Macromolecular Symposia

Spassky, N.; Sekiguchi, H.

doi: 10.1002/masy.19910470102pmid: N/A

doi: 10.1002/masy.19910470101pmid: N/A

Farina, Mario; Di Silvestro, Giuseppe; Sozzani, Piero; Yuan, Cui Ming

doi: 10.1002/masy.19910470103pmid: N/A

Different aspects of radical polymerization have been investigated in the author&s laboratory.

Hogen‐Esch, T. E.; Sundararajan, J.; Toreki, W.

doi: 10.1002/masy.19910470104pmid: N/A

A series of macrocyclic poly(2‐vinylpyridine)&s were synthesized by high dilution (∼10−5 M) coupling of the two‐ended living precursor dianions with 1, 2‐ and 1, 4‐bis‐(bromomethyl)benzene (1, 2‐ or 1, 4‐DBX). SEC measurements indicate that the macrocycles contain less than 5% linear precursor and that the hydrodynamic size of the macrocycles is substantially (∼30%) less than that of the linear precursor. At very low MW, the sizes of macrocyclic and linear polymers differ less, particularly for the case of the 1, 2‐DBX product. Viscometry measurements in THF of linear and macrocyclic polymers also indicated substantial size differences of linear and macrocyclic P2VP.

Höcker, Hartwig

doi: 10.1002/masy.19910470105pmid: N/A

1, 1‐Diphenylethylene is not capable of being homopolymerized, neither by radical nor by anionic mechanism. This is due to both electronical and sterical reasons. 1, 1‐Diphenylethylene, however, is eligible to electron transfer reactions to yield the radical anion which subsequently upon combination reaction forms the dimeric dianion. On the other hand, 1, 1‐diphenylethylene may be subjected to the nucleophilic addition of strong nucleophiles such as carbanions, e.g., butyllithium or polystyryllithium. Upon this reaction, a carbanion is formed the nucleophilicity of which is significantly reduced as compared with that of the starting carbanion. Molecules containing the characteristic group of 1, 1‐diphenylethylene twice, in analogous reactions, may be subjected to polycombination reactions upon electron transfer. The polymers exhibit cyclic or linear structure depending on the molecular structure of the starting divinylidene compound. Upon reaction with carbanionic species, biscarbanions are formed which may be used as initiators for the anionic polymerization of suitable monomers. A variety of divinylidene compounds and their specific features are presented.

Kennedy, Joseph P.

doi: 10.1002/masy.19910470106pmid: N/A

The most important recent development in cationic polymerizations is the emergence of living polymerizations leading to a variety of new potentially useful well‐defined macromolecules under conventional laboratory conditions. Three requirements have to coexist for living carbocationic polymerization to occur: Controlled initiation controlled chain‐transferless propagation and controlled (quasiliving) termination. The first part of this presentation will briefly discuss the road to these three key requirements. The second part will concern practical consequences and select systems. The synthesis of narrow‐molecular‐weight‐distribution (M̄w/M̄n = 1.1 ‐ 1.3) tert‐chlorine telechelic polyisobutylenes over a wide molecular weight range (M̄n from ∼1000 to ∼125, 000 g/mole) will be outlined together with recent work on aromatic olefins, e.g., styrene, tert‐butylstyrene and p‐chlorostyrene. These developments led to the combination of these living systems for the synthesis of block copolymers by sequential monomer addition. Tri‐ or higher block copolymers comprising glassy outer segments and rubbery inner segments, for example, poly(styrene‐b‐isobutylene‐b‐styrene, poly(p‐chlorostyrene‐b‐isobutylene‐b‐p‐chlorostyrene), have been prepared. These new thermoplastic elastomers exhibit phase‐separated microstructures and an interesting combination of physical‐mechanical properties.

Sawamoto, Mitsuo; Higashimura, Toshinobu

doi: 10.1002/masy.19910470107pmid: N/A

This paper focuses on two recent topics in living cationic polymerization of vinyl monomers, i.e.,

Kaminsky, W.; Bark, A.; Arndt, M.

doi: 10.1002/masy.19910470108pmid: N/A

With homogenous catalysts on the basis of chiral metallocenes and methylaluminoxane it has become possible to polymerize cyclic olefins like cyclobutene, cyclopentene or norbornene. No ring opening reaction occurs. The crystalline polycycloalkenes show extremly high melting points between 400 and 600°C. Copolymers of cyclopentene with propene are amorphous. They have a low molecular weight and glass transition point. On the other hand the glass transition temperature of norbornene/ethene copolymers exceeds 130°C. These copolymers could be used as materials for optical discs and fibers.

Spitz, R.; Pasquet, V.; Joly, J.‐F.

doi: 10.1002/masy.19910470109pmid: N/A

An approach of the special problems observed in copolymerization with Ziegler‐Natta heterogeneous catalysts is given on the basis of linear low‐density polyethylene synthesis in gas phase reaction. The reaction is controlled by chemistry and not by diffusion. The ethylene‐l‐butene copolymerization reactivity computed from the kinetic study varies with the copolymer composition, and this is due to the fact that the comonomer acts as a ligand of the active centers. The reactivities computed from NMR analysis are also not really reliable as the copolymer is a mixture of copolymers with different compositions.

Heitz, W.

doi: 10.1002/masy.19910470110pmid: N/A

Soluble LC polymers were synthesized with the aim to approach molecular reinforcement. Chemical modification results in a decrease of the crystallinity and an increase of the solubility. Substitution of the amide hydrogen in poly(4‐aminobenzoic acid) by a methyl group reduces the stiffness of the polymer very much, and as a result no lyotropic solutions are obtained. Poly(p‐phenylene terephthalate) with substituents on the hydroquinone or on both monomer units were synthesized. With one phenylalkyl group in the repeating unit the polyesters are crystalline with melting points > 300°C. With two substituents the polymers form in many cases amorphous anisotropic glasses at room temperature. 2‐Biphenyl is the most effective substituent with regard to increase of solubility. These polyesters form isotropic solutions in chloroform. Isotropic films obtained from these solutions become anisotropic on heating above the glass transition temperature. Films of polyester/polycarbonate blends show additivity of E‐modulus with respect to both compounds.