Effect Of Tail Length On The Liquid Crystalline Behavior Of Poly(Methacrylate)s With Biphenyl Side Groups

Side-chain liquid-crystal polymers have been obtained by rod-like molecules intothe side chain. Side-chain liquid-crystal polymers are currently of considerableinterest to science and industry because not only they combine properties ofanisotropic liquid crystals and macromolecular compounds with the ability to formfilm but also they provide a demanding challenge to our understanding of themolecular factors that promote self-organization in condensed phases.For tails of the side chain, as an important part of the polymer, it plays animportant role to establish the role of the molecular structure with respect to thethermal and physical properties of side-chain liquid-crystal polymers. However,compared to the flexible spacer, side-chain tails have gained less attention in theresearch of side-chain liquid-crystal polymers. In this article, we focus on the effect ofthe length of tail on the liquid crystalline behavior of poly(methacrylate)s withbiphenyl side groups.In this article, we reported the synthesis and characterization of11homologuesof poly[ω-(4′-n-alkyloxybiphenyl-4-oxy)hexyl methacrylatels (P-6biCm, m is thenumber of the carbons of alkyl tails, m=1,2,3,4,6,8,10,12,14,16and18).The chemical structure of the monomers was confirmed by1H NMR. Themolecular characterizations of the polymers were performed with1H NMR, TGA andGPC. The phase behaviors were investigated by the combination of techniquesincluding DSC, POM and1D-WAXD. The results showed that the length of alkyl tailsplayed an important role in the phase behaviors of these polymers. For m=1,2,3and4, they formed smectic E phase and smectic A phase. For m=6and8, the polymersshowed smectic A phase. For m=10,12,14,16and18, the polymers presentedsmectic B phase and smectic A phase. On the other hand, the clearing point increasedwith the increasing of m.