Cyclo‐ and cyclized diene polymers. I. Polymerization of conjugated dienes to ladder cyclo‐polymers with complex catalysts

Abstract

Polymerization of isoprene, butadiene, and chloroprene with complex catalysts consisting of alkyl or arylmagnesium bromide or triethylaluminum and excess TiCl4 leads to the formation of powdery, insoluble, probably crosslinked polymers with high density and high heat resistance (>370°C). The structure of these polymers differs from that of those prepared at higher molar ratios of organometallic compound to titanium tetrachloride. The infrared analysis of the powdery polymers and comparisons with the spectra of cyclized 3,4‐polyisoprene and cyclized 1,4‐cis‐polyisoprene indicate that the polymer chain consists of fused six‐membered saturated rings in the form of a linear ladder or spiral ladder structure. The residual linear segments with 1,4 units, present in the predominantly cyclic polymers, may be isomerized to a cyclic form by the action of H2SO4. Removing the linear segments from the polymer chain further improves the heat resistance. It is proposed that the cyclic structure is formed during the polymerization from 1,2‐polymer and not as a result of the action of catalyst components on primarily formed linear chains. The cyclic structure may be ascribed to all three investigated polymers.

Structural characterization of polybutadiene synthesized via cationic mechanism

“…Considerably, less attention is paid to the investigation of cationic polymerization of 1,3‐butadiene . This is consistent with the high sensitivity of the cationic polymerization to impurities in the monomer as well as with the complexity of the structure of cationic polybutadiene (CPB) . In previous works, the structure of CPB was investigated by infrared spectroscopy.…”

“…The content of 1,2‐units varied from 17 to 33 mol % depending on the nature of Lewis acid and the polymerization conditions. The content of 1,2‐units in the unsaturated part of polymer chain of CPB synthesized with TiCl 4 /EtAlCl 2 initiating system was reported in works (a,b) to be between 2 and 18 mol %, while the other structural units possessed trans ‐1,4 configuration. Although infrared spectroscopy allowed determining the structure of polybutadiene and estimating the content of various structural units, it is not possible to reveal the distribution of different units in a chain, determine the structure of head and end groups, as well as calculate properly the content of all structural units .…”

Polymérisation de dérivés du cyclopropane. II. Polymérisation du spiropentane

“…La mol6cule mod6le ii 4 motifs isoprenoides cycliske (XIII) fait apparaitre dans l'infrarouge les bandes prec6demment cit6es ii 2960, 2925 et La pr6sence de l'acide de LEWIS dans le milieu reactionnel explique l'isom6risation de la structure (XVI) en structure (XVII) puis le passage ii la forme cyclis6e (XVIII) du type cyclopolyisopr6ne-l,4 [14][15][16][17][18][19][20][21].…”

One‐electron transfer initiated polymerization reactions I. Initiation through monomer cation radicals

“…I n contrast to the polymerization reactions described thus far, wherein a one-electron transfer from a monomer to a suitable electron acceptor results in the formation of a monomer cation radical which propagates through either a cationic or a radical mechanism, the polymerization of conjugated dienes such as butadiene, isoprene, and chloroprene with cationic catalysts involves monomer cation radicals which propagate through consecutive cation and radical addition steps (87)(88)(89)(90)(91)(92)(93)(94)(95)(96)(97).…”