Mesogen-jacketed liquid crystal like block copolymers: synthesis and self-assembly to prepare 1D PC thin films

Abstract

One dimensional photonic crystals (1D PCs) show great potential application in light control, sensors and functional displays. Self-assembly of block copolymer is a facile method to prepare 1D PCs in large area and easy processing. However, due to the low refractive index of polymer and the chain entanglement at very high molecular weight, it is difficult to prepare 1D PCs by self-assembly of linear block copolymers. In this work, mesogen-jacketed liquid crystals like block copolymers with two different lumbar connected benzene terephthalate derivatives and polynorbornene backbone are designed and synthesized. The big steric hindrance of the mesogenic benzene terephthalate derivatives extends the polymer backbone to be rigid, and the resultant block copolymers are rapidly self-assembled into lamellar structures with big domain spacing. The refractive indexes of the two blocks is differentiated by selecting the phenyl and decyl substitute group of benzene terephthalate derivatives. Hence, 1D PCs are prepared by self-assembly of mesogen-jacketed liquid crystals like block copolymers. The maximum reflectance is ranged from ultraviolet to near infrared by increasing the polymerization degree of the block copolymers from 400 to 1400 gradually. The lamellar structures are characterized by cross section scanning electron microscope and small angle X ray scattering. Mesogen-jacketed liquid crystal like block copolymer is favored in 1D PC preparation for its facile synthesis and flexible structure design.