Flexibilized styrene-N-substituted maleimide copolymers. I. Multiblock copolymers prepared from styrene-maleimide telechelics and polytetrahydrofuran

Telechelic copolymers of styrene and different N-substituted-maleimides (SM Is) with a molecular weight of 2000-8000 g/mol were synthesized using the s tarved-feed-reactor technique and were nearly bifunctional when the monomer feed had a high styrene concentration. The COOH-terminated rigid SMI block s were poly-condensated with OH-terminated poly(tetrahydrofuran) (PTHF) blo cks, with a molecular weight of 250-1000 g/mol,which are the flexible parts in the generated homogeneous multiblock copolymer. The entanglement densit y, which is closely related to the toughness of materials, increased in the se flexible SMI copolymers (nu(e) = 5.2 . 10(25) m(-3)) compared to the unf lexibilized ones (nu(e) = 2.4 . 10(25) m(-3)). The glass transition tempera ture of these flexibilized, single-phase multiblock copolymers was still hi gh enough to qualify them as engineering plastics. (C) 2000 John Wiley & So ns, Inc.