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Stabilization of Poly(methyl methacrylate) Nanofibers with Core–Shell Structures Confined in AAO Templates by the Balance between Geometric Curvature, Interfacial Interactions, and Cooling Rate

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journal contribution
posted on 15.02.2017, 00:00 by Chen Zhang, Linling Li, Xiaoliang Wang, Gi Xue
The glass transition behaviors of poly­(methyl methacrylate) (PMMA) nanofibers confined in pristine and surface-modified AAO templates are investigated by differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). During an ultraslow cooling process (0.1 K/min) across the Tg, two glass transition temperatures (Tg,low and Tg,high) are clearly identified by DSC and BDS, which correspond to the core and shell, respectively. The Tg,high originates from the transition of the adsorbed layer and is mainly dominated by the geometric curvature radius of the nanopores rather than the chemical nature of the wall surface. A dramatic change in the glass transition behaviors is detected when the cooling rate is changed from 40 to 0.1 K/min, which reflects the inherent evolution between the shell and the core through a nonequilibrium interlayer. Furthermore, by studying the system before and after surface modification of the nanopores by silanization, we suggest that such evolution could be sped up through the benefit of the stronger interfacial interactions. Our findings provide insight into achieving stable glassy polymer structures confined in nanopores by balancing the geometric curvature, interfacial interactions, and cooling rate.