Temperature Dependence of Segmental and Terminal Relaxation in Atactic

It has been established for more than 35 years that homopolymer melts can exhibit thermorheological com-plexity, i.e., different relaxation processes which con-tribute to viscoelasticity have different temperature dependences.1,2 In particular, segmental and terminal relaxation processes are known to have different tem-perature dependences for polystyrene,3 poly(vinyl ace-tate),4 polypropylene glycol,5,6 poly(phenylmethylsilox-ane),7 polyisoprene,8,9 and polyisobutylene.10,11 Atactic polypropylene (aPP) is an interesting model polymer for understanding melt dynamics, being the simplest vinyl polymer which is completely amorphous. The purpose of this communication is to show the relationship between recent NMR and dielectric relaxation results on aPP with earlier light scattering, creep, and dynami