Synthesis and properties of pentaarmed poly(l-lactide)s on N-dichlorophosphoryl-P-trichlorophosphazene derivative core

N-Dichlorophosphoryl-P-trichlorophosphazene was synthesized by two steps and N-di[p-(hydroxylmethyl)phenoxy]phosphoryl-P-tri[p-(hydroxylmethyl)phenoxy]phosphazene was prepared by the reaction of N-dichlorophosphoryl-P-trichlorophosphazene with the sodium salt of 4-hydroxybenzaldehyde and subsequent reduction of aldehyde groups to alcohol groups by using sodium borohydride. The hydroxyl-terminated pentaarmed compound as initiator for the synthesis of pentaarmed poly(l-lactide)s in the presence of stannous octoate was studied. Effects of molar ratio of monomer to initiator and monomer to catalyst on polymerization were investigated. The results indicate that the molecular weight of the polylactides linearly increases with the molar ratio of l-lactide to initiator. Thermal analysis demonstrates that pentaarmed poly(l-lactide)s possess lower melting point and crystallinity but higher maximum decomposition temperature than those of linear poly(l-lactide)s.