Paper TF-MoA9
Structure and Properties of Ultra-High Molecular Weight PHEMA Synthesized Using Solvent-Free Initiated Chemical Vapor Deposition (iCVD)

Monday, October 18, 2010, 4:40 pm, Room Pecos

Initiated chemical vapor deposition (iCVD) is a low temperature variant of hot-wire chemical vapor deposition (HWCVD) which has been used to produce a wide variety of free radical polymers like fluoropolymers, acrylic polymers and silicone polymers without the use of solvents. An initiator is activated in the gas phase by a resistively heated filament array. The radicals thus generated undergo surface polymerization on a cooled substrate by attaching to multiple monomer units. In this work, we produced thin films of poly(2-hydroxyethyl methacrylate) (PHEMA), an important hydrogel, for potential biomaterials applications such as skin substitutes. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies showed that the chemistry of PHEMA obtained by iCVD synthesis matched closely to PHEMA obtained from solution synthesis. Deposition kinetics were tuned to achieve high deposition rates (~1.5 μm/min), which yielded mechanically robust ultra-high molecular weight polymer films. As a result, the films displayed a high degree of physical chain entanglement giving rise to high tensile modulus and storage modulus. This eliminates the need for chemical crosslinking, thus preserving maximum hydrophilicity for cell growth. The films showed good water transport and swellability. In vitro cytotoxicity studies of adult human dermal fibroblasts on PHEMA showed these films were non-cytotoxic and displayed viable cell adhesion. Non-specific protein adsorption was shown to be reduced compared to controls.