Synthesis And Properties Of Liquid Crystalline Ionomers And PBT/PP Blends Containing Liquid Crystalline Ionomers With Different Ion

Recently, Liquid crystalline polymers (LCPs) with high strength and stiffness, high chemical resistance, good dimensional stability and low linear thermal expansion coefficient are attractive high performance engineering materials. Most LCPs and thermoplastic are immiscible at the molecular level. The incompatibility between the matrix polymers and dispersed LCP phase leads to poor interfacial adhesion. Accordingly, the mechanical strength of the LCP/thermoplastic blends is considerably lower than that expected from theoretical calculation. Therefore, compatibilization with appropriate agents is required to improve the adhesion between the LCP fibril and thermoplastic blends interface, for example copolymer induced polar groups, chemistrical modify induced polar group, graft, block copolymer-blend, adding compotibilizer, forming IPN network, and hydrogen bond.In this paper, the compatibilizing method is adding liquid crystalline ionomer containing ion group in blend. Liquid crystalline ionomers (LCIs) are liquid crystalline polymers containing ionic groups and the properties of LCIs are superior to the LCPs because of the compatibilization in composites by the function of ionic groups between the molecule chains. Moreover, the mesogenic phase has high degree of long-range order that enabling them to orient along the flow direction during processing. This leads to the formation of fine fibrils at an appropriate range of LCP concentration under certain processing conditions. The fine fibrils reinforce the matrix of thermoplastics effectively, giving rise to the development of polymer composites that commonly known as in situ composites. Therefore, LCIs are one new kind of function polymer materials and have been one of important research project in the field of LCPs. It is necessary and interesting to study LCIs, which provides theoretical basis and novel thought to synthesize and prepare the composites with other polymers, especially in the fields of the blends with advantageous properties.In this paper, a series of main-chain liquid crystalline ionomers containing sulfonic ion (MLCI-Sns) are prepared by an interfacial condensation reaction of enantiotropic nematic mesogenic monomer (1,4-phenylene-dicarbonic acid bis (4-carboxyl phenyl) ester,1,10-sebacoyl dihydroxy,1,12-dodecanedioyl dihydroxy and brittle yellow (BY content between 0 and 8%). For MLCI-Sns, the glass transition temperature increases slightly with increasing the sulfonate group content. However, the melt temperature becomes increase first and then decrease with increasing the sulfonate group content. The liquid crystalline mesogenic regions of the MLCI-Sns become broad first and then narrow with increasing sulfonate group content. The decomposed temperature is up to 300℃, so the MLCI-Sns exhibited good thermal stability. They are main-chain liquid crystalline ionomers with nematic schlieren textures.A main-chain liquid crystalline ionomer containing carboxylic ion (MLCI-C5) by use of an interfacial condensation reaction from 4-phenylene-dicarbonic acid bis (4-carboxyl phenyl) ester,1,10-sebacoyl dihydroxy,1,12-dodecanedioyl dihydroxy and 2,5-dihydroxybenzoic acid is synthesized. It is main-chain liquid crystalline ionomers with nematic schlieren textures. The liquid crystalline mesogenic region of the MLCI-C5 is 172℃. The MLCI-C5 exhibits good thermal stability.The MLCI-S5 and MLCI-C5 has been blended with PBT and PP, respectivley. DSC result shows the Tg of PBT decreased with the increase of MLCI-S5 content. It can be explained to improve interphase adhesion between a PBT-rich phase and PP-rich phase by adding the MLCI-S5. DSC result shows that some specific interaction is occurred between PBT (and PP) and MLCI-C5, which increase the Tm of PBT (and PP) component in the polymer blends. The crystallization rate of PBT is retarded due to hydrogen-bonding interactions between the MLCI-C5 and PBT in the blend. SEM and FTIR analysis identifies the intermolecular interaction between MLCI-S5 and PBT/PP phase, and the interaction results in a stronger interfacial adhesion between PBT and PP phase, and a much finer dispersion of the PP in PBT matrix, while excess of MLCI-S5 leads to coagulation of MLCI-S5 and PP phase. The addition of MLCI-C5 (9wt%) lead to finer and better dispersed of PP polymer in the blends relative to the blends with no MLCI-C5 added. A small amount of added MLCI-S5 will improve tensile strength and elongation at break, but MLCI-S5-rich domains form with excess MLCI-S5 addition will impair the mechanical performances. The mechanical properties are improved when the proper amount of MLCI-C5 is added, which enable improve adhesion at the interface.The SLCI-C5 containing 4-(4-ethoxybenzyloxy)-4’-allyloxybiphenyl as enantiotropic nematic mesogenic monomer M2 and 4-allyoxybenzoic acids as ionic monomer M3 is synthesized by graft copolymerization upon polymethylhydrosiloxane. It is side-chain liquid crystalline ionomers with nematic schlieren textures. The liquid crystalline mesogenic regions of the SLCI-C5 are 149℃. The SLCI-C5 exhibits good thermal stability.The SLCI-N5 containing 4-(4-ethoxybenzyloxy)-4’-allyloxybiphenyl as mesogenic monomer M2 and allytriethlammonium bromide as ionic monomer M4 is synthesized by graft copolymerization upon polymethylhydrosiloxane. The liquid crystalline mesogenic regions of the SLCI-N5 are 251℃. The SLCI-N5 exhibits good thermal stability. It is side-chain liquid crystalline ionomers with nematic schlieren textures.The side-chain liquid crystalline ionomer containing carboxylic ion (SLCI-C5) and the side-chain liquid crystalline ionomer containing ammonium ion (SLCI-N5) are used in the blends of PBT and PP by melt-mixing, respectivly. DSC results of PBT/PP/SLCI-C5 and PBT/PP/SLCI-C5 blends are the same to the results of PBT/PP/MLCI-C5 blends.SEM and FTIR observation shows that the addition of SLCI-C5 and SLCI-N5significantly reduces the size of the dispersed phase and improves PP dispersion within the PBT matrix. The utilization of SLCI-C5 results in a stronger interfacial adhesion between PP and PBT phases and improves the mechanical performances of PBT/PP/SLCI-C5 blends. The mechanical properties of PBT/PP/SLCI-N5 blendsalso increase with the addition of SLCI-N5. When the SLCI-N5 content is 7wt%, the mechanic properties are best. The utilization of SLCI-N5 results in a stronger interfacial adhesion between PP and PBT phases and improves the mechanical performances of PBT/PP/SLCI-N5 blends. However, when the content of SLCI being added to the blends is surplus, the mechanical performances of blends are decreasing.