| Chiral liquid crystal polymers (CLCPs) contain chiral groups in their sructures and usually are cholesteric and chiral smectic. They have attracted considerable interest for their unique optical and electricical properties, for example, selective reflection, optical rotation, circular dichroism, electro-optic effect and magneto-optic effect, due to their helical structure. The structure of convention liquid crystal is rod-like. Recently, star-shaped multi-arms liquid crystals, which deviate greatly from the conventional rod-like shape, have been synthesized. They display nematic phase of rod-like LCs, as well as the columnar phase of disk-like LCs. The chiral mesophases of star-shaped LCs have seldom been reported. The multi-arms liquid crystals taking glocose, maltose, melitose and sorbital as chiral cores, have not only been first synthesized and expanded the types of star-shaped LCs, but also first put forward and prove that chiral core can induce the cholesteric phase of multi-arms LCs containing nematic LC arms and provided some theoretical bases and experiment data in design and synthesis of cholesteric star-shaped LCs. Maltose modified can be taken as new chiral groups for synthesizing chiral main-chain liquid crystal polymers.Multi-arms compounds are synthesized by different arms and four chiral cores. The condition for forming multi-arms LC, influence of structures of chiral cores and liquid crystal arms on properties of multi-arms liquid crystals, whether chiral core can induce cholesteric LC or not, which only containing nematic arms, are studied. The chiral main-chain liquid crystal polymers containing maltose modified as chiral groups have been synthesized. The influence of chiral groups on properties of main-chain liquid crystal polymers (MLCPs) is studied.In this dissertation, we will report the design and synthesis of five liquid crystal monomers, one non-liquid crystal monomer, one chiral monomer, fifteen multi-arms compounds, and three series of MLCPs. The liquid crystal monomers are 10 - (4’-(benzoyloxy) biphenyl-4-yloxy)-10-oxodecanoic acid (M1),10-(4’-(4- methoxybenzoyloxy)biphenyl-4-y1oxy)-10-oxodecanoic acid(M2),10-(4’-(4-ethoxybenzoyloxy)biphenyl-4-yloxy)-10-oxodecanoic acid(M3),6-(4-(4一methoxybenzoyloxy)phenoxy)-6-oxohexanoic acid(M5),6 (4-(4-ethoxy benzoyl oxy)phenoxy)-6-oxohexanoic acid(M6).The non-liquid crystal monomer is 6-(4-(benzoyloxy)phenoxy)-6-oxohexanoic acid(M4).Chiral monomer is 6,6’-hydroxy-hexa-o-acetyl-α,β—maltose ester(MA).The multi-arms compouds are penta{10-(4’-(alkoxybenzoyloxy)biphenyl-4-yloxy)-10-oxodecanoic acid}glucose ester(a1-a3),penta{6-(4-(alkoxybenzoyloxy)phenoxy)-6-oxohexanoic acid}glucose ester(a4-a6),hexa {10-(4’-(alkoxybenzoyloxy)biphenyl-4-yloxy)-10-oxodecanoic acid} sorbitol ester(b1-b3),octo{6-(4-(alkoxybenzoyloxy)phenoxy)-6-oxohexanoic acid} maltose ester(c1-c3)and hende{6-(4-(alkoxybenzoyloxy)phenoxy)-6-oxohexanoic acid}melitose ester(d1-d3).Main-chain liquid crystal polymers P1,P2 and P3 series.To our knowledge,the obtained multi-arms compounds and the MLCPs have never been reported up to nowThe structures and properties of the obtained monomers,multi-arms compounds, and MLCPs are investigated by FT—IR spectroscopy,1H—NMR spectroscopy, differential scanning calorimetry(DSC),polarizing optical microscopy(POM), Polarimeter,X-ray measurement and elemental analysis. Their structure-property relationships are discussed in detail.MA is a chiral monomer,which display non-mesophase.The specific rotation (SROT)of MA is +76.0°(in CHCl3).M4 is not a liquid crystal monomer and only showed melting transition and crystal transition on heating and cooling cycle.M 1,M2, M3,M6 are thennotropic and enantiotropic LC monomers,and showed schlieren texture of nematic mesophase in heating and cooling cycle.M5 is a thermotropic and monotropic LC monomer, and only showed crystal-isotropy transition on heating cycle.But on cooling cycle,M5 exhibited schlieren txture of nematic mesophase.The multi-arms compounds all are chiral ones,which specific rotation are opposite as compared with their parent cores.For example,glucose,maltose and melitose are all right-hand helicity, but their corresponding multi- arms compounds synthesized are all left-hand helicit y.Sorbitol used in this dissertation is left-hand helicity, while the corresponding multi-arms compounds are right-hand helicity. Generally, solvent, temperature, chain length and substituent play an important effect on handedness of chiral compounds. The long side arms play an important effect on the change of the behavior of SROTs for the chiral star-shaped compounds comparing with their parent cores. The specific rotation of the multi-arms comopunds increased with the terminal chain length of arms increased.The multui-arms compounds all exhibit cholesteric mesophases excepet for a4, c1 and d1. The multi-arms compounds are LCs when the arms display mesophase. But their mesophases are different. The arms are nematic LCs, and the corresponding multi-arms compounds are cholesteric LCs. They displayed the typical textures of cholesteric phase, such as finger texture, grandjean texture, oily streak texture and broken focal-conic texture. This indicates that chiral cores play an important role on inducing cholesteric mesophase.al-a3 are five-arms star-shaped LCs (SSCs), which take glucose as cores and M1-M3 as side arms. Their melting temperatures decreased from 123.0℃to 85.0℃, and mesogenic region increased from 51℃to 123.0℃with the length of terminal chain in the side arms increased.b1-b3 are six-arms SSCs, which take sorbitol as cores and M1-M3 as side arms. Their melting temperatures decreased from 111.5℃to 81.5℃, and mesogenic region increased from 48.5℃to 110.5℃with the length of terminal chain in the side anus increased.al-a3 and bl-b3 contain the same mesogenic arm but different cores. a1-a3 take glucose as cores, and b1-b3 take sorbitol as cores. The multi-arms LCs containing sorbitol as cores, have lower Tm, Ti and narrower mesogenic region. Sorbitol is more flexible than glucose, for its chain structure. The structure of bl-b3 were much more irregular than that of a1-a3. So bl-b3 exhibited lower Tm, Ti and narrower mesogenic region.a4-a6 are five-arms star-shaped compounds (SSCs), which take glucose as cores and M4-M6 as side arms. a4 is a non-LC. a5 and a6 are five-arms SSCs. Their melting temperatures decreased from 151.2℃to 145.5℃, and mesogenic region increased from 42.3℃to 67.3℃with the length of terminal chain in the side arms changed from CH3O to C2H5O.c1-c3 are eight-anus SSCs, which take maltose as cores and M4-M6 as side arms. c1 is a non-LC. c2 and c3 are eight-arms SSCs. Their melting temperatures decreased from 148.7℃to 133.1℃, and mesogenic region increased from 39.0℃to 53.7℃with the length of tenninal chain in the side arms changed from CH3O to C2H5O.d1-d3 are eleven-arms SSCs, which take melitose as cores and M4-M6 as side arms, d1 is a non-LC. d2 and d3 are eleven-arms SSCs. Their melting temperatures decreased from 150.4℃to 121.1℃, and mesogenic region increased from 43.5℃to 68.0℃with the length of terminal chain in the side arms changed from CH3O to C2H5O.This indicated that increasing flexibility of terminal chain in side anus can make the SSLCs melting temperature decrease and mesogenic region increase. This can be prone to stabilize the LC phase.a5、c2、d2 and a6、c3、d3 contain the same mesogenic ann (M5 and M6), but different cores (glucose, maltose and melitose, respectively). The mesogenic region of the multi-arms LCs changed a little with the increase of the number of sugar ring.The result of specific rotation indicated that P1 series and P2 series are right-hand helicity. The absolute of specific rotation of P1 series increased with the content of MA in the P1 increased. The contents of MA in P2 series are same, the specific rotations of the polymers are similar.The liquid crystal properties of the three series of main-chain liquid crystal polymers (MCLCPs) are investigated by DSC, POM and X-ray measurement. The results indicated that P1| is a smectic MCLCP, P12-P15 are chiral smectic MCLCPs, P16-P17 are cholesteric MCLCPs. P2 series are cholesteric main-chain liquid crystal ionomers (MCLCIs), P3 series are smectic MCLCIs. To our knowledge, the obtained MCLCPs have never been reported up to nowP1 series were synthesized with SD, MA and BP by condensation polymerization. The Tg, Tm and Tiof P1 series decreased with the content of MA increased. The mesophase changed from smectic to cholesteric when the content of MA reached 20%[n(MA)/n(MA+BP)]. The results indicated that the introduction of MA into P1 played an important role on the thermal behavior and the type of mesophase. P2 series were synthesized with SD, MA, BP and MC by condensation polymerization and neutralization reaction. P3 were synthesized with SD, BP and MC by condensation polymerization and neutralization reaction. P3, which had the similar content of MC-Na as compared with P2, were synthesized to study the effect of chiral groups on properites of the LCIs. P2 were optical activity, while P3 were not. P3 were smectic MCLCPs, while P2 were cholesteric MCLCPs. The introduction of MA into P2 induced the optical activity and the change of mesophase of P2, which changed from semctic to cholesteric mesophase. The introduction of MA into P2 also played an important role on thermal behavior of P2. The Tg, Tm and Ti decreased with the increase of MA in P2 duo to the flexibility of main-chain increasing with MA increasing.The introduction of MC-Na into P2 and P3 Played an effect on their thermal behavior, but did not change the mesophase type. The introduction of ions will bring two effects. On the one hand, the rigidity of polymer chain decreased with the ions increased and BP decreased. On the other hand, the interaction between polymer chain increased with the ions increased. The content of BP in them are different. These factors interacted and made the thermal behavior of P2 and P3 changed differently. The introduction of small ions will widen the mesophase region and stabilize the mesophase, but large ions introduced will destroy the mesophase. |
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