Synthesis And Properties Of Novel Environmental Friendly Polyester

A novel polyester like block copolymer poly(3,4-dihydroxycinnamic acid)-b-poly (ethylene glycol) PDHCA-b-PEG was synthesized by thermal polycondensation of 3,4-dihydroxycinnamic acid (DHCA) and poly(ethylene glycol) (PEG). The structures and molecular weight of the PDHCA-b-PEG copolymers were characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). The properties of the polyester were investigated by differential scanning calorimeter (DSC), fluorescence spectroscopy and X-ray diffraction (XRD). It was found that PDHCA-b-PEG copolymers have evident glass transition temperature (Tg). The polyester showed the lowest Tg of 73.42℃under 15 wt% PEG in feed. The fluorescence spectroscopy indicated that the PDHCA-b-PEG copolymer solution had the strongest fluorescence emission at 5wt% ratio of PEG to DHCA. The XRD results indicated that PDHCA and PDHCA-b-PEG were amorphous and these copolymers may have good biodegradation performance. Bacterial culture in vitro proved that the PDHCA-b-PEG copolymer solutions have inhibition against staphylococcus albus bacteria.PDHCA-co-PLA copolymer was synthesized by the thermal polycondensation method based on the DHCA and D,L-lactic acid (LA). It was found that Tg of the PDHCA-co-PLA copolymers decreased from 132.26℃to 99.12℃through the LA ratio increased from 0 to 50mol%. The fluorescence spectroscopy indicated that the copolymer has the strongest fluorescence emission at 20mol% ratio of LA to DHCA. The copolymer could undergo a photochemical reaction. The cross-linked particles still have good fluorescence after 65 min UV-irradiation. The XRD results showed that PDHCA-co-PLA copolymers were amorphous and these copolymers may have good biodegradable performance. Copolymer rectangular samples buried in soil for degradation experiments showed that the more LA contents in copolymer, the slower degradation rate of the copolymer.Poly (3, 4-dihydroxycinnamic acid)-co-poly (p-hydroxybenzoic acid) (PDHCA-co-PHA) copolymers were synthesized by thermal polycondensation between DHCA and p-hydroxybenzoic (HA). The Tg of the PDHCA-co-PHA decreased when HA feeding increased. Microspheres were prepared by solvent transformation between trifluoroacetic acid (TFA) and N,N-dimethylform amide (DMF). The size of these microspheres was between 1 ~ 2μm and they could be used in drug delivery area.