Study On Preparation, Structure And Properties Of Rod-Coil Copolymer Based On Polyaniline And Poly (Ethylene Oxide)

The rod-coil copolymers, consisting of both flexible chain segments and rigid chain segments, are novel self-assembling materials with the double properties of block or graft copolymers and liquid crystal. Because of the competition between micro-phase separation and the orientability of the rigid chain segments, the rod-coil copolymers may self-assemble into variable hierarchy supra-molecular structures and are widely used as functional materials and nano-materials. The rod-coil copolymers containing conjugated rigid chain segments are especially attractive as they show special optical and electric properties, and the incorporation of flexible chain segments into the rigid molecules often improve the solubility and the processiblity of the conjugated rigid polymer. In this dissertation, the 2 kinds of rod-coil copolymers containing polyaniline rigid chain segments and poly(ethylene glycol) flexible chain segments (PAn-co-PEG) were synthesized via chemical oxidation copolymerization. Then, the self-assembling behavior, solubility, processability and electric properties of the copolymers were studied sysmetically. The electrorheological (ER) fluids were also based on the rod-coil copolymers suspending into methyl silicon oil. The properties of the ER fluids were tested in detail as functions of the chemical structure and electric properties of the copolymer particles, electrical strength and temperature etc.Such two derivatives of aniline as polyethylene glycol (PEG) substituent methoxyl poly(ethylene glycol) o-aminophenyl ether(o-PEGAPE) and α,ω -bis(P-aminophenyl) poly(ethylene glycol) (BAPPEG) were designed and synthesized. And then, the grafted copolymers PAn-g-PEG and the triblock copolymer PAn-PEG-PAn were prepared by chemical oxidation copolymerization. The copolymers were characterized by FTIR, ultraviolet-visible spectrum, elemental analysisTG, DSC, TEM etc. Their thermal stabilities, crystal ability, solubility and their ability to form film were studied in detail. Relationship between the chemical composition, structure and properties of copolymers were investigated as well. The results showed that with the molar feed ratio of An to o-PEGAPE or BAPPEG (co ) increasing, the PAn segments length in the copolymer increased and the thermal stabilities were enhanced. With the PEG molecular weight decreasing, the crystallinity of PEG decreases but that of polyaniline increasing. The results also showed that when the PEG segments length or its content in the grafting copolymers are increased, the solubility and film-forming property of PAn-g-PEG improve remarkably, and the former was more effective than the latter.The amphiphilic copolymers based on rid (PAn) and coil(PEG) segments can self-assemble into fascinating aggregation structure. The composition of copolymers, solvent ect. All can effect on the self-assembly structures. PAn-g-PEG can aggregate into spherical structure in water, while with the Zpah increasing, the aggregates structures of PAn-PEG-PAn copolymer in water change from spherical, rod or rod-based net structures, and ends in spherical structure. If the length of PAn segments near to that of PEG segments, the PAn-PEG-PAn copolymer aggregates into rod structure. We found with the solubility parameters of solvent increasing, the aggregation structures of PAn-PEG-PAn copolymer in different solvents change from spherical to vesicular and then to fiber.The compositions, structures, pH, the molar ratio of [Li+]/[EO] and temperature all effect on the conductivity and dielectric properties of PAn-g-PEG and PAn-PEG-PAn copolymers. The results showed that both the conductivity of PAn-g-PEG and PAn-PEG-PAn copolymers lower than that of polyaniline. With the pH increasing, the conductivity of copolymers decreased. The rod or net structure is helped to increase the polarization strength of PAn-PEG-PAn copolymer, while the coexistence of particles with different shapes are helped to increase its polarizationrate. When the molar ratio of [Li+]/[EO] equals to 0.1, the PAn-g-PEG/ LiC104 complex has the higher conductivity and dielectric constant.The PAn-g-PEG and PAn-PEG-PAn copolymers can be used to prepare ER materials, which show somewhat high ER effects. The influences of compositions, structures, pH and temperature on properties of the ER fluids were studied in detail. At the same conditions, the ER fluids based PAn-PEG-PAn copolymers have higher shear stress and lower current density than those of ER fluids based on polyaniline. The particles with rod, or rod-based net structures, and the coexistence of rod and spherical structures show stronger ER properties. With the molar ratio of [Li+]/[EO] increasing, the electric field induced shear stress of ER fluids based on PAn-g-PEG/LiC104 copolymers reaches the optimal value when the molar ratio of [Li+]/[EO] equals to 0.1.