Sequential homo‐interpenetrating polymer networks of poly(2‐hydroxyethyl methacrylate): Synthesis, characterization, and calcium uptake

Abstract

AbstractFormation of homo‐interpenetrating polymer networks (homo‐IPNs) of poly(2‐hydroxyethyl methacrylate) (PHEMA) and their capacity for calcification are investigated. A sequential method is established to generate IPNs of rank I and II, containing two or three crosslinked networks. Although the networks are chemically identical, thermo‐mechanical analysis (DSC, DMA) suggests some phase separation. Calcification of PHEMA hydrogels, thought to be controlled by the free volume pathways accessible to calcium ions, is investigated by positron annihilation lifetime spectroscopy (PALS) and experimental calcium deposition. While calcium uptake is reduced in IPNs, the size of the free volume elements estimated by PALS remain constant at radii of 2.6 Å (dry) and 2.9 Å (hydrated), both in PHEMA and IPNs. The reduction of calcium uptake cannot be therefore associated with the size reduction of the angstrom‐size free volume elements detectable by PALS, and is attributed to the effect of chain packing on pores too large to be detected by PALS. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012