Crystallization, Orientation, and Solid–Solid Crystal Transition of Polybutene-1 Confined within Nanoporous Alumina
2020
Shi, Guangyu | Wang, Zefan | Wang, Ming | Liu, Guoming | Cavallo, Dario | Müller, Alejandro J. | Wang, Dujin
The effect of confinement on the crystallization, crystal orientation, and polymorphic crystal transition of bulk and infiltrated polybutene-1 (PB-1) within anodic aluminum oxide (AAO) templates were studied. After cooling from the melt, PB-1 within AAO templates crystallized into tetragonal Form II directly. The nucleation process inside the AAO pores was probably homogeneous when pore diameters were below 200 nm. The crystal orientation of Form II was investigated by grazing incidence X-ray scattering. Form II to I transition was investigated as a function of time and modeled with the Avrami equation. The rate of Form II to I transition for infiltrated PB-1 within 400 nm AAO was unexpectedly higher than that of the bulk. The stress generated because of the mismatch of the thermal expansion coefficients between PB-1 and AAO greatly enhanced the nucleation of Form I within the Form II matrix. A slower Form II to I transition was observed when the pore diameter of AAO decreased. The transition degree decreased with the decreasing pore diameter and was completely inhibited for PB-1 infiltrated within the 30 nm AAO template. A stable Form II interfacial layer with a thickness of ∼12 nm was postulated to account for this phenomenon.
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