A raman spectroscopic determination of the interlamellar forces in crystalline n‐alkanes and of the limiting elastic modulus Ec of polyethylene
A raman spectroscopic determination of the interlamellar forces in crystalline n‐alkanes and of the limiting elastic modulus Ec of polyethylene
复制标题
拉曼光谱测定结晶正烷烃的层间力和聚乙烯的极限弹性模量 Ec
DOI：
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发表时间：
1976
期刊：
影响因子：
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通讯作者：
R. Eckel
中科院分区：
文献类型：
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作者：
G. Strobl;R. Eckel
基于连续介质力学的简单处理表明，晶体正构烷烃中较弱的层间力会导致纵向声（LA）模式频率的特征向上移动，该频率与链长无关，与模式阶数成反比。拉曼光谱对一系列不同正构烷烃的LA模式频率的测定证实了理论结论，并允许推导出层间力的力常数特征。通过讨论，得到了在声学极限下正交正构烷烃的LA模频率的新公式，并给出了结晶聚乙烯极限弹性模量Ec的新计算方法。得到的值Ec = 2.9 × 1012达因/cm2，明显小于Schaufele和Shimanouchi忽略层间力对LA模态频率的影响而得到的值。
A simple treatment based on continuum mechanics shows that weak interlamellar forces in crystalline n-alkanes should result in a characteristic upward shift of the frequencies of the longitudinal acoustical (LA) modes, which is independent of the chain length and decreases inversely with the mode order. A raman spectroscopic determination of the LA mode frequencies of a series of different n-alkanes confirms the theoretical conclusion and permits a derivation of a force constant characteristic of the interlamellar forces. The discussion results in a new formula valid for the LA mode frequencies of the orthorhombic n-alkanes in the acoustical limit and yields a new determination of the limiting elastic modulus Ec of crystalline polyethylene. The value obtained, Ec = 2.9 × 1012 dyne/cm2, is markedly smaller than the value derived by Schaufele and Shimanouchi neglecting the influence of the interlamellar forces on the LA mode frequencies.