bluuebunny/crossref_metadata_2025 huggingface dataset:
Tri‐armed star polymers by living cationic polymerization, 3. Synthesis of tri‐armed star poly(p‐methoxystyrene)
Authors: Shohi Hajime , Sawamoto Mitsuo , Higashimura Toshinobu
Published: April 2003

Tri‐armed star polymers of p‐methoxystyrene (pMOS) were synthesized by living cationic polymerization with a trifunctional initiator CH3C[(p‐)C6H4OCH2CH2OCH(CH3)I]3 (6) or C6H3(1,3,5‐)[COOCH2CH2OCH(CH3)I]3 (9) with zinc iodide as activator in toluene at −15°C. The number‐average molecular weight (Mn) of the polymers increased proportionally to the monomer conversion and further increased upon addition of fresh feed of pMOS to completely polymerized reaction mixtures; the polymers invariably exhibited very narrow molecular‐weight distributions (MWD) (Mw/Mn < 1,1). The living polymers were terminated with 2‐hydroxyethyl methacrylate to give a tri‐armed macromonomer where each arm is capped with a methacrylate group, and the quantitative end‐capping, in turn, showed the existence of three living ends per molecule. When the ester‐type initiator residue (core) of the poly(pMOS), obtained with the 9/ZnI2 system, was hydrolyzed under alkaline conditions, Mn was reduced to one third of the original value, with the narrow MWD being unchanged, thus indicating that the polymer possesses three arms with uniform and controlled length.
Cationic copolymerization of norbornadiene with styrene by AlEtCl2/tert‐butyl chloride catalyst system, 1. Effect of norbornadiene/styrene feed ratio
Authors: Sagane Toshihiro , Minami Shuuji
Published: April 2003

The cationic copolymerization of norbornadiene (NBD) and styrene (St) was carried out with the AlEtCl2/tert‐butyl chloride catalyst system in CH2Cl2 at −50°C, and the effect of NBD/St feed ratio on the solubility, the glass trtansition temperature (Tg) and the molecular weight of the copolymers was investigated. A soluble copolymer was prepared at 40 mol‐% (or above) of St in the feed, although the NBD homopolymer comprised an insoluble fraction which might have been formed by a crosslinking reaction between the double bonds in the NBD units of the polymer. The copolymer has a statistically random sequence distribution of the two monomeric units not only in the polymer chain but also over the whole molecular weight range (from 103 to 106). The Tg of the amorphous copolymer is controlled by the NBD/St composition in the range from 100°C through 290°C. A soluble copolymer with highest Tg (ca. 170°C) could be prepared at a NBD/St feed ratio of 60/40 mol‐%.
Ring‐opening metathesis polymerization of syn‐ and anti‐7‐methylbicyclo[2.2.1]hept‐2‐ene initiated by Mo(CHCMe3)(NC6H3‐2,6‐i‐Pr2)(OCMe3)2
Authors: Feast W. James , Gibson Vernon C. , Ivin Kenneth J. , Khosravi Ezat , Kenwright Alan M. , Marshall Edward L. , Mitchell Jonathan P.
Published: April 2003

The ring‐opening metathesis polymerization of syn‐ and anti‐7‐methylbicyclo[2.2.1]hept‐2‐ene (Ms and Ma) by Mo(CHCMe3)(NC6H3‐2,6‐i‐Pr2)(OCMe3)2 has been followed by 1H and 13C NMR spectroscopy in C6D6 and CD2Cl2 as solvents. The anti monomer Ma polymerizes first, followed much more slowly by the syn monomer Ms, leading to a block copolymer. The reaction is considerably faster in CD2Cl2, where it proceeds to completion, than in C6D6. In C6D6kpa/kia = 9, as determined from the proportion of residual initiator. The double bonds formed are mainly trans (80–90%) in both blocks and the diads embracing the trans double bonds in the Ma blocks have an isotactic bias: (σm)t = 0,69 in C6D6, independent of monomer concentration; the diads in the Ms bloks have a slight tactic bias, probably isotactic. The tacticity is interpreted in terms of control of addition of monomer by the configuration of the chiral carbons in the C5 ring nearest to the molybdenum centre in the propagating metal‐carbene complex.
Ceric ion consumption in graft copolymerization of methacrylonitrile/methacrylate mixtures onto amylomaize
Authors: Vázquez Blanca , Goñi Isabel , Gurruchaga Marilo , Areízaga Javier , Valero Miguel , Guzmán Gonzalo M.
Published: April 2003

A study on the Ce(IV) consumption in the graft copolymerization of methacrylonitrile/n‐alkyl methacrylate mixtures methyl, ethyl and butyl methacrylate/methacrylonitrile (MMA/MAN, EMA/MAN and BMA/MAN) was carried out. Ce(IV) consumption increased with increasing mole fraction of the methacrylate in the monomer feed and with increasing the n‐alkyl group length of the methacrylate, but in no case the consumption was total. The molecular weight distribution of the copolymers was obtained through gel‐permeation chromatography. For all systems investigated, both number‐average molecular weight (Mn) and weight‐average molecular weight (Mw) increased with increasing methacrylate concentration in the monomer feed. The ratios Mw/Mn increased in the following order: MMA/MAN < EMA/MAN < BMA/MAN. For the MAN/MMA system, the number of grafted chains (in mmol) increased as the methyl methacrylate content increased in the monomer feed, and for the MAN/EMA and MAN/BMA systems, this parameter presented a maximum value. The number of D‐anhydroglucose units per grafted chain (frequency) decreased with increasing methacrylate concentration in monomer feed for the MAN/MMA system, and this parameter reached a minimum value at a methacrylate mole fraction of 0,5 for the other two systems.
Emulsion copolymerization of styrene and butyl acrylate with itaconic acid
Authors: Václavová Eva , Hrivík Alexander , Chrástová Viera
Published: April 2003

The emulsion copolymerization of styrene with itaconic acid and butyl acrylate with itaconic acid (methylenesuccinic acid), initiated by a redox system in the presence of a nonionic emulsifier, was studied at 40°C. Examination of the influence of itaconic acid on the copolymerization with both monomers showed that the presence of itaconic acid had a negative influence on copolymerization conversion and on the rate of copolymerization. the reaction order with respect to itaconic acid is −0,34 for the copolymerization of itaconic acid with styrene and −1,40 for its copolymerization with butyl acrylate. In the case of the copolymerization with styrene, itaconic acid has no effect on particle number concentration and particle size. Itaconic acid participates in particle nucleation during its copolymerization with butyl acrylate. Formation of oligomeric radicals in the water phase led to a decreasing number of particles and to increasing particle size.
Solid‐solid‐liquid phase transfer reactions catalyzed by polymer‐supported ureas
Authors: Kondo Shuji , Okamura Takeshiro , Takesue Masakazu , Kunisada Hideo , Yuki Yasuo
Published: April 2003

Polymer‐supported ureas were prepared by copolymerization of the corresponding vinyl monomers and divinylbenzene with 2,2′‐azoisobutyronitrile. These polymers show catalytic activity in the reaction of 1‐bromooctane with solid potassium thiocyanate, although the corresponding monomeric ureas are inactive. The catalytic activity is enhanced remarkably by replacing the amino hydrogen for a methyl group. Further, the catalytic activity is affected by some experimental parameters such as stirring, particle size of the catalyst, degree of crosslinking, and solvent. On the basis of the above results, a plausible catalytic reaction mechanism consiting of collisional contact between the solid catalyst and the reagent is proposed.
Solution copolymerization of monomethyl itaconate and methyl methacrylate
Authors: Kelemen Peter , Hrivík Alexander
Published: April 2003

The copolymerization of monomethyl itaconate (M1) (4‐methyl 1‐hydrogen 2‐methylene‐succinate) with methyl methacrylate (M2) was studied in bulk and in ethyl acetate solution. The reactivity ratios were determined to be r1 = 0,56 ± 0,02 and r2 = 1,56 ± 0,05. The dependences of copolymerization rate and degree of polymerization on initiator concentration, total monomer concentration and composition of monomer feed were measured. The reaction order with respect to the initiator concentration was near to the theoretical one (0,5), while that with respect to the total monomer concentration was considerably higher than predicted by theory (1,0). It could be explained by the influence of transfer reactions and diffusion control of termination reactions. Transfer reactions contribute to the reaction order mainly at low monomer concentration, while the influence of the medium viscosity becomes predominant at high monomer concentration.
Is 1,2‐bis(2,4‐octadecadienoyl)‐sn‐glycero‐3‐phosphorylcholine (DODPC) an efficient chiral probe to study conformational changes in lipid membranes?
Authors: Faupel Peter , Buβ Volker
Published: April 2003

In order to study its possible use as a chiral membrane probe, small unilamellar vesicles of 1,2‐bis(2,4‐octadecadienoyl)‐sn‐glycero‐3‐phosphorylcholine (DODPC, 1), a doubly unsaturated phospholipid molecule, and vesicles of 1,2‐dipalmitoyl‐ or 1,2‐dimyristoyl‐sn‐glycero‐3‐phos‐phorylcholine or egg‐lecithin, containing DODPC, were prepared and investigated by UV and circular dichroism (CD) spectroscopy. The phase transitions that are clearly manifest in the UV effect reproducible but only small changes in the CD. This indicates that at least in the area of unsaturation the molecule is rather stiff and insensitive to its micro‐environment. A non‐membrane‐forming short‐chain model compound, 1,2‐bis(2,4‐hexadienoyl)‐sn‐glycero‐3‐phos‐phorylcholine, 2, was used to study the chiroptic properties of the isolated molecule; the results are in agreement with calculations and support the contention that bis‐unsaturated lipid molecules should in principle be able to function as chiral labels.
2H NMR study of solvent and solute mobility in polymer solution, gel and glass states
Authors: Sentosa Petrus , Fujara Franz , Sillescu Hans
Published: April 2003

2H spin relaxation times, T1 and T2 and solid echo line shapes were investigated in 2‐propanol (2‐POH) solutions of poly(butyl methacrylate) (PBMA) in a wide concentration and temperature range, covering the solution, gel and glass states. From the results in deuterated 2‐POH‐d6 we found that the polymer influence upon solvent mobility is largely suppressed in the gel and glass states in contrast to normal polymer solutions where below the glass transition an increasing amount of solvent slows down with decreasing temperature. From 2H NMR of deuterated butyl side groups in the PBMA‐d9/2‐POH system we found that the side group motion is anisotropic and largely independent of solvent concentration in the gel and glass states which confirms that polymer‐polymer interaction via side group interpenetration should be considered as the main cause for gel formation in this system.
Synthesis of high‐molecular‐weight poly(dimethylsiloxane) of uniform size by anionic polymerization, 1. Initiation by a monofunctional lithium siloxanolate
Authors: Maschke Ulrich , Wagner Thomas , Coqueret Xavier
Published: April 2003

An improved procedure for the anionic polymerization of hexamethylcyclotrisiloxane (D3) initiated by a monofunctional lithium derivative is reported. The initiator seeding solution is preferably prepared in benzene, and tetrahydrofuran is used as a cosolvent which makes the presence of additional promoters useless. The main advantage of this procedure is that it delays the appearance of bimodality which is believed to result from a sudden change in aggregate molecularity during the course of the reaction. Applying this method, poly(dimethylsiloxane) samples having a single functional endgroup and possessing high molecular weights and narrow molecular weight distributions (1,03 ≤ M̄w/M̄n ≤ 1,06) were prepared on the 100 g scale.
Synthesis and thermal properties of poly(arylene‐1,2,4‐oxadiazole)s with flexible, linear alkoxymethyl side branches
Authors: Park Sang‐Bong , Jung Jin Chul
Published: April 2003

Poly(arylene‐1,2,4‐oxadiazole)s (PAOs) bearing flexible, linear side chains, 3a‐c, were prepared by solution cyclodehydration of their precursors, poly(arylene acyloylamide oxime)s (PAAs), 2a‐c, which were synthesized by solution polycondensation of 2,5‐bis(n‐alkoxymethyl)‐terephthaldiamide oximes (DIS‐TADO), 1a‐c, with terephthaloyl dichloride (TPC). The length of the n‐alkoxy group was varied from methoxy via butoxy to octyloxy. The reduction of the phase transition temperatures and the enhancement of the solubilities of 3a‐c were greatly affected by the length of the side chains. PAOs with longer side chains, 3b and 3c, are nematic type liquid‐crystalline polymers.
Basic studies on the inifer mechanism, 1. Interaction of 1,4‐bis(1‐chloro‐1‐methylethyl)benzene with BCl3
Authors: Dittmer Thomas , Pask Stephen D. , Nuyken Oskar
Published: April 2003

A mixture of 1,4‐bis(1‐chloro‐1‐methylethyl)benzene (1) and BCl3 at −80°C in CH2Cl2 yields a red colour, which is explained as a result of the formation of a charge transfer (CT) complex between the carbenium ion formed after Cl− abstraction from 1 and the aromatic π‐system of 1. This view is supported by UV/VIS and conductivity measurements. These measurements and their consequences for the cationic polymerization are discussed in detail.
Basic studies on the inifer mechanism, 2. Interaction of 1,4‐bis(1‐methoxy‐1‐methylethyl)benzene with BCl3 in CH2Cl2
Authors: Dittmer Thomas , Pask Stephen D. , Nuyken Oskar
Published: April 2003

1,4‐Bis(1‐methoxy‐1‐methylethyl)benzene is a representative of a novel generation of inifers, initiator/transfer agents for cationic polymerizations. In contrast to the classical initiator 1,4‐bis(1‐chloro‐1‐methylethyl)benzene its activation needs an excess of BCl3. This behavior is closely related to a complex formation between the ether and BCl3. On the basis of combined UV/VIS and conductivity measurements a mechanism for the ion formation is suggested.
Liquid‐crystalline side‐group polyesters with definite lengths of the main‐chain spacers
Authors: Böhme Axel , Lindau Jürgen , Rötz Uwe , Hoffmann Frank , Fischer Hartmut , Diele Siegmar , Kuschel Frank
Published: April 2003

New liquid‐crystalline polyesters 1 with 4‐(phenylazo)azobenzene moities as mesogenic side groups and a polyester backbone structure characterized by a systematic variation of the length of the flexible non‐mesogenic main‐chain segments were synthesized. The polyesters were investigated by differential scanning calorimetry, polarizing microscopy, miscibility studies and X‐ray diffraction. With increasing number of methylene groups in the backbone spacer, the thermal stability of the nematic and/or smectic phases first decreases and then increases.
Determination of surface morphology of diblock copolymers of styrene and butadiene by atomic force microscopy
Authors: Annis Brian K. , Schwark Dwight W. , Reffner John R. , Thomas Edwin L. , Wunderlich Bernhard
Published: April 2003

A detailed study by atomic force microscopy of the surfaces of diblock copolymers which exhibit lamellar and spherical microphase domains in the bulk is presented. The surface morphology of the lamellar samples consists of corrugations. Transmission electron microscopy of cross sections which include the surface and near surface demonstrate the connection between the corrugations and the bulk lamellae. The surface of a sample with spherical bulk domains was found to consist of a series of pits that can be linked with centers on the faces of the cubic cell arrangement of the bulk. Disclinations and intersections of lamellae could be found. The latter result in lamellar break‐up in the contact area of the two lamellar orientations. Lamellar tilt can lead to variation in periodicity and depth of the surface morphology. Damage due to scanning was observed, but only for the sample with spherical morphology.
Cleavage of oligopeptide p‐nitroanilides attached to N‐(2‐hydroxypropyl)methacrylamide copolymers by guinea pig intestinal enzymes
Authors: Kopečková Pavla , Ikesue Koichi , Kopeček Jindřich
Published: April 2003

N‐(2‐Hydroxypropyl)methacrylamide copolymers containing oligopeptide side chains terminated with p‐nitroaniline, and low‐molecular‐weight oligopeptide p‐nitroanilides, were synthesized. They were used as substrates to evaluate the enzymatic activity in the gastrointestinal tract of guinea pigs. Brush border membrane enzymes and luminal enzymes (supernatant and pellet) were isolated from guinea pig small intestine and colon, and the cleavage of the substrates was studied in vitro. The results indicate the presence of endopeptidase activity in both small intestine and colon brush border. Phosphoramidon, a potent inhibitor of endopeptidase‐24.11, was effective in the cleavage of low‐molecular‐weight substrates, but ineffective in the cleavage of polymeric substrates, indicating the participation of a different endopeptidase in the cleavage of the latter. Luminal enzymes were more active in the cleavage of polymeric substrates (when compared to low‐molecular‐weight ones) in accordance with the physiological function of the gastrointestinal tract. The enzymatic activity, both luminal and brush border, was considerably lower in the colon than in the small intestine. This suggests that the colon might be a suitable site for the oral delivery of peptides and proteins.
Synthesis of polymers containing pseudohalide groups by cationic polymerization 4. Cocatalysis as a direct route to end‐capped poly(2‐methylpropene) with pseudohalide groups
Authors: Cheradame Hervé , Habimana Jean de la Croix , Chen Frank J.
Published: April 2003

The possibility to functionalize poly(2‐methylpropene) (PIB) by direct synthesis with functions containing nitrogen derived from the group of pseudohalogens, is demonstrated. Polymerization by cationic polyaddition of 2‐methylpropene using a suitable cocatalyst, here hydrazoic acid HN3 or hydrocyanic acid HCN, in the presence of titanium tetrachloride is carried out in methylene dichloride. The highest functionalization efficiency (f = 0,7) is obtained for a mole ratio catalyst‐to‐cocatalyst close to one. Part of the macromolecules is found to contain twice as many tert‐butyl groups as internal unsaturations. This finding is explained by the occurrence of some dimerization of macromonomers, which are formed by a PIB backbone terminated by one disubstituted unsaturation.
Observation of a nematic phase displayed by a polysiloxane with trinitrofluorenones as side groups
Authors: Möller Manfred , Tsukruk Vladimir V. , Wendling Jürgen , Wendorff Joachim H. , Bengs Holger , Ringsdorf Helmut
Published: April 2003

The synthesis and the results of the structural study of two copolysiloxanes with laterally fixed trinitrofluorenone (TNF) units is reported. The two copolysiloxanes having 2,4 (1a) and 5,3 (1b) dimethylsiloxane comonomer units per TNF side group differ significantly in their phase behaviour as evident from optical microscopy, differential scanning calorimetry and X‐ray scattering: 1b shows a nematic mesophase whereas 1a is an amorphous material. The different phase behaviour is discussed in terms of microphase separation between the siloxane backbone and TNF side groups.
High‐conversion emulsion polymerization
Authors: Maxwell Ian A. , Verdurmen Edwin M. F. J. , German Anton L.
Published: April 2003

The four important factors that determine the rate of emulsion polymerization are the propagation rate coefficient, the latex‐particle concentration, the monomer concentration in the latex particles, and the free‐radical concentration in the latex particles. Both theoretical considerations and experimental evidence suggest that the important factors that may reduce the rate of emulsion polymerization at high conversion are the propagation rate coefficient and the monomer concentration in the latex particles, and not the free‐radical concentration in the latex particle, if the initiator is not depleted. Various approaches for increasing the rate of emulsion polymerization at high conversion are suggested.
Synthesis of biodegradable polyesteramides with pendant functional groups
Authors: in't Veld Peter J. A. , Dijkstra Pieter J. , Feijen Jan
Published: April 2003

Morpholine‐2,5‐dione derivatives having substituents with benzyl‐protected carboxylic acid, benzyloxycarbonyl‐protected amine and p‐methoxy‐protected thiol groups, respectively, were prepared in 29–58% yield by cyclization of the corresponding N‐[(2RS)‐bromopropionyl]‐L‐amino acids. Polyesteramides with protected pendant functional groups were obtained by ring‐opening copolymerization of either ϵ‐caprolactone or DL‐lactide with morpholine‐2,5‐dione derivatives having protected functional substituents. The copolymerizations were carried out in the bulk at 130°C using stannous octoate as an initiator and using low mole fractions (0,05, 0,10 and 0,20) of morpholine‐2,5‐dione derivatives in the feed. The molecular weight of the resulting copolymers ranged from 1,4 to 8,3 · 104. The ring‐opening homopolymerization of morpho‐line‐2,5‐dione derivatives with protected functional substituents was not successful. Polyesteramides with either pendant carboxylic acid groups or pendant amine groups were prepared by catalytic hydrogenation of the corresponding protected copolymers. Treatment of copolymers having pendant p‐methoxybenzyl‐protected thiol groups with trifluoromethanesulfonic acid resulted not only in the removal of the p‐methoxybenzyl group but also in severe degradation of the copolymers, due to acidolysis of main‐chain ester bonds.
Preparation and catalytic action of an asymmetric ethylene/vinyl alcohol copolymer‐copper complex membrane
Authors: Miyata Takashi , Yoshida Naoto , Nakamae Katsuhiko
Published: April 2003

An ethylene/vinyl alcohol copolymer (EVA)‐copper complex membrane was prepared by casting an EVA‐CuCl2 mixture (solvent: water‐propanol (1:1 v/v) mixture) on a polyethylene substrate and then immersing it in 0,1 M KOH aqueous solution. In the membrane, Cu was distributed asymmetrically in the direction of the membrane cross section. The distribution of Cu could be controlled by the temperature during preparation. The oxidation of hydroquinone during permeation through the complex membrane was performed using membranes with different Cu distribution. This distribution influences the permeation reaction. These results are well reproduced by a relation composed of Fick's law and Michaelis‐Menten type reaction kinetics. Therefore, a good reactor can be developed by controlling the catalyst distribution.
Synthesis of carboxy‐ and chloro‐terminated poly(propylene)s using Zn(C2H5)2 as chain transfer reagent
Authors: Shiono Takeshi , Kurosawa Hiroki , Soga Kazuo
Published: April 2003

Propene was polymerized with conventional and Solvay‐type TiCl3 combined with Al(C2H5)2Cl using Zn(C2H5)2 as a chain transfer reagent. The produced terminal Zn‐carbon bonds of the polymer were reacted with carbon dioxide and chlorine in the presence of N‐methylimidazole followed by hydrolysis to obtain terminally carboxylated and chlorinated poly(propylene) in approximately 50% yield.
Derivatization of hydroxyl into α‐chloro ether: application to the synthesis of block copolymers from hydroxy‐telechelic polymers
Authors: Cramail Henri , Deffieux Alain
Published: April 2003

It has been recently shown that a‐halogeno ether, when activated by a weak Lewis acid such as ZnX2, may be used as initiator for the living cationic polymerization of vinyl ethers. A route to the a‐halogeno ether function is the action of dry hydrogen halide on an alcohol in the presence of an aldehyde or a cyclic acetal. The quantitative preparation of α‐chloro ethers by this route, as well as the use of such compounds to initiate the “living” cationic polymerization of vinyl ethers, was examined. This procedure was then applied to hydroxy‐telechelic polybutadiene to give a macro‐initiator with α‐chloro ether terminal groups. The latter was used to initiate the polymerization of vinyl ethers. The synthesis of poly(butadiene‐block‐ethyl vinyl ether) and poly(butadiene‐block‐2‐chloroethyl vinyl ether) is reported, as well as the preparation of other copolymers by chemical modification of the chloroethyl vinyl ether units.
Spontaneous polymerization of amphiphilic vinyl monomers, 1. Spontaneous polymerization of sodium dodecyl 2‐hydroxy‐3‐methacryloypropyl phosphate
Authors: Yasuda Yutaka , Rindo Katsuhiko , Aoki Shuzo
Published: April 2003

Sodium dodecyl 2‐hydroxy‐3‐methacryloyloxypropyl phosphate as an amphiphilic vinyl monomer was found to polymerize spontaneously without initiator in water. The polymerization takes place at a monomer concentration higher than the critical micelle concentration via a free‐radical mechanism, and complete conversion is achieved even at a very low initial monomer concentration (3 mmol/L) and a rather low temperature (35°C). In benzene, capable of forming inverse micelles, the polymerization also occurs spontaneously. In methanol, which gives an isotropic solution, the spontaneous polymerization proceeds only at high concentration (near 300 mmol/L). The 1H spin‐spin relaxation time (T*2) of the monomer changes discontinuously in a range of monomer concentration from 250 to 300 mmol/L in CD3OD, suggesting that some kind of monomer mutual interaction takes place in methanol too. Thus, it can be concluded that the micellar aggregation monomer molecules triggers the polymerization.
Synthesis of silicone macrocycles having a single functional side group by hydrosilylation under high dilution
Authors: Coqueret Xavier , Wegner Gerhard
Published: April 2003

Macrocyclic poly(dimethylsiloxanes) (PDMS) having a single ester side group were prepared by coupling hydrosilane end‐groups of telechelic PDMS and olefinic functions of methyl 3,5‐diallyloxybenzoate under high‐dilution conditions. The theoretical and preparative aspects of the continuous‐flux technique that was used to perform the Pt‐catalyzed hydrosilylation reaction were examined in the light of the results of a previous kinetic study. Excessive amounts of catalyst, or high temperature, lead to the formation of colloidal Pt, the poor chemical selectivity of which is not acceptable. When the addition reaction is performed under conditions allowing homogeneous catalysis, the reaction takes place with a steady‐state concentration in reactive groups as low as 2 · 10−3−4 · 10−3 mol/L over periods as long as 24–36 h. the isolation of the monofunctional cyclic products by semi‐preparative size‐exclusion chromatography techniques from the linear condensation products and from more complicated multifunctional cycles is possible if the starting telechelic PDMS is of narrow molecular weight distribution.
Polyurethane elastomer‐LiClO4 complexes as a polymeric solid electrolyte
Authors: Seki Miharu , Sato Kojiro , Yosomiya Ryutoku
Published: April 2003

A polymeric solid electrolyte with high ionic conductivity was prepared by complexing a polyurethane elastomer with LiClO4. The ionic conductivity of these complexes increases proportional to the increase of the content of poly(tetramethylene oxide) component in the polyurethane elastomer and with increasing LiClO4 concentration, and reaches a value of 10−4 S/cm at 80°C for [LiClO4] = 1,20 mmol/g polymer. The polyurethane elastomer‐LiClO4 complex has good mechanical properties compared with poly(ethylene oxide)‐and poly(propylene oxide)‐based complexes.
Synthesis of two novel heparinizable polymeric materials starting from an ethylene/vinyl alcohol/vinyl acetate terpolymer
Authors: Barbucci Rolando , Benvenuti Manuela , Magnani Agnese , Tempesti Federica
Published: April 2003

A partially hydrolyzed ethylene/vinyl acetate (EVA) copolymer was modified through the covalent binding of a heparin‐complexing polymer, in order to improve its blood compatibility. Two different heparinizable polymeric materials (EVAPA I and II) were obtained by a two‐step reaction between an ethylene/vinyl alcohol/vinyl acetate (EVALVA) terpolymer and a poly‐(amido‐amine) (N2LL) using either hexamethylene diisocyanate (HMDI) or 1,1'‐carbonyldimidazole (CDI) as bifunctional agents. EVALVA terpolymer was prepared by a homogeneous saponification process, and the percentage of hydrolysis was determined by an analytical method. EVAPA I and II syntheses were followed by FT‐IR/ATR (Fourier Transform Infrared/Attenuated Total Reflection) spectroscopy.
Synthesis and phase‐transfer catalytic activity of hydroxyl‐containing polyetheramines bound to soluble or insoluble polystyrenes
Authors: Kohno Yutaka , Ogawa Nobuyuki , Chung Kwang Bo , Fukuda Wakichi , Tomoi Masao
Published: April 2003

Soluble or insoluble polystyrenes with hydroxyl‐containing polyetheramine structures were prepared by the reaction of linear or crosslinked polystyrenes containing haloalkyl, tosyloxyalkyl, or epoxy groups with bis(2‐(2‐hydroxyethoxy)ethyl)amine(ATEG). The soluble polystyrenes with ATEG residue afforded polymeric alkoxides by the reaction with aqueous NaOH or KOH under two‐phase conditions. The introduction of oxygen‐containing spacer chains between ATEG residue and the polymer backbone resulted in the formation of cryptand‐like alkoxides, in which the counter cations were bound by cooperative coordination of the oxygen donors in the ATEG residue and in the spacers. The soluble and insoluble polymers with ATEG residue exhibited high catalytic activity for the dehydrobromination of 2‐bromoethylbenzene with aqueous NaOH or KOH under two‐and three‐phase conditions, respectively. The extra coordination of the oxygen donors in the spacers resulted in increased catalytic activity.
Phase separation of liquid‐crystalline graft copolymers
Authors: Blankenhagel Marita , Springer Jürgen
Published: April 2003

The phase separation behavior of graft copolymers containing poly(methyl methacrylate) grafts attached to a side‐chain liquid‐crystalline backbone is described and examined with respect to the share and the length of the grafts. Only copolymers with a low PMMA content show microphase separation. An increasing PMMA content leads to a miscibility of the components.
Synthesis and characterization of some new photochromic side‐chain liquid‐crystalline polymers
Authors: Ruhmann Ralf , Zschuppe Veit , Dittmer Manfred , Wolff Dietmar
Published: April 2003

The synthesis and characterization of a series of liquid‐crystalline copolymethacrylates containing side chains with both azobenzene and benzanilide moieties is described. The phase behaviour of the polymers is discussed in dependence of their copolymer composition. The copolymers are suitable for optical investigations on the photochemical trans‐cis isomerization of the azo group.
Poly(2,6‐Dimethyl‐1,4‐Phenylene oxide)/crosslinked polystyrene semi‐interpenetrating networks: Synthesis and properties
Authors: Penco Maurizio , Villa Anna Maria , Gobbi Cristina , Pegoraro Mario , Silvestro Giuseppe Di , Higgins Julia S.
Published: April 2003

Semi‐interpenetrating networks (semi‐IPN's) based on linear poly(phenylene ether)s and crosslinked polystyrene can be prepared by reactive moulding of crosslinkable polymeric mixtures. These materials show thermomechanical properties which strongly depend on both the ratio of the two polymeric matrices and the degree of crosslinking in the polystyrene network. Samples based on a 50/50 weight ratio of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/crosslinked polystyrene show glass transition temperatures (Tg) which are very dependent on the degree of crosslinking. It is therefore possible to obtain materials with desired Tg, ranging from the Tg of the corresponding linear blend to that of poly(2,6‐dimethyl‐1,4‐phenylene oxide) alone.
Recent developments in the field of micellar polymers
Authors: Anton Peter , Köberle Peter , Laschewsky André
Published: April 2003

This article describes recent achievements in the field of micellar polymers, or “polysoaps”. Taking advantage of zwitterionic model polymers, systematic variations of the molecular architecture have provided an improved understanding of the relationship between the molecular structure of the polymers and their key properties such as surface activity and solubilization capacity. Useful rules are established, which take into account much of the previous data in the literature.
Synthesis and characterization of poly(5‐alkyl‐2‐norbornene)s by cationic polymerization. Effect of alkyl substituent length on monomer reactivity, polymer structure and thermal properties
Authors: Sagane Toshihiro , Mizuno Akira
Published: April 2003

Cationic polymerizations of various 5‐alkyl‐2‐norbornenes (RNB, where RH, CH3, C2H5, C5H11, C7H15, and C10H21) were carried out by the AlEtCl2/tert‐butyl chloride catalyst system, and the effect of the length of the alkyl substituents on the monomer reactivity and polymerizability, polymer structure, and softening point (SP) were investigated. The introduction of an alkyl substituent into 5‐position of the norbornene ring remarkably reduces the monomer reactivity and polymerizability, although the length of alkyl group does not affect them. 13C NMR structural analysis of poly(RNB)'s revealed that not only the normal 5‐or 6‐alkyl‐2,3‐unit but also other structures such as 5‐ or 6‐alkyl‐2,7‐, 4‐alkyl‐3,6‐units, etc., are the most plausible structures for the repeating units. Furthermore, the existence of the 4‐alkyl‐3,6‐repeating unit and of the alkylidene type end‐group indicates the presence of an intermediate tertiary cation (5‐alkyl‐5‐norbornyl cation), which causes the low reactivity and polymerizability of the monomers. The SP of oligomers of equal molecular weight (DPn = 3–5) decreases in the following order: HNB, CH3NB,C2H5NB>C5H11NB>C7H15NB>C10H21NB. The effect the alkyl substituent length on the SP is discussed on the basis of the 13C spin‐lattice relaxation times (T1) for the carbons in the alkyl group.
Studies on chitosan 5. Reactivity of partially N‐acetylated chitosan in aqueous media
Authors: Aiba Sei‐ichi
Published: April 2003

The reactivity of the amino groups of partially N‐acetylated chitosans (PAC‐H) was investigated using cyanuryl dichloride, pyrocarbonates, activated ester, carbodiimide and epoxy‐activated polymethacrylamide beads. The maximal reactivity was attained at neutral pH in the cases of the reaction with a monomethoxypoly(ethylene glycol) succinimidyl succinate, and with isonicotinic acid mediated by a water‐soluble carbodiimide. On the contrary, the maximal reactivity was attained under weakly basic conditions in the cases of reactions with diethyl pyrocarbonate, dimethyl pyrocarbonate and cyanuryl dichloride. The highest amount of PAC‐H was immobilized on the surfaces of epoxy‐activated polymethacrylamide beads at weakly alkaline pH. From these results it was concluded that PAC‐H's are favorable for preparing randomly substituted derivatives and for immobilizing them on surfaces because their solutions are stable at neutral and alkaline pH in contrast to conventional chitosans. The structure of the products was analyzed by IR spectroscopy, and a method for estimating the degree of substitution by IR is proposed.
Polysilanes fonctionnels, 3. Synthèse d'α,ω‐bis(triméthylsilyl)oligo(méthylphénylsilane)s précurseurs des α,ω‐bis(triméthylsilyl)oligo(chlorométhyl‐silane)s. Charactérisation des heptaméthyl phényl‐2 trisilane et octaméthyl diphényl‐2,3 tétrasilane
Authors: Reyx Danièle , Martins José Manuel Natário , Campistron Irène , Noireaux Patrick
Published: April 2003

Low‐molecular‐weight organosilane polymers were prepared by sodium coupling of dichloro‐methylphenylsilane (1) with chlorotrimethylsilane (2). Gel permeation chromatography (GPC), IR and NMR (1H, 13C and 29Si) analysis of the crude product (3) were performed and compared with those of the isolated first oligomers, trisilane (3a) and tetrasilane (3b). The GPC characteristics, especially high resolution ones, in accordance with the α,ω‐bis(trimethylsilyl)‐oligo(methylphenylsilane) structure are compared with those of hydrocarbon polymers. The relations of the NMR characteristics of the methylphenylsilanediyl unit with the position along the chain and the configuration of the diads are approached. Some spectroscopic indications of the secondary structure are discussed.
Azo‐dyes as labels and as photoisomerizable units in chiral polyisocyanates
Authors: Müller Manfred , Zentel Rudolf
Published: April 2003

Polyisocyanates (nylon 1) with azochromophores in the side chains were prepared for the first time. For this purpose we have synthesized two new azo dyes containing isocyanato groups. The monomers were copolymerized with alkyl isocyanates to prepare chiral dye‐containing polyisocyanates. Optical rotatory dispersion and circular dichroism measurements support the helical polymer structure with predominantly one twist sense (due to the chiral side chains, P and M helices are diastereomeric). The completely reversible photochemical isomerization (trans to cis) of the azochromophores reaches high conversions (about 80%), but does not change the conformation of the main chain.
Photo and thermal oxidative polyrecombination of some captodative substituted methane derivatives
Authors: Tanaka Hitoshi , Tsunemine Naoki , Sato Tsuneyuki , Ota Tadatoshi
Published: April 2003

Photo and thermal polyrecombinations of some captodative substituted cyano‐, methoxycar‐bonyl‐, and phenylmethane derivatives were carried out using peroxides as oxidizing agents at room temperature and 130°C. Cyano‐substituted methane derivatives easily gave a polymer with a molecular weight of several thousands by both photo and thermal polyrecombinations. Especially, phenylacetonitrile afforded a polymer in good yield even under conditions at which diphenylmethane gave no polymer. Methyl methoxyacetate gave no polymer in the thermal reaction, but afforded a polymer when using high concentrations of an oxidizing agent in the photoreaction. 1H nuclear magnetic resonance and electron paramagnetic resonance spectra demonstrated the production of a polymer with a structure mainly consisting of 1,1‐disubstituted methylene units and the generation of a captodative substituted methyl radical in the reaction medium.
Regulation in free‐radical polymerization of vinyl acetate and synthesis of end‐group modified poly(vinyl alcohol)s
Authors: Sato Toshiaki , Okaya Takuji
Published: April 2003

A kinetical investigation on the consumption of a chain transfer agent in the free‐radical polymerization of vinyl acetate (VAc) was carried out. A new method to control the degree of polymerization of poly(vinyl acetate) (PVAc) or poly(vinyl alcohol) (PVA) as well as the end group content by continuous addition of a chain transfer agent, whose chain transfer constant is much larger than unity such as thiol compounds, during the course of VAc polymerization was proposed. The method using 2‐mercaptoethanol was applied to the preparation of lowmolecular‐weight PVAc and PVA with M̄w/M̄n ≈ 2.
Factors affecting the role of SiO2 in MgCl2‐supported Ziegler‐Natta copolymerization catalysts
Authors: Wang Jian‐Guo , Pang De‐Ren , Cheng Xiao‐Tan , Huang Bao‐Tong
Published: April 2003

This paper describes the roles of silica (SiO2), the butoxy ligand (OBu) and ethyl benzoate (EB) on ethylene/1‐butene copolymerization with MgCl2/SiO2‐supported titanium catalysts. The distribution of SiO2 and of the elements Mg and Ti was observed by means of an energy‐dispersed X‐ray micronalyzer on a scanning electron microscope (SEM). An inversed Si/Mg ratio results, at invariant Ti/Mg ratio andOBu content, in higher catalyst efficiency and higher comonomer incorporation, with a correspondingly decreased crystallinity of the copolymers. Thus, the inert carrier SiO2 favors copolymerizability, as seen from the values of the reactivity ratios. The copolymer compositional distribution is also affected by the SiO2 content, as seen from the DSC curves of the copolymers. As to the copolymer morphology, addition of SiO2 makes the copolymer particles larger and more uniform.
Stability of helical conformation and reactivity of optically active poly(triphenylmethyl methacrylate) in solution
Authors: Hosoda Masahiro , Schönhausen Ursula , Pino Piero
Published: April 2003

The stability of the helical conformation in optically active poly(triphenylmethyl methacrylate) (PTrMA) was investigated by heating the polymer solutions at 100°C. The optical rotation slowly disappeared with time, and some preliminary experiments showed that this phenomenon is not due to a typical racemization process, as it is accompanied by a loss of triphenylmethyl (Tr) groups due to secondary reaction. Experimental results in the presence of methanol indicated that the decrease of optical activity occurs according to first‐order kinetics and qualitatively methyl triphenylmethyl ether was isolated from the final solution. In order to explain the above results, full characterization of copolymers obtained by interrupting the methanolysis at different conversions was performed. As a working hypothesis, it was assumed that the reaction starts at the end of the helices with a Tr‐oxygen bond fission and the reaction proceeds along the chain mainly with formation of block copolymers consisting of one block of PTrMA and one block of a probably random methacrylic acid anhydride/methacrylic acid copolymer.
Pivalolactone, 1 interchange reactions with polypivalolactone
Authors: Tijsma Edze Jan , van der Does Leen , Bantjes Adriaan , Vulic Ivan
Published: April 2003

Ester interchange, alcoholysis, and acidolysis of polypivalolactone (PPVL) were studied by melting PPVL with bisphenol diacetates, 1, 4‐butanediol, or aromatic diacids. Interchange of PPVL with the diacetates and the diol occured readily, in particular in the presence of a titanium catalyst. Melting PPVL with 10 mol‐% of bisphenol‐Adiacetate in the presence of 0,5 wt.% tetrabutylorthotitanate resulted in an incorporation of 33% of the diacetate in the polymer chains, whereas the logarithmic viscosity number decreased by 81%. The ester interchange was suggested to proceed by an initial cleavage of ester bonds in the polymer chain of PPVL, resulting in the formation of shorter chains, followed by a reaction between the newly formed ester end‐groups and initially present hydroxyl chain ends. The acidolysis of PPVL with the diacids proved to be less effective; in the case of the acidolysis of PPVL with 10 mol‐% isophthalic acid, less than 1% of the diacid was incorporated in the polymer chains and a decrease in the logarithmic viscosity number of only 22% was found. Both the high stability of the ester bond in PPVL towards acids in general and the heterogeneity of these systems were supposed to cause the behaviour of PPVL with respect to acidolysis. The results concerning the interchange reactions with PPVL were compared with studies on other polyesters.
New polymers with coronand structure
Authors: Klemm Elisabeth , Alhakimi Gamil , Schütz Heidrun
Published: April 2003

New polymers with an alternating sequence of non‐polar aliphatic chains and coronands were synthesized via Diels‐Alder addition polymerization of bis(2‐pyrones) with bismaleimides; number‐average molecular weight M̄n: 18000 (vapour pressure osmometry), glass transition temperature T̄g: 250°C. The chemical structures of these polymers are supported by NMR spectra and model reactions. The reaction mechanism is discussed.
Inter‐ and intramolecular interactions in polyelectrolyte complex formation with polyampholytes
Authors: Kötz Joachim , Hahn Mathias , Philipp Burkart , Bekturov Esen A. , Kudaibergenov Sarkyt E.
Published: April 2003

Employing polyampholytes (inclusively polybetaines) of different chemical structure containing carboxylic groups and various basic nitrogen functions, homosymplex formation, as well as the competition between homo‐ and heterosymplex formation on addition of an appropriate polyelectrolyte, was investigated in dependence of pH and ionic strength by means of viscometry and turbidimetry. With most, but not with all, of the polyampholytes, the expected viscosity minimum at the isoelectric point, with its steepness depending on polyampholyte structure, was observed. Competition of homo‐ and heterosymplex formation at and near the isoelectric point is mainly governed by the pK values of the species involved, the level of zwitter‐ion formation of the polyampholyte and the effect of non‐Coulombic interactions, for example, via hydrogen bonds.
Synthesis of new cycloaliphatic epoxy resins and their crosslinking
Authors: Roig Antoni , Galià Marina , Cádiz Virginia , Mantecón Ana , Serra Angels
Published: April 2003

The reaction of cycloaliphatic and glycidylic oxiranes with primary amines was examined; no reaction was observed for the former. From unsymmetrical cycloaliphatic glycidylic imide derivatives and primary amines, it was possible to obtain well defined epoxy‐terminated biscycloaliphatic resins containing imide rings, which were identified by 13C NMR spectroscopy and elemental analysis. These epoxy resins were crosslinked by simple heating without hardeners and epoxide/amine‐networks were obtained. The action of phthalic anhydride as curing agent gave different results depending on the nature of the starting cycloaliphatic group. Thus, while tetrahydrophthalimide derivatives, N‐(2,3‐epoxypropyl)perhydro‐4,5‐epoxyphthalimide (2), underwent crosslinking, nadimide derivatives, N‐(2,3‐epoxypropyl)‐5,6‐epoxybicyclo [2.2.1] heptane‐2,3‐dicarboximide (1) did not react. Differential scanning calorimetry was used to follow the reaction; in all the cases, only the dynamic method was applied, in order to obtain kinetic parameters. The values for activation energies are comparable to those reported for the curing of epoxide systems.
A dilatometric study on antiplasticized and plasticized poly(vinyl acetate)
Authors: Knoglinger Johann , Schausberger Alois
Published: April 2003

By use of mercury dilatometry the volume expansion coefficients in the molten and in the glassy state, as well as the glass transition temperatures, were determined for poly(vinyl acetate) samples containing moderate quantities of soluble water‐free salts. These measurements were completed by the investigation of samples containing only plasticizer as additive or a combination of plasticizer and soluble water‐free salts. The flex energy and the hole formation energy were calculated from the theory of Gibbs and DiMarzio. One finds a correlation between the effectiveness of glass transition elevation by the salts and the effectiveness of the salts to support the thermal degradation of poly(vinyl acetate).
Zwitterionic polysoaps with reduced density of surfactant side groups
Authors: Anton Peter , Laschewsky André
Published: April 2003

Several zwitterionic polymers were prepared by radical homopolymerization of surfactant monomers which bear diallyl, diene or vinylcyclopropane moieties. These polymer systems were complemented by alternating copolymers of appropriate zwitterionic vinyl compounds. Thus, polymers with reduced (as compared with simple vinylic homopolymers, or statistical copolymers) and well defined density of surfactant side groups are obtained. The solubilities found for these polymers are dominated by polymer geometry rather than by the balance of hydrophilic and hydrophobic fragments, thus corroborating a “main‐chain spacer” model proposed recently. All water‐soluble polymers exhibit characteristic features of classical polysoaps, as shown by surface tension measurements and by solubilization of hydrophobic dyes. In contrast, the water‐insoluble copolymers are capable to form stable monolayers at the air‐water interface.
Mechanisms and kinetics of the anionic polymerization of acrylates, 3. Effect of lithium chloride and lithium tert‐butoxide on the oligomerization of tert‐butyl acrylate
Authors: Janata Miroslav , Lochmann Lubomír , Müller Axel H. E.
Published: April 2003

The influence of lithium tert‐butoxide (tBuOLi) and of lithium chloride on the oligomerization of tert‐butyl acrylate (tBuA) initiated by tert‐butyl α‐lithioisobutyrate (tBiB‐Li) was investigated. These additives affect both the kinetics and the product distribution. Whereas the addition of LiCl leads to a narrower molecular‐weight distribution (MWD) the presence of tBuOLi induces broader MWD's, characterized by a very high fraction of the dimer. Both additives decrease the rates of propagation to different degrees. These effects are discussed on the basis of the formation of aggregates and adducts, the lithiated dimer having a higher tendency to form aggregates than the other oligomers. The stability of the growth centres in this oligomerization is increased in the presence of these additives, tBuOLi exhibiting a much stronger effect than LiCl. The interaction of the lithiated dimer with the additives could not be demonstrated in the IR spectra of these mixtures.