Synthesis And Characterization Of Polycarbonate Liquid Crystalline Materials Containing Cholesteryl Groups

Recently, biodegradable polymer materials especially the functional polycarbonate materials have draw more and more attention, because of their broad applications in biological system. It is known that cholesterol is a fundamental composition of mammalian membranes, and it has high thermodynamic affinity for the cell membrane and ability to change the membrane’s permeability and fluidity. These characteristics make cholesterol an interesting component of bioactive biomaterials since it could have universal effects regardless of cell type and receptor map on the membrane. The main idea of this article is to introduce cholesteryl into polycarbonate materials containing hydroxyl group, and expected to get excellent performance and have widely used value of the biological degradation of the liquid crystal polymer material.In the second chapter, The compound 5-benzyloxy-trimethylene carbonate (BTMC) was synthesized, and the homopolymer poly(5-benzyloxy-trimethylene carbonate) (PBTMC) was obtained by ring-opening polymerization in bulk at 150℃ using stannous octanoate as an initiator; amphiphilic polymer mPEG-PBTMC was synthesized by ring-opening polymerization of 5-benzyloxy-trimethylene carbonate with poly (ethylene glycol) monomethyl ether (mPEG) as an initiator and Sn(Oct)2 as catalyst; amphiphilic block copolymer mPEG-PBTMC-PCL was synthesized by the copolymerization of BTMC and CL with mPEG as initiator and Sn(Oct)2 as catalyst. The protective benzyl groups in polymer chains was removed by catalytic hydrogenolysis Pd/C and Pd(OH)2/C as catalyst under hydrogen atmosphere. The sturcture and molecular weight of the copolymers were characterized by FT-IR and 1H NMR, thermal properties was characterized by DSC and TG. The result showed that the introduce of mPEG and PCL made the Tg and Td decrease.In the third chapter, four cholesteryl derivatives were synthesized and named as 4-cholesteroxy-4-oxobutanoic acid (C1),6-cholesteroxy-6-oxocaproicacid (C2),8-cholesterox-y-8-oxoctanoic acid (C3), and 10-cholesteroxy-10-oxodecanoic acid (C4). Then four cholesteryl derivatives were reacted with mPEG-PHTMC respectively to get four new amphiphilic graft copolymers (mPEG-PHTMC-C1～mPEG-PHTMC-C4). Moreover, C2 was reacted with PHTMC and mPEG-PHTMC-PCL to get PHTMC-C2 and mPEG-PHTMC-PCL-C2. The structure of cholesteryl derivatives and polymers was characterized by FT-IR and 1H NMR; thermal properties and optical textures were characterized by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). X-ray diffraction (XRD) was used to investigate their liquid crystal structure. The effect of the methylene length on the phase transition temperature of the cholesteryl derivatives and polymers were studied.POM and DSC results showed that Ci did not show any mesomorphism, C2-C4 exhibited typical oily texture and focal conic texture of cholesteric phase on heating and cooling cycles, In addition, with the methylene flexible chain in molecular structure increasing, the melting temperature (Tm) and isotropic temperature (Ti) of C1-C4 were decreased and the mesophase temperature ranges narrowed because the corresponding Ti decreased more than Tm. While, with the methylene flexible chain in molecular structure increasing, the glass transition temperature (Tg) and Ti of mPEG-PHTMC-C1-mPEG-PHTMC-C4 also decreased, but the mesophase temperature ranges broadened. Comparing Tg and Ti of PHTMC-C2、mPEG-PHTMC-C2. mPEG-PHTMC-PCL-C2, the introduce of mPEG made the Tg and Ti of mPEG-PHTMC-C2 increase, but the mesophase temperature ranges broadened; the introduce of PCL make Tg decrease and Ti have no change, the mesophase temperature ranges broaden. XRD result showed that C2 belonged to cholesteric phase, and mPEG-PHTMC-C2 belonged to smectic phase.