ISSN:0007-1641    

DOI:10.1002/pi.4980190301

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980190302

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980190303

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractMethods are described by which various organolithium species are reacted with triphenylborane to generate materials possessing borate functionality. Comparison is made between experiments involving simple alkyllithium compounds, and those involving living anionic polybutadienes. Evidence is presented to show that using living polybutadienes at temperatures below 0°C, the reaction proceeds with very high efficiency, and that overall conversion to borate‐functionalised polymer is virtually quantitati

ISSN:0007-1641    

DOI:10.1002/pi.4980190304

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractWe present an overview on general methods allowing synthesis of block copolymers. Different transformations have been examined: anion to free radical, anion to cation and reverse, cation to free radical and reverse, anion to Ziegler‐Natta transformation, and coupling reactions of anion and cation.This approach greatly extends the range of possible monomer combinations in block copolymer

ISSN:0007-1641    

DOI:10.1002/pi.4980190305

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractReactions in tetrahydrofuran (THF) of anionically produced polystyryllithium (PsLi) with excess mercury(II) compounds, HgX2(X = Cl, Br, OAc), or PhHgCl form mercury‐terminated polymers, PsHgX (X = Cl, Br, OAc or Ph, respectively), which have been characterised by g.p.c. and by elemental analyses using neutron activation. Similar reactions of PsLi with half‐molar quantities of HgX2yield no mercury‐containing products, such as Hg(Ps)2, and produce only coupled homopolystyrene, Ps‐Ps, accompanied by PsX and PsH. Also, PsLi and HgI2, in various reactant ratios, produce only Ps2and PsI. Reactions of PsHgX (X = Cl or Br) with PsLi, n BuLi and HgX2are reported.Thermolysis of PsHgX (X = Cl or Br) in the presence of methyl methacrylate (MMA) at temperatures ≥90°C afford block copolymers Ps‐PMMA via homolytic cleavage of Ps‐Hg bonds and radical propagation. Homolytic cleavage of Ps‐Hg by oxidation with CuBr2or by reaction with HgBr2in the presence of MMA also forms diblock copolymer. G.p.c. and other studies on the diblock copolym

ISSN:0007-1641    

DOI:10.1002/pi.4980190306

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractAn anionic to metathesis transformation reaction has been devised to study the mechanism of initiation of the metathesis ring‐opening polymerisation of cyclic alkenes and, by inference, the metathesis of alkenes also. The products of the reaction have been analysed by g.p.c. using a dual detector system to establish that block copolymers are formed when polystyryl lithium and tungsten hexachloride are used as initiator for the polymerisation of cyclopentene. A mechanism is proposed for the incorporation of polystyrene segments during the initiation step involving the formation of a bimetallic bridged complex that rearranges to form the active centre. There is also evidence that polystyrene segments are introduced during the termination reaction of the kinetic chai

ISSN:0007-1641    

DOI:10.1002/pi.4980190307

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe advantages of halo‐isocyanates as ‘transformation’ reagents in the synthesis of block and graft copolymers are elaborated. These compounds permit polymeric blocks of vinyl units to be attached to a wide range of starting materials, natural or synthetic. Two stages are involved—isocyanation and grafting—and both may be carried out homogeneously or heterogeneously. Attention is here focused on poly(ether‐urethanes), e.g. Biomer, dextran and poly(ethylene glycol) to which chains of several water‐soluble polymers have

ISSN:0007-1641    

DOI:10.1002/pi.4980190308

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper extends our previous study of the morphology and properties of polyblends of a polycarbonate and poly(methyl methacrylate) to an investigation of the influence of small amounts of added graft copolymer. The results demonstrate that, in spite of the complexity of the molecular species involved, graft copolymers can act as effective surfactants in polymer blends. The dominant effect is to form finer dispersions of one component in the other, with commensurate increases in interfacial area. A preliminary investigation of the influence of molecular parameters in the graft copolymer is reported; in all cases the molecular weight of the poly(methyl methacrylate) in the copolymer was kept constant and greater than that of the homopolymer whereas the molecular weight of the polycarbonate was varied. Finer dispersions and greater modifications to the relaxation behaviour were found as the molecular weights of the polycarbonate blocks in the copolymer increased and became comparable with the molecular weight of the homopolymer, and as the copolymer content increased.

ISSN:0007-1641    

DOI:10.1002/pi.4980190309

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractE.s.r. spectra of spin‐labelled poly(vinyl acetate) plasticised to varying extents with dibutyl phthalate have been analysed to yield the temperature,T50G, at which the separation of the extrema is 50 G. As in the case of spin‐probed, plasticised poly(vinyl acetate), the reciprocal ofT50Gshows a linear dependence on the weight fraction of polymer. This observation supports the view that in the region ofT50Gthe label responds to the glass‐to‐rubber relaxation. At temperatures immediately belowT50Gthe low‐field peak in the spectrum is split, indicating that motion of the label occurs with a distribution of correlat

ISSN:0007-1641    

DOI:10.1002/pi.4980190310

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY