A new telechelic polyisobutylene diol, HOCH2PIBCH2OH, carrying two terminal primary hydroxyl end groups has been prepared from α,ω‐di(isobutenyl)polyisobutylene, CH2C(CH3)‐ CH2PIBCH2C(CH3)CH2, by regioselective hydroboration followed by alkaline hydrogen peroxide oxidation. Infrared (IR) spectra, 1H‐NMR analysis of the pure and silylated products, and ultraviolet (UV) spectra of phenylisocyanate‐treated diols indicate quantitative yields and two CH2OH termini per polyisobutylene chain. The viscosity of HOCH2PIBCH2OH is higher than that of the starting α,ω‐diolefin. The telechelic diol prepolymer opens new avenues to the synthesis of many new materials, e.g., polyurethanes.
Detailed understanding of the mechanism of initiation and chain transfer in BCl3‐coinitiated isobutylene polymerization led to the efficient synthesis of symmetric telechelic polyisobutylenes carrying ∼CH2C(CH3)2Cl groups at either end of the molecule Cl‐PIB‐Cl. The synthesis is based on the use of inifers, i.e., bifunctional initiator‐transfer agents that effect controlled initiation and propagation in the absence of chain transfer to a monomer. Specifically, the synthesis of Cl‐PIB‐Cl was achieved by the p‐dicumyl chloride/BCl3/isobutylene/CH2Cl2 system. According to the inifer mechanism each Cl‐PIB‐Cl contains two terminal tertiary chlorines and one phenyl group at the interior of the chains. The structure of this new symmetric telechelic polymer has been established by detailed characterization studies including a sensitive new gel permeation chromatography (UV plus RI) analysis method, 1H‐NMR, kinetic experiments, and chemical derivatization. The Cl‐PIB‐Cl molecule is a key intermediate for the synthesis of hosts of new materials, e.g., triblock copolymers, α,ω‐diolefins, and α,ω‐difunctional polymers.
A thorough examination of some cationic copolymerization systems by a new method has shown that many published r values have to be corrected significantly and that some are erroneous and meaningless, because for these systems the conventional copolymer compositions equation does not hold. Available information in regard of cationic copolymerizations has been treated in terms of three classes: (a) Systems in which the conventional copolymer composition equation adequately describes the copolymerization mechanism and previous authors justifiably used the two parameter model to calculate reactivity ratios. Our results show that the discrepancy between published r values and the more precise values obtained in this work is about ±23%. (b) Systems in which the approximations implicit in the conventional copolymer composition equation do not hold and the calculated r values are erroneous and misleading. Monomer pairs comprising monomers of significantly different reactivities belong to this class indicating that in copolymerizations in general and in cationic copolymerizations in particular a strong cast system exists, i.e., copolymerization can readily occur within the cast (between monomers of similar reactivities); however, only with difficulty if at all between casts (between monomers of differing reactivities). (c) Systems in which the use of the copolymer composition equation is completely unjustified, the calculated r values are meaningless and in some cases the existence of true copolymers is questioned.
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