Preparation And Properties Of Biodegradable Hyperbranched Polymers And Cross-linked Microgel

Polylactic acid (or Polylactide) (PLA) which was widely used in many field because of its biodegradable and biocompatible properties, have gained enormous attention recently . Hyperbranched polymers synthesised by Lactic acid-based copolymer are a type of dendritic macromolecules that constitute a novel class of highly branched polymers with a multitude of end groups. Because of their highly branched three-dimensional andsphere-like molecular architecture , hyperbranched polymers have shown very different properties from those of their linear analogues , such as low viscosity , no inter chain entangling and high solubility. It is mainly applied in coating, polymer blending modifier , drug delivery carrier , medicine slow releasing agent etc. The synthetic method is easy and the cost is low.Poly(L-tyrosine-co-lactic acid-co-glycolic acid) (PTLG), a pH sensitive polymer, was synthesized by simply heating a mixture of L-tyrosine (Tyr), DL-lactic acid and glycolic acid in the present of stannous chloride. The linear architecture comprising of poly(lactic acid)unit and poly(glycolic acid) unit and poly(L-tyrosine) unit was confirmed by NMR spectrum. Molecular weights were determined by 1H-NMR end-group analysis and GPC. The PTLG was soluble in many organic solvents and aqueous solution of sodium hydroxide (pH≧9.0). The thermal properties were evaluated using thermogravimetric analysis(TGA).(Glutamic acid-lactic acid-pyromellitic dianhydride), an biodegradable and pH-sensitive hyperbranched polymers, was synthesized by simply heating a mixture of L-glutamic acid (Glu), DL-lactic acid and pyromellitic dianhydride with the present of stannous chloride. The unique branched architecture comprising of glutarimide unit, polyester unit and polyamide unit was confirmed by NMR spectrum. Copolymer obtained has a good pH sensitivity and was soluble in aqueous solution of sodium hydroxide (pH≧7.4).(Glutamic acid-lactic acid-pentaerythritol), an biodegradable and hyperbranched polymers, was synthesized by simply heating a mixture of L-glutamic acid (Glu), DL-lactic acid and pentaerythritol with the present of stannous chloride. The unique branched architecture comprising of glutarimide unit, polyester unit and polyamide unit was confirmed by NMR spectrum. Copolymer obtained also has a good pH sensitivity and was soluble in aqueous solution of sodium hydroxide (pH≧7.4).Finally, Two kinds of degradable drug-loaded microgels were synthesized by condensated poly (lactic acid - glutamic acid) and PEG600(adipic acid)with DCC as condensation agent. Physical and chemical properties of the microgel obtained was studied, containing the release properties in vitro. The microgel obtained is biodegradable and can be used as drug delivery carrier.