Synthesis, characterization and biodegradability of polysaccharide-g-poly(epsilon-caprolactone) copolymers

In this thesis, work has been directed toward developing a range of polysaccharide-g-poly(caprolactone) copolymers to obtain materials that are melt processible, biodegradable and that can be tailored to have desirable interfacial properties for blends. A method has been developed by which cellulose acetate d.s. 1.7 (CA) is dissolved in epsilon-caprolactone (CL) in bulk to which an organo-metallic catalyst is added. The reaction between the dissolved cellulose acetate free hydroxyl groups and the organo-metallic catalyst occurs and generates polysaccharide macro-initiators formed in-situ. The graft copolymers were analyzed by 1H NMR, and it was determined that the products had variable graft lengths, degrees of substitution and weight % of cellulose acetate in the copolymers. Analysis by size exclusion chromatography showed that, in all cases, the graft copolymers gave unimodal peaks with molecular weights higher than the starting cellulose acetate. The thermal properties of the graft copolymers were investigated using differential scanning calorimetry and showed no observable melting transitions for the poly(caprolactone) grafted side chains. In addition, the tensile properties of the graft copolymers were evaluated by producing solution cast films and subjected to mechanical testing. The biodegradation of the graft coplymers was investigated by using a polymer mineralization test under controlled composting conditions.; In addition to the above method, an additional technique has been developed by which modified HYLON VII starch granules were produced using a coating process where the starch granules were coated with epsilon-caprolactone and reacted in a rotating drum reactor. The new materials were evaluated for the possible use as interfacial agents to improve polymer interactions in blends of poly(caprolactone) and starch. 1H NMR analysis showed the presence of both poly(caprolactone) and starch repeat units are present in the modified graft products. Particle size analysis was employed to determine the actual size of the products and showed a substantial increase in the size of the granules with increasing epsilon-caprolactone content in the initial feed ratio. Blends of poly(caprolactone), unmodified starch and modified starch granules were produced and their tensile properties were evaluated using Instron testing equipment.