反应温度对亲核试剂引发点击化学制备聚合物分散液晶电光性能的影响

光聚合诱导相分离法是应用最广泛的制备聚合物分散液晶(PDLC)膜的方法。为了提高PDLC的对比度(CR),通常在PDLC膜中引入二色性染料。然而,目前商业化的染料掺杂PDLC膜还很少,因为光聚合诱导相分离法使用的紫外光会使染料分解;另外,染料会吸收紫外光导致预聚物的聚合速率变慢。亲核试剂引发点击化学反应是最近合成化学的研究热点,可在无紫外光的条件下发生。因此,用亲核试剂引发点击化学反应制备PDLC膜,有望克服传统光聚合诱导相分离法的缺点。本论文,采用亲核试剂引发巯基-烯烃点击化学反应制备PDLC膜,并研究了反应温度对PDLC电光性能的影响。结果表明,温度的改变导致液晶微滴的尺寸发生变化,进而对PDLC的电光性能产生影响。温度升高使得开态透过率(Ton)变小,阈值电压(V_(th))和饱和电压(V_(sat))升高。

Effects of reaction temperature on electro-optical properties of polymer-dispersed liquid crystal films fabricated by nucleophile-initiated thiol-ene click reaction

Photo-polymerization-induced phase separation is a most widely used method to fabricate polymer dispersed liquid crystal (PDLC) films. Meanwhile, dichroic dye is usually introduced into PDLC films to enhance the contrast ratio. However, until now, commercial dye-doped PDLC films are still very few, because UV-light can make dye decompose in the process of photo-polymerization-induced phase separation and dye absorbs UV-light causing the polymerization rate of the prepolymer to slow down. Recently, nucleophile-initiated click reaction, which can be processed without UV-light, is a research hotspot in synthetic chemistry. Thus, fabricating PDLC films via click reaction initiated by nucleophile may hopefully overcome the shortcomings of traditional photo-polymerization-induced phase separation method. In our work, PDLC films were prepared via thiol-ene click reaction initiated by nucleophile. The influences of reaction temperature on electro-optical properties of PDLC were investigated. It was found that reaction temperature influenced the electro-optical properties of PDLC films by changing the droplets size of liquid crystal. With the increase of reaction temperature, ON state transmittance (T_on) decreases, while threshold voltage (V_th) and saturation voltage (V_sat) increases.