端基含36个己氧基偶氮苯基元的二代碳硅烷光致变色液晶树状高分子的光化学研究

研究了含36个己氧基偶氮苯介晶基元的二代(G2)光致变色液晶树枝状高分子在氯仿和四氢呋喃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,光化学回复异构化正逆反应速率常数及其平衡常数,G2和G1的光致变色反应速率常数kp为10-1s-1,而含偶氮基元光致变色液晶聚硅氧烷的kp为10-8s-1,因此液晶树状高分子的光响应速率比后者快107倍.

STUDIES ON PHOTOCHEMISTRY OF A CARBOSILANE PHOTOCHROMIC LIQUID CRYSTALLINE DENDRIMER OF SECOND GENERATION CONTAINING THIRTY-SIX 4-HEXYLOXYAZOBENZENE MESOGENIC GROUPS IN ITS PERIPHERY

The photochemical behavior of a photochromic carbosilane liquid crystalline(LC) dendrimer of second generation(G2) in chloroform and tetrahydrofuran were described.Thirty-six 4-hexyloxyazobenzene mesogenic fragments were attached in its periphery.The maximum absorption wave length and molar extinction coefficient of G2 were determined.The reaction rate constants of trans/cis photochemical isomerization and positive/counter photochemical back-isomerization and the equilibrium constant of photochemical back-isomerization reaction for G2,G1 and M3 were discussed.Their absorbance A_(360) in CHCl_3 and maximum absorption wave length λ_(max) in CHCl_3 and THF around 360 nm are in G2>G1>M3 and G2C_6H_6>CHCl_3> THF>EtOH.Their molar extrinction coefficient ε_(360) in CHCl_3 and THF and their reaction ratio constant of photochemical isomerization k_p in CHCl_3 are in G2>G1>M3 and G2