单体结构对全息聚合物分散液晶光栅稳定性的影响

INFLUENCE OF CHEMICAL STRUCTURE OF MONOMERS ON THERMO-STABILITY OF HOLOGRAPHIC POLYMER DISPERSED LIQUID CRYSTAL GRATINGS

使用3种不同化学结构的单体材料制备了全息聚合物分散液晶光栅,并从光栅形貌、衍射能力、驱动特性、聚合物热稳定性4个方面评价了光栅的热稳定性.研究发现,含有刚性结构单体材料体系的光栅形貌、衍射能力等方面在200℃的温度下没有明显变化.表明光栅的热稳定性与单体材料的化学结构密切相关,单体材料中含有刚性结构有助于光栅热稳定性的提高.利用热重分析(TGA)对光栅中聚合物材料热分解温度进行了测定,并结合Freeman-Carroll微商法计算出了上述聚合物的分解活化能和分解反应级数.结果发现,含有刚性结构的聚合物材料的热分解温度、分解活化能和分解反应级数都高于柔性链结构材料,进一步验证了材料体系中刚性结构的添加有助于提高光栅的热稳定性.

The thermo-stability of acrylate based holographic polymer dispersed liquid crystal （ H-PDLC） gratings has been evaluated with regard to their morphology,diffraction efficiency,remained almost unchanged up to Bragg angle and electro-optical tunable performance. These experimental results showed that the morphology,diffraction efficiency,Bragg angle and electro-optical tunable performance of two H-PDLC gratings containing rigid rings in the polymer structure remained almost unchanged up to 200℃ . The studies indicate that the chemical structure of the monomers plays an important role in the thermo-stability performance of H- PDLC gratings. Normally,a rigid molecular structure forms a hard polymer network which is very stable at high temperatures,subsequently,enhances the thermo-stability of H-PDLC gratings. Thermo-gravimetry （ TG） was used to analyze the decomposition temperature of three kinds of polymer materials. The decomposition activation energies and the corresponding reaction orders of the polymers have been calculated by the Freeman- Carroll differential method. The tested results showed that the decomposition temperature,the decomposition activation energy and the corresponding reaction order of polymers which contained rigid ring structure were all higher than those of a polymer with flexible chain structure. In addition,the ring rigidity increases interactions between molecules and restricts the motion between them,thus enhances the thermo-stability.