Synthesis And Phase Behavior Of Side-chain Liquid Crystal Polymers With Precise Side Chain-spacing Based On ADMET Polymerization

It is of great significance to regulate the relationship between the size of the mesogen graft density and the change of the flexible spacer group,which have an important influence on the multi-level ordered structure and phase transition path in the side chain liquid crystal polymers（SCLCPs）.In this dissertation,a series of end-on side chain liquid crystalline polymers with precise side-chain spacing are designed and synthesized via acyclic diene metathesis（ADMET）polymerization method.The effect of different spacer length on the phase behaviors in the SCLCPs systems is discussed in depth.The dissertation mainly contains two parts as following.Firstly,precise SCLCPs systems with different spacer length,h-P11-Sn（11denotes that every 11 carbon atoms in the polyolefin backbone contains one grafted mesogenic unit;n represents the lengths of the flexible spacer.）was successfully designed and synthesized vial ADMET polymerization method.With shorter spacer length of h-P11-S2 further exhibits smectic A phase structure.Under long time annealing at room temperature,h-P11-S4 and h-P11-S6 after shear orientation can gradually evolve into a three-dimensional（3D）soft crystalline phase,named SC₄ and SC₆,respectively.With the side-chain mesogen parallel and cross to the relatively rigid polymer backbones in the crystal lattice,h-P11-S8 can quickly form the three-dimensional（3D）soft crystalline phase.The soft crystal growth of the samples is largely kinetically controlled.Further increasing the length of flexible spacer,h-P11-S10 and h-P11-S12 will form the crystal phase structure.Then,precise SCLCPs,h-P11-EBR-Sn（n=4,8）were synthesized and characterized.The results of h-P11-EBR-Sn（n=4,8）show that h-P11-EBR-S4 and h-P11-EBR-S8exhibit smectic I（Sm I）phase at room temperature,wherein the long axis of the mesogens is titled at a certain angle away from the normal of the layer surface.Meanwhile,the orientation of polymer samples under external shear can accelerate and optimize the formation of Sm I phase structure.Further examination reveals that the self-assembly property of methoxybiphenyl is not affected by the spacer length,which only influences the size of the smectic layer through synergistic interplay of the-main and-side chain of SCLCPs.