摘要:

AbstractRecently rediscovered evidence supports the conclusion that the bimodality of molarmass distributions in polystyrenes initiated by HCIO4is not, as widely believed, the consequence of independent chain‐growth by different propagating species, but originates from lack of uniformity in reagent concentrations during the earliest stage of the polymerization, where the time‐scale of the growth and decay of the transient ionic population is short compared with that of mixing, in conventional preparative experime

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170301

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractA novel group transfer polymerizationviahetero‐Diels‐Alder reaction is described. When 1‐trimethylsiloxybenzocyclobutene (1) was treated with a catalytic amount ofp‐anisaldehyde (4‐methoxybenzaldehyde) and TASF (tris(dimethylamino)sulfonium difluorotrimethylsilanide) at room temperature for 0.5 h, poly[1,2‐phenylene‐1‐(trimethylsiloxy)ethylene] was obtained quantitatively. The number‐average molecular weight of the polymer was M̄n= 2000 and the molecular weight distribution was narrow (ratio of weight‐to number‐average molecular weights M̄w/M̄n= 1.18). Structural characteristics suggested a polymerization mechanism involving isomerization of1too‐quinodimethane and successive hetero‐Diels‐Alder reaction leading to poly[1,2‐phenylene‐1‐trimethylsiloxy ethylene]. The living‐like nature of the polymerization was supported by a monomer addition experiment in which the molecular weight increased accordin

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170302

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractIn 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

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170303

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractCycloaliphatic 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 activ

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170304

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe anionic polymerization of methyl methacrylate was carried out in the presence of potassiumtert‐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 crypta

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170305

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractSmall‐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 pre

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170306

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractEthylene was polymerized in toluene using methylalumoxane (MAO) activatedrac‐(Me2SiOSiMe2)[Ind]2ZrCl2(1) andrac‐(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 × 106at low polymerization temperature (<20°C) under atmospheric pressure. The titanocene catalyst3shows lower activity and produced lower molecular weight polyethylene than zirconocenes1and2.Replacement of aromatic rings in1by cyclohexane rings, leading to2, increases activity and reduces molecular weight. The catalyst systems show a dependency of the activity on tem

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170307

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY

ISSN:1022-1336    

DOI:10.1002/marc.1996.030170308

出版商:Hüthig&Wepf Verlag    

年代:1996

数据来源: WILEY