STUDIES ON QUANTUM YIELD,ACTIVATION ENERGY AND PHOTOISOMERIZATION CONVERSION PERCENTAGE OF A PHOTOCHROMIC LIQUID CRYSTALLINE DENDRIMER G2

The photochemical behavior of a photochromic liquid crystalline(LC) dendrimer of the second generation(G2) in chloroform and tetrahydrofuran was described.Thirty-six 4-n-hexyloxyazobenzene mesogenic fragments were attached in its periphery.The photochemical behavior of carbosilane dendrimer of the second generation(G2) was compared with that of the carbosilane dendrimer of the first generation(G1) and the mesogenic unit compound(M3).The quantum yield Φ and intensity of light absorption I_a of G2,G1 and M3 were determined.In chloroform and tetrahydrofuran(THF) Φ was in an order of M3G1G2,while I_a in chloroform and tetrahydrofuran(THF) had orders of G2G1M3 and M3G1G2,respectively.The reaction rate constant of the thermal back-isomerization k_H at different temperature and the activation energy E of G2,G1and M3 were discussed.At the same temperature,k_H in chloroform and tetrahydrofuran(THF) was in an order of G1G2M3.The photoisomerization conversion percentage and(trans/cis) isomer absorbance ratio at the thermal back-isomerization of G2,G1 and M3 were described.The photoisomerization conversion percent were in chloroform and tetrahydrofuran(THF) showed orders of G1M3G2 and G2G1M3,respectively.The(trans/cis) isomer absorbance ratio at the thermal backisomerization A′/A′_0 in chloroform and tetrahydrofuran(THF) was in order of G2G1M3.