Influence of entanglements on glass transition of atactic polystyrene
Influence of entanglements on glass transition of atactic polystyrene
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DOI：
10.1002/polb.20513
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发表时间：
2005-08
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影响因子：
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通讯作者：
W. Rong;Zhongyong Fan;Yin-e Yu;H. Bu;Michael Wang
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文献类型：
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作者：
W. Rong;Zhongyong Fan;Yin-e Yu;H. Bu;Michael Wang
将无规立构聚苯乙烯（a-Ps）在苯中的稀溶液（浓度范围为1 × 10 - 1 ~ 2 × 10 - 5g/mL）制成冻干样品，用差示扫描量热法测定其玻璃化转变温度（Tg）。结果发现，低于临界浓度（Cg），样品的Tg随溶液对数浓度的降低而线性下降。将冷冻干燥的样品在恒定温度下退火不同时间或在不同温度下退火相同时间段。从低于Cg浓度的溶液制备的样品的Tg被观察到随着退火温度或退火时间的增加而向更高的温度偏移，最终接近本体样品的Tg。测定了冻干样品的傅里叶变换红外（FTIR）光谱，并与散装样品进行了比较。在冷冻干燥样品的光谱中观察到线宽和吸收强度的显著变化，表明片段的堆积处于更澄清的状态。在退火过程中，样品中片段的堆积逐渐接近本体样品的堆积，从而减小了冻干样品和本体样品之间FTIR光谱的差异。实验观察进行了讨论，并认为链内和链间缠结可能发挥重要作用的玻璃化转变。
Freeze-dried samples were prepared from dilute solutions of atactic polystyrene (a-Ps) in benzene in a concentration range of 1 x 10 -1 to 2 x 10 -5 g/mL, and their glass transition temperatures (Tg) were determined by differential scanning calorimetry. It was found that below a critical concentration (Cg), the Tg of samples decreases linearly with decreasing logarithmic concentration of solutions. The freeze-dried samples were annealed at a constant temperature for various times or at various temperatures for the same period of time. The Tg of samples prepared from solutions of concentration below Cg was observed to shift to higher temperature with increasing annealing temperature or annealing time, finally approaching that of the bulk sample. Fourier transform infrared (FTIR) spectra of the freeze-dried samples were determined and were compared with the bulk sample. Significant changes in line width and absorption intensity were observed in the spectra of the freeze-dried samples, indicating that the packing of segments is in a more dilatant state. During annealing, the packing of segments in the samples gradually approaches that of the bulk sample, diminishing the differences in FTIR spectra between the freeze-dried sample and the bulk sample. The experimental observations are discussed, and it is assumed that intrachain and interchain entanglements may play an important role in glass transition.