Study On The Compsites Of Polythiophene And Natural Polymers Of Polysaccharides

There are many tissues that have been targeted for regeneration, including nerve, bone, skin, liver, heart, cartilage, vascular, tendon, and ligament. Tissue engineers are interested in making interactive scaffolds that not only perform a mechanical and physical role, but also a biological function. It is known that electrical stimulation in vivo and in vitro leads to enhanced regeneration of some tissues include peripheral nerves. Conducting polymers, especially those based on polyanilines, polypyrroles, polythiophenes and polyphenylenes, have received significant attention throughout the course of the past three decades owing to their tunable electro-optical properties and high degree of processability. Among the conducting polymers that have been developed, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3-thiophene acetic acid) (PTAA) have been considered as the two of the most successful polythiophene derivatives because of their interesting properties.Polysaccharide is one of the three important biomacrmolecules besides protein and nucleic acid. It widely exists in the body of animal, plant and microorganism and possessing important physiological functions. Polysaccharides are naturally produced polymers of simple sugar building blocks with inherently desirable bioactivity, biocompatibility and biodegradability. It has been reported that conducting polymer-polysaccharides composites could be electroactive, biodegradable, and biocompatible materials and used to enhance the regeneration of severed peripheral nerves and other tissues.In this work, three kinds of blends were prepared and systematically studied. The first one was the aqueous mixtures of methylcellulose (MC) and the salts of PTAA, the second was the aqueous dispersion and the composite film of curdlan and PEDOT, and the last one was the PEDOT film doped with polyanionic polysaccharides such as carboxymethylcellulose, hyaluronan, xanthan, pectin and gellan gum. The main contents and conclusions are listed as follows.1. The aqueous mixtures of polysaccharide of MC and two kinds of salts of PTAA, ammonium poly(3-thiophene acetic acid) (PTAA-NH4) and sodium poly(3-thiophene acetic acid) (PTAA-Na) were prepared. The effects of PTAA-NH4 and PTAA-Na on the rheological and thermal properties of MC solution were investigated. The ?ow curves could be satisfactorily ?tted by the power law and Cross model. The mixture solutions of MC and PTAA-NH4 or PTAA-Na showed more remarkable shear thinning behavior than pure MC solutions at low temperatures. The pseudoplastic character of the mixtures became more pronounced as the concentration of PTAA-NH4 or PTAA-Na increased. Significant viscous synergism depending on shear rate and concentration of PTAA-NH4 or PTAA-Na was found for the mixtures, indicating a special interaction between the two amphiphilic polymers of MC and PTAA-NH4 or PTAA-Na. PTAA-NH4 has more significant synergistic effect with MC than PTAA-Na. In comparison with pure MC solutions, the mixtures showed much more evident shear thinning characteristics. When the concentration of PTAA-NH4 added was higher than 0.15%, or the concentration of PTAA-Na added was higher than 0.35%, weak gel-like behavior of the mixtures was also observed at low temperatures. In addition, though the gelation and degelation patterns of MC were not changed by the addition of PTAA-NH4 or PTAA-Na, both rheological and calorimetric measurements showed that the presence of PTAA-NH4 or PTAA-Na shifted the sol-gel transition temperature of MC solution to higher temperature with increasing of the concentration of PTAA-NH4.2. The aqueous dispersion and the composite film of curdlan and PEDOT were prepared. The aqueous dispersion of curdlan and PEDOT showed remarkable shear thinning behavior. The apparent viscosity and storage modulus of the aqueous dispersion of curdlan and PEDOT were lower than the curdlan aqueous suspension of the same concentration of curdlan, but increased with the concentration of PEDOT. Both rheological and calorimetric measurements showed that the thermal reversibility of the low-set gel formed from the aqueous dispersion of curdlan and PEDOT were lower than the low set-gel formed from the curdlan aqueous suspension of the same concentration of curdlan, but the thermal irreversibility increased with the concentration of PEDOT. Under low relative humidity, the resistance of the curdlan film was very big, and the presence of PEDOT could reduce resistance obviously. With the increase of relative humidity, the influence of PEDOT on the resistance of the curdlan film getting smaller. The resistance of the curdlan film and the composite film of curdlan and PEDOT changes with the relative humidity, so the films could be used as humidity sensor.3. PEDOT doped with polyanionic polysaccharides such as carboxymethyl cellulose, sodium hyaluronate, xanthan gum, pectin, gellan gum were prepared by electropolymerization in aqueous solutions. Some other dopants of potassium nitrate, potassium sulfate, sodium poly(styrenesulfonate) and sodium polyacrylate were used in comparison with the polyanionic polysaccharides. The optimum working electrodes, potential range and pH to obtain the electroactive PEDOT films were determined from the experiments of linear sweep voltammetry. The experiments indicated that indium tin oxid (ITO) conductive glass was suitable for the electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) in aqueous solution and the potential should be about 1.2 V which was between the oxidation potential and the overoxidation potential of EDOT in the solutions used. It was found that at acidic conditions, EDOT had lower polymerization and overoxidation potentials; the optimum pH range for film forming was 6-8 except sodium polyacrylate system, in which PEDOT film can only be formed under acidic conditions. The infrared spectra confirmed that all the anions were successfully doped into the PEDOT films. The electrochemical properties and stability of the obtained PEDOT films were also investigated. Results showed that the dopant had a great influence on the electrochemical synthesis and property of the PEDOT film. The PEDOT films doped with natural polyanionic polysaccharides were smoother and denser than those doped with inorganic salts and synthetic polyanions. In addition, the PEDOT films doped with natural polyanionic polysaccharides were of more stable electrochemical properties and better adhesion properties to the ITO conductive glass.