Crystallization kinetics of syndiotactic polypropylene confined in nanoporous alumina

Crystalline polymers can exhibit anomalous crystallization behaviors as restricted into nanodomains. Herein, syndiotactic polypropylene (sPP) was infiltrated into nanoporous alumina templates with different pore diameters, and their nonisothermal and isothermal crystallization kinetics were investigated. As located inside nanopores, the crystallization of sPP becomes sluggish. The crystallization temperatures reveal a pronounced cooling rate dependence for sPP in large nanopores. At fast cooling rates, the homogeneous nucleation is dominated. While, at slow cooling rates, the splits of crystallization peaks can be ascribed to fractionated crystallizations initiated by heterogeneous and homogeneous nucleation, respectively. For sPP in small nanopores, the homogeneous nucleation always predominates, which induces less cooling rate effect. In addition, based on the Avrami equation and Lauritzen-Hoffman growth theory, isothermal crystallization experiments indicate that the characteristic crystallization times of sPP under confinement are much longer, and both of the nuclei density and secondary nucleation rate are decreased for sPP confined in nanopores.