bluuebunny/crossref_metadata_2025 huggingface dataset:
α‐olefin oligomers with narrow molar mass distributions from zirconocene/methylaluminoxane catalysts — An examination of the structure‐reactivity relationship
Authors: Janiak Christoph , Lange Katharina C. H. , Marquardt Peter
Published: April 2003

A series of tert‐butyl substituted zirconocene/methylaluminoxane catalysts illustrates the potential for the tailoring of olefin oligomers with extremely narrow molar mass distributions, which are explained on the basis of a chain‐length dependent propagation rate. Comparative oligomerization experiments provide a means to estimate the relative rates for chain propagation versus chain transfer as well as a correlation with the metallocene structure.
Synthesis of novel hydrophobically modified water soluble polymers by ring‐opening metathesis polymerization
Authors: McArdle Clare M. , Hamilton James G. , Law Edwina E. , Rooney John J.
Published: April 2003

Ring‐opening metathesis polymerization has been used to prepare a series of water soluble polymers based on the Diels‐Alder adducts of furan and cyclopentadiene. Hydrophobically modified forms of these polymers were obtained either by copolymerization with 5‐decylbicyclo[2.2.1]hept‐2‐ene, post‐polymerization modification of the acid forms of the polymers with 1‐decylamine or chain transfer to 1‐hexadecene. Polymers were characterized by NMR specroscopy and viscometry.
Polymerisation of methyl methacrylate with tert‐butyllithium and triisobutylaluminium in toluene: mechanism of initiation and termination by matrix‐assisted laser desorption ionisation time‐of‐flight mass spectrometry (MALDI TOF MS)
Authors: Hunt Kirsty H. , Crossman Martin C. , Haddleton David M. , Lloyd Paul M. , Derrick Peter J.
Published: April 2003

The polymerisation of methyl methacrylate (MMA) using triisobutylaluminium/tert‐butyllithium in hydrocarbon at 0°C and −78°C has been investigated by matrixassisted laser desorption ionisation time‐of‐flight mass spectrometry (MALDI TOF MS). Although the system gives extremely good control over molecular weight and narrow molecular weight distribution, initiation of polymerization can be complicated by formation of small amounts of tert‐butyl isoprenyl ketone (1), and termination of polymerization can occur by end cyclisation of the end unit of 3. Both complications in initiation and termination can be avoided by suitable reaction conditions. Incorporation of 1 is suppressed by increasing the alkylaluminium content and by higher temperature. Termination by cyclisation has been found to occur over much longer time scales than propagation and can therefore be avoided by controlled termination after the appropriate reaction time.
Synthesis of a new microphase‐separated polymer system by “counterion coupling” and its X‐ray characterization
Authors: Antonietti Markus , Maskos Michael
Published: April 2003

A new type of highly ordered, microphase‐separated polymer material is synthesized by simple ionic coupling of a commercial styrene/ethylene oxide twoblock copolymer with a charged end group to an oppositely charged polyelectrolyte by common precipitation from aqueous solution. The characterization of the polymer/polymer complex by small‐angle X‐ray scattering and polarization microscopy reveals that the comb‐like addition complexes formed by ionic grafting build up a mesophase with lamellar morphology and a periodicity of d = 7.1 nm which is easily oriented in mechanic fields.
ESCA surface study of polystyrene photodegradation accelerated by 2‐(2‐methoxy‐5‐methylphenyl)‐2H‐benzotriazole
Authors: Bottino Francesco A. , Di Pasquale Giovanna , Pollicino Antonino , Short Robert D.
Published: April 2003

The accelerated ageing of polystyrene by means of 2‐(2‐methoxy‐5‐methylphenyl)‐2H‐benzotriazole, under conditions reproducing the outdoor environment, was studied. The results show that this benzotriazole derivative appreciably accelerates the rate of photodegradation at the surface of polystyrene.
Fluorospectroscopy monitoring aggregation of block ionomers in aqueous media
Authors: Li Mei , Liu Lu , Jiang Ming
Published: April 2003

A new type of aggregation behavior of block ionomers, i.e. functionalized polystyrene‐block‐poly[ethylene‐co‐(1‐butene)]‐block‐polystyrene (SEBS) with respective contents of 3.2 mol‐% and 8.3 mol‐% sodium carboxylate groups in polystyrene blocks has been studied using steady‐state fluorescence techniques. It is found that the block ionomers could form a stable dispersion in water although both the slightly ionized polystyrene block and the ethylene/1‐butene block are hydrophobic. The intensity ratio of the first to third vibronic band (I1/I3) of pyrene varies from 1.8, characteristic of the aqueous medium, to about 0.8, characteristic of hydrophobic microenvironment when the ionomer concentration in water is increased from 8 × 10−4 g/L to 2 × 10−1 g/L. Meanwhile, the emission intensity ratio of excimer to monomer (Ie/Im) of pyrene increases with increasing polymer concentration first, then passes through a maximum and eventually falls off to zero. Both of the methods show the same critical aggregation concentration (8 × 10−4 g/L). Besides the non‐radiative energy transfer efficiency between naphthalene and anthracene shows a considerable increase when the concentration reaches 0.01 g/L. All of these three approaches lead to the fact that the block ionomers could form hydrophobic aggregates in water stabilized by the rare ionic groups.
Evaluation of propagation rate constants for the free radical polymerization of methacrylonitrile by pulsed laser photolysis
Authors: Shipp Devon A. , Smith Trevor A. , Solomon David H. , Moad Graeme
Published: April 2003

Propagation rate constants for the free radical polymerization of methacrylonitrile (MAN) have been obtained by pulsed laser photolysis (PLP). The temperature dependence of the propagation rate constants indicates a frequency factor of 10(6,43 ± 0,26) L · mol−1 · s−1 and an activation energy of 29,7 ± 1,5 kJ · mol−1. These parameters suggest that the relatively slow rate of propagation in MAN polymerization in relation to other common monomers (methyl methacrylate, styrene) can be attributed to the relative steric bulk and stability of the propagation species.
Photoinitiated thermolysis of poly(phenylenevinylene) precursor and photochemical doping of poly(phenylenevinylene)
Authors: Cho Iwhan , Kim Jinbaek , Lee Sungho
Published: April 2003

The photoinitiated elimination of methoxy groups of poly(p‐phenylene‐1‐methoxyethylene) and the photochemical doping of the resulting poly(phenylenevinylene) (PPV) were investigated. Upon irradiation and then heat treatment at 150°C, poly(p‐phenylene‐1‐methoxyethylene) containing triphenylsulfonium hexafluoroantimonate was converted to PPV. The resulting PPV was observed to be conductive, and its conductivity was 10−2–10−3 S/cm. By a lithographic procedure, we produced a conducting pattern doped photochemically in a nonconjugated poly(p‐phenylene‐1‐methoxyethylene) matrix.
Liquid‐crystalline epoxies dispersed liquid crystals
Authors: Lin Cui‐Lian , Chien Liang‐Chy
Published: April 2003

Dispersing liquid crystal droplets in a rigid polymer matrix results in an electrically controllable light scattering medium. A polymer with high glass transition temperature phase‐separated with a low molecular weight liquid‐crystalline material is a good binder for polymer dispersed liquid crystals (PDLC). Main‐chain liquid‐crystalline epoxies were synthesized for the phase separation with low molecular weight nematic liquid crystals E7 (mixture of 4‐alkyl‐4′‐cyanobiphenyls) and studied for their mesomorphic properties and response to an applied electrical field.
Structural characterization of syndiotactic 1,2‐poly(4‐methyl‐1,3‐pentadiene)
Authors: Meille Stefano V. , Capelli Silvia , Ricci Giovanni
Published: April 2003

4‐Methyl‐1,3‐pentadiene was polymerized with the MAO/CpTiCl3 (MAO: methyl‐aluminoxane, Cp: Cyclopentadienyl) system to yield a highly stereoregular syndiotactic 1,2‐polymer. Fiber diffraction patterns indicate two crystalline modifications: a major one with a repeat of 11.73 Å and minor amounts of a zig‐zag planar polymorph (axial repeat 5.05 Å). Energy calculations account for three nearly isoenergetic conformations: the more stable one, with repeat of 11.65Å, is (T6G2T2G2) analogous to the one recently reported for syndiotactic poly(propylene) (Chatani et al., 1991).
Olefin polymerization with metallocene catalysts supported on polysiloxane derivatives
Authors: Soga Kazuo , Arai Takashi , Hoang Ban The , Uozumi Toshiya
Published: April 2003

Three kinds of zirconocene catalysts, supported on polysiloxanes substituted with methylindenyl, methyl‐fluorenyl and two indenyl groups, respectively, were prepared and applied to propene and ethylene polymerizations using methylaluminoxane as cocatalyst. Both the activity and stereospecificity of these catalysts were found to lie between those of corresponding homogeneous and SiO2‐supported catalysts. Surprisingly, all the catalysts gave a mixture of atactic and isotactic poly(propylene), plausible reasons for which are briefly discussed.
Facilitated oxygen transport in an ionomer membrane containing cobaltous ions
Authors: Zhang Ziyong , Lin Shangan
Published: April 2003

A new oxygen/nitrogen separation membrane based on an ionomer of sulfonated EPDM (ethylene‐propene‐diene terpolymer) containing Co2+ ions was synthesized and investigated. It was found that the oxygen permeability coefficient and the separation factor for O2/N2 of the ionomer membrane are simultaneously enhanced at lower gas pressure difference. This result is believed to be caused by a polymer coordinate complex formed in the ionomer. ESR spectra provided an evidence of the cobalt‐oxygen adduct.
Ethene polymerization with modified‐polypropene‐supported highly stable Ziegler catalyst
Authors: Mori Hideharu , Ohnishi Kouki , Terano Minoru
Published: April 2003

A modified‐polypropene‐supported Ziegler catalyst was prepared using polypropene containing a small amount of poly(7‐methyl‐1,6‐octadiene) as a starting polymer for bromination, lithiation, and reaction with TiCl4. The polymerization of ethene was carried out using the catalyst with Al(C2H5)3 in toluene at 60°C up to 100 h. The polymer yield increased linearly with polymerization time, which indicates that the active sites of the modified‐polypropene‐supported Ziegler catalyst are practically stable without deactivation even for 100 h and are able to propagate further polymerization of ethene.
Styrene‐butadiene copolymerization initiated by organopotassium compounds in hydrocarbon medium
Authors: Nakhmanovich Boris I. , Arest‐Yakubovich Alexander A. , Prudskova Tatyana N. , Litvinenko Galina I.
Published: April 2003

The following values of monomer reactivity ratios were found: rS = 3,3 ± 0,3; rB = 0,12 ± 0,02 (cyclohexane, 25 °C). The comparison of the kinetic parameters obtained with Li, Na and K counter‐ions shows that the great difference between coordination polymerization with Li and “typically anionic” polymerization with K is mainly determined by the variation of the cross‐propagation rate constant kBS with the nature of the counter‐ion. No evidences for the specific role of the solvation of Li counter‐ion with butadiene monomer were found.
Synthesis of monodisperse hydroxyl‐containing polystyrene via chemical modification
Authors: Zhu Lei , Liu Lu , Jiang Ming
Published: April 2003

A facile synthesis of linear monodisperse hydroxyl‐containing polystyrene, poly{styrene‐co‐[p‐(1‐hydroxyethyl)styrene]} and poly{styrene‐co‐[p‐(2‐hydroxypropan‐2‐yl)styrene]}, was carried out via chemical modification of polystyrene by a two‐step procedure, i. e. monodisperse polystyrene was acetylated under mild conditions, followed by processes of reduction with LiAlH4 and addition with CH3MgBr, respectively. 1H NMR and FTIR spectra showed that in both cases, the reaction of acetyl to hydroxyl is complete. Sizeexclusion chromatography demonstrated that both molecular weight and monodispersity of the final products were basically unchanged.
New optical properties of polyelectrolyte hydrogels
Authors: Budtova Tatiana , Vilesov Alexander , Bertsev Vladimir , Elikina Galina , Suleimenov Ibragim , Tolmachev Yurii
Published: April 2003

A new optically active medium for lasers — a polyelectrolyte hydrogen swollen in a mixture of water + alcohol + dye — is presented. An anomalous dependence of the absorbance on the composition of the mixture is observed. It shows a maximum which corresponds to the composition when the hydrogel starts to swell as a hydrophilic network.
Preparation and properties of macromolecular complexes consisting of chitosan derivatives, iron(III) hydroxide sulfate, and poly(potassium vinyl sulfate)
Authors: Kikuchi Yasuo , Kubota Naoji , Fukuma Hirofumi , Mitsuishi Hiroshi
Published: April 2003

Glycol chitosan (GC) and methyl glycol chitosan (MGC) were separately reacted with poly(potassium vinyl sulfate) (PVSK) in the presence of iron(III) hydroxide sulfate (IHS) to form water‐insoluble macromolecular complexes (MC's). The chemical compositions and properties of MC's obtained were compared with each other. The solubility of MC in the MGC‐IHS‐PVSK system was lower than that in the GC‐IHS‐PVSK system, and it was suggested that MGC contributes to the properties of MC.
Living diradical polymerization
Authors: Hammouch Saïd Oulad , Catala Jean‐Marie
Published: April 2003

A diradical initiator containing two thermoreversible bonds was prepared and used for the polymerization of styrene at 90°C. The monomer consumption and the variation of the molecular weight were monitored with time. The results show that the process can be considered as living and that the polymerization rate is independent of the radical initiator concentration. By elemental analysis of the chain ends it was concluded that the propagation reaction occurs at both ends.
Topologically unique side‐chain polyrotaxanes based on triacetyl‐β‐cyclodextrin and a poly(ether sulfone) main chain
Authors: Born Markus , Ritter Helmut
Published: April 2003

The synthesis and NMR‐spectroscopical characterization of the topological arrangements of new side‐chain polyrotaxanes (3a) bearing about 80% of peracetylated cyclodextrins in the side‐chains of a functionalized poly(ether sulfone) is described. The characterizations have been conducted in relation to a similar model compound bearing no cyclodextrins (3b). The results strongly indicate that the cyclodextrins are uniformly located on the side chains, with the bigger opening over the aromatic anilide components of the barrier group. The glass transition temperature (Tg) of the polyrotaxane 3a is in the region of 143°C, which is significantly higher than that of the model polymer 3b having a value of 111°C.
Novel photocrosslinking of polymers bearing pendant acyloxyimino groups in the presence of p‐benzoquinone
Authors: Ito Ken‐ichi , Shigeru Yoshitaka , Tsunooka Masahiro
Published: April 2003

Films of polymers bearing pendant acyloxyimino (AOI) groups become insoluble when irradiated by ultraviolet light in the presence of p‐benzoquinone. Post‐heating of these films after irradiation also induces further the insolubilization. In the photocrosslinking, it is deduced that p‐benzoquinone serves not only as sensitizer for the decomposition of AOI groups but also as crosslinker during the photo‐irradiation and heating after irradiation.
Synthesis, optical absorption and fluorescence of new poly(p‐phenylene)‐related polymers
Authors: Remmers Marcus , Schulze Margit , Wegner Gerhard
Published: April 2003

The synthesis and properties of soluble, conjugated polymers consisting of oligo(p‐phenylene) sequences linked by ethylene, vinylene, or ethylene, units are reported. Benzene‐, stilbene‐, diphenylacetylene‐ and 1,2‐diphenylethane derivatives serve as monomers and are connected by the Suzuki‐coupling method. A wide range of poly‐(p‐phenylene)‐related polymers are available by the combination of different AA/BB‐type monomers in various concentrations. The optical properties of the resulting polymers can therefore be tailored. Number‐average degrees of polymerization of up to X̄n = 137 were reached under optimized conditions. Photoluminescence quantum yields of these materials in solution are nearly one.
Vanadium‐based Ziegler‐Natta catalyst supported on MgCl2(THF)2 for ethylene polymerization
Authors: Czaja Krystyna , Białek Marzena
Published: April 2003

A supported magnesium‐vanadium‐aluminium catalyst was prepared by depositing –with the use of a milling technique–VOCl3 on the MgCl2(THF)2 support and subsequent activation with diethylaluminium chloride. Catalytic activity of the obtained system for ethylene polymerization was evaluated as a function of Mg/V and Al/V ratios as well as catalyst ageing time and polymerization temperature. High concentrations of THF in the catalytic system and considerable excess of an organoaluminium co‐catalyst were found to have no deactivating action on vanadium active sites. The catalyst obtained is stable and its activity for ethylene polymerization is high. It yields polyethylene with higher molecular weight and higher melting point than offered by the materials produced with the use of a corresponding unsupported vanadium catalyst or a titanium‐based system on the same magnesium support. Kinetic investigations confirmed stability of this catalyst irrespective of its concentration in the polymerization medium or of monomer concentration. Moreover, analysis of the kinetic findings revealed that over 80% of vanadium employed forms active polymerization sites.
Synthesis of poly(ethylene glycol) block copolymers by a redox process and their spectral characterization
Authors: Nagarajan Soundappan , Srinivasan Kalathur Sabdham Vangepuram
Published: April 2003

Novel block copolymers of poly(ethylene glycol) (PEG) with acrylamide (AAm) and methacrylic acid (MAA) were synthesized using a redox system consisting of ceric ions and PEG in aqueous acidic medium. The molecular weight of PEG in the redox system was varied to obtain a series of block copolymers with differing molecular weights of PEG segment. The polymerization proceeded via macroradical generation, which was substantiated by ESR spectroscopy. This macroradical acted as a redox macroinitiator for the block copolymerization of the vinyl monomers. The formation of the block copolymers was confirmed by fractional precipitation technique.
Aggregate of a peptide‐containing block copolymer with a lipase
Authors: Naka Kensuke , Yamashita Rie , Nakamura Tohru , Ohki Akira , Maeda Shigeru , Aoi Keigo , Tsutsumiuchi Kaname , Okada Masahiko
Published: April 2003

The peptide‐containing block copolymer poly(N‐acetyliminoethylene)‐block‐poly(L‐phenylalanine) (1) formed large water‐soluble aggregates in water due to the hydrophobic and hydrogen‐bonding character of the poly(L‐phenylalanine) block. The solution properties of 1 were compared with those of the block copolymer poly(N‐acetyliminoethylene)‐block‐poly(N‐benzoyliminoethylene) (2) with an analogous structure. 1 formed aggregates even though the poly(phenylalanine) segment was short as compared with 2 in which hydrophobic interaction may be the only driving force to form aggregates. The aggregates have strong capability of incorporating Lipase P and largely increase the hydrolysis activity against p‐nitrophenyl propionate as compared with that of free Lipase P.
Solid‐like states of a dendrimer liquid displayed by scanning force microscopy
Authors: Sheiko Sergei S. , Eckert Gabi , Ignat'eva Galina , Muzafarov Aziz M. , Spickermann Jochen , Räder Hans J. , Möller Martin
Published: April 2003

Adsorption and aggregation of carbosiloxane dendrimers on mica and pyrolytic graphite were investigated by scanning force microscopy (SFM). The aggregation process started from (i) single molecules which coagulated to (ii) clusters and (iii) fluid droplets followed by formation of (iv) a complete layer on the solid substrate. The molecules were displayed as a globular particle with a diameter of about 2.5 nm. Tapping SFM of the liquid was possible due to the fact that the dendrimer undergoes a transition to a viscoelastic state below the tapping frequency of about 360 kHz. Dynamic shear compliance experiments have shown a plateau of 5 · 10−7 Pa−1 around this frequency. Dendrimer droplets slowly spread into polygonal lamellae with a thickness of two molecular layers. The structures indicate a rather regular dense packing of the globular molecules.
Well‐defined side‐chain liquid‐crystalline polysiloxanes
Authors: Hempenius Mark A. , Lammertink Rob G. H. , Vancso G. Julius
Published: April 2003

A route to well‐defined side‐chain liquid‐crystalline polysiloxanes (ratio of weight‐to number‐average molar masses M̄w/M̄n < 1.2 is reported. Anionic ring‐opening polymerization of pentamethylvinylcyclotrisiloxane yielded a poly(dimethylsiloxane‐co‐methylvinylsiloxane) backbone. A flexible disiloxane spacer was used to connect 4‐(ω‐alkenyloxy)‐4′‐cyanobiphenyl mesogenic molecules to the vinyl groups which belong to the backbone, leading to a side‐chain liquid‐crystalline polysiloxane (SCLCP) which has its mesogens distributed regularly along the main chain. Preliminary measurements indicate an electro‐optic switching time τs = 1 min at 20°C and 7 s at 32°C (dc, 5 V/μm)).
A deuteron NMR study on order and phase behaviour of liquid‐crystalline copolymers
Authors: Martin Andreas , Tefehne Christoph , Gronski Wolfram
Published: April 2003

Liquid‐crystalline (LC) block copolymers of lamellar morphology were prepared via anionic polymerization of polystyrene‐block‐1,2‐polybutadiene and subsequent introduction of a deuterated mesogen by polymer analogous reaction. Deuteron NMR measurements show that the first‐order nematic/isotropic transition in the block copolymer is changed to a critical behaviour under the influence of shear. In the nematic phase the order parameter is reduced with respect to the homopolymer, and there is no evidence of an isotropic boundary layer of the LC‐block at the nematic/isotropic interface.
Syndiotactic‐specific polymerization of propene with a Ni‐based catalyst
Authors: Pellecchia Claudio , Zambelli Adolfo
Published: April 2003

Polymerization of propene at −78°C in the presence of a homogeneous catalytic system based on a Ni(II) diimine derivative and methylaluminoxane affords prevailingly syndiotactic crystalline poly(propylene) (rr triad content ≈80%). 13C NMR analysis of the polymer microstructure indicates that the stereochemistry of the monomer insertion is controlled by the configuration of the methine carbon of the growing chain end (unlike‐1,3 asymmetric induction). This is the first example of stereospecific homopolymerization of propene promoted by a late transition metal catalyst.
Polymerization of o‐quinodimethanes, 1. Radical polymerization of 1‐methoxy‐o‐quinodimethane formed in situ by thermal isomerization of 1‐methoxy‐benzocyclobutene
Authors: Chino Keisuke , Takata Toshikazu , Endo Takeshi
Published: April 2003

The first radical polymerization of 1‐methoxy‐o‐quinodimethane (2) generated by thermal ring‐opening isomerization of 1‐methoxybenzocyclobutene (1) is described. The polymerization of 1 in the presence of a radical initiator afforded an MeOH‐insoluble polymer (3) in moderate yield at temperatures above 90°C. The structure of the obtained polymer is consistent with a ring‐opening polymerization. The yield of the polymer increased with the amount of initiator. Radical copolymerization with methyl acrylate was carried out. Treatment of 3 with acid gave poly(o‐phenylenevinylene), quantitatively.
Rate constants for the reaction of hydrated electrons and hydroxyl radicals with acrylate monomers
Authors: Bíró Ággnes , Takács Erzsébet , Wojnárovits Laszlo
Published: April 2003

The hydrated electron (e−aq) and hydroxyl radical rate constants with 18 acrylate‐, methacrylate‐, crotonate‐, fumarate‐ and maleate esters are discussed. The constants approach the diffusion‐controlled limit. k(e−aq) and k(OH) change in opposite direction; if k(e−aq) is high then k(OH) is small. This tendency is connected with the nucleophilic character of e−aq and the electrophilic character of OH, although the site of attack of e−aq and OH is different: carbonyl versus vinyl group.
Ring‐opening polymerization of cyclic urethanes and ring‐closing depolymerization of the respective polyurethanes
Authors: Neffgen Stephan , Keul Helmut , Höcker Hartwig
Published: April 2003

The cationic ring‐opening polymerization of trimethylene urethane (tetrahydro‐2 H‐1,3‐oxazin‐2‐one) in the melt with methyl trifluoromethanesulfonate as initiator results in poly(trimethylene urethane) in yields of ≈70%. Under the same reaction conditions 2,2‐dimethyltrimethylene urethane (5,5‐dimethyltetrahydro‐2H‐1,3‐oxazin‐2‐one) cannot be polymerized. Poly(2,2‐dimethyltrimethylene urethane), however, was obtained via polycondensation polymerization. Both polymers exhibit a uniform microstructure as deduced from NMR spectroscopic analysis. Ring‐closing depolymerization in the melt with dibutyltin dimethoxide or titanium tetraisopropoxide at 140°C results the respective monomers in yields of ≈90%.
Thermoreversible gelation of isotactic poly(methyl methacrylate) in butyl acetate: a differential scanning calorimetry study
Authors: Spěváček Jiří , Saiani Alberto , Guenet Jean‐Michel
Published: April 2003

The thermal behaviour of thermoreversible gels prepared well below room temperature from isotactic poly(methyl methacrylate) (i‐PMMA) in butyl acetate (BAC) was investigated by means of differential scanning calorimetry. Gel‐formation and gel‐melting enthalpies together with melting enthalpy of the solvent were determined as functions of polymer concentration. The results are consistent with the existence of a polymer/solvent complex with a stoichiometry of 1,5–2 BAC molecules per i‐PMMA monomeric unit.
Synthesis of vinyl ether‐capped telechelic poly(tetrahydrofuran)
Authors: Hashimoto Tamotsu , Furukawa Tomohiro , Kodaira Toshiyuki
Published: April 2003

Vinyl ether‐terminated telechelic poly(tetrahydrofuran) (poly(THF)) was synthesized by the reaction of a bifunctional living cationic polymer of THF with an excess of Na⊕⊖OCH2CH2OCHCH2 in THF at 0°C. The obtained polymer has narrow molecular weight distribution and end functionality close to two.
Hysteresis in the glucose permeability versus pH characteristic for a responsive hydrogel membrane
Authors: Baker John P. , Siegel Ronald A.
Published: April 2003

A side‐by‐side diffusion cell was used to study the permeability of glucose through a temperature‐ and pH‐sensitive poly(N‐isopropylacrylamide‐co‐methacrylic acid) hydrogel membrane. At fixed temperature (37°C), lowering pH in one side of the cell induced hydrogel volume collapse and strongly attenuated glucose permeation across the membrane. Hysteresis was observed in the glucose permeability versus pH characteristic.
The use of photoinitiated free‐radical cyclopolymerization in the preparation of novel side‐chain liquid‐crystalline polydienes
Authors: Hall Alan William , Lacey David , Buxton Peter Ian
Published: April 2003

The technique of photoinitiated free‐radical cyclopolymerization has been used to produce a variety of novel side‐chain liquid‐crystalline (SCLC) polymers in which an alicyclic ring structure is incorporated into a polymer backbone. Most of the SCLC polymers gave glass transition temperatures (Tg) around room temperature and clearing points around 60–70°C. However, the poly(1,5‐hexadiene) was the exception to this, exhibiting a Tg value of 14.5°C and a clearing point of 132.5°C. Confirmation of the structure of the alicyclic ring along the polymer backbone is extremely difficult to obtain, but evidence is given in the paper to support the ring structure.
Miscibility of semirigid thermotropic liquid crystalline polycarbonate with poly(vinyl chloride)
Authors: Sato Moriyuki , Ujiie Seiji
Published: April 2003

Miscibility and morphology of polymer blends of semirigid thermotropic liquid crystalline (LC) polycarbonate (LCPC) with three commercial amorphous poly(vinyl chloride)s (PVC) having various molecular weights were investigated by means of differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). No phase separation was observed in the LCPC/PVC polymer blends. LCPC forms miscible polymer blends with the PVCs independent of molecular weight. The dynamic storage modulus of the LCPC/PVC polymer blends changes systematically with blend composition.
Phase equilibria in polymer/solvent systems, 8. Swelling of chemically crosslinked polymers in mesogenic substances in different states
Authors: Frahn Stephanie , Borchard Werner
Published: April 2003

Swelling curves of chain end‐linked polyurethane networks in mesogenic swelling agents were determined gravimetrically. Different slopes of the swelling curves are observed above and below the transition temperature of the liquid‐crystalline to the isotropic state. From the sign of the slope it can be derived that the swelling agent is not in the liquid‐like state in the gel if the pure swelling agent is liquid‐crystalline.
Dielectric and dynamic mechanical relaxation of poly(ether ether ketone)/poly(etherimide) blends below the glass transition
Authors: Goodwin Andy , Marsh Robert
Published: April 2003

Dielectric relaxation spectroscopy (DRS) and dynamic mechanical thermal analysis (DMTA) were used to investigate the secondary relaxation behaviour of poly(ether ether ketone) (PEEK), poly(etherimide) (PEI) and a miscible PEEK/PEI blend. The data from each technique, for the γ‐process, did not lie on the same Arrhenius line, while the rate of molecular motion of the γ‐process in the blends was largely an average of each component's motions. The β‐process in PEI was plasticised by the presence of PEEK.
Gel synthesis by transesterification of glycol‐modified poly(N‐isopropylacrylamide) with O,O‐diethyl dithiophosphate
Authors: Bromberg Lev
Published: April 2003

Synthesis of poly(N‐isopropylacrylamide‐co‐2‐hydroxyethyl methacrylate‐co‐ethylene glycol dimethacrylate) gels containing pendant mercapto groups via transesterification of 2‐hydroxyethyl methacrylate moieties with O,O‐diethyl dithiophosphate is described and the gel structure elucidated by 1H and 31P NMR and elemental analysis. The gels respond to changes in their liquid environment.
Thermally switchable polyrotaxane as a model of stimuli‐responsive supramolecules for nano‐scale devices
Authors: Fujita Hiroaki , Ooya Tooru , Kurisawa Motoichi , Mori Hideharu , Terano Minoru , Yui Nobuhiko
Published: April 2003

A polyrotaxane consisting of many β‐cyclodextrins (β‐CDs) and a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) capped with bulky end‐groups was synthesized as a model of stimuli‐responsive supramolecules for nanoscale devices. The polyrotaxane was reversibly soluble‐insoluble in water in response to temperature. This was achieved through the assembled and dispersed states of β‐CDs along the block copolymer. It is considered that intermolecular hydrogen bondings of β‐CDs, as well as the PEG segment length of the copoloymer, are predominant factors for regulating such thermally switchable behavior of the polyrotaxane.
Functionalization of polypropylene by grafting with itaconic acid
Authors: Yazdani‐Pedram Mehrdad , Vega Héctor , Quijada Raúl
Published: April 2003

Grafting of polypropylene was carried out in both boiling xylene and decalin as solvent medium with itaconic acid (2‐methylenesuccinic acid) as functional polar monomer using 2,5‐dimethyl‐2,5‐bis(tert‐butylperoxy)hexane (Lupersol 101) as radical initiator. It was found that the temperature influenced the percentage of monomer grafted onto polypropylene and that the amount of monomer incorporated was practically constant after 5 min. The results also show that the amount of monomer incorporated is proportional to the initial monomer concentration used in the grafting reaction, although for higher initiator concentrations a reduction in the percentage of grafting was found.
Synthesis and photo‐crosslinking of oriented side‐chain liquid crystalline polymers
Authors: Kawatsuki Nobuhiro , Takatsuka Hirohumi , Yamamoto Tohei , Sangen Osamu
Published: April 2003

New photo‐crosslinkable side‐chain liquid‐crystalline methacrylate polymers comprising m‐[4′‐(n‐cinnamoyloxyalkoxy)biphenyl‐4‐yloxy]alkyl groups (m, n = 2, 6) were synthesized. All polymers exhibit a nematic liquid‐crystalline phase depending on the spacer length (5a–5d). Aligned thin films could be obtained using a rubbed polyimide‐coated substrate, and they could be photo‐crosslinked without change in the aligned structure. The photo‐crosslinked film of 5d (m = n = 6) showed a stable alignment up to 300°C.
Polymeric mesoions, 3. Synthesis of polymeric mesoionic 1,3‐diazinium‐olates via polymer analogous modification of a polythiourea from m‐phenylenediamine and p‐phenylene diisothiocyanate
Authors: Deutschmann Thomas , Ritter Helmut
Published: April 2003

Mesoionic poly(1,1′‐(1,3‐phenylene)‐3,3′‐(1,4‐phenylene)‐bis(5‐decyl‐2‐decylthio‐4,6‐dioxo‐1,3‐diazine)) (6) was prepared by cyclisation of the isothiourea component of poly(1,1′‐(1,3‐phenylene)‐3,3′‐(1,4‐phenylene)‐bis(2‐decylisothiourea)) (4) with decylmalonic acid (5) by use of dicyclohexylcarbodiimide (DCC). Polymer 4 was obtained by polymer analogous alkylation of poly(1,1′‐(1,3‐phenylene)‐3,3′‐(1,4‐phenylene)‐bisthiourea) (3). For comparison of spectroscopic data, 5‐butyl‐2‐propylthio‐4,6‐dioxo‐1,3‐diphenyl‐1,3‐diazine (9) was synthesized as low molecular weight model compound.
Piezoelectricity of mechanically oriented S‐elastomers
Authors: Eckert Tobias , Finkelmann Heino , Keck Mario , Lehmann Walter , Kremer Friedrich
Published: April 2003

Ferroelectricity and thus piezoelectricity are well known features of low molar mass chiral smectic C (Sc*) liquid crystals. We present a new technique to orientate macroscopically the director as well as the smectic layers of a Sc*‐polymer network by applying a suitable mechanical field. The uniform orientation of the network film is checked by X‐ray diffraction. According to the phase symmetry electromechanical measurements indicate the existence of a polar axis of the network and the direct as well as the inverse piezoelectric effect is demonstrated.
Investigation of metal clusters dispersed in styrene‐co‐(ethyl methacrylate) copolymers by means of high resolution transmission electron microscopy
Authors: T. Galo Cárdenas , C. Elizabeth Salgado , L. Viviana Vera , Yacamán Miguel J.
Published: April 2003

Styrene/ethyl methacrylate (SEMA) colloids were obtained by cocondensation at 77 K of the monomers with several metals such as Au, Pd, In and Sn. The colloids were polymerized with 2,2′‐azoisobutyronitrile and dibenzoyl peroxide as radical initiators at 60°C for 3.5 h. A viscosity average molecular weight (104 < Mv < 105) was obtained depending upon the metal used. The particle size of these clusters dispersed in the copolymers ranges from 20 to 31 Å. The metal clusters are incorporated in the copolymers.
Unsymmetric 1,4‐naphthylene‐containing polysulfones
Authors: Douglas Judy E. , Wang Zhi Yuan
Published: April 2003

The design and synthesis of a new unsymmetric monomer, 1‐chloro‐4‐(4‐fluorobenzenesulfonyl)naphthalene (1), was accomplished and polymerized with several bisphenols. Three of these polymers represent the successful incorporation of a bulky 1,4‐naphthylene unit into the commercially known polysulfones, Udel, Radel R and Victrex. All unsymmetric polysulfones obtained were determined to be amorphous and displayed glass transition temperatures in the range of 218–288°C. The gas permeability suffered while the permselectivity was marginally improved with naphthyl insertion into Udel.
Microemulsions with polymerizable surfactants. γ‐ray induced copolymerization of styrene and 11‐(acryloyloxy)undecyl(trimethyl)ammonium bromide in three‐component cationic microemulsion
Authors: Dreja Michael , Tieke Bernd
Published: April 2003

Styrene and the cationic surfactant 11‐(acryloyloxy)undecyl(trimethyl)ammonium bromide (AUTMAB) form transparent, globular microemulsions in water without any addition of a cosurfactant. Upon γ‐irradiation, the two monomers copolymerize at room temperature and form nanolatex particles of about 21 nm in diameter consisting of a copolymer with a mole ratio of styrene to surfactant of approximately 1.5:1. Excess surfactant is polymerized in the micellar solution by formation of homopolymer. A structure model is presented taking into account that the surfactant most likely forms the particle shell. Due to the polar, covalently bonded shell the polymer particles can be easily redispersed.
Experimental discrimination between competing nucleation theories in microemulsion polymerizations
Authors: Kim Dong Ryul , Napper Donald H.
Published: April 2003

The particle nucleation processes involved in the microemulsion polymerizations of styrene and methyl methacrylate have been investigated using pyrene fluorescence intensity measurements as a function of conversion. Very distinctive differences were observed between the results for the two different monomers. The styrene fluorescence results were consistent with nucleation occurring within the microemulsion droplets, followed by the subsequent heterocoagulation of the nucleated particles with remaining droplets. The very different methyl methacrylate data were consistent with a homogeneous nucleation mechanism.
A facile synthesis of polyamides from aromatic diisocyanates and dicarboxylic acid catalyzed by Lewis acids
Authors: Wei Yen , Jia Xinru , Jin Danliang , Davis Franklin A. , Starner William E.
Published: April 2003

Aromatic polyamides were prepared by an AlCl3 or HCl‐catalyzed polymerization of toluene diisocyanate or methylenebis(phenyl isocyanate) with adipic acid at low temperatures (≤100°C) in a short reaction time (3–4 h). The intrinsic viscosity of the polymers was approximately 1.1 dL/g as determined at 25°C with m‐cresol as solvent, indicating that the polyamides obtained by this method have relatively high molecular weights. The polymers exhibit high glass transition temperatures and good thermal stability.
On the crystallization of γ‐isotactic polypropylene: A high pressure study
Authors: Brückner Sergio , Phillips Paul J. , Mezghani Khaled , Meille Stefano V.
Published: April 2003

The non‐parallel chain structure determined for γ‐phase isotactic polypropylene (γ‐iPP) is confirmed by Rietveld analysis for highly isotactic high molecular mass iPP crystallized at 200 MPa. The new refinement shows that: (i) stereoregularity or crystallization pressure do not significantly influence the lattice dimensions; (ii) defect inclusion in γ‐iPP crystals is unlikely. The α and γ forms have nearly identical bulk internal energy and density, but α‐iPP should be normally kinetically favored over γ‐iPP which may in turn predominate due to its greater ability to host defects at the crystalline‐amorphous interface.
Crystal structure and crystallinity of poly(aryl ether biphenyl ether ketone ketone)
Authors: Liu Tianxi , Mo Zhishen , Wang Shanger , Zhang Hongfang , Na Hui , Wu Zhongwen
Published: April 2003

The crystal structure of poly(aryl ether biphenyl ether ketone ketone) (PEDEKK) was determined to comprise a two‐chain orthorhombic unit cell with dimensions a = 0.778 nm, b = 0.606 nm and c = 2.375 nm by using wide‐angle X‐ray diffraction (WAXD). According to the orthorhombic system, the 12 reflections of this polymer were indexed. The crystallite size increases with increasing the crystallization temperature. The results of the degree of crystallinity (Wc,x) calculated from WAXD were compatible with those from density (Wc,d) and calorimetry (Wc,h) measurements.
Preparation of a uniform poly(methyl methacrylate) macromonomer and its polymerization
Authors: Hatada Koichi , Nishiura Takafumi , Kitayama Tatsuki , Hirotani Shuji
Published: April 2003

Syndiotactic poly(methyl methacrylate) (st‐PMMA) macromonomer having methacryloyl end group was prepared from st‐PMMA living anion and separated into uniform macromonomers by means of supercritical fluid chromatography. A uniform macromonomer with the degree of polymerization of 32 was polymerized radically in benzene at 60°C. The uniform dimer, trimer and tetramer of the uniform macromonomer were isolated from the polymerization product by means of gel‐permeation chromatography (GPC). The intrinsic viscosity ([η]) in tetrahydrofuran of these uniform comblike polymers was determined by GPC/differential viscometric analysis. The plot of logarithmic [η] against logarithmic molecular weight indicated that the trimer and tetramer assume a little shrinking molecular shape as compared with the unimer and dimer.
New side‐chain poly(methacryl‐rotaxanes) bearing cyclodextrins as non‐covalently anchored ring components. Chemoenzymatic synthesis and degradation
Authors: Noll Olaf , Ritter Helmut
Published: April 2003

The chemoenzymatic synthesis of new side‐chain polyrotaxanes (6) bearing non‐covalently attached cyclodextrins is described. Starting from 11‐methacryloylaminoundecanoic acid, up to 8 units of 12‐hydroxylauric acid were condensed in the presence of a lipase from Candida antarctica. They were copolymerized with methyl methacrylate to comb‐like polymers (4) bearing free carboxylic groups at the end of the oligoester side chains. These free carboxylic groups were then condensed chemically with a nucleophilic barrier group, N‐(4‐aminobutanoyl)‐4‐triphenylmethylaniline (5), in the presence of dimethylated β‐cyclodextrin, yielding new polyrotaxanes that contain statistically more than 1 ring component per side chain.
Smectic A liquid single crystal elastomers showing macroscopic in‐plane fluidity
Authors: Nishikawa Etsushi , Finkelmann Heino , Brand Helmut R.
Published: April 2003

The mechanical response of a smectic A liquid single crystal elastomer (LSCE) to stress applied perpendicular and parallel to the layers is described. We find that the static modulus perpendicular to the layers is two orders of magnitude larger than the modulus parallel to the layer direction, where the latter is completely due to the crosslinking. Macroscopically the width of the smectic A LSCE does not shrink when a mechanical stress is applied parallel to the layers while the length of the film increases by a factor of 2 thus demonstrating the in‐plane fluidity of the smectic layering.
Dual influence of lithium chloride on the reactivity of polystyryllithium in ethereal solvents
Authors: Van Beylen Marcel , Van Lierde Paul , Zimm Bruno H. , Szwarc Michael
Published: April 2003

Addition of LiCl to ethereal solutions of polystyryllithium retards propagation of the polymerization at low polymer concentration, but accelerates it at higher polymer concentrations. This phenomenon is accounted for by the dual action of LiCl. Its dissociation yielding free common Li+ ions which diminish the concentration of the reactive free polystyryl anions dominates at low electrolyte concentrations. However, at their higher concentrations the Li+ scavenging action of LiCl, resulting in the formation of LiClLi+ triple ions, becomes important, it reduces the concentration of the free Li+ ions and increases, therefore, the proportion of the reactive free polystyryl anions.
Propene polymerization with Ziegler‐type catalysts formed from Me2Si(Ind)2ZrMe2 and cation‐generating reagents
Authors: Hahn Sabine , Fink Gerhard
Published: April 2003

Kinetic and polymer analytical results obtained with the systems Me2Si(Ind)2ZrMe2/[B(C6F4Si(i‐Pr)3)4]− [(C6H5)3C]+ (2) and Me2Si(Ind)2ZrMe2/[B(C6F5)4]− [(C6H5)3C]+ (3) in olefin polymerizations are compared (Me: methyl; Ind: indenyl). Both systems show that the polymerization rate increases with increasing metallocene concentration in a surplus due to the formation of binuclear species. The expected influence of increasing cation‐anion distance on the stereo‐errors of the poly(propylene)s when changing from system 3 into system 2 could not be detected.
Dielectric relaxation spectroscopy of amorphous and liquid‐crystalline side‐chain polycarbonates
Authors: Wübbenhorst Michael , Van Koten Ernout M. , Jansen John C. , Mijs Wim , van Turnhout Jan
Published: April 2003

The molecular dynamics of amorphous and liquid‐crystalline (LC) side‐chain polycarbonates was studied by dielectric spectroscopy at frequencies from 10−2 to 106 Hz and at temperatures from −160 to 180°C. ‘Model’ compounds containing no mesogenic side‐groups showed two relaxations, which originate from the carbonate group (α, βm‐relaxation). By contrast, in LC‐polycarbonates bearing a mesogenic nitrostilbene side group around and above the glass transition temperature Tg up to three relaxation modes were distinguished (α‐, λ1‐, λ2‐process); below Tg four secondary relaxations (γ‐, βm‐, βs‐, βsc‐relaxation) were observed. The γ‐relaxation was found only in compounds possessing an aliphatic spacer linked to the backbone by an ether bond. Apart from βm‐, two additional β‐processes were identified as relaxations associated with the mesogenic unit in the glassy (βs) or in the crystalline state (βsc).
Synthesis of polymeric organic‐inorganic hybrid materials. Partially deacetylated chitin‐silica hybrid
Authors: Retuert Jaime , Nuñez Alicia , Martínez Francisco , Yazdani‐Pedram Mehrdad
Published: April 2003

This work reports the synthesis of a novel polymeric organic‐inorganic hybrid. The inorganic component is a silica network obtained by controlled hydrolysis of tetraethyl orthosilicate via sol‐gel process and the organic counterpart is partially deacetylated chitin (CHI). The resulting polymer hybrids were homogeneous transparent film forming glassy materials being compatible through a wide composition range. Simultaneous thermal analysis of a CHI/silica 1:1 mixture confirms the intermolecular complex formation between organic and inorganic polymers.
Refractive index decrease during photocrosslinking in photopolymers suitable for holographic recording
Authors: Nagata Akira , Sakaguchi Toru , Ichihashi Taichi , Miya Masaru , Ohta Koji
Published: April 2003

Photosensitive polymers of cyclobutane formation type have been found to show a decrease in their refractive indices with progress of photocrosslinking, when studied by the waveguide method. The decrease in refractive index is considered to be due to a decrease of exaltation in molar refraction. This phenomenon is of potential importance in holographic recording.
Synthesis and liquid crystal properties of bipyridine‐containing aromatic polyamides
Authors: Yu Sze Chit , Chan Wai Kin
Published: April 2003

A series of novel aromatic polyamides containing 2,2′‐bipyridine moiety were synthesized by polycondensation of 2,2′‐bipyridine‐5,5′‐dicarboxylic acid (2) with various aromatic diamines in hexamethylphosphoramide (HMPA) containing lithium chloride. The resulting polyamide solutions in 98% sulfuric acid and in HMPA‐LiCl exhibited lyotropic liquid crystal phases. The phase transition behaviors were studied by polarizing microscopy and X‐ray diffraction. The polyamides also formed metal complexes with cis‐dichlorobis(bipyridine)ruthenium dihydrate [cis‐Ru(bpy)2Cl2 · 2H2O] which was supported by changes in electronic spectra.
Imaging of a pH‐sensitive polymer brush on a porous membrane using atomic force microscopy in aqueous solution
Authors: Ito Yoshihiro , Park Yong Soon , Imanishi Yukio
Published: April 2003

Poly(methacrylic acid) was grafted on a nanoporous polycarbonate membrane using the glow‐discharge method. Atomic force microscopy showed that the pore size is dependent upon pH in such a way that a low pH the graft chains are protonated and contracted to open the pore, whereas at high pH, the graft chains became extended, thus reducing the pore size. Water permeation through the graft membrane is regulated by the pH value. The permeation rate is low at high pH value and high at low pH. This phenomenon corresponds to the pore size.