含硝基二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36个硝基偶氮苯端基新型二代碳硅烷光致变色液晶树枝状大分子(G₂)在溶液中的最大吸收波长, 摩尔消光系数, 反-顺光异构化反应速率常数, 热回复异构化反应速率常数, 光化学回复异构化反应平衡常数及速率常数. G₂的光致变色反应速率常数的数量级为10^－1 s^－1, 而含偶氮端基侧链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. G₂的光化学回复异构化反应平衡常数k_t/k_c为1.77～1.97, 有作为光控开关材料的应用前景.

Photochemical Study of Photochromic Liquid Crystalline Dendrimer of the Second 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 (G₂) of the second generation containing nitroazophenyl groups on its periphery in solution were described. Photochromic reaction rate constant of G₂ in CHCl₃ and THF was 10^－1 s^－1, but that of photochromic side-chain polysiloxanes containing azophenyl moieties was 10^－8 s^－1, thus the photoresponsitive rate of the liquid crystalline dendrimer G₂ is 10⁷ times larger than that of the latter. The equilibrium constant k_t/k_c of photochemical back-isomerization reaction of G₂ are 1.77～1.97 approaching to 1, and thus it is applicable to photoswitch materials.