Synthesis Of Liquid Crystalline Polymers Containing Fluorocarbon Chains And Chiral Groups

As the fluorine has many special natures, such as electronic effect, simulated effect, obstacle effect and penetration effect, the introduction of fluoride in the liquid crystal material can make many natures of liquid crystal changed. Due to the advantages of fluorinated liquid crystals, such as low viscosity, high resistivity, rapid response, increasing dielectric constant and so on, Fluorined liquid crystal has broad application prospect.Chiral liquid crystalline polymers (LCPs) were a hotspot of liquid crystalline research domains at the present time. Due to the unique photo-electrical property, they have obtained more and more attention. LCPs with helical supermolecular structure can form cholesteric phase and chiral smectic C (Sc*) phase.In this dissertation, four liquid crystalline monomers and two liquid crystalline crosslinking agents were synthesized, which include:4’-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentad-ecafluorooctanoyloxy)biphenyl-4-yl undecanoate(M1),4’-(allyloxy)biphenyl-4-yl2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoate(M2),10,13-dimethyl-17-(6-methylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-yl3-(4-(allyl-oxy)phenyl)acryl-ate(M3),10,13-dimethyl-17-(6-methylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-ylundec-10-enoate(M4),hexahydr-ofuro[3,2-b]furan-3,6-diylenoate(M5),hexahydrofuro[3,2-b]furan-3,6-diylbis(4-(allyloxy)ben-zoate)(M6). M1,M2are fluorinated monomers,M3,M4are chiral monomers. Then fluorinated monomers and chiral monomers were grafted to linear polymethylhydrogensiloxanes, so two series of fluorinated liquid crystalline polymers (LCPs) with different chemical structures and characters were synthesized. Fluorinated monomers and liquid crystalline crosslinking agents were grafted to linear polymethylhydrogensiloxanes, so two series of fluorinated liquid crystalline elastomers (LCEs) were synthesized.The structures and properties of the obtained LC monomers, crosslinking agent, polymers, elastomers were investigated by FT-IR spectroscopy,1H-NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), and polarizing optical microscopy (POM).The results show that:the chemical structure of the synthesized monomers are consistent with the molecular design. Both the LC monomers M1and M2 exhibited droplet texture and focal-conic texture on heating process and cooling cycle, the LC monomers M3and M4are cholesteric liquid crystal, M5and M6did not show any texture and mesomorphic properties. The polymers of P1～P4series were all cholesteric liquid crystals and exhibited cholesteric Grand-jean textures on heating process and cooling cycle. With the increasing of the LC monomers M1content, Tg and Ti of Pi series decreased; With the increasing of the LC monomers M2content, Tg of P2-1-P2-6decreased, but Tg of P2-7increased, Ti of P2series increased; With the increasing of the LC crosslinking agent M5content, Tg and Ti of P3series decreased firstly, and then increased; With the increasing of the LC crosslinking agent M6content, Tg of P4series decreased firstly, and then increased, Ti of P4series decreased. Polymers of P1and P2series were all optical active, and had good thermal stability.