含偶氮苯类星型液晶化合物的光致变色

研究了一种以Si为中心外围含4个丁氧基偶氮苯液晶基元的星型液晶化合物Si(AZO)4的光致变色规律,利用紫外-可见吸收光谱研究了在氯仿和四氢呋喃溶液中的量子产率、光致变色和光回复反应.实验结果表明样品在各溶液的光致变色和光回复反应均为一级动力学反应,并求算了光致变色反应的正、逆反应速率常数均为10-1s-1数量级,是偶氮类侧链液晶高分子的速率常数的107倍,表明Si(AZO)4的星型结构对末端偶氮基团的吸收光谱没有明显影响,产物具有类似小分子的光致变色性,并且Si(AZO)4的正、逆反应速率常数比值小于液晶基元的比值,表明具有更好的光可逆性,有望作为光控开关和新型信息功能材料.

Photochromism of the Star-like Liquid Crystals Containing Azobenzene

The photochromism of a new star-like liquid crystal that was written by Si(AZO)_4 centered by Si and containing four butoxyazobenzene mesogens in its periphery was described. The quantum yield, photoisomerization and photo back-isomerization of Si(AZO)_4 in CHCl_3 and THF are studied by UV/Vis absorption spectra. The results indicate that the photochromism and photo back-isomerization of Si(AZO)_4 in CHCl_3 and THF were in accordance with the first order kinetics. The photochromism and photo back-isomerization rate constants are (10~(-1) s~(-1)), which are 10~7 times larger than that of side-chain liquid crystalline polymers containing the same azobenzene moieties. These results indicate that the star-like structure does not significantly affect the photoisomerization activity of the azobenzene mesogen in its periphery. The k_t/k_c of Si(AZO)_4 is less than that of azobenzene mesogen which shows that the Si(AZO)_4 has better photo-reversibility. So the star-like liquid crystal has potential applications and will become a new type photocontrolable switch and information functional material.