Influence Of Alkyl Tails And Spacer Length On Phase Behaviors Of Side-chain Liquid-Crystalline Polymers Containing Hemiphasmidic Mesogens

In this dissertation,two series side-chain liquid-crystalline polymers containing hemiphasmidic mesogens(SCLCPs,denoted as PTmBMA and P-n-BP,m is the carbon number of alkyl tails,and n is the carbon number of flexible spacer)were designed,synthesized and characterized.With varying the length of alkyl tails in the pendant groups and flexible spacer between the main chain and side chain,the influence of side-chain space volume and coupling effect(or decoupling effect)on the phase behaviors and self-organization of SCLCPs were investigated by the combination of techniques including thermal analysis and X-ray diffraction.Hence,we have fully studied the phase behaviors and morphology of PTmBMA and P-n-BP series as follows:1.A new series of side-chain liquid-crystalline polymers containing hemiphasmidic mesogens,named poly [4'-(3,4,5-trialkan-1-carbonylbenzoate)]-biphenyl methacrylates(denoted as PTmBMA,m =6,8,10,12,14,16,18,which is the carbon number of the alkyl tails in the side chains),were designed and synthesized via free radical polymerization.Consequently,the liquid-crystalline phase structures and self-organization behaviors of the polymers were found to be influenced by the alkyl tail length.While PT6 BMA form a long-range ordered smectic A(SmA)phase at the temperature before isotropization,PTmBMA(m?8)have a first order transition from hexagonal columnar mesophase(?h)to isotropic phase.Meantime,in the ?h phase,the supermolecular column is consisted of a bundle of chains(~4-5)in its building block because of the microphase separation between the alkyl tails and the rod-like multi-benzene core and space effect of side-chain.More importantly,the number of repeating units reduces with the increasing of alkyl tail length.2.A series of side-chain liquid-crystalline polymers containing different flexible spacer length between the main chain and hemiphasmidic mesogens in the side chains,named poly [4'-(3,4,5-tridecyoxy-1-carbonylbenzoate)]biphenyl-n-methacrylates(denoted as P-n-BP,n=2,4,6,8,10,which is the carbon number of spacer)were designed and synthesized via free radical polymerization.As a result of coupling effects and decoupling effects imposed by spacer between the main-chain and side-chain,the dynamic balance of interaction and self-organization behaviors for this system are completely different.P-2-BP and P-4-BP exhibit ?h phase at room temperature,but for P-4-BP,there is a transition from ?h1 phase to ?h2 phase before isotropization.With longer spacers,P-6-BP and P-8-BP form semctic phase at room temperature,which will transform to ?h phase at higher temperature,while P-10-BP only possesses a single transition from a smectic phase to isotropic state.