Infrared spectroscopic study of polytypic effects on the crystal-growth mechanism of n-hexatriacontane(n-C_(36)H_(74))

摘要

The solution-crystallization mechanism was investigated for two polytypes in the M_(011)modification of n-hexatriacontane(n-C_(36)H_(74)),single-layered structure Mon,and double-layered one Orth II.The crystal growth under controlled supersaturation was followed with a micro-Fourier-transform-infrared spectrometer equipped with an optical system for oblique transmission measurements.Supersaturation dependence of growth behavior was significantly different between Mon and Orth II.Although the Mon crystal continued growing at a supersaturation of 0.27,the overgrowth of Orth II on the(001)face of the Mon crystal was confirmed at supersaturations below 0.21.Such a polytypic transformation was not observed for the Orth II crystal at any supersaturation below 0.30.The growth rate of Mon showed a quadratic dependence on supersaturation,while that of Orth II was approximately linear,suggesting spiral growth and two-dimensional-nucleation mechanisms for Mon and Orth II,respectively.