Direct formation of isotactic poly(1-butene) form i crystal from memorized ordered melt

摘要

Crystallization from memorized ordered melt (MOM) of isotactic polybutene-1 (iPB-1) is investigated with in situ Fourier transformation infrared microspectroscopic imaging and wide- and small-angle X-ray scattering. After being partially melted at high temperature, a small portion of form I crystal of iPB-1 recovers back when the temperature is lowered. This is different from a disordered melt, which crystallizes into form II directly. The recovery of form I crystal is attributed to the presence of MOM, which may keep the conformation order of form I crystal. Experimental evidence show that MOM possesses three characteristics, namely: (i) associating with the preserved form I; (ii) occupying only a small portion of the melt in the partially melted sample; (iii) being stable at high temperature. All this experimental evidence suggests that MOM locates at the boundary of crystal and melt. This is in line with the physical picture of nonclassical nucleation and growth theory or the multistage approach, where a partially ordered melt layer locates at the boundary of crystal and melt.