It seems that the degree of dissociation and the conformation of MGC, EA, and PVSK change with pH. PEC membranes were made by casting from solutions of all kinds of PEC, and transport phenomena through the membrane of PEC prepared in 4 wt.‐% HCl solution were investigated under various conditions. The driving force of the transport depends on the membrance potential, Donnan potential, and diffusion potential, according to measurements of the transport ratio of Na+ and the electric potential difference between the left‐ and right‐hand side of the membrane. Moreover, the permeability of K+ is higher than that of Na+.
Spectroscopic characterization of chromic transition in polydiacetylenes, 3
Authors: Chang Chih , Coyne Laurence D. , Hsu Shaw Ling
Published: April 2003

From optical absorption and infrared data, we have been able to establish the existence of a direct relationship between the weakening of the hydrogen‐bonding properties of the side‐chain and the chromic transition of the main chain for poly{1,2‐bis{4‐[N‐(butoxycarbonylmethyl)‐carbamoyloxy]butyl}‐1‐buten‐3‐ynediyl} (poly4BCMU), a family of soluble polydiacetylenes disubstituted with 4‐[N‐(butoxycarbonylmethyl)carbamoyloxy]butyl side chains. This observation is in contrast to the lack of correlation found for polydiacetylene film. Our data also show that this chromic transition is unaffected by the gelation process found for this family of polydiacetylenes.
Coil expansion and dimensions of poly(dimethylsiloxane) in alkane/2‐butanone mixtures
Authors: Celda Bernardo , Gómez Clara , Gavara Rafael , Tejero Roberto , Campos Agustin
Published: April 2003

The intrinsic viscosities, [η], for the ternary systems alkane (1)/2‐butanone (2)/poly(dimethylsiloxane) (PDMS)(3), with the alkanes decane, dodecane and hexadecane, are determined at 20,0°C. The constants a of the Mark‐Houwink equation and the constant of the unperturbed dimensions, KΘ, of the polymer are evaluated over the whole composition range of the binary solvent mixture. [η] shows a pronounced maximum at intermediate compositions as found in cosolvent mixtures. In these cosolvent mixtures, the numerical values of KΘ are higher than in the single‐component solvents, because the cosolvent mixtures correspond to a mixed solvent with an excess free energy, GE ≥ 0, the increase in KΘ being only moderate though. A new procedure taking into account ternary interactions, to evaluate the intrinsic viscosity in ternary systems from GE values is proposed. The influence of ternary interactions through a constant (1–2aχ) is also investigated. From these new expressions the constant of the apparent polymer unperturbed dimensions, K, and (1–2aχ) are calculated and compared with those directly evaluated from second virial coefficients.
Polymerization of lactams, 79. Preparation of the cyclic dimer of 2‐pyrrolidone
Authors: Brožek Jiří , Roda Jan , Králíček Jaroslav
Published: April 2003

An alternative method for the preparation of the cyclic dimer 3 of 2‐pyrrolidone is presented, which is based on hydrolysis of 1‐(1‐pyrrolin‐2‐yl)‐2‐pyrrolidone (4, x = y = 3), and some physicochemical properties of 4 and its hydrolytical products are discussed.
Dielectric and viscometric behaviour of poly(dibenzyl itaconate) as a function of temperature
Authors: Gargallo Ligia , Yazdani‐Pedram Mehrdad , Radić Deodato , Hernández‐Fuentes Irmina , Horta Arturo
Published: April 2003

The dielectric and viscometric behaviour of poly(dibenzyl itaconate) (1) in 1,4‐dioxane is studied as a function of temperature. The dipole moments at 25°C and at 33°C are determined by measuring the dielectric constant as a function of polymer concentration at fixed temperature. Also, the variation of the dielectric constant for a fixed concentration is determined at several temperatures in the temperature range between 15 and 39°C. The dipole moment is by 10% higher at 33°C than at 25°C, and the variation of the dielectric constant with temperature shows a stepwise increase between 25°C and 30°C. Viscosity measurements demonstrate an anomalous behaviour of 1 in 1, 4‐dioxane at approximately the same range of temperatures. At ca. 25°C the value of the Huggins constant drops to practically zero. By measuring samples with different molecular weights the unperturbed dimensions, interaction parameter, and Mark‐Houwink‐Kuhn‐Sakurada exponent are obtained. All of these parameters exhibit a discontinuity at ca. 25°C. The variations in the dielectric and viscometric behaviour with temperature are attributed to a conformational change of the macromolecules of 1 in 1, 4‐dioxane.
Polymerization of bicyclic acetals, 14. Synthesis of an amphiphilic block copolymer via ring‐opening polymerization of 6,8‐dioxabicyclo[3.2.1]octane with a polysaccharide macroinitiator
Authors: Okada Masahiko , Sumitomo Hiroshi , Ito Takahiro
Published: April 2003

A polysaccharide macroinitiator (M̄n = 5000 to 28000) (1), having a reactive chlorine atom at the reducing end, was prepared by ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucose (TBLG) with antimony pentachloride as initiator in presence of acetyl chloride in dichloromethane at −60°C. Macroinitiator 1 in combination with silver hexafluoroantimonate was found to induce the polymerization of 6,8‐dioxabicyclo[3.2.1]octane (DBO) in tetrahydrofuran, 2‐methyltetrahydrofuran, or tetrahydropyran at −78 to 0°C. Fractionation of the reaction products gave a block copolymer (2) composed of poly(TBLG) and poly(DBO) segments. Debenzylation of 2 provided an amphiphilic block copolymer (3) consisting of hydrophilic (1→6)‐α‐D‐glucopyranan (dextran) and hydrophobic poly(DBO) [(1→6)‐linked polysaccharide skeleton] segments. Block copolymer 3 is soluble in dimethyl sulfoxide and swells in water and chloroform.
Solution properties and chain dimensions of poly(trimethylene sulfide)
Authors: Sánchez Angeles , Bello Antonio , Marco Carlos , Fatou José G.
Published: April 2003

Poly(trimethylene sulfide) (PTS) synthesized by means of anionic polymerization was studied with regard to its solubility behaviour and unperturbed chain dimensions. The Flory‐Huggins interaction parameter was used to determine the solubility parameter of PTS, δ = 10,0 cal1/2 · cm−3/2, which agrees with the calculated one. PTS fractions were isolated by means of fractional precipitation from chloroform/hexane at 50°C. Their number‐average molecular weight, M̄n, and the intrinsic viscosity, [η], were measured in chloroform at 25°C. From these data the relation [η] = 3,10 · 10−4 M̄ was estimated. A value of the characteristic ratio, 〈r2〉0/(n l2) = 4,0, was determined from the Burchard‐Stockmayer‐Fixman plot, which shows that this chain molecule has high flexibility.
Longitudinal volume viscosity of isotactic polypropylene
Authors: Alonso‐Abengozar Ana , Aleman Jose V.
Published: April 2003

The volume flow of isotactic polypropylene (i‐PP) with number‐average molecular weight M̄n = 103 200, melting temperature Tm = 426 K and glass transition temperature Tg = 238 K, has been measured. The elastic modulus of the longitudinal wave, longitudinal volume viscosity, initial longitudinal volume viscosity, and retardation times, are described for compression rates between ca. 1,0·10−5 and 200,0·10−5 s−1, and at temperatures between 443 K and 473 K as well as pressures up to 150 MPa at which no sign of crystallization was detected. The longitudinal volume viscosity decreases with increasing compression rate and with decreasing volume deformation, the behaviour being in all cases a typical non‐equilibrium one. The longitudinal volume viscosity increases with increasing temperature, the volume flow activation energy being about 78,08 kJ/mol.
Reactivity mediated by the conformation of polysaccharide hosts: Hydrolysis of 2‐chloro‐N‐dodecylpyridinium iodide in the presence of amylose derivatives
Authors: Hui Yongzheng , Gai Yonghua
Published: April 2003

The effects of three kinds of helix‐forming derivatives of amylose, namely, carboxymethylamylose (CMA), methylamylose (MA) and aminoethylamylose (AEA), on the hydrolysis of 2‐chloro‐N‐dodecylpyridinium iodide (CDPI) in aqueous alkaline media were studied. Based on the fact whether it is an intermolecular or intramolecular process, different results, i. e., retardation or acceleration caused by adding the host, are interpreted in terms of helical inclusion complex between the derivative of amylose and the substrate. As a polyelectrolyte, CMA forms inclusion complex only at higher ionic strength when the strong repulsion between charged groups is shielded. This conclusion was proved by the fact that all values of Kd*, which represents the stability of complex, as well as of ηsp/c and absorbance of the polyiodide complex, indicate that for MA the helix‐forming ability is independent of ionic strength, because it is a neutral polymer, but for CMA it changes drastically in the same region of ionic strength. Compared with MA, the higher retarding efficiency offered by CMA as well as by the anion micelle, SDS, can be attributed to the negatively charged groups surrounding the helix which hinder an approach of OH− to the reaction site.
Polymerization of β‐propiolactones by nickel carboxylate/tributylphosphine complexes
Authors: Carrière François J. , Blottiau Rolande , Sekiguchi Hikaru
Published: April 2003

The kinetics of polymerization of β‐lactones — β‐propiolactone, α‐ethyl‐α‐phenyl‐ and α‐benzyl‐α‐ethyl‐β‐propiolactone — was investigated using nickel carboxylate/phosphine complexes as initiators. The apparent rate constants of initiation and propagation, ki and kp, were calculated assuming first order kinetics. The variations of ki values with monomer concentration suggest that the mechanism is more complex, with a reaction order which is not as admitted for calculation. The infrared study has shown that the polymerization initiated by the complex is of zwitterionic type, and the kinetic curves indicate that the nickel carboxylate participates in the reaction.
Liquid‐crystalline polyurethanes, 4. Polyurethanes containing an azobenzene group in the side chain
Authors: Tanaka Mamoru , Nakaya Tadao
Published: April 2003

Polyurethanes with azobenzene side groups attached via an alkyl spacer of different length were synthesized from N‐[4‐phenylazophenyl]‐ω‐[bis(2‐hydroxyethyl)amino]alkanamides (5) and equimolar amounts of diisocyanates such as hexamethylene diisocyanate (HDI), 4,4′‐methylenedicyclohexyl diisocyanate, 1,3‐cyclohexylenedimethyl diisocyanate, 2,4‐toluylene diisocyanate, and 4,4′‐methylenediphenyl diisocyanate. Polyurethanes obtained from diols 5 with HDI have a mesomorphic phase as determined by DSC and polarizing microscopy and are crystalline at room temperature as evidenced by X‐ray studies.
Mathematical modelling of polymers, 3. Enumeration and generation of repeating irreducible sequences in linear bi‐, ter‐, quater‐ and quinquenary copolymers and in stereoregular homopolymers
Authors: Balaban Alexandru T. , Artemi Cristian
Published: April 2003

Irreducible sequences in n‐ary copolymers are defined. An exhaustive and non‐redundant lexicographically ordered list of irreducible sequences of comonomers in binary (n = 2), ternary (n = 3), quaternary (n = 4) and quinquenary (n = 5) copolymers is presented. The numbers of irreducible sequences may be found either by an explicit formula in terms of the number n of comonomers and of the length m of the sequences, or by applying the Polya‐de Bruijn theorem, as shown in detail in the first two parts of this series. For stereoregular vinyl homopolymers, or for the geometrical (E/Z) isomerism in polyalkenes, irreducible sequences are the same as in binary copolymers. A nomenclature is proposed for m‐ads in stereoregular homopolymers with m > 2, i. e. beyond isotactic for m = 1, and syndiotactic for m = 2.
Melting, crystallization, and solution behavior of chain molecules with hydrocarbon and fluorocarbon segments
Authors: Höpken Jens , Pugh Coleen , Richtering Walter , Möller Martin
Published: April 2003

Melting, crystallization, and solution behavior of n‐alkanes with fluorocarbon segments of twelve carbon atoms on one end, F(CF2)12(CH2)nH, or on both ends, F(CF2)12(CH2)n(CF2)12F were investigated by DSC, MAS 13C NMR, light scattering, and birefringence studies. Both triblock F(CF2)m(CH2)n(CF2)mF and diblock F(CF2)12(CH2)nH compounds with 4 ≦ n ≦ 14 melt by a two‐step process. In the first step, the alkyl segment conformations gain nearly liquid like trans/ gauche ratios, while the perfluorinated segments remain ordered. “Gels” which incorporate the entire solvent are formed by crystallization from even dilute solutions of hydrocarbon and fluorocarbon solvents. The gels are built up of extremely long, interdigitated needles of the pure solute. Due to the bilayer structures and different degrees of ordering of the hydrocarbon and the fluorocarbon segments, the crystals grow preferentially in the direction parallel to the lamellar surface. Light scattering experiments in octane demonstrated the formation of micelle type associates.
The effect of crosslinking on the aggregation of syndiotactic poly(methyl methacrylate) — an investigation using nmr and infrared spectroscopy
Authors: Spěváček Jiří , Schneider Bohdan , Štokr Jan , Vlček Petr
Published: April 2003

Using NMR and infrared (IR) spectroscopy, the effect of crosslinking on the aggregation of syndiotactic (s) poly(methyl methacrylate) (PMMA) in toluene or o‐dichlorobenzene gels was investigated. A conclusion was drawn from the integrated band intensities in the 1 H NMR high resolution spectra that the values of fractions of aggregated units decrease with increasing crosslinking, and that the corresponding aggregates of crosslinked s‐PMMA decompose (melt), compared with uncrosslinked s‐PMMA, at somewhat lower temperatures. Already loose crosslinking markedly slows down the aggregation process. The IR spectra showed that fractions of long s‐sequences, which form helices having a high number of units per turn (conformation close to the all‐trans one), are greatly reduced due to crosslinking, and the structure of aggregated sequences is less defined. Unlike the uncrosslinked s‐PMMA, the structures arising by aggregation in gels of crosslinked s‐PMMA do not persist in the solid state.
Synthesis of polysiloxane/polyamine block copolymer using uniform size poly(dimethylsiloxane) with reactive end‐groups
Authors: Kazama Hideki , Tezuka Yasuyuki , Imai Kiyokazu , Goethals Eric J.
Published: April 2003

Poly(dimethylsiloxane) (poly(DMS))/poly(N‐tert‐butylaziridine) (poly(TBA)) block copolymer was synthesized by two different techniques; (1) the coupling reaction of poly(DMS) having a dimethylaminopropyl end‐group (1) with living poly(TBA) (2) which was prepared with methyl trifluoromethanesulfonate as an initiator, and (2) the polymerization of N‐tert‐butylaziridine (5) using poly(DMS) having a p‐toluenesulfonyl ester end‐group (4) as macromolecular initiator, respectively.
13C NMR study of monomer composition and sequence distribution in ethylene/propylene/1‐octene terpolymers
Authors: Ye Hongwei , Xu Zhikang , Zhu Qinqin , Yan Shilin , Chen Hongzhang
Published: April 2003

A series of ethylene/propylene/1‐octene terpolymers with different composition is examined by 13C NMR. Assignments of the various carbon resonances are accomplished by comparison with spectra of ethylene/propylene, ethylene/1‐octene, and propylene/1‐octene copolymers and by INEPT multi‐pulse technique. The polymers obtained with a high‐mileage titanium‐magnesium catalyst contain no inverted propylene sequences. The intensities of all the lines are used in the calculation, and this approach allows the terpolymer composition and the sequence distribution to be determined.
X‐ray and optical investigations on polymers with mesogenic side groups
Authors: Hans Karin , Zugenmaier Peter
Published: April 2003

Based on polarisation microscopic observation of polymers with mesogenic side groups at the phase transition isotropic‐smectic, a domain‐like structure has to be assumed for smectic phases. Two different regular‐shaped nuclei are formed at the phase transition on slightly different conditions which grow after twinning into bǎtonnets. The Avrami equation can be applied for a quantitative description of the growth of the anisotropic areas as shown for one form of the nuclei. Unoriented and sheared samples maintain their morphology when cooled from the liquid‐crystalline to the partially crystalline phase. The crystalline phase of polymers with mesogenic side groups was investigated by X‐ray diffraction on differently oriented samples. It was found that the crystallites have the same internal structure despite the fact that they exhibit different uniaxial fibre axes. Optical investigations provide helpful supplementary information for deciding what kind of layered structure is present in the crystalline and smectic phase.
Dynamic mechanical relaxations in a copolyterephthalate based on ethylene glycol and 1,4‐cyclohexanedimethanol
Authors: Benavente Rosario , Pereña José M.
Published: April 2003

The dynamic mechanical relaxations of poly(ethylene terephthalate) (PET), poly(1,4‐cyclo‐hexylenedimethylene terephthalate) (PCHDMT), and a copolymer of them (COP) were measured in the temperature range from −150 to 150°C by use of a dynamic viscoelastometer. The viscoelastic relaxations of COP are studied and compared with those of PET and PCHDMT. The anisotropy of the viscoelastic properties of stretched COP samples was also studied in order to distinguish between main and secondary relaxations.
Polymerization of methyl acrylate photoinitiated by 4‐dimethylamino‐4′‐isopropylbenzophenone
Authors: Mateo José L. , Bosch Paula , Vázquez Esperanza , Sastre Roberto
Published: April 2003

The initial rate of the polymerization of methyl acrylate photoinitiated by 4‐dimethylamino‐4′‐isopropylbenzophenone (2) varies linearly with monomer concentration and the square‐root of light intensity. For small absorbances, the initial polymerization rate, Rp, varies linearly with the square‐root of the photoinitiator concentration. For high absorbance values, Rp is independent of the photoinitiator concentration in a well‐stirred system and decreases as the photoinitiator concentration increases in an unstirred system. This marked differences between the polymerization kinetics in well‐stirred and unstirred systems is discussed. The ratio of the propagation rate constant and the square‐root of the termination rate constant, kp/k, and the quantum yield of photoinitiation were determined and related to the results previously obtained in a study on the photoreactivity of 2.
New polymer syntheses, 29. Thermotropic (co)polyesters of 2‐phenylthioterephthalic acid and various diphenols
Authors: Kricheldorf Hans R. , Döring Volker , Eckhardt Volker
Published: April 2003

2‐Phenylthioterephthalic acid (1a) was prepared from thiophenol and dimethyl‐2‐nitroterephthalate. Homopolyesters of this diacid were prepared by transesterification with the diacetates of hydroquinone, methylhydroquinone, or 2,5‐biphenyldiol. Copolyesters were prepared from equimolar amounts of hydroquinone and 4,4′‐biphenyldiol or from hydroquinone and 4‐hydroxybenzoic acid in various mole ratios. Inherent viscosities in the range of 0,4–2,0 dl/g were found. DSC‐measurements indicate that in the case of (co)polyesters from hydroquinone the homopolyester has the highest glass‐transition temperature (Tg = 181°C) and the highest melting point (Tm = 332°C). Also the homopolyesters from 1a and methyl‐ or phenylhydroquinone are crystalline. Furthermore, the homopolyesters from hydroquinone and 2‐(p‐tolylthio)terephthalic acid or 2‐(4‐chlorophenylthio)terephthalic acid were prepared. Microscopic observation under polarized light and WAXS‐measurements confirmed that all polyesters form a nematic melt above Tg or Tm. In most cases the mesophase extents up to ca. 460°C where thermal decomposition prevents further observation. The homo‐ and copolyesters from 1 a and hydroquinone were also subjected to thermomechanical analyses by means of the penetration method.
Tactic copolymers derived from poly(methacrylohydrazide) and functional α‐amino acids
Authors: Thevissen Josef , Klesper Ernst
Published: April 2003

Lactic acid and N‐tert‐butoxycarbonyl protected L‐alanine, L‐histidine and L‐serine were condensed with syndiotactic poly(methacrylohydrazide) (1) in aqueous solution in the presence of N‐ethyl‐N′‐(3‐dimethylaminopropyl) carbodiimide. By incomplete conversion of (1) copolymers 4a – d were obtained containing methacrylohydrazide monomeric units. By complete conversion with L‐histidine and L‐serine simultaneously, copolymers 5 containing both amino acid moieties were obtained. The N‐tert‐butoxycarbonyl protecting group was removed from the polymers by acidolysis. This reaction was followed by CD spectroscopy. All polymers were characterized by 1H and 13C NMR spectroscopy.
Thermotropic liquid‐crystalline main‐chain polyesters containing cyclooctylene units, 6. Cholesteric copolymers
Authors: Cowie John M. G. , Wu Hak H.
Published: April 2003

A series of chiral nematic copolymers were prepared based on the new mesogenic unit cis‐1,5‐cyclooctylene bis(p‐hydroxybenzoate) (COHB). The copolymers were prepared by linking COHB coupled with (+)‐3‐methyladipic acid to COHB units combined with terephthalic acid and its bromo and nitro derivatives. A biphasic region was observed in most of the samples which made phase diagrams more difficult to establish. Mesophase stability could normally be sustained up to 50 mol‐% content of the methyladipic acid group in the copolymer. They were also sensitive to both temperature changes and shearing forces.
Some features of a novel organozinc complex, [{MeOCH2CH(Me)OZnOCH(Me)CH2OMe}2 · {EtZnOCH(Me)CH2OMe}2], as an enantiomorphic catalyst for stereoselective polymerization of propylene oxide
Authors: Yoshino Norio , Suzuki Chiaki , Kobayashi Hiroshi , Tsuruta Teiji
Published: April 2003

Some significant features of a novel organometallic complex, [{MeOCH2CH(Me)OZnOCH(Me)CH2OMe}2 · {EtZnOCH(Me)CH2OMe}2] (3), as an enantiomorphic catalyst for stereoselective polymerization of propylene oxide (PO) are reported. Populations of triad tacticities of poly(PO) obtained with complex 3 as catalyst fit nicely with the theoretical curves of the one‐parameter equations for the enantiomorphic catalyst sites model. The observed σ2 value was much higher than that observed with other organozinc complexes (1 and 2) reported previously. Every molecule of complex 3 was proved to exist as a monomeric form in benzene and its structural feature was retained in solution even after the initiation stage of polymerization. The number of active sites of complex 3 for the oxirane polymerization was determined to be one by determining the 1‐methoxy‐2‐propanol liberated from the unreacted methoxypropoxy groups. The initiation and propagation mechanisms are discussed.
Transient electric birefringence of poly(sodium p‐styrenesulfonate) solutions at very low field strengths
Authors: Oppermann Wilhelm
Published: April 2003

Measurements of the electric birefringence were performed on dilute, aqueous solutions of a poly(sodium p‐styrenesulfonate). The concentrations were chosen to be somewhat below and above the critical concentration (c*) where, on grounds of theoretical considerations, the rod‐to‐coil transition is expected to occur. The measurements were conducted at very low field strengths E, viz. in the order of E = 104 V · m‐1, using d. c. pulses as well as 30 kHz a. c. pulses. When an a. c. field is applied, birefringence is always negative and shows a monotonous rise and decay. The same holds true for a d. c. field provided the concentration of the polymer is below c*. However, when a d. c. pulse of very low field strength is applied to a solution the concentration of which is above the critical concentration, some strange features occur: At the beginning of the pulse the birefringence is negative, but then it reverses its sign and approaches a positive steady‐state value. After cessation of the pulse the birefringence passes through a maximum before decaying to zero. The whole birefringence curve looks like a superposition of two signals with opposite signs. These features disappear at higher field strengths. On the basis of an analysis of the field‐strength dependence, it is tentatively concluded that other mechanisms besides the rotational orientation of the molecules contribute to birefringence. One such process could be migration of the macroions giving rise to flow birefringence.
Studies on planar orientation and trap depth of poly(ethylene terephthalate) film
Authors: Zhou Yigin , Zhang Jixiang , Zhang Xingyuan , Yang Jengtsong
Published: April 2003

Poly(ethylene terephthalate) films with various degrees of planar orientation of the macromolecules were prepared by uniaxial and biaxial stretching. Fourier transform infrared spectra indicate that the content of gauche conformation decreases linearly with the degree of planar orientation, while the content of trans conformation increases linearly. A linear relationship between the trap depth calculated from Thermally Stimulated Current spectra and the degree of planar orientation was observed.