摘要:

AbstractRecent investigations indicate that the base‐promoted polymerization reaction of a 1,4‐phenylenebis(methylene)disulfonium salt in a aqueous solution involves the formation of a highly reactivep‐xylylene intermediate, which polymerizes through formation of a sulfur ylide active center by an anionic mechanism. If so, it would be expected that the concentration of this intermediate should be very important in controlling both polymer yield and molecular weight, so it should be possible to increase the concentration of that intermediate by removing the organic sulfide released in the initial elimination reaction by extraction into an organic solvent. This expected effect was verified by the very large increases in both reaction conversion and polymer intrinsic viscosity obtained when the polymerization reaction was carried out in the presence of pentane. The effect was greater with the cyclic sulfide monomer than with the dimethyl sulfide monomer, presumably because of the higher water solubility of the l

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989101

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractAnionic ring opening polymerization of 5,5‐dimethyl‐1,3‐dioxan‐2‐one (2,2‐dimethyltrimethylene carbonate) (1) initiated bysec‐butyllithium, sodium methoxide or potassium dihydronaphthylide was found to proceed via alcoholate anions. This finding is based on31P NMR spectroscopic studies of the polymer end groups, which result from the reaction of the living polymer with diphenyl ch

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989102

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractComplexes of antimony pentachloride with acyl chlorides such as acetyl chloride or 1‐naphthoyl chloride polymerize various completely methylated cyclosiloxanes such as hexamethylcyclotrisiloxane (D3) or dodecamethylcyclohexasiloxane (D6) with high rates of initiation and propagation, their activity being unchanged in the presence of the proton‐trap 2,6‐di‐tert‐butyl‐4‐methylpyridine. For polymerization of D3conducted at −10°C in methylene dichloride, there is a simultaneous and proportional formation of high‐molecular‐weight polymer (HP), of small cycles of the D3xtype (concentrations [D6]>[D9]>[D12]>…) and of macrocycles. A linear increase of the molecular weight (M) of HP is observed up to at least 50% conversion, in agreement with the presence of a constant number of macromolecules of high molecular weight, mainly consisting of a living polymer population. For higher conversions,Mmay grow more rapidly which may be explained by an increasing copolymerization of D6and D9with D3. Homopolymerization of D6occurs under similar conditions with a rate smaller than that for D3, but also with linearly increasingMof HP with conversion. The simultaneous formation of the various products is attributed to the presence of two populations of macromolecules. One of these would bear either two active centres or one active centre and one non‐reacting end‐group, and the other population would bear one active centre and one reacting end‐group, giving by end‐to‐end ring closure, macrocycl

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989103

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractSome results are reported on the alkyllithium‐initiated polymerization of butadiene in cyclopentane in presence of 2,′2‐bis(4,4,6‐trimethyl‐1,3‐dioxane). The effect of this lithium chelating agent on one‐unit model active centres is also reported. Comparisons are made with another highly efficient polymer structure modifier, 1,2‐dipiperidinoethane. Conclusions are reached on the reasons why both are particularly effective in inducing the formation of polydienes having extremely hig

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989104

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractPolyvinylpyridines activated by tris(π‐allyl)chromium and by tetrakis (σ‐allyl)molybdenum or tetrakis(σ‐allyl)tungsten, complexed with tetrahydrofuran, were used for grafting with acrylonitrile. The products obtained, differing in the degree of branching, were characterized by various physical methods. Block copolymers of the types butadiene‐acrylonitrile and styrene‐oligobutadiene‐acrylonitrile were synthesized by the use of tris(π‐butadienyl)chromium as the initial active agent. Some molecular parameters of these block copolymers

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989105

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe kinetics of propagation in the polymerization of propylene oxide proceeding by the activated monomer (AM) mechanism is studied. Propagation in this system involves addition of a protonated monomer molecule to the terminal hydroxyl group of the growing oligomer. A kinetic analysis of the reaction allowed the determination of the equilibrium constantK, governing the distribution of protons between monomer and HO‐ groups, which in turn enables to calculate the propagation rate constantkp. This composite value has been further separated into the rate constants of four reactions, involving two different modes of ring opening in reactions with two different types of hydroxyl groups, viz. primary and secondary ones. The corresponding values are (all rate constants in mol−1· L · s−1and for CH2Cl2at 25°C):K= 5,3;k1,1= 0,170,k1,2= 0,190,k2,1= 0,105,k2

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989106

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractPolymerization of 1,3‐dioxolane (1) with terephthaloyl ditriflate as initiator in dichloromethane at −40°C produces poly(1)s with molecular weights given by {([Monomer]0‐ [Monomer]e)/([Initiator])} ([Monomer]e= monomer conc. at equilibrium). Termination with triethylamine leads to poly(1)s with two quaternizeda‐aminoether functions as end groups. These end groups react with carboxylate ions in apolar solvent to form the corresponding hemiacetal esters. This reaction sequence allows to produce a variety of well defined poly(1) tel

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989107

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe free cationic copolymerization behavior of styrene derivatives in methylene dichloride solution was examined. The copolymerization behavior of all monomer pairs was found to be strongly ideal. The relationships between reactivity ratios of the monomer pairs can be accurately correlated by a number of simple models. Hammett plots give very similar values for reaction constants for the different cations, and the copolymerization behavior can also be correlated by a generalized Hammett relation using an overall reaction constant. This suggests that under the particular reaction conditions of this work, the cations do not differ greatly in their absolute reactivity. This idea is briefly discussed in light of other work that has been done concerning the nature of the propagating cations in the polymerization of styrene derivatives.

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989108

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe change of tacticity of methacrylate blocks in the anionic block copolymerization of ethylene oxide with methyl methacrylate ortert‐butyl methacrylate as function of the number of monomeric units in the poly(ethylene oxide) (PEO) sequences formed in the first polymerization step, was studied. The fraction of the syndiotactic triads of the polymethacrylates was found to increase with the DP of the PEO precursor. When the plateau value was reached, the tacticity was similar to that of poly(methyl methacrylate) initiated by alkali alkoxides when solvated with crown ethers. The variation of the tacticity was smaller withtert‐butyl methacrylate than with methyl methacrylate. The growth reaction of methacrylate monomers was found to follow Bernoullian statistics. It is assumed that the solvation of the counterions increases with increasing of the monomeric units in the starting poly(ethylene oxide) blo

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989109

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe thermal reaction of a bis(biphenylene) monomer,N,N′‐bis(biphenylene‐2‐yl)‐4,4′‐hexafluoroisopropylidenediphthalimide (3), with either of two diacetylenic monomers, bis(4‐ethynylphenyl) ether (4) or bis[4‐(phenylethynyl)phenyl] ether (5), gave polymers that contain phenanthrene units as a result of the reaction of the biphenylene groups with the acetylene groups. The reaction could be carried out in solution or in the melt, and in the latter case, reaction exotherms were found at 367°C and 386°C, respectively, for4and5. Polymer6, obtained from the melt reaction of3with5, is insoluble in all solvents and thermally stable, showing no weight loss in air up to 480°C and

ISSN:0025-116X    

DOI:10.1002/macp.1989.020151989110

出版商:Hüthig&Wepf Verlag    

年代:1989

数据来源: WILEY