零代光致变色液晶树状物的光响应行为研究

研究了含4个己氧基偶氮苯基元的零代(G0)光致变色液晶树状物在氯仿和四氢呋喃中的吸收光强、最大吸收波长、摩尔消光系数、量子产率、活化能、异构转换率、反-顺光异构化反应速率常数、热回复异构化反应速率常数、光回复异构化反应平衡常数及速率常数.G0的光致变色反应数率常数为10-1s^-1,而含偶氮基元液晶聚硅氧烷的光致变色反应数率常数为10^-8s^-1,前者比后者快107倍.

Photoresponse Behavior of a New Photochromic Liquid Crystalline Dendrimer of the Zero Generation

The photoresponsive behavior of a new photochromic liquid crystalline(LC) dendrimer of the zero generation(G0) in CHCl_3 and THF was described. Four 4-hexyloxyazobenzene mesogenic fragments were attached in its periphery. The intensity of light absorbed, molar extinction coefficient, maximum absorption wave length, quantum yield and activation energy were determined. The reaction rate constants of trans/cis of photochemical isomerization, photo back-isomerization and thermal back-isomerization and the equilibrium constant of photochemical back-isomerization reaction were discussed. The rate constant of the photochromic reaction of G0 is 10~-1 s~-1 , but that of photochromic LC polysiloxanes containing the azobenzene moieties is 10~-8 s~-1 , thus the photoresponsive rate of the LC dendrimer G0 is 107 times larger than that of the latter.