Abstract
The crystallization behavior of two long-chain branched bisphenol A polycarbonates (PC-Bs) was studied in supercritical CO2 using differential scanning calorimetry (DSC), wide-angle X-diffraction, and atomic force microscopy (AFM), with a linear polycarbonate (PC-L) as reference. All the PCs had similar molecular weights and molecular weight distributions. Positron annihilation lifetime spectroscopy measurement indicated that the increase in free volume fraction of 13.1% (PC-B1) and 11.8% (PC-B2) was obtained with incorporating long-chain branches compared to PC-L. This increased segmental mobility decreased the energy barrier for PC crystallization and hence increased the crystallization kinetics for PC-Bs. Two melting peaks (Tm1 and Tm2) observed during DSC heating scan were associated with the melting of secondary and primary crystallization, respectively. The Tm2 of PC-Bs was about 2−4 °C lower than that of PC-L of at the same treatment time, pressure, and temperature. These results, qualitatively con...
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