| Discotic liquid crystalline(DLCs) polymers have attracted great attention due to they can be applied in organic superconducting materials or in organic materials having unusual magnetic behavior. Among them, triphenylene(Tp) side chain liquid crystalline polymers(SCLCPs) have been investigated because of their relatively easy synthesis, thermally and chemically stable, and varieties of mesophases. This dissertation is focused on the investigation of the phase behavior and phase structures of SCLCPs containing Tp Discotic Mesogen Unit as side groups. Design, synthesis and characterization of novel side chain Tp DLCs polymers with different chemical structures were first carried out. Meantime, the phase behavior and phase structures of polymers can be tailored through copolymerization and block(co) polymerization. Through the research, we can obtain knowledge about the phase behavior and get the information of the structure variation of the polymers, and then packing mode molecular chain. Via study the phase behavior and phase structures of these novel Tp DLCs polymers, it will be useful for the fundamental research and real applications. The main research works of this paper are as follows:(1) A novel series of SCLCPs with Tp mesogen unit direct connected to the main chain without flexible spacer(PATS, PMTS, PVTS, PBTCS), were first reported and synthesized via conventional free radical polymerization. The phase behavior and phase structures of the polymers have been investigated by DSC, POM, 1D and 2D WAXD. The results showed that, without spacer, all the polymers formed columnar(Φ) phases developed by the Tp moieties and the main chain as a whole, due to the strong coupling effect of the Tp moieties and the main chain. According to the different rigidity of the main chain, the PMTS formed rectangular columnar(ΦR) phases, and the PATS, PVTS and PBTCS formed the symmetry hexagonal columnar(ΦH) phase. As expected, when the flexible spacer was abolished, the ―coupling effect‖ increased, leading to overcoming the π- π interaction of Tp mesgeon and the polymers got a relatively high glass transition temperature.(2) A series of SCLCPs containing Tp units in the side chains, denoted as PMTS(without spacer) and PMTnS(n = 2, 3, 4, 6, which is the number of the methylene units between the main chain and Tp moieties in the side chains), with different length of spacer were synthesized through conventional free radical polymerization. The phase behavior and phase structures of the polymers have been investigated by DSC, POM, 1D and 2D WAXD. The results showed that the length of spacer has significant effects on the LC phase behavior of polymers. For PMTS and PMT2 S, they displayed the columnar phase developed by the Tp moieties and the main chain as a whole due to the strong coupling effect of the Tp moieties and the main chain. For the PMT3 S, PMT4 S and PMT6 S, they formed the symmetry hexagonal columnar(ΦH) phase owing to the decoupling effect. All of these indicated that the ―decoupling effect‖ or ―coupling effect‖ depended on the length of spacer, leading to the different LC phase formation mechanism.(3) Two series of SCLCPs containing Tp units in the side chains, named poly((3, 6, 7, 10, 11-pentakis(hexyloxy)-2-oxytriphenylene) methacrylate)(PMTS with no flexible spacer) and poly(6-(3, 6, 7, 10, 11-pentakis(hexyloxy)-2-oxytriphen-ylene) hexyl methacrylate)(PMT6S with 6 methylene units as flexible spacer), with different molecular weights(Mn) and low molecular weight distributions have been successfully synthesized via atom transfer radical polymerization(ATRP). The experimental results revealed that the LC phase structures of PMTS were found to be strongly Mn dependent. The PMTS were amorphous when the Mn is lower than a critical Mn of approximately 2.03 × 104 g mol-1. With Mn higher than this critical value, the PMTS displayed columnar(ΦR) phase. On the contrary, the PMT6 S displayed symmetry hexagonal columnar(ΦH) phase, which were independent of Mn, regardless of Mn higher or lower. The comparison between PMTS and PMT6 S suggested that the spacer played an important role in the constructing of LC ordered structure. For the former, the PMTS without the spacer formed rectangular ΦR phases developed by the Tp moieties and the main chain as a whole, due to the strong coupling effect of the Tp moieties and the main chain. For the later, the PMT6 S presented a higher symmetry ΦH phase owing to the decoupling and self-organization of the Tp moieties.(4) A series of SCLCPs with different length of tail of the side chain Tp units, denoted as PMTSm(m = 1, 2, 3, 4, 6, 8, 10, 12, 14, which was the number of the carbons of the alkoxy chain), were synthesized through conventional free radical polymerization. The phase behavior and phase structures of the polymers have been investigated by DSC, POM and 1D WAXD. The results showed that PMTSm formed different columnar LC phases depend on the tail lengths. The isotropization temperature and glass transition temperature decreases initially with the length of tail(2 ≤ m ≤ 8) but increase more than 320 oC on further extension(10 ≤ m). For PMTS10, PMTS12 and PMTS14, they formed more ordered columnar phase with the increase of the temperature.(5) Based on two liquid crystalline monomers,(3, 6, 7, 10, 11-pentakis(hexyloxy)-2-oxytriphenylene) methacrylate(MTS) and 6-(3, 6, 7, 10, 11-pentakis(hexyloxy)-2 –oxytriphenylene) hexyl methacrylate(MT6S), a novel series of binary copolymers poly(MTSx-co-MT6Sy), were prepared by free radical polymerization 2, 2’-azo-bisisobutyronitrile(AIBN) as initiator. The copolymers of poly(MTSx-co-MT6Sy)(P2 ~ P7) were characterized by 1H NMR and GPC. The results showed that the content of PMT6 S has significant effect on the LC phase behavior and phase structures of copolymers. The properties of samples(P2 ~ P5) whose molar content of PMT6 S below 75% were similar to the property of the homopolymer PMTS, forming columnar(Φ) phases. But the properties of samples(P6 and P7) whose molar content of PMT6 S above 80% were similar to the property of the homopolymer PMT6 S, presenting the symmetry hexagonal columnar(ΦH) phase.(6) A novel double liquid crystalline block copolymer(PMTS-b-PMT6S) composed of poly((3, 6, 7, 10, 11-pentakis(hexyloxy)-2-oxytriphenylene) methacryl-ate)(PMTS with no flexible spacer) and poly(6-(3, 6, 7, 10, 11-pentakis(hexyloxy)-2-oxytriphenylene) hexyl methacrylate)(PMT6S with 6 methylene units as flexible spacer), was successfully synthesized by reversible addition-fragmentation chain transfer(RAFT) polymerization. The experimental results revealed that the phase transition temperature and glass transition temperature decreased with the increase of volume fraction of PMT6S(fPMT6S). When the volume fraction of PMT6S(fPMT6S) is lower than 58.1%, the block copolymer(PMTS-b-PMT6S-1 ~ PMTS-b-PMT6S-3) displayed columnar(Φ) phase. With the volume fraction of PMT6S(fPMT6S) is higher than 58.1%, the block copolymer(PMTS-b-PMT6S-4 and PMTS-b-PMT6S-5) displayed symmetry hexagonal columnar(ΦH) phase. |
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