Cooling Condition Determines the Transition Degree at Saturation of Form II in Isotactic Polybutene-1 Confined within Nanopores

The crystal transition from Form II to Form I of isotactic polybutene-1 (PB-1) occurs spontaneously and irreversibly when the polymer is stored at room temperature. The transition kinetics is influenced not only by the thermal history, but also by spatial confinement. In this study, the crystal transition of infiltrated PB-1 within 400 nm anodic aluminum oxide (AAO) templates was studied by grazing incidence wide-angle X-ray scattering. Before annealing, different crystallization conditions were applied to the samples, including different final temperatures at a fixed cooling rate (10 °C/min) and different cooling rates to a fixed temperature (25 °C). We found that cooling to a lower temperature was beneficial for a faster transition, but the transition degree at saturation (XI∞) was unvaried. On the other hand, the XI∞decreased significantly with the increasing applied cooling rate. As a comparison, the XI∞of bulk PB-1 changed slightly with cooling rates. The results may be explained morphologically: "loosely packed" or "fragmented" Form II crystals formed near the AAO wall, where the nucleation rate of Form I was extremely slow and adjacent Form I could not grow into them.