Self-organization of polymers in bulk, thin films, and solutions: Studies of semiflexible perfluorocyclobutyl polyaryl ethers and rigid rod dialkyl para-phenyleneethynylenes.

摘要

The structures and dynamics of two classes of polymers have been explored. The first class of polymers, containing an α-methylstilbene mesogenic group and a low interfacial energy perfluorocyclobutyl ring, forms lyotropic lamellar mesophases over a wide range of temperatures and molecular weights. The interfacial characteristics of these lyotropic mesophases are affected by the low surface energy moiety. At interface with glass, a homeotropic alignment was observed. In thin film, the polymers exhibit surface ordering characterized by a periodicity of about 15 to 20 Å that propagates about 100 Å into the film. The fluorinated segments segregated to the air surface and the protonated segments segregated to the SiOx layer at the Si substrate. The effects of the low interfacial energy film on the ordering of small molecule liquid crystal was investigated.; The second class of polymers, consisting of a rigid conjugated backbone and alkyl side chains, exhibits lamellar structure. Its morphology and ordering are governed by the polymer architectures. In thin films, the self-assembly process takes place on two length scales leading to lamellar ordering on the 2 nm scale and to rodlike structures on the 20–50 nm scale. When immersed in toluene, the polymers associate, forming large flat aggregates. The dimensions and volume fraction of the aggregates increase with the polymer concentration. When concentration is increased high enough, the aggregates come into contact with each other, restricting their motion as well as the solvent, consequently transforming into a fragile gel phase. The effects of concentrations and molecular architectures on the association and gelation have been investigated.