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Reexamining the Crystallization of Poly(ε-caprolactone) and Isotactic Polypropylene under Hard Confinement: Nucleation and Orientation

Shi, Guangyu, Liu, Guoming, Su, Cui, Chen, Haiming, Chen, Yu, Su, Yunlan, Müller, Alejandro J., Wang, Dujin
Macromolecules 2017 v.50 no.22 pp. 9015-9023
aluminum oxide, crystallization, differential scanning calorimetry, nanopores, polypropylenes, porosity, temperature, texture, wide-angle X-ray scattering
The crystallization of poly(ε-caprolactone) (PCL) and isotactic polypropylene (iPP) infiltrated in nanoporous anodic alumina oxide (AAO) templates was reexamined to demonstrate the importance of obtaining polymer-free, clean AAO surfaces on the nucleation, size dependence of crystallization temperature (Tc), and texture. The AAO pore diameters cover a broad range from 400 to 20 nm. When the AAO templates were completely free of any residual polymer on their surfaces, differential scanning calorimetry (DSC) experiments exhibited a single crystallization peak for all the samples with different AAO pore sizes. A drastic decrease in Tc with density of domains indicated a transition from heterogeneous to homogeneous/surface nucleation. A regular decrease of Tc with pore size was observed in the low Tc regime, as a result of the volume dependence of nucleation events. The chain alignment of the two polymers infiltrated in AAO was studied by two-dimensional wide-angle X-ray scattering (WAXS). By comparing the experimental and simulated WAXS patterns, the orientation modes of the polymers were identified and compared with previous studies.