Cross-linked and functionalized polyester materials constructed using ketoxime ether linkages.

A modular and simple approach to the graft functionalization and cross-linking of ketone-containing poly(ε-caprolactone)s has been investigated for the preparation of novel gel and nanoparticulate materials. Poly(ε-caprolactone--2-oxepane-1,5-dione) (P(CL--OPD)), was grafted by reaction with 1-aminooxydodecane and cross-linked by reaction with 1,6-bis(aminooxy)hexane, each at room temperature in tetrahydrofuran at 1 and 10 wt% polymer in the absence of an acid catalyst, and at 1, 5 and 10 wt% polymer in the presence of -toluenesulfonic acid. The grafting process served as a model system for the cross-linking reactions, affording products that were fully characterizable and retained the physical properties of (P(CL--OPD)), with a slight increase in measured molecular weight and characteristic spectroscopic signatures for the dodecyl chains and the newly introduced ketoxime functionalities. Early stages of the intermolecular cross-linking were followed by gel permeation chromatography and atomic force microscopy. Ultimately, insoluble, but tetrahydrofuran-swollen gelled products were obtained, which were characterized by infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis. These materials exhibited interesting melting transition profiles, undergoing melting at lower temperatures and broader temperature ranges than observed for their polymer precursors. This study represents an advance in the development of rapid and efficient chemistry for the preparation of functional and robust hydrolytically-degradable polymer materials with degradable linkages.