含硝基一代光致变色液晶树枝状大分子的光化学研究

研究了树外围含12个硝基偶氮苯基元新型一代碳硅烷光致变色液晶树枝状大分子G1和基元小分子M1在溶液中的最大吸收波长、摩尔消光系数、反-顺光化学异构化反应速率常数、热回复异构化反应速率常数、光化学回复异构化反应平衡常数及速率常数. G1的光致变色反应速率常数的数量级为10^－1 s^－1, 而含偶氮基元液晶聚硅氧烷的光致变色反应速率常数的数量级为10^－8 s^－1, 因此液晶树枝状大分子的光响应速率比后者快10⁷倍. G1的光回复异构化反应平衡常数k_t /k_c为1.76～1.77, 有作为光控开关材料的应用前景.

Study on Photochemistry of Photochromic Liquid Crystalline Dendrimer of the First Generation Containing Nitro Groups

The molar extinction coefficient, maximum absorption wavelength, reaction rate constants of trans-cis photochemical isomerization, thermal back-isomerization and photochemical back-isomerization and equilibrium constant of photochemical back-isomerization reaction of a novel photochromic liquid crystalline dendrimer G1 of the first generation containing nitroazophenyl groups on its periphery and small molecular azophenyl moiety M1 in solution were described. Photochromic rate constant of G1 in CHCl₃ and THF was 10^－1 s^－1, but that of photochromic liquid crystalline polysiloxanes containing azophenyl moieties was 10^－8 s^－1, thus the photoresponsitive rate of liquid crystalline dedrimer G1 is 10⁷ times larger than that of the latter. The equilibrium constants k_t/k_c of photochemical back-isomerization reaction of G1 are 1.76～1.77 approaching to 1, and thus it is appliable to photoswitch material.