摘要:

AbstractA new class of macromolecules has been synthesized based on a skeletal structure of alternating phosphorus and nitrogen atoms (I). These are the first high polymers with an inorganic backbone to be developed on a broad scale since the discovery of the poly(organosiloxanes) in the 1940's.The preferred synthesis route makes use of highly reactive polymeric intermediates (I, X = C1 or F) used as substrates for halogen replacement by organic nucleophiles. Structural diversity is achieved either by changes in the nucleophile or by chemical modification of the side groups after they are attached to the backbone. Using these principles, a wide range of different polymers has been prepared ranging from elastomers to carrier molecules for steroids, transition metals, metalloporphyrins, or carboranes. Biodegradable and biocompatible macromolecules have also been synthesized. The critical role of small molecule model reactions is stressed, and examples are given of recently discovered organometallophosphazenes that are expected to have a profound influence on future polyphosphazene syntheses.

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981101

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractInclusion polymerization consists in the polymerization of unsaturated monomers inserted, as guest molecules, into the crystal lattice of a different host molecule. Polymers thus obtained often possess a high constitutional and configurational regularity. In some cases they also present optical activity and an extended‐chain macroconformation in the nascent state. Structural, kinetic, and thermodynamic studies provide evidence that the reaction takes place in the solid phase. Various types of reaction control are examined and data are presented, showing that asymmetric induction is transmitted through space and not through bond

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981102

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractA model for the generation and amplification of optical activity, involving crystallization of achiral monomers in chiral crystals combined with topochemical polymerization, is described. Taking into consideration some empirical rules of crystal‐packing, seven achiral or chiral racemic monomers were selected as reactants for these studies, which were indeed found to pack in chiral crystals with the motif suitable for a topochemical solid‐state polymerization with quantitative enantiomeric yield. The chiral products (dimers, trimers, and oligomers), obtained in a first successful generation experiment, proved to be powerful asymmetry inducing agents in a fresh crystallization of the starting materials. From the totally consistent results of a large number of experiments, the following “inversion rule” was derived: dimers, trimers, and oligomers generated in a “d” crystal always induce preferential crystallization of the monomers in the enantiomorphic “l” phase and vice versa. A mechanism of preferential adsorption of the chiral impurity on that crystalline phase which is stereochemically similar to it is proposed, and evidence for the validity of this hypothesis is presented. Viewed in more general terms, the inversion rule can be extended to include conglomerates as well, and examples from the literature as well as new systems have been demonstrated to undergo resolutionviathis mechanism. Finally the implications of this mechanism for the possible resolution of racemic polymers wi

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981103

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe important factors which control the stereochemistry of polymerization, and thereby the crystalline properties of the polymers so formed, are considered for four different types of reactions including: (1) the cationic polymerization of substituted α‐methylstyrenes to form syndiotactic polymers; (2) the anionic ring‐opening polymerization of substituted β‐propiolactones to form crystalline polyesters; (3) the metathesis ring‐opening polymerization of 1,5‐cyclooctadiene to form poly(1,3‐butadiene)s of controlledcis‐transcontents; and (4) the condensation polymerization of α‐methylbenzyl chloride to form isotactic po

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981104

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe stereospecific polymerization of diolefins using new catalytic systems based on less conventional transition metal complexes is reviewed. In particular, two families of catalysts based on new complexes of π‐allyl type of actinide and lanthanide elements, as well as three component systems formed by rare‐earth metal alkoxides, aluminum alkyls, and a Lewis acid are described. A peculiarity of both actinide and lanthanide catalysts is their ability to give, at very low concentration, extremely highcisdiolefin polymers and copolymers in aliphatic solv

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981105

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThis paper is concerned with the sequence regulation of monomeric units in a series of binary and ternary copolymerizations which proceed without any added catalyst or initiator. The binary copolymerization is consisted of the combination of a nucleophilic monomer (MN) and an electrophilic monomer (ME). The interaction between the two monomers generates a zwitterion of a 1:1 adduct, which is the key intermediate in the copolymerization producing 1:1 alternating copolymer. The varieties of MNand MEmonomers, the structures of key intermediates of zwitterions, and the schema of copolymerizations have been discussed. In addition, the “Sequence–Ordered 1:1:1 Terpolymerization” (producing terpolymers of a type .…ABCABCABC….) and “2:1 Binary Copolymerization” (producing copolymers of a type of .…ABBABBABB….) are described, which have been developed on the basis of the above binary 1:1 alternating

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981106

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981107

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe synthesis and conformational analysis of several polydepsipeptides containing alkyl or polar residues are reported. Five separate routes to the synthesis of depsipeptide monomers and two methods of polymerization are decribed. Polydepsipeptides containing alanine, valine, leucine, lactic acid, α‐hydroxyisovaleric acid, glutamic acid, and lysine were prepared and their conformations in solution analyzed. Helix‐to‐coil transitions for specific polydespsipeptides are obsurved in single organic solvents such as chloroform, tetrahydrofuran, or trifluoroethanol. A statistical thermodynamic theory of polymer melting successfully describes the observed transitions and allows quantitative determination of the tendency of specific amino acid residues to form helical

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981108

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe value to polymer chemistry of certain recent developments in NMR is discussed. The techniques in question are: (i) high‐field operation, (ii) multinuclear studies, and (iii) the dipolar decoupling/cross‐polarization/magic angle rotation experiments on solids. Examples of polymer spectra obtained by these methods are gi

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981109

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe structure and optical compensation of polymers having asymmetric carbon atoms in the main chain are discussed. When rectus (R) and sinister (S) isotactic (it) polymers mix in a 1:1 ratio giving a racemic crystalline sample, three kinds of optical compensation can be con sidered; (a) optical compensation in a unit cell, (b) compensation in a crystallite, and (c) intercrystallite compensation. it‐Poly(tert‐butylethylene oxide) form I, it‐poly(tert‐butylethylene sulfide), and it‐poly(isopropylethylene sulfide), are of case (a). it‐Poly(isopropylethylene oxide), it‐poly(propylene sulfide), it‐Poly‐β‐hydroxybutyrate, it‐Poly(β‐ethyl‐β‐propiolactone), and it‐poly(tert‐butylene oxide) form II correspond to case (c). The results of the x‐ray analyses of these polymers clearly show a stereoselective mechanism of polymerization in

ISSN:0025-116X    

DOI:10.1002/macp.1981.020041981110

出版商:Hüthig&Wepf Verlag    

年代:1981

数据来源: WILEY