NVP在全息聚合物分散液晶光栅中的反应动力学研究

为了提高全息聚合物分散液晶(简称HPDIC)光栅的衍射效率并得到良好的光栅表面形貌,在制备光栅的反应体系中添加了具有吡咯烷酮结构的单官能度小分子NVP,并进一步阐述了NVP对HPDLC光栅在反应动力学方面的影响.分析表明,NVP的添加显著增加了预聚单体的聚合速率,并且能使原本被困在聚合物网络当中的双键继续发生反应,从而大大提高了反应体系的双键转化率;另外,NVP的添加使得光栅的相分离更加彻底,在获得良好的表面形貌的同时也增大了光栅的折射率调制度,从而提高了HPDLC光栅的衍射效率.总之,在添加了NVP之后,体系的聚合速率和预聚单体的反应度都大大提高,从而使得光栅的表面形貌和衍射效率也得到较大的改善和提高,衍射效率提高到96.36%.

Reaction kinetics investigation of NVP in HPDLC gratings

In order to get the HPDLC grating with high diffraction efficiency and perfect surface morphology, NVP was added into the reaction system of fabricating gratings and then the influence of NVP on the reaction kinetics of HPDLC was described. The analysis showed that NVP significantly increased the rate of polymerization in HPDLC photopolymerization, and as the highly cross-linked polymer network forms, the small mono-vinyl NVP appeared to react preferentially with double bonds inthe reaction system, facilitating additional conversion of pendant double bonds otherwise trapped in the polymer network. Furthermore, NVP also enhanced the degree of phase separation and got perfect surface morphology as well as higher refractive index modulation. So, the diffraction efficiency of HPDLC gratings was remarkably improved. However, the surface morphology and diffraction efficiency of HPDLC gratings would be worse when the concentration of NVP was too high. In a word, the addition of NVP could significantly increase the polymerization rate and reaction extent of reaction monomer and ultimately get the HPDLC grating with high diffraction efficiency (96.36%) and perfect surface morphology.