The crown conformer of a calix[4]resorcinarene (CRA) possessing eight carboxymethylated units at the lower rim and four cinnamoyl residues at the upper rim was prepared to fabricate photofunctional monomolecular layers. The CRA derivative was adsorbed on a fused silica plate from a THF solution to form a monomolecular layer through hydrogen bonds. The monolayer exhibited photocycloaddition, together with photoisomerization, upon UV irradiation. Whereas the desorption of the macrocyclic compound from the plate occurred partially in polar solvents including ethanol, UV irradiation exhibited a suppressive effect on the desorption, suggesting that the number of hydrogen bonds between the molecules and a silica surface per molecule are much enhanced by intermolecular photodimerization of the cinnamoyl residues leading to an increment of the molecular weight of the adsorbate. The monolayer of the CRA on a silica plate exhibited the ability to transform the alignment
of a nematic liquid crystal upon UV irradiation from homeotropic (perpendicular) to planar (parallel) orientation. The photoalignment of the liquid crystal was stabilized toward heat treatment possibly owing to the photodimerization of cinnamoyl units.
为了制造光功能单分子层,我们制备了
钙[4]
间苯二酚(CRA)的冠构象,其下缘具有八个羧甲基单元,上缘具有四个肉桂酰残基。CRA 衍
生物从
四氢呋喃溶液中吸附到熔融石英板上,通过氢键形成单分子层。该单分子层在紫外线照射下表现出光环加成和光异构化。在极性溶剂(包括
乙醇)中,大环化合物会从平板上部分解吸,而紫外线照射对解吸有抑制作用,这表明由于肉桂酰残基的分子间光二聚化导致吸附剂分子量增加,分子与
二氧化硅表面之间的氢键数量大大增加。
二氧化硅板上的单层 CRA 在紫外线照射下能够将向列液晶的排列从各向同性(垂直)方向转变为平面(平行)方向。可能是由于肉桂酰单位的光二聚化作用,液晶的光排列在热处理后趋于稳定。