涤纶晶体结构三级红外光谱研究

采用红外(IR)光谱研究涤纶的晶体结构(v-crystal-涤纶).研究发现:涤纶主要存在着v-crystal-1-涤纶(1335 cm-1)、v-crystal-2-涤纶(969 cm-1)和v-crystal-3-涤纶(847 cm-1)等3大晶体特征吸收谱带.采用变温红外(TD-IR)光谱开展了涤纶的晶体结构热稳定性研究.实验发现:在353～393K的温度范围内,随着测定温度的升高,涤纶v-crystal-涤纶对应的吸收强度及频率有明显的改变.这主要是因为玻璃化温度后,会进一步破坏涤纶晶体的结构.采用二维红外(2D-IR)光谱,以涤纶v-crystal为研究对象,进一步开展了涤纶玻璃化转变研究机理.在加热过程中,涤纶大分子链表现出不同的运动状态.玻璃化温度前(313～343 K),涤纶分子发生分子运动的冻结,玻璃化温度后(353～393 K)涤纶即将进入高弹态.本项研究拓展了三级IR光谱(包括:IR光谱,TD-IR光谱和2D-IR光谱)在涤纶结构,热稳定性及玻璃化转变的应用研究范围.

Three-step Infrared Spectrum of Dacron Crystal Structure

The dacron crystal structures(ν-crystal-dacron)were studied by infrared(IR)spectrum,for instance,ν-crystal-1-dacron(1335 cm^-1),ν-crystal-2-dacron(969 cm^-1),andν-crystal-3-dacron(847 cm^-1).In addition,the dacron thermostability was studied by temperature-dependent infrared(TD-IR)spectrum.We obtained that the corresponding absorption intensity and frequency of dacronν-crystal-dacron were changed(353-393 K)because its crystal structure was destroyed by the temperature.We further studied the glass transition of dacronν-crystal-dacron was by two-dimensional infrared(2D-IR)spectrum.During heating,the dacron macromolecular chain showed different motion states.The dacron molecules froze in molecular motion before the glass transition temperature(313-343 K);however,these molecules nearly entered a high elastic state after the glass transition temperature(353-393 K).This study demonstrated the key roles of three-step infrared spectrum(including IR spectrum,TD-IR spectrum,and 2D-IR spectrum)in the analysis of structure,thermostability,and glass transition of the important polymer material(dacron).