基于量子级联激光器的Pump-Probe光路球晶雕刻实验  

Engraving the Polymer Spherulites with the Pump-Probe Setup Based on Quantum Cascade Laser

作　　者：吕艳坤 卢杰 苏凤梅[1] 纪又新[1] 李良彬[1] 

机构地区：[1]国家同步辐射实验室中国科学技术大学,合肥230026

出　　处：《高分子学报》2018年第3期374-379,共6页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号51227801;51633009)资助项目

摘　　要：利用2台中红外量子级联激光器(QCL)组成的泵浦探测(pump-probe)光路通过红外共振吸收对高分子球晶进行选择性熔融进而实现球晶雕刻.当QCL激光频率和分子基团振动频率相同时,会发生共振吸收,产生强烈的热效应,诱导样品快速熔融;QCL激光具有高偏振性,优先诱导振动方向和红外激光偏振方向一致的基团发生共振吸收,因此可以实现选择性熔融;高分子球晶中有沿着各个方向的分子链并且取向方向确定,可以通过pump球晶不同部位来验证球晶雕刻的可行性.一台激光器(pump)对应分子链中基团的强吸收峰,共振加热诱导晶体熔融;另一台激光器(probe)对应分子特征基团(构象)的吸收峰,追踪结构变化;pump光可以选择性定点熔融,pump和probe 2束光均能在线追踪样品熔融程度,是该检测方法的突出优点.选用聚丁烯-1(iPB-1)为研究对象,实验结果显示,球晶熔融程度随基团振动方向与pump光偏振方向夹角的增大而减弱,证明了利用QCL在球晶尺度上进行雕刻是可行的,为原位在线研究快速熔融过程提供了新的研究途径,为定点调控晶型转变及晶体聚集态结构形态提供了思路.A pump-probe setup consisting of two mid-infrared quantum cascade lasers（QCLs） is designed to engrave polymer spherulites via selective melting induced by infrared resonance absorption. When the wavelength of QCL is tuned to the infrared absorbance peak of specific molecular group and the vibration direction of the group is the same as the direction of light polarization, infrared resonance absorption results in strong thermal effect. Combing with the high polarization property of QCL, selective melting can be realized. The molecular chains in polymer spherulites are aligned in all directions and the corresponding orientation direction is fixed, suitable for verifying the feasibility of the spherulites engraving by pumping different parts of the spherulites. The wavelength of the pump beam is set to a strong absorption peak in the infrared spectrum, inducing crystal melting by resonant heating, while the wavelength of the probe beam is turned to the conformation absorption peak of specific groups to trace the structure change. There are mainly three highlights of this method：（1） the melting process and the melting degree are studied in situ based on the change of the transmission intensity;（2） both pump and probe beams can reflect the structure information;（3） selectively melting of designated position in spherulites can be realized. Results of isotactic polybutene-1（iPB-1） show that, when the energy of the pump stays constant, the melting effect is different at distinct positions of the spherulites. Melting degree of the sample decreases with the increase of the angle between the vibration direction of the groups and polarization direction of the pump beam, which proves feasible to use QCL to perform engraving on spherulite scale. Selective melting induced by infrared resonance absorption provides a new way for in situ study of rapid melting process and a guideline for controlling crystal form transition and aggregation morphology at specific position.

关 键 词：中红外量子级联激光器 Pump-probe光路 偏振红外 红外共振吸收 球晶雕刻 

分 类 号：TN24[电子电信—物理电子学]