Synthesis and assembly of biodegradable/ compatiblegraft copolymers for biomedical applications

Sammanfattning: The synthesis and characterization  of nanostructured block copolymers is described.Block copolymers were grafted onto a backbone polymer  that consists of themonomer  MTC-BuOBn.  The block copolymers have a part consisting of PTMC(trimethylene  carbonate) and a part consisting of PLLA. The purpose with this thesiswork was to demonstrate the efficacy of block polymer formation. TMC serves  as amodel for other cyclic carbonates which can be readily functionalized.Thenanostructure  was synthesized using ring opening polymerization  with anorganocatalyst under mild conditions. The conversion and the solution conformationwere monitored by 1H NMR spectroscopy. The molecular weight (Mn) andPolydispesity Index (PDI) were obtained by gel permeation chromatography (GPC). Iorder to confirm the formation of the nanostuctures, the individual molecules weredeposited on silicon wafers and imaged by atomic force microscopy (AFM). The AFM images show that the backbone with blocks consisting of with PLLA, PTMC and PLLA and PTMCrespectively form elongated structures.  The phase transition behavior,  e.g. glass transitiontemperature, Tg,crystallization temperature Tc and melting temperature Tm, were characterized  bydifferential  scanning calorimetry (DSC).  The thermal  analyses results  indicate  that the PLLA-and the PTMC-grafted backbones are semicrystalline while the backbone grafted with both PLLA andPTMC is amorphous.  While the grafted backbone forms an elongated structure,  an analogouPLLA-grafted dendrimer  forms a spherical structure,  as expected. In sum, we have shown that we can control macromolecule  shape through chemistry