Cyclic Siloxane Liquid Crystalline Compounds with Steroidal Mesogens

摘要

The phnse behavior of a side-chain liquid crystalline polymers based on cyclosiloxane backbones has been extensively examined for systems possessing rm-sogens based on Ciir:s of cholesterol1 2. These ring Lompounds form cholesterit: 'phases' exhibiting selective reflection in the visible. The ability to quench this structure into glassy transparent films, thus forming-,Iridescent films is promising for filter and storage applications'3'4. X-ray analysis of these. materials ha? shown a complex molecular architecture present. wherein two types of layered packing domains, each exhibiting a separate X-ray reflection occurs5'6'7. Each reflection has been attributed to a layered structure that corresponds to a different degree of ms'so.njen Interdigitation.. In systems with lonj, spacer groups, a reflection corresponding approximately to the length, of an extended nitisugun (Including spacer) was observed. In systems with short spacer groups, a reflection with a d-spadrig greater than the length of the extended mesogen indicating oniy partial liuerdialtation of mesogens is observed, the apparent result, of musogtiiik: stfiric hlnderanca.s Tim hiii'leiance to packing has been attributed to the flexible aliphatic tail .off the I7fi carbon of the tetrucycllc core of the cholHyterol molflty. Both reflections (fully and partially Interttlgltated) appear with lniemu'diutc length spacer j;roups.