bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid‐crystalline polyimides, 16. Chiral thermotropic copoly(ester‐imide)s based on isosorbide and N‐(4‐carboxyphenyl)trimellitimide
Authors: Kricheldorf Hans R. , Probst Nicolas
Published: April 2003

A series of chiral copoly(ester‐imide)s was prepared by polycondensation of N‐(4‐carboxy‐phenyl)trimellitimide with mixtures of isosorbide and phenylhydroquinone. All copolyesters are non‐crystalline. They form a cholesteric melt, when containing more than 50 mol‐% of phenyl‐hydroquinone. Containing 5 or 10 mol‐% of isosorbide a “Grand‐Jean” texture is detected above 300°C and 350°C, respectively.
Rigid rod polymers with regularly spaced silicon‐centered phthalocyanine units in the backbone
Authors: Lauter Ulrich , Schulze Margit , Wegner Gerhard
Published: April 2003

We describe the synthesis of new rigid rod polymers possessing a backbone of silicon phthalo‐cyanine units and stiff 4,4′‐dioxybiphenyl or 2,6‐dioxynaphthalene spacers. These modified phthalocyaninato‐polysiloxane derivatives are characterised by mass, absorption and 13C‐CPMAS spectroscopies, differential scanning calorimetry and X‐ray powder diffractometry. UV/VIS spectra show only slight differences to the corresponding phthalocyanine monomers, which indicates the absence of excited state interactions between the chromophores within the polymer backbone.
Polymerizations of ethylene and styrene initiated with trisiloxane‐bridged dinuclear titanium metallocene/MMAO catalyst systems
Authors: Lee Dong‐ho , Yoon Keun‐byung , Lee Eok‐hyung , Noh Seok‐kyun , Byun Gyu‐gum , Lee Chul‐soo
Published: April 2003

Two kinds of the trisiloxane‐bridged dinuclear titanium metallocene‐type complexes were synthesized. They are monocyclopentadienyl and biscyclopentadienyl dinuclear titanocenes with trisiloxane bridges. The above complexes with modified methylaluminoxane (MMAO) cocatalyst initiate the polymerizations of ethylene and styrene to produce high‐density polyethylene and syndiotactic polystyrene. In addition, a copolymer of ethylene and styrene was obtained.
Pressure and temperature dependence of the propagation rate coefficient in free‐radical polymerization of butyl methacrylate
Authors: Bergert Ute , Buback Michael , Heyne Joachim
Published: April 2003

The propagation rate coefficient in free‐radical bulk polymerization of butyl methacrylate has been studied at temperatures between −10°C and 60°C up to a maximum pressure of 2 000 bar. The data were obtained by means of the PLP‐GPC technique which combines pulsed‐laser polymerization with product analysis by gel‐permeation chromatography.
Poly[2,4‐bis(chloroamino)‐6‐vinyl‐1,3,5‐triazine] as a recyclable oxidizing agent of alcohols
Authors: Kondo Shuji , Kawasoe Shinya , Ohira Mari , Atarashi Tadashi , Ikeda Kazahisa , Kunisada Hideo , Yuki Yasuo
Published: April 2003

A polymer containing dichlorotriazine moiety was prepared readily by the reaction of poly(2,4‐diamino‐6‐vinyl‐1,3,5‐triazine) with tert‐butyl hypochlorite. This polymer oxidizes various primary and secondary alcohols to the corresponding carbonyl compounds under mild conditions, while the reaction of the monomeric analogue N,N′‐dichloroacetoguanamine with alcohols does not proceed. The polymer reagent can be handled easily and recycled for further use.
The structure of azomethine block copolymers from X‐ray powder diffraction data
Authors: Brückner Sergio , Destri Silvia , Porzio William
Published: April 2003

The crystal structure of a block copolymer, constituted by the periodic alternation of three thienyl‐ and two phenyl fragments separated by azomethine residues, has been determined and refined on powder X‐ray diffraction data. Polymers of this kind are particularly interesting because of some evidences of electronic confinement, i. e. possible realization of multiple‐quantum‐dot sequences have been detected. Although the quality of the measured profile was poor, a molecular model is proposed giving a satisfactory agreement with the observed data.
Effect of catalyst aging on catalyst activity and stereospecificity for MgCl2/ethyl benzoate or dioctyl phthalate/TiCl4‐triethylaluminium for propene polymerization
Authors: Yang Chun B. , Hsu Cheng C.
Published: April 2003

The aging of the MgCl2/dioctyl phthalate (DOP) or ethyl benzoate (EB)/TiCl4 catalyst was studied. Because of the strong complexation of DOP with the catalyst, only a small fraction of DOP was extracted by cocatalyst triethylaluminium (TEA) during aging, resulting in converting some highly isospecific sites into aspecific ones. No change of the overall number of sites was detected. EB, on the other hand, could be readily removed by TEA, resulting in a large increase in aspecific sites. Clustering of those sites facilitated catalyst deactivation.
Syndiospecific polymerization of styrene with arene titanium(II) complexes as catalyst precursors
Authors: Kaminsky Walter , Park Young‐Whan
Published: April 2003

The divalent titanium compounds [(η6‐C6H5Me)Ti(Cl2AlCl2)2] (1) and [(η6‐C6Me6)Ti(Cl2AlCl2)2] (2) are syndiospecific catalysts in the polymerization of styrene when activated with methylaluminoxane. The polystyrene is of exceptionally high molecular weight.
Heterogeneity of active species in metallocene catalysts
Authors: Soga Kazuo , Uozumi Toshiya , Arai Takashi , Nakamura Shuji
Published: April 2003

From a detailed analysis of poly[ethylene‐co‐(1‐hexene)] obtained with typical metallocene catalysts, it was found that metallocene catalysts give two kinds of copolymers which differ in crystallinity. It may be thus plausible to assume that there are two kinds of active species in metallocene catalysts.
Solubilization of polyaniline in water by interpolymer complexation
Authors: Liao Yun‐Hsin , Levon Kalle , Laakso Jukka , Österholm Jan‐Erik
Published: April 2003

Water solubility of electro‐active polymers in their doped state may provide a possibility for environmentally feasible manufacturing processes. Because previous results in this direction require expensive modifications or impractical template polymerization methods, we created a simple method of mixing components with a large molecular weight difference. The polymer which acts as an acidic dopant and provides water solubility, has to have the higher molecular weight. The formed complex resembles a block copolymer but in this case the polyaniline block is attached to the sulfonated polystyrene chain by strong physical interactions instead of chemical end‐to‐end linkage.
The effect of mixing time on the morphology and physical properties of liquid crystalline polymer based blends
Authors: Zaldua Ane M. , Muñoz M. Eugenia , Peña Juan J. , Santamaría Anton
Published: April 2003

Rheological and thermal analysis results of blends of a thermotropic copolyesteramide and polyarylate of bisphenol A depend on the thermo‐mechanical treatment during mixing. The changes observed as mixing time increases are the following: (a) melt viscosity and loss factor increase, (b) glass transition temperature decreases. The morphological analysis of the blends shows the inability of the treated blends to form an oriented liquid crystalline polymer (LCP) phase, which explains the observed viscoelastic properties.
A fast catalyst system for the ring‐opening polymerization of cyclosiloxanes
Authors: Molenberg Aart , Möller Martin
Published: April 2003

Methanol, in combination with a non‐ionic phosphazene base, was used to initiate the polymerization of octamethylcyclotetrasiloxane. In bulk, an instantaneous and large increase in viscosity was observed upon addition of the initiator. In toluene solution, the equilibrium state was reached in approximately 1 min. In addition to its high polymerization rate, another advantage of this system, as compared with e.g. alkali metal hydroxides, is that it is homogeneous.
A method for the prediction of metallocene‐type catalyst activity in olefin (co)polymerisation reactions
Authors: Pieters Paul J. J. , van Beek Johannes A. M. , van Tol Maurits F. H.
Published: April 2003

The use of ultraviolet/visible spectroscopy (UV‐Vis) for the prediction of metallocene catalyst potential for the polymerisation of olefins is described. Upon addition of methylaluminoxane (MAO) to rac‐[C2H4(1‐indenyl)2ZrCl2] ([Al]/[Zr] = 200) the ligand‐to‐metal charge transfer band shows a hypsochromic shift while a bathochromic shift is observed when more MAO is added ([Al]/[Zr] = 2000). These shifts can be explained by assuming that methylation of the zirconocene by MAO occurs in the case of [Al]/[Zr] = 200 while a cationic complex, the active catalytic system, is formed upon addition of more MAO, e.g., [Al]/[Zr] = 2000.
A novel synthesis of linear high‐molecular‐weight poly(4‐vinylphenol) and poly[styrene‐co‐(4‐vinylphenol)]
Authors: Xiang Maoliang , Jiang Ming , Feng Linxian
Published: April 2003

A novel synthesis of linear high‐molecular‐weight poly(4‐vinylphenol) (PVPh) and poly[styrene‐co‐(4‐vinylphenol)] (STVPh, 2) via demethylation reaction is developed. The parent polymers, poly(4‐methoxystyrene) and poly[styrene‐co‐(4‐methoxystyrene)] produced by free‐radical polymerization, are converted to PVPh and STVPh (2), respectively, by being treated with trimethylsilyl iodide (TMSI) at room temperature. Both 1H NMR and 13C NMR data show that methoxy is completely cleaved and converted to hydroxy after hydrolysis without crosslinking and other side reactions. In addition, size‐exclusion chromatography data show that no chain scission occurs during group conversion.
Evidence of interchange reaction in a poly(ethylene 2,6‐naphthalenedicarboxylate)/poly(bisphenol‐A carbonate) blend
Authors: Fernandez‐Berridi Maria Jose , Iruin Juan Jose , Maiza Iñaki
Published: April 2003

The existence of interchange reactions in a poly(ethylene 2,6‐naphthalenedicarboxylate)/poly(bisphenol‐A carbonate) blend (PEN/PC) has been proven by means of solubility tests, DSC and FTIR and NMR spectroscopies. In addition, DSC results reveal that these interchange reactions are responsible for the miscibilization of the initially immiscible system.
Polymerization of ethylene over metallocenes confined inside the supercage of a NaY zeolite
Authors: Woo Seong Ihl , Ko Young Soo , Han Taek Kyu
Published: April 2003

Metallocene catalysts entrapped inside the supercages of NaY zeolite were prepared by reacting NaY with methylaluminoxane (MAO) or trimethylaluminium (TMA) and then with Cp2ZrCl2 (Cp: cyclopentadienyl) or Cp2TiCl2. NaY/MAO/Cp2ZrCl2 and NaY/MAO/Cp2TiCl2 catalysts could polymerize ethylene. The amount of additional MAO for the polymerization was lowered to a mole ratio of Al/Zr of 186. Molecular weights and melting points of polyethylene polymerized with NaY‐supported catalysts were higher than those of polyethylene obtained with homogeneous metallocene catalysts. It could be confirmed by extraction experiments that the metallocene catalyst was confined securely inside the supercage of the NaY zeolite.
Polymeric substitution in a pH oscillator
Authors: Giannos Steven A. , Dinh Steven M. , Berner Bret
Published: April 2003

The iodate pH oscillator, which oscillates between pH 6.5 and 4.0, is reproducible in a semibatch reactor. pH oscillations of similar period and amplitude were observed when poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) was substituted for sulfuric acid. Therefore, a polymer may be used as an alternative reagent, where the polymer actively participates in the reaction instead of serving as an inert reaction medium.
Silica‐supported metallocenes: stereochemical comparison between homogeneous and heterogeneous catalysis
Authors: Sacchi Maria Carmela , Zucchi Debora , Tritto Incoronata , Locatelli Paolo , Dall'Occo Tiziano
Published: April 2003

Propylene was polymerized in the presence of the isospecific Et(Ind)2ZrCl2 (Et: ethylene, Ind: indenyl) and the aspecific (Ind)2ZrCl2 complexes in solution and anchored to SiO2 and SiO2/MAO (MAO: methylaluminoxane) supports. From the stereochemical analysis of the polypropene samples obtained it can be deduced that (i) the same active species is formed when a metallocene is in solution and when it is anchored to the SiO2/MAO support and (ii) a completely different active species is formed when the metallocene is anchored to the silica. The fact that both systems Et(Ind)2ZrCl2SiO2 and (Ind)2ZrCl2SiO2 produce the same prevailingly isospecific polymer suggests that only isospecific centers are formed in this case, independently of the metallocene stereochemical structure.
Study of polystyrene‐poly(tert‐butyl acrylate) heteroarm star copolymers in dilute solutions
Authors: Tsitsilianis Constantinos , Kouli Ourania
Published: April 2003

Heteroarm star copolymers with polystyrene and poly(tert‐butyl acrylate) arms are studied in dilute solutions by means of viscometry and static light scattering. In a weakly selective solvent a segregated‐nonsegregated conformational transition is observed induced by temperature change. In a strongly selective solvent association phenomena take place and the heteroarm star molecules form multimolecular micelles.
Study of the chain transfer reaction by hydrogen in the initial stage of propene polymerization
Authors: Mori Hideharu , Tashino Kunihiko , Terano Minoru
Published: April 2003

The chain transfer reaction by hydrogen in the initial stage of propene polymerization with MgCl2‐supported Ziegler catalyst was studied by means of the stopped‐flow polymerization. The yield and molecular weight of polypropene produced in the initial stage were not affected by hydrogen. Thus, the method was successfully applied to find the region in which hydrogen does not act as a chain transfer reagent. On the other hand, a chain transfer reaction proceeded in the initial stage of polymerization by using Zn(C2H5)2. Furthermore, when the catalyst was treated with Al(C2H5)3 before polymerization, the molecular weight of the produced polymer was decreased by using hydrogen, indicating that it acted as a chain transfer agent for the catalyst modified by pre‐treatment.
Ferroelectric liquid‐crystalline elastomers with short switching times
Authors: Brehmer Martin , Zentel Rudolf
Published: April 2003

The crosslinking of ferroelectric liquid‐crystalline (LC) polysiloxanes — performed within the region of microphase separation — allows the preparation of LC‐elastomers which combine macroscopic form stability (insolubility) with nearly unchanged switching time (compared to the uncrosslinked polymers).
Polymerization of cyclic monomers, 1. Radical polymerization of unsaturated spiro orthocarbonates
Authors: Moszner Norbert , Zeuner Frank , Rheinberger Volker
Published: April 2003

7‐Methyl‐2‐methylene‐ (1) and 7‐methyl‐2,3‐dimethylene‐1,4,6,9‐tetraoxaspiro[4.4]nonane (2) were synthesized and characterized by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. Radical polymerization of the spiro orthocarbonates (SOC) 1 and 2 show that they undergo primarily vinyl polymerization with a low degree of ring‐opening reaction. Homopolymerization of 2 at 120°C with di‐tert‐butyl peroxide gives a transparent crosslinked polymer and the polymerization generates a 12,5% shrinkage in volume.
Strain‐induced director reorientation in nematic liquid single crystal elastomers
Authors: Kundler Isabel , Finkelmann Heino
Published: April 2003

The strain‐induced director reorientation process in nematic liquid single crystal elastomers is investigated for the case of an arbitrary angle between the original director and the external stress axis. If the mechanical stress is applied perpendicular to the original director axis, the reorientation process sets in at a threshold strain. The mesogens are realigning ‘clockwise’ or ‘counter‐clockwise’ towards the axis of external stress, simultaniously the monodomain structure is distorted and a periodic pattern formation is observed. If the mechanical stress is applied obliquely with respect to the original director axis, a uniform director reorientation is obtained with retention of the monodomain structure. No threshold strain is observed for this process. The existence of a threshold strain in the case of a perpendicular arrangement of the director to the external stress axis can be understood as a consequence of the distortion of the monodomain structure.
Control of photochemistry of stilbazolium ion by adsorption to poly(potassium vinylsulfate) and to hectorite clay
Authors: Nakahira Takayuki , Hama Masayuki , Fukuchi Osamu , Okamura Toshiya , Iwabuchi Susumu , Shimazu Shogo , Uematsu Takayoshi , Kikuchi Hideo
Published: April 2003

Adsorption or intercalation of trans‐1‐methyl‐4‐(2‐phenylvinyl)pyridinium ion (stilbazolium ion, SB (1)) to a polyelectrolyte, i. e., poly(potassium vinylsulfate) (PVSK), and to a hectorite clay is studied and its effect on the photochemistry of SB examined. trans‐cis Photoisomerization of SB molecularly adsorbed to PVSK proceeds efficiently as with free SB in water, while that of SB molecularly intercalated in the clay is markedly suppressed. Photodimerization proceeds efficiently with SB intercalated in the clay in the aggregated form. Overall photodecoloration, however, proceeds more efficiently with SB adsorbed to PVSK under multiple adsorption conditions apparently due to the higher mobility of PVSK‐adsorbed SB compared to that of clay‐intercalated SB.
Dielectric properties of a hydrogen‐bonded liquid‐crystalline side‐chain polymer
Authors: Araki Kazuo , Kato Takashi , Kumar Uday , Fréchet Jean M. J.
Published: April 2003

The dielectric properties of a hydrogen‐bonded side‐chain liquid‐crystalline polysiloxane have been examined over wide ranges of frequency and temperature. This polymer has a side‐chain mesogenic moiety consisting of a benzoic acid and a stilbazole. The observed dielectric loss curves contain a component from dipole reorientation of the hydrogen‐bonded mesogenic group. It has been found to be possible that, using electrical and thermal treatments, such a polymer built through hydrogen bonding can align homeotropically.
Synthesis of novel glycopeptide‐polyoxazoline block copolymers by direct coupling between living anionic and cationic polymerization systems
Authors: Tsutsumiuchi Kaname , Aoi Keigo , Okada Masahiko
Published: April 2003

A novel glycopeptide‐containing block copolymer, poly[O‐(tetra‐O‐acetyl‐β‐D‐glucopyranosyl)‐L‐serine]‐block‐poly(2‐methyl‐2‐oxazoline) (5), was synthesized by mutual termination of living polymerizations of a sugar‐substituted α‐amino acid N‐carboxyanhydride (NCA) (1) and 2‐methyl‐2‐oxazoline (3). 5 was deacetylated to provide the glycopeptide‐polyoxazoline block copolymer, poly[O‐(β‐D‐glucopyranosyl)‐L‐serine]‐block‐poly(2‐methyl‐2‐oxazoline) (6).
Miscible blends containing a crystallizable component: poly(vinyl alcohol)/poly(ethyleneimine)
Authors: Guo Qipeng
Published: April 2003

Blends of poly(vinyl alcohol) (PVAI) with poly(ethyleneimine) (PEI) were prepared by casting from a common solvent. All blends show a single, composition dependent glass transition temperature (Tg), indicating that the blends are miscible in the amorphous state and in the melt. The overall crystallization rate of PVAI in the blend decreases with increasing PEI content. The crystallinity index of PVAI in the blend does not decrease greatly with PEI content up to a composition of 70/30 PVAI/PEI, since the Tg of the crystallizable component PVAI is larger than that of the non‐crystallizable component PEI. The Tg of the system PVAI/PEI decreases with increasing PEI content. The interaction parameter B of the two polymers in the melt was found to be −24 J/cm3.
A metallocene catalyst system for olefin polymerization using a heteropolyacid as the counter‐anion
Authors: Soga Kazo , Uozumi Toshiya , Kishi Naoya
Published: April 2003

Polymerization of ethylene and propene were conducted with bis(cyclopentadienylzirconium dichloride) (Cp2ZrCl2) and ethylenebis(1‐indenyl)zirconium dichloride (Et(Ind)2ZrCl2) combined with trialkylaluminium compounds using heteropolyacids as the counter‐anions, giving linear polyethylene and isotactic polypropene, respectively. No polymer was obtained when using Cp2Zr(CH3)2 instead of Cp2ZrCl2. The mechanism of the formation of active species is briefly discussed on the basis of these results.
X‐ray photoelectron spectroscopic study of poly[4,4′‐isopropylidenebis(1,4‐phenyleneoxyethylene) diacrylate] photocured in the presence of a fluorine containing monomer
Authors: Pollicino Antonino , Siracusa Valentina , Bongiovanni Roberta , Priola Aldo
Published: April 2003

A preliminary X‐ray photoelectron spectroscopic (XPS) investigation on poly[4,4′‐isopropylidenebis(1,4‐phenyleneoxyethylene) diacrylate] samples obtained by photocuring on several substrates in the presence of a fluorine containing acrylic monomer is reported. Quantitative calculations based on F1s/C1s area ratios and C1s peak fitting show a noticeable fluorine surface enrichment that ranges, depending on the substrate, from 17 wt.‐% to 59 wt.‐% of fluorine containing moiety. The calculations also reveal the presence of a concentration gradient at the surface.
A latent entanglement model for the draw of semicrystalline polymers
Authors: Ottani Stefano , Porter Roger S.
Published: April 2003

A novel molecular model, the latent entanglement, is proposed to explain the relationships between ductilities of polyethylene reactor powders and different conditions of synthesis. According to Hoffman's variable cluster model, irregularities in the crystallite fold surface increase as the synthesis temperature is decreased. The concept of latent entanglement stems from the potentiality of these defects to convert into active entanglements when the involved chain segments are drawn out of the crystals.
Polystyrene‐supported metallocene catalysts for olefin polymerizations
Authors: Nishida Hiroto , Uozumi Toshiya , Arai Takashi , Soga Kazuo
Published: April 2003

Several kinds of polystyrene‐supported metallocene catalysts were prepared and used in the polymerizations of propylene and ethylene with methylaluminoxane (MAO) as cocatalyst. It was found that these catalysts are stable even at 70°C. They display fairly high activities when the polymerizations are conducted at high temperatures.
Temperature‐responsive swelling and deswelling of the copolymers from vinyl ether of ethylene glycol and butyl vinyl ether
Authors: Kudaibergenov Sarkyt E. , Nurkeeva Zauresh S. , Mun Grigorii A. , Ermukhambetova Bayana B. , Nam Irina K.
Published: April 2003

Linear and crosslinked copolymers of a vinyl ether of ethylene glycol (2‐hydroxyethyl vinyl ether, (1)) and butyl vinyl ether (2) are synthesized by α‐irradiation polymerization. It is shown that the linear copolymers exhibit a phase separation phenomenon in dependence of the temperature due to the destruction of hydrogen bonds and the enhancement of hydrophobic interaction in aqueous solution. The processes of reversible swelling or shrinking upon temperature change are demonstrated for polymer networks.
Non‐ionic surfactant effects on polymer diffusion in poly(butyl methacrylate) latex films
Authors: Kawaguchi Seigou , Odrobina Ewa , Winnik Mitchell A.
Published: April 2003

The influence of non‐ionic surfactant molecules on polymer interdiffusion in poly(butyl methacrylate) (PBMA) latex films was investigated using the non‐radiative energy transfer technique. It was found that nonylphenoxypoly(ethylene oxide) surfactants such as NP‐20 and NP‐100 act as plasticizers to enhance the polymer diffusion rate. The increase in diffusion rate with the increase in surfactant concentration is in complete accord with the Fujita‐Doolittle free volume model. This suggests that by the time the latex dispersion is dry, the surfactant has diffused uniformly into the latex polymer.
Synthesis of poly(L‐lactide)‐block‐polyisobutylene‐block‐poly(L‐lactide), a new biodegradable thermoplastic elastomer
Authors: Sipos László , Zsuga Miklós , Deák György
Published: April 2003

The anionic ring‐opening polymerization of L‐lactide was initiated by dipotassium‐poly‐isobutylene‐alcoholate telechelic polymer to yield poly(L‐lactide)‐block‐polyisobutylene‐block‐poly(L‐lactide) triblock copolymer, a partially biodegradable thermoplastic elastomer. The pure triblock copolymer was obtained by gradient column chromatography on silica gel. The molar mass and molar mass distribution of the block copolymer was ascertained by SEC and quantitative 1H NMR spectroscopy. It showed two glass transitions and microphase separation.
Study on the sorption of water into epoxy resins by means of electrochemical impedance spectroscopy
Authors: Luo Xiao‐Wen , Yun Ze‐Yong , Li Shan‐Jun , Zhou Wei‐Fang
Published: April 2003

In this work the relationship between structure and water sorption for epoxy films was studied using electrochemical impedance spectroscopy. It is shown that the electrochemical impedance spectroscopy can be applied to obtain information about the amount of water absorbed by the epoxy film and the water permeation through the film, while only the amount of water absorbed is obtained from the “sorption method”. The free volume is the decisive factor for both the amount of water in the cured epoxy film and water permeation through the film.
Lanthanoid isopropoxide as a novel initiator for anionic polymerization of isocyanates
Authors: Fukuwatari Naoko , Sugimoto Hiroshi , Inoue Shohei
Published: April 2003

Lanthanum isopropoxide was found to serve as a novel anionic initiator for the polymerization of hexyl isocyanate affording poly(hexyl isocyanate) with very high molecular weight (Mn > 106) under appropriate conditions. Other lanthanoid alkoxides, such as samarium, ytterbium and yttrium isopropoxides, also brought about the polymerization of hexyl isocyanate. Butyl, isobutyl, octyl and m‐tolyl isocyanates also underwent the polymerization reaction to form the corresponding polymers by using lanthanum isopropoxide as initiator, while polymerizations of tert‐butyl and cyclohexyl isocyanates with lanthanum isopropoxide did not occur under identical conditions.
Inversion of stereoselectivity in a metallocene catalyst
Authors: Shiomura Tetsunosuke , Asanuma Tadashi , Inoue Norihide
Published: April 2003

Inversion of stereoselectivity of a particular metallocene (Me2Si(Flu) (N‐t‐Bu)ZrCl2) (Me: methyl, Flu: fluorenyl, t‐Bu: tert‐butyl) from syndiospecific into isospecific was observed by changing the cocatalyst from methylaluminoxane (MAO) to [Ph3C]+ [B(C6F5)4]−/AliBu3 (iBu:isobutyl). The change of the solvent‐separated ion pair (in case of MAO as cocatalyst) into the contact ion pair (in case of the more polar and less bulky borate anion) was proposed as the plausible explanation of this phenomenon.
Synthesis of adjustable poly(vinyl chloride) networks
Authors: Reinecke Helmut , Hidalgo Manuel , Mijangos Carmen
Published: April 2003

2‐Mercaptobenzyl alcohol and 4‐mercaptobenzyl alcohol were synthesized in good yields starting form thiosalicylic acid and p‐toluenesulfonic acid, respectively. Poly(vinyl chloride) (PVC) reacts selectively with the thiol group of these bifunctional compounds leading to modified PVC with free hydroxy groups. In a second step the polymer chains can be partially crosslinked by reaction with hexamethylene diisocyanate. According to the degree of PVC modification, the network density of the resulting elastomers is freely adjustable.
Characterization of pyrene end‐labeled poly(ethylene glycol) by high resolution MALDI time‐of‐flight mass spectrometry
Authors: Whittal Randy M. , Li Liang , Lee Sam , Winnik Mitchell A.
Published: April 2003

We report the characterization of a sample of poly(ethylene glycol) (PEG, Mn = 3841, Mw/Mn = 1.01), and its derivative end‐labeled with pyrenebutyrate groups, using high resolution MALDI time‐of‐flight mass spectrometry. A matrix of 2‐(4‐hydroxyphenyl‐azo)benzoic acid containing a trace of either sodium chloride or potassium chloride was employed for laser desorption. Peaks due to the sodium or potassium cationized polymers were obtained, equally spaced at 44 mass units apart. For the pyrenebutyrate diester, the analysis shows that 80 ± 2% of the chains were doubly labeled, with the ramaining chains containing only a single pyrene group. Molecular weight determinations for both sets of samples were entirely consistent with size‐exclusion chromatography measurements, but were obtained with greater accuracy and less ambiguity about the influence of the end groups on the hydrodynamic radius of the polymer.
Molecular imprinting of the endogenous neuropeptide Leu5‐enkephalin and some derivatives thereof
Authors: Andersson Lars I. , Müller Ralf , Mosbach Klaus
Published: April 2003

We have undertaken the molecular imprinting of Leu5‐enkephalin, and derivatives related to this endogenous neuropeptide, in highly cross‐linked methacrylic acid/ethylene dimethacrylate copolymers. The underivatized enkephalin peptide yielded polymers with poor recognition abilities, since the imprinting of this compound had to be performed using dimethyl sulfoxide, which was found to interfere with the imprint inducement, as the solvent of polymerisation. In order to circumvent this problem, the amino‐ and carboxy‐protected derivatives Boc‐Leu5‐enkephalin and Leu5‐enkephalin anilide, which are soluble in apolar solvents, were investigated as alternative imprint molecules. Both compounds led to polymers which are highly specific for the imprint species. The anilide derivative was shown to be a good substitute for the free peptide since the resultant polymers showed efficient recognition of the parent enkephalin structure.
Study of the thermal degradability of poly(α‐methylstyrene) with modified end groups
Authors: Nagasaki Yukio , Yamazaki Noriyuki , Kato Masao
Published: April 2003

To induce degradabilities in polymers in response to environmental conditions, endm odification reactions of poly(α‐methylstyrene) (PMS) derivatives were carried out. 2‐Phenylallyl halide derivatives such as 2‐phenylallyl bromide, 2‐(p‐tolyl)allyl bromide, and α‐trifluoromethylstyrene were found to be suitable end‐modification agents. For example, the ω‐2‐phenylallyl‐PMS derivative was prepared with almost quantitative functionality by the reaction of the living PMS derivative with 2‐phenylallyl bromide. In a similar way, ω‐3,3‐difluoro‐2‐phenylallyl‐ and ω‐2‐(4‐toly)allyl‐PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: ω‐hydrogen‐ > ω‐3,3‐difluoro‐2‐phenylallyl‐ > ω‐2‐phenylallyl‐ > ω‐2‐(p‐tolyl)allyl‐PMS. Actually, the onset temperature of ω‐2‐(p‐tolyl)allyl‐PMS derivatives was 50°C lower than that of ω‐H‐PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2‐phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism.
Anionic polymerization of oxirane in the presence of the polyiminophosphazene base t‐Bu‐P4
Authors: Eßwein Beate , Steidl Norbert M. , Möller Martin
Published: April 2003

The use of the polyiminophosphazene base t‐Bu‐P4 (1) for the anionic polymerization of ethylene oxide is described. Polymerization initiated by a monoalkoxide of the protonated base leads to well‐defined poly(ethylene oxide)s with low polydispersity (Mw/Mn ≈ 1.1). Furthermore, graft copolymers of poly[ethylene‐co‐(vinyl alcohol)] (PEVA) with poly(ethylene oxide) and a star macromolecule were synthesized from multifunctional polyalkoxides in high yields.
Ion‐selective gel that is sensitive to temperature, pH, and redox reactions
Authors: Bromberg Lev , Levin Gideon
Published: April 2003

In this communication we describe ion‐selective poly[N,N‐diethylacrylamide‐co‐(2‐hydroxyethyl methacrylate)] gels functionalized by dialkyldithiophosphate group due to ester exchange reaction with the HEMA moieties. The gels are sensitive to temperature and pH in the surrounding aqueous solutions. Redox reactions cause gels to shrink due to crosslinking via disulfide bond formation.
(η3‐allyl)palladium(II) catalysts for the addition polymerization of norbornene derivatives with functional groups
Authors: Reinmuth Annette , Mathew Joice P. , Melia Jennifer , Risse Wilhelm
Published: April 2003

Cycloaliphatic polyolefins with functional groups were prepared by the Pd(II)‐catalyzed addition polymerization of norbornene derivatives. Homo‐ and copolymers containing repeating units based on bicyclo[2.2.1] hept‐5‐en‐2‐ylmethyl decanoate (endo/exo‐ratio = 80/20), bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid methyl ester (exo/endo = 80/20), bicyclo[2.2.1]hept‐5‐ene‐2‐methanol (endo/exo = 80/20), and bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid (100% endo) were prepared in 49–99% yields with {(η3‐allyl)Pd(BF4)} and {(η3‐allyl)Pd(SbF6)} as catalysts. The catalyst containing the hexafluoroantimonate ion was slightly more active than the tetrafluoroborate based Pd‐complex.
Effect of tetraalkylammonium salts on the tacticity of poly(methyl methacrylate), 2.. Initiation by potassium tert‐butoxide
Authors: Novakov Christo P. , Tsvetanov Christo B.
Published: April 2003

The anionic polymerization of methyl methacrylate was carried out in the presence of potassium tert‐butoxide (t‐BuOK)/quaternary ammonium salts (QAS) in toluene and tetrahydrofuran at −60°C. It was found that in toluene some QAS additives substantially increase the syndiotacticity of poly(methyl methacrylate). Two types of QAS were distinguished, quite different in their action. The addition of QAS with one or two longchain alkyl groups (>C12), does not change significantly the mode of the monomer addition, whereas the polymerization in the presence of tetraalkylammonium salts with four equal substituents and dimethyldidodecylammonium bromide yields predominantly a syndiotactic polymer with high conversion and comparatively low polydispersity (M̄w/M̄w = 1.3−1.5). In some cases QAS additives are more effective modifiers than cryptand [2.2.2].
Hard domain compression of triblock‐copolymer gels by high pressure X‐ray small‐angle scattering
Authors: Lorenzen Maren , Bösecke Peter , Riekel Christian , Reynders Karen , Reynaers Harry , Overbergh Noel
Published: April 2003

Small‐angle X‐ray scattering using synchrotron radiation at pressures up to 700 MPa has been performed on triblock‐copolymer gels, polystyrene‐rubber‐polystyrene with poly(ethylene/butylene) as the rubber mid‐blocks. A 2‐stage pressure behaviour could be verified by comparison of the experimental data with the Tait‐equation and a model of pressure screening.
Ethylene polymerization with ansa‐metallocene systems rac‐(Me2SiOSiMe2)[Ind]2ZrCl2‐MAO and rac‐(Me2SiOSiMe2)[IndH4]MtCl2‐MAO; (Mt = Zr, Ti)
Authors: Liang Bo , Li Yong , Xie Guanghua
Published: April 2003

Ethylene was polymerized in toluene using methylalumoxane (MAO) activated rac‐(Me2SiOSiMe2)[Ind]2ZrCl2 (1) and rac‐(Me2SiOSiMe2)[IndH4]2MtCl2 (Mt = Zr (2); Mt = Ti (3)). All three catalyst systems polymerize ethylene with high activity. The molecular weight of polymer produced with zirconocene (1) was up to a weight‐average molecular weight M̄w = 1.1 × 106 at low polymerization temperature (<20°C) under atmospheric pressure. The titanocene catalyst 3 shows lower activity and produced lower molecular weight polyethylene than zirconocenes 1 and 2. Replacement of aromatic rings in 1 by cyclohexane rings, leading to 2, increases activity and reduces molecular weight. The catalyst systems show a dependency of the activity on temperature.
Double‐stimuli‐responsive degradable hydrogels: interpenetrating polymer networks consisting of gelatin and dextran with different phase separation
Authors: Yamamoto Nobuyuki , Kurisawa Motoichi , Yui Nobuhiko
Published: April 2003

Biodegradable interpenetrating polymer network (IPN)‐structured hydrogels consisting of gelatin (Gtn) and dextran (Dex) were prepared by sequential crosslinking reactions of Gtn and methacryloylated Dex. Phase separation of these hydrogels is dominated by preparation conditions, i.e., above or below the sol‐gel transition temperature (Ttrans) of Gtn. Enzymatic degradation by either α‐chymotrypsin or dextranase is hindered for the IPN‐structured hydrogel prepared below Ttrans whereas this hydrogel is perfectly degradable in the presence of both enzymes. Such a specific feature of enzymatic degradation was not observed for the hydrogel prepared above Ttrans. These results suggest that double‐stimuli‐responsive degradation of IPN‐structured hydrogels is related to their phase separation.
Mechanism of the anionic copolymerization of anhydride‐cured epoxies – analyzed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS)
Authors: Leukel Jörg , Burchard Walther , Krüger Ralph‐Peter , Much Helmut , Schulz Günter
Published: April 2003

The mechanism of the strictly alternating anionic copolymerization of phenyl glycidyl ether (PGE) and phthalic anhydride (PA) was initiated by various imidazoles. Because of the strictly alternating copolymerization polyesters with a repeating unit of PGE‐PA were obtained. The mechanism of the reaction was analyzed by means of matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). With this technique the molar masses of the oligomers, the molar mass of the repeating unit, the weight‐average molar mass M̄w and the number‐average molar mass M̄n, their ratio M̄w/M̄n and the residual molar mass could be calculated. The strictly alternating copolymerization was easy to prove because the molar masses of PGE and PA are slightly different. The question whether the initiator remains chemically bound during the whole reaction could be solved. To this end polyesters obtained by initiation with various imidazoles with different molar masses were synthesized. The calculated residual molar masses correspond exactly to the molar masses of the imidazoles.
Synthesis of a dibenzylchitin‐type polysaccharide by acid‐catalyzed polymerization
Authors: Kadokawa Jun‐ichi , Watanabe Yoshikatsu , Karasu Masa , Tagaya Hideyuki , Chiba Koji
Published: April 2003

This paper describes the polymerization of 2‐methyl‐(3,6‐di‐O‐benzyl‐ 1,2‐dideoxy‐α‐D‐glucopyrano)‐[2,1‐d]‐2‐oxazoline (1) with an acid catalyst. The polymerization proceeds involving stereoregular glycosylation to give polysaccharide 2. The polymer structure, 2‐acetamido‐3,6‐di‐O‐benzyl‐2‐deoxy‐(l→4)‐β‐D‐glucopyranan was determined by means of 1H NMR, 13C NMR, and IR spectra as well as elemental analysis. The molecular weight was at most 4900 (degree of polymerization ≈ 13).
A new method for the polymerization of methyl methacrylate
Authors: Reetz Manfred T. , Herzog H. Martin , Könen Werner
Published: April 2003

Dialkyl iodomethylmalonates in the presence of tetrabutylammonium iodide initiate the polymerization of methyl methacrylate, but not of methyl acrylate or acrylonitrile. Typically, at 60°C in 1,3‐dimethyltetrahydro‐2‐1H‐pyrimidone (DMPU) as the solvent, poly(methyl methacrylate (PMMA)) is obtained in the number‐average molecular weight range of 2 000 to 8 000, the molecular weight distribution being fairly narrow (ratio of weight‐ to number‐average molecular weights M̄w/M̄n 1.2–1.3).
Poly(methacrylates) with different kinds of dendritic moieties as side groups
Authors: Chen Yong‐Ming , Chen Chuan‐Fu , Liu Wei‐Hong , Li Yu‐Fei , Xi Fu
Published: April 2003

Alkyl methacrylate monomers with three kinds of dendritic fragments as alkyl groups, two kinds of Fréchet‐type and a new type with 3,5‐diphenoxybenzyl as first generation, were prepared by reaction of the corresponding dendritic bromides with methacrylic acid in good yield and were homopolymerized with a radical initiator. Polymers with side groups in first generation had a degree of polymerization (P̄n) of 17–24, markedly higher than those with side groups in second generation, P̄n ≈ 6–7.
Isospecific homo‐ and copolymerization of styrene with ethylene in the presence of VCl3, AlCl3 as catalyst
Authors: Riberio M. Rosário , Portela Manuel F. , Deffieux Alain , Cramail Henri , Rocha Manuel F.
Published: April 2003

The homopolymerization of styrene and its copolymerization with ethylene in the presence of a vanadium‐based supported catalyst, {VCI3, 1 AICI3}, associated to triethylaluminium is examined. As indicated by means of 13C nuclear magnetic resoance and differential scanning calorimetry analysis, the homopolystyrenes obtained present a highly isotactic microstructure and are semicrystalline (melting temperature 220°C).

In the case of styrene/ethylene random copolymerization, the formation of both, polyethylene blocks and isotactic polystyrene sequences was identified by analysis of the crude polymer. Solubility characteristics and structural characteristics from nuclear magnetic resonance spectra of these products support the formation of copolymers with ethylene and isotactic styrene blocks rather than that of two distinct homopolymers.
Metal‐polymer “superglue” for dirty polymer surfaces
Authors: Noolandi Jaan , Shi An‐Chang
Published: April 2003

Current methods of bonding metals to polymeric surfaces involve chemical reactions between atomically clean surfaces (S. Paul, Surface Coatings, Wiley, New York 1985). We propose a novel method of attaching metals to polymeric surfaces which does not require chemical bonding and is designed to be effective for polymeric surfaces which are not clean.
Enzymatic synthesis of a soluble polyphenol derivative from 4,4′‐biphenyldiol
Authors: Kobayashi Shiro , Kurioka Hideharu , Uyama Hiroshi
Published: April 2003

Enzymatic oxidative polymerization of 4,4′‐biphenyldiol was performed in an aqueous organic solvent using horseradish peroxidase as catalyst. In the polymerization using a mixture of 1,4‐dioxane and phosphate buffer (pH 7.0) (80:20 vol‐%) as solvent, the monomer was quantitatively consumed to give powdery polymeric materials in a high yield. The resulting polymer is soluble in polar solvents such as N,N‐dimethylformamide, dimethyl sulfoxide, and acetone. The molecular weight of the methylated product is 7.3 × 103. The polymer exhibits high thermal stability under nitrogen.
Polymerization of styrenes carrying dendrons of the first, second and third generation
Authors: Neubert Ingo , Amoulong‐Kirstein Evelin , Schlüter A.‐Dieter , Dautzenberg Herbert
Published: April 2003

The synthesis of styrene monomers 5(G‐1,2,3) with Fréchet‐type dendrons of the first, second and third generation, and their radically initiated polymerization to result in high molecular weight dendrimers 6(G‐1,2,3) are reported. First light‐scattering investigations using 6(G‐2) show that this polymer is best described as a Gaussian chain.
Polymerization of an azastyrene derivative, 1. 1,6‐addition polymerization of 2,6‐diisopropyl‐N‐methyleneaniline
Authors: Hashidzume Akihito , Kajiwara Atsushi , Harada Akira , Kamachi Mikiharu
Published: April 2003

The polymerizability of an azastyrene derivative, 2,6‐diisopropyl‐N‐methyleneaniline (DiPMAn), was studied. Although DiPMAn could not be polymerized by radical and anionic initiators, it was polymerized with cationic initiators, such as trifluoroacetic acid (TFA), TiCl4‐TFA, and SnCl4‐TFA. The polymer is formed by 1,6‐addition with electrophilic substitution of an activated monomer in para‐position of the aromatic ring.
Command surfaces, 20. Fixation of surface‐assisted homogeneous alignment of nematic liquid crystals by cationic photopolymerization
Authors: Ichimura Kunihiro , Kidowaki Masatoshi , Akiyama Haruhisa , Kudo Kazuaki , Strehmel Veronika , Strehmel Bernd
Published: April 2003

The surface‐assisted alignment of a nematic liquid crystal yields a persistent ordered structure upon cationic photopolymerization of liquid‐crystalline epoxides. Linearly polarized light irradiation of a photocrosslinkable polymer containing azobenzene moieties played a crucial role in this procedure since the photoinduced alignment is not deteriorated by heating for polymerization.
Synthesis of a polystyrene‐arm‐polybutadiene‐arm‐poly(methyl methacrylate) triarm star copolymer
Authors: Hückstädt Hanno , Abetz Volker , Stadler Reimund
Published: April 2003

The straightforward synthesis of a polystyrene‐arm‐polybutadiene‐arm‐poly(methyl methacrylate) triarm star copolymer has been successfully realized by a sequence of reactions which involves the sequential addition of a living polybutadienyllithium to a polystyrene macromonomer with a terminal 1,1‐diphenylethylene unit and subsequent polymerization of methyl methacrylate. The high‐molecular‐weight polystyrene‐arm‐polybutadiene‐arm‐poly(methyl methacrylate) star copolymer shows microphase separation into three phases.
First application of an X‐ray imaging plate system for the accurate evaluation of the crystallite modulus of polymers
Authors: Tashiro Kohji , Nishimura Hirokazu , Kobayashi Masamichi
Published: April 2003

An X‐ray imaging plate system has been applied for the first time to evaluate the crystallite modulus Ec of orthorhombic polyethylene along the chain axis. The Ec evaluated by using the 002 reflection was 234.9 ± 12.6 GPa and that for the 004 reflection was 236.7 ± 3.4 GPa. The dispersion of the data was smaller for the 004 reflection than that for the 002 reflection. The so evaluated modulus has been found to be in good agreement with that reported by previous researchers.
New evidence of the presence of internal electron donors in active sites of heterogeneous Ziegler‐Natta catalysts
Authors: Xu Junting , Feng Linxian , Yang Shilin , Wu Yinan , Yang Yiqing , Kong Xiangming
Published: April 2003

Poly(propylene) samples produced by heterogeneous Ziegler‐Natta catalysts containing different internal electron donors were fractionated by using temperature rising elution fractionation; some key fractions were analyzed with 13C NMR. It was found that internal electron donors with different structures can convert aspecific active sites into different isospectrific ones. The employment of bis(2‐ethylhexyl) phthalate as internal electron donor leads to chemically inverted structures in the atactic fraction. This suggests that an internal electron donor may also exist in the environment of aspecific active sites.
Novel amine‐containing biodegradable polyester via copolymerization of aspartic anhydride and 1,4‐cyclohexanedimethanol
Authors: Won Chee‐Youb , Chu Chih‐Chang , Yu Tarng‐Jenn
Published: April 2003

A novel biodegradable polyester having pendant amine functional groups was snythesized from N‐(benzyloxycarbonyl)‐L‐aspartic anhydride (2) and 1,4‐cyclohexanedimethanol (3) by polycondensation reaction using p‐toluenesulfonic acid as a catalyst. The synthesized polymer 4 shows the characteristic ester carbonyl absorption peak at 1732 cm−1 in the IR spectrum, and the NMR spectra were consistent with the IR data. Also, the elemental analysis showed that the experimental and calculated values were very close to each other. The weight‐average molecular weight of the polymers ranged from 1140 to 5050 and increased with increasing reaction time. This new polymer would have the potential of a drug delivery biomaterial.
Synthesis and characterization of poly(1‐benzoylsemicarbazide) and poly(1,3,4‐oxadiazole amine) from 2‐(p‐aminophenyl)‐1,3,4‐oxadizolin‐5‐one via ring‐opening
Authors: Saegusa Yasuo , Ozeki Yasuhiro , Nakamura Shigeo
Published: April 2003

A novel thermally stable and semiconducting polyheterocycle, poly(1,3,4‐oxadiazole amine), was synthesized from 2‐(p‐aminophenyl)‐1,3,4‐oxadiazolin‐5‐one via ring‐opening. The polymer is a new class of ordered alternating copoly(aniline) containing 1,3,4‐oxadiazole heterocyclic units. The polymer is highly thermally stable and exhibits no weight loss up to 370°C in air. Its electric conductivity is less than 10−10 S · cm−1 at ambient temperature, but markedly increases to 6,5 · 10−7 S · cm−1 upon doping with iodine.
The first report on a convenient synthesis of novel reactive amphiphilic polysaccharides
Authors: Heinze Thomas , Rahn Kerstin
Published: April 2003

New amphiphiles with reactive tosylate groups and ionic sulfuric acid half esters based on the rod‐like polysaccharide cellulose were designed via homogeneous tosylation followed by sulfation with the SO3‐pyridine complex in N,N‐dimethylacetamide. At appropriate degrees of functionalization the polymers are soluble both in water and dimethyl sulfoxide, and they are promising starting materials for self‐organizing systems.