Synthesis And Properties Of Polyesters Based On Cinnamic Acid

Green polymer PDR, PDH and PDP polyesters were synthesized by meltpolycondensation of 3,4-dihydroxycinnamic acid (DHCA, coffeic acid) with ricinoleic acid (RA),10-hydroxydecanoic acid (HDA) or polyethylene glycol(PEG).The chemical structure of the copolymers were characterized by flourier transform infrared (FTIR) and nuclear magnetic resonance (1H-NMR). The properties of the copolymers were investigated by gel permeation chromatography(GPC) and differential scanning calorimeter(DSC). It was found that the glass transition temperature(Tg) of copolymers decreased with the increase of the flexible chain content, and the copolymers were so flexible that can be molded by thermal processing.The PDR copolymers were transformed from resin to elastomer by adjusting the molar ratio of the rigid units and flexible ones (i.e. the ratio of DHCA and RA units), meanwhile the tensile strength of copolymers were increased to 10.46 MPa and then decreased. After photo-cross-linking, the crosslinking degree of elastomer were increased. PDH exhibited higher fluorescence emission intensity than DHCA monomer. The crystallization of the PDH was characterized by X-ray diffraction (XRD) measurement. The results showed that PDH was hard to crystallize and exhibited amorphous, due to its branched structure. Hydrolysis experiments revealed that the degradation rate of PDH was slower than that of PD, and could be controlled by adjusting the molar ratio of the monomers.PDH copolymers exhibited fairly good tensile properties and the elongation at break was enhanced with increasing the content of HDA. After UV photo-crosslinking, the tensile strength was further improved and elongation at break slightly decreased. The hydrolysis experiments revealed that copolymers are facile biodegradable, and the degradation rate could be controlled by adjusting the segment composition.PDH/HA nanocomposites were prepared by situ polymerization of PDH and nano-hydroxyapatite(n-HA). The effect of segment composition (i.e. the ratio of DHCA and HDA units), content and size of n-HA on the mechanical properties were discussed. The tensile strength of the composites was increased up to 14 times to PDH. the degradation rate of PDH/HA was slower than that of PDH, and could be controlled by adjusting the content of n-HA.PDP micelles with different diameters were prepared by mixing N,N-dimethylformamide as a good solvent and water as a poor solvent. The effect of segment composition, ratio of DMF and water, PDP solution concentration on average diameters and morphologies of the micelles were discussed. Under certain conditions, the morphology of micelles changed from spherical to bowl shape. The morphology and size can be controlled by alter any of the factors mentioned above.