Synthesis and surface properties of fluorocarbon end-capped biodegradable polyesters

We report the synthesis and characterization of a new class of materials ba sed on combining hydrolytically degradable polyesters and fluorocarbon surf ace chemistry. These materials have surface properties which overcome some of the limitations of polymeric materials in controlled cellular or tissue adhesion properties. Fluorocarbon chains of two lengths (CF3(CF2)(m)(CH2)n, where F7C1 and F10C2 represent m = 6 and n = 1 and m = 9 and n = 2, respec tively) have been synthesized as the terminal end groups to L- and DL-polyl actides (PLA) and poly(lactide-co-glycolide) copolymers. Using both ring-op ening polymerization and the substitution of the fluorocarbon at terminal h ydroxyl groups, polyesters with 1, 2, and 4 fluorocarbon end groups were ob tained (F-polyesters). Angular dependent X-ray photoelectron spectroscopy ( XPS or ESCA) revealed that end groups are segregated at the surface. Furthe r, the results show their the surface coverage of fluorocarbon groups incre ases with increasing the concentration and the length of fluorocarbon end g roups. The surface composition of F-polyesters can be controlled by blendin g these polymers with polyesters or by changing the architecture of fluoroc arbon end groups. From ESCA data of F-polyesters after in-vitro hydrolysis at pH = 11.4, results from the F-polyester with a longer fluorocarbon end g roup (F10C2-) show that the surface erosion occurs at the topmost surface r egion during the initial hydrolysis period. The F-polyester having a short fluorocarbon group (F7C1-) shows a progressive decrease of surface fluoroca rbon concentration as a function of hydrolysis time. This result is explain ed by a longer retardation time for water permeation into the sample bulk o f F10C2-L-PLA due to greater segregation of fluorocarbon groups at the topm ost; surface.