The enhanced II–I transition behaviors of an isotactic polybutene-1 alloy by a TAB-3

Polymer crystallization and crystal transition mechanisms are charming but elusive long-lasting questions in polymer physics due to theoretical and industrial importance. Interestingly, after a TAB-3 incorporated into an isotactic polybutene-1 (iPB-1) alloy, its II–I transition was sharply enhanced at room temperature, whereas the "nucleation" was inversely inhibited at low temperatures T_lows around − 10 °C or almost kept fixed at room temperature. Moreover, with II–I transition preceding, the peak melting point T_m,peak of the remained form II decreased, while the T_m,peak of the resulting form I increased inversely. And the crystallinity increase of the neat iPB-1 alloy during II–I transition turned as decrease after TAB-3 incorporation. All the results were difficult to be interpreted according to the traditional solid–solid nucleation-growth II–I transition mechanism with nucleation as the rate-determining step. We looked back and reconsidered the II–I transition mechanism and preferred a "form II"–"form-II-favored packed mesophase"–"form I" process with crystals reorganized. Formation of the intermediate form-II-favored packed mesophase from form II crystals promoted by TAB-3 incorporation controls the entire II–I transition and accounts for the characteristic "growth-controlled" II–I transition kinetics of the iPB-1 alloy. The results are triggering to deep theoretical understanding to the II–I transition for further extended industrial applications of iPB-1. Graphic abstract: