| 摘要 |
<p>Novel triblock copolymers are provided. The triblock copolymers have a midblock which is a copolymer of an isoolefin monomer and a vinyl aromatic monomer. Preferably, the midblock is a copolymer of isobutylene and alkylstyrene. The end blocks of the triblock copolymer are either a homopolymer of a vinyl aromatic monomer or a copolymer of two or more monomers selected from the group consisting of vinyl aromatics, styrene, methylstyrene, butylstyrene, halostyrene, p-allylstyrene and p-3-butenylstyrene. In addition, a process is provided for preparing a triblock copolymer. The process involves: a) initiating a "living" polymerization of an isoolefin monomer (monomer A) and a first vinyl aromatic monomer (monomer B) in a reaction vessel using carbocationic polymerization conditions and a catalyst capable of carbocationically polymerizing monomer A and monomer B; b) allowing the polymerization to continue for a period of time T1, during which additional monomer A and/or monomer B may be optionally added; c) at the completion of time T1, continuing the polymerization by adding only additional monomer A for a period of time T2; d) at the completion of time T2, continuing the polymerization by adding a second vinyl aromatic monomer (monomer C) for a period of time T3; e) at the completion of time T3, quenching the polymerization; and f) recovering a triblock copolymer.</p> |
