Study On The Synthesis And Properties Of New Modified Poly(Lactic Acid)

Polylactic acid (PLA) has become one of the most important materials in the fieldof biodegradable medical materials due to its good biocompatibility, biodegradability,good mechanical properties and processing proformance. However, there were somedefects in properties of polylactic acids, for example, the hydrophobic surface of PLAreduced its biocompability, long-term degradation in human body resulted in difficultlycontrolled degradation cycles, and high local acidity leaded to non-infectiousinflammation. In order to overcome the above-mentioned defects of the polyactic acid,many modified works of PLA were conducted by introduced protein and peptide. Inthis paper, collagen was introduced into PLA by grafting condensation, the mainproperties of the modified PLA was studied for its applation in the future.PLA was directly synthesized by melt polycondensation with stannous chloride(Sncl2) as catalyst.The properties of PLA were characterized by FTIR and HNMR, therelative molecular mass was about10000. This study describes the synthesis ofcopolymer (CPLA) based on both ends of PLA on which short blocks of hydrolyzedcollagen were grafted. Hydrolyzed collagen was covalently coupled via dehydrationwith dicyclohexylcarbodiimide (DCC) as a dehydrating agent. The characterization ofcopolymers was studied by infrared spectroscopy and differential scanning calorimetry(DSC) and by fluorescence emission and excitation spectroscopy. The hydrolyzedcollagen grafted on the PLA was quantitatively determined by ninhydrin. Analysis ofFTTR and fluorescence spectrum indicated that collagen has successfully introducedinto PLA. DSC analysis showed that the Tgof PLA and CPLA was56℃and41.7℃respectively, and only one glass transition temperature. This result also indicated thatthe above conclusion.The study found that the water contact angle of CPLA was less than PLA and itswater absorption was higher than PLA. The research of degradability showed thatCPLA had a high degradation rate in the first two weeks, then the rate was relativelyuniform without acid-catalyzed self-accelerating degradation process, however, PLAhas this phenomon during the degradation process. The results of cell compatibility testrevealed that the surface adhesion, spreading and growth on the CPLA are better thanPLA. These indicated that the cell compatibility was improved by introducing collagento PLA.CPLA microspheres were preparated by O/W emulsion-solvent evaporation technique through optimizing preparation conditions. SEM and particle size analysisshowed that the microspheres had a smooth spherical surface with an average particlesize of3.10and a span of0.6548. The FTIR analysis results showed that themicrosphere preparation process did not change the chemical structure of CPLA, justchanged its form. DSC analysis showed the glass transition temperature decreased by10.06Cand the cold crystallization temperature dropped12.45Cafter PLA graftedby hydrolyzed collagen.