The glass transition temperature of polymer melts
The glass transition temperature of polymer melts
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DOI：
10.1021/jp0523266
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发表时间：
2005-11-17
影响因子：
3.3
通讯作者：
Douglas, JF
中科院分区：
文献类型：
--
作者：
Dudowicz, J;Freed, KF;Douglas, JF
我们开发了一种分析理论来估计聚合物熔体的玻璃化转变温度T-g作为链主链和侧基的相对刚性、单体结构、压力和聚合物质量的函数。我们的计算是基于一个扩展的serniempirical林德曼标准的熔融定位T-G和使用先进的平均场晶格集团理论（LCT）治疗的系统包含结构单体，半柔性聚合物链的热动力学。林德曼准则被翻译成一个条件，通过表达这个关系的特定体积的T-g，和这个自由体积条件是用来计算T-g从我们的热力学理论。的T-g的质量依赖性相比，其他的玻璃形成的特征温度。这些额外的特征温度是从LCT构型熵的温度变化确定的，结合长波长结构弛豫的Adam-Gibbs模型。我们的理论解释了一般观察到的趋势，在T-g的变化与聚合物的微观结构，我们发现，T-g可以向上或向下调整，通过增加侧链的长度，这取决于侧基和链骨架的相对刚性。阐明聚合物液体中T-g的分子起源对于设计和加工新的合成材料以及理解生物物质的动力学和控制保存是有用的。
We develop an analytic theory to estimate the glass transition temperature T-g of polymer melts as a function of the relative rigidities of the chain backbone and side groups, the monomer structure, pressure, and polymer mass. Our computations are based on an extension of the serniempirical Lindemann criterion of melting to locate T-g and on the use of the advanced mean field lattice cluster theory (LCT) for treating the themodynamics of systems containing structured monomer, semiflexible polymer chains. The Lindemann criterion is translated into a condition for T-g by expressing this relation in terms of the specific volume, and this free volume condition is used to calculate T-g from our thermodynamic theory. The mass dependence of T-g is compared to that of other characteristic temperatures of glass-formation. These additional characteristic temperatures are determined from the temperature variation of the LCT configurational entropy, in conjunction with the Adam-Gibbs model for long wavelength structural relaxation. Our theory explains generally observed trends in the variation of T-g with polymer microstructure, and we find that T-g can be tuned either upward or downward by increasing the length of the side chains, depending on the relative rigidities of the side groups and the chain backbone. The elucidation of the molecular origins of T-g in polymer liquids should be useful in designing and processing new synthetic materials and for understanding the dynamics and controlling the preservation of biological substances.