聚氨酯丙烯酸酯的分子结构对聚合物分散液晶形貌和性能的影响

Influence of the molecular structure of polyurethane acrylates on the morphology and properties of polymer dispersed liquid crystals

聚合物分散液晶(PDLC)是液晶畴均匀地分散在聚合物基体内形成的一种复合材料,因其制备简单、无需偏振片和取向层,在智能窗、柔性显示和可穿戴设备等领域具有广泛的应用前景。为了拓宽其在柔性显示器件上的应用,本文以聚氨酯丙烯酸酯(PUA)低聚物作为聚合物基体,采用紫外光聚合法制备PDLC器件,研究PUA的分子结构对聚合物分散液晶的形貌和性能的影响。实验结果表明,以丙烯酸酯基团进行封端的聚合物单体聚合速率快,形成了聚合物网孔状结构,且随着分子结构由脂肪族到芳香族的变化,聚合物网孔尺寸逐渐减小,使PDLC的驱动电压增高。利用聚氨酯中氨基甲酸酯键在分子链间形成的氢键增强与塑料基板的粘附性,获得了具有优异综合性能的PDLC器件。对比芳香族PUA,脂肪族PUA制备的PDLC样品具有较低的驱动电压(V_(th)=9.14 V,V_(sat)=35.50 V)、较高的对比度(CR=73.25)、较好的粘附性(20.11 N/cm^(2))以及在弯曲曲率半径为4 cm下弯曲前后光电性能变化幅度较小的特点,基本满足柔性PDLC在安全隐私保护以及弯曲表面的使用要求。

Polymer dispersed liquid crystal(PDLC)is a composite material formed by uniform dispersion of liquid crystal domains within a polymer matrix.Because of its simple preparation and no need for polarizer and orientation layer,it has a wide range of application prospects in the fields of smart windows,flexible displays and wearable devices.In order to broaden its application scenarios in flexible display devices,this paper uses polyurethane acrylate(PUA)oligomers as the polymer matrix to prepare PDLC devices by ultraviolet photopolymerization.The effect of the molecular structure of PUA on the morphology and properties of polymer dispersed liquid crystals is investigated.The results show that the speed of the polymer monomer polymerization with acrylate groups for capping is fast,forming a polymer mesh-like structure,and the size of the polymer mesh decreases gradually with the change of the molecular structure from aliphatic to aromatic,resulting in an increase in the driving voltage of PDLC.The hydrogen bonding formed between the molecular chains by utilizing the urethane urethane bonding enhances the adhesion with the plastic substrate,thus obtaining PDLC devices with excellent overall performance.Compared with the aromatic PUA,the PDLC samples prepared from aliphatic PUA are characterized by lower driving voltage(V_(th)=9.14 V,V_(sat)=35.50 V),higher contrast(CR=73.25),better adhesion(20.11 N/cm^(2)),and smaller changes in the optoelectronic properties before and after bending at a bending radius of 4 cm.