THERMAL-EXPANSION OF AMORPHOUS POLYMERS AT ATMOSPHERIC-PRESSURE .2. THEORETICAL CONSIDERATIONS
THERMAL-EXPANSION OF AMORPHOUS POLYMERS AT ATMOSPHERIC-PRESSURE .2. THEORETICAL CONSIDERATIONS
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DOI：
10.1021/ma60036a023
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发表时间：
1973-01-01
期刊：
影响因子：
5.5
通讯作者：
WILSON, PS
中科院分区：
文献类型：
--
作者：
SIMHA, R;WILSON, PS
我们分析了一些结构不同的系统。一个简单的插值表达式精确地表示了先前推导的液体理论状态方程的隐式形式，并便于数值计算。预测值与实测值之间的吻合度很好，与早期观测值雅阁。热膨胀系数，a，估计的最大误差，平均在所有系统的调查，为3.7%。0的理论温度依赖性为<<T1 '2。然而，实验结果更好地近似为线性函数或随T增加而减小的比例因子。不同的聚合物的体积和温度标度参数进行了比较。特征温度T* 与Tg呈平行趋势。但是，毫不奇怪，Tg不是严格的对应温度。因此，在Tg下的空穴分数1- y不是恒定的，而是随着降低的和基本上实际的玻璃化温度的增加而增加。液态和玻璃态之间的联系是由y的温度依赖性提供的，如前所述，在玻璃中y也是有限的，并在理论状态方程中被当作一个可调量。从玻璃和过冷液体的实验和理论y之间的差异，分别，可以推导出一个特征冻结分数随Tg降低而增加。与已知的宏观特征雅阁，甲基丙烯酸正烷基酯系列中的冻结级分相对较小，并表现出作为侧链长度的函数的最小值。
We analyze a number of structurally diverse systems. A simple interpolation expression represents accurately the implicit form of the theoretical equation of state for the liquid derived previously, and facilitates numerical evaluations. The very good agreement between predicted and measured volumes is in accord with ear-lier observations. Thermal expansivities, a, are estimated with a maximum error, averaged over all systems investigated, of 3.7%. The theoretical temperature dependence of o is «T1'2. However, the experimental results are better approximated by a linear function or by a proportionality factor which decreases with increasing T. The volume and temperature scaling parameters are compared for different polymers. The characteristic temper-ature T* shows a parallel trend with Tg. But, not surprisingly, Tg is not strictly a corresponding temperature. Hence the hole fraction 1- y at Tg is not constant, but increases with increasingreduced, and essentially actual glass temperature. A connection between the liquid andglassy states is provided by the temperature dependence of y, finite also in the glass, as shown earlier, and treated there as an adjustable quantity in the theoretical equa-tion of state. From the difference between the experimental and theoretical y’s for the glass and supercooled liquid, respectively, a characteristic frozen fraction can be deduced which increases with decreasing Tg. In accord with well-known macroscopic characteristics, thefrozen fractions in the series ofn-alkyl methacrylates are com-paratively small and exhibit a minimum as a function of side-chain length.