Synthesis and characterisation of phosphorylcholine-based polymers useful for coating blood filtration devices

Copolymers of 2-methacryloyloxyethylphosphorylcholine (MPC) and lauryl methacrylate (LMA) of molar ratios MPC: LMAX where x = 1, 2 or 4, have been synthesised by two different free-radical polymerisation techniques. The solubility characteristics of the resulting materials were investigated in a variety of water: alcohol solvent mixtures and found to be influenced not only by the molar ratio of MPC: LMA, but also the method of synthesis. A window of solubility was observed for certain copolymers and the alcohol used in the solvent mixture was also found to have a profound influence on the solubility profile of the polymers. These materials were soluble in a wider range of aqueous methanol mixtures compared to aqueous mixtures of higher aliphatic alcohols, such as ethanol or isopropyl alcohol, which was rationalised in terms of the affinity of the phosphorylcholine headgroup for the various alcohols relative to water. 1H nuclear magnetic resonance spectroscopy was used to further examine the solution properties of the copolymers in various solvents. The copolymer MPC: LMA2 was coated onto a variety of substrates from both alcohol-only and water: alcohol solvent systems and the surface properties of the films compared by static and dynamic contact angle, atomic force microscopy (AFM) and attenuated internal reflectance Fourier transform infrared spectroscopy (ATR-IR). The coating formed from the water: alcohol solvent was found to be hydrophilic in nature, possessing spontaneous wettability, whereas films formed from alcohol-only solvents were hydrophobic, and only on conditioning with water were more wettable surfaces attained. This phenomenon was applied in the coating of leukocyte filtration material, where the aqueous-based systems demonstrated lower critical wetting surface tension (CWST) and shorter wetting times relative to both uncoated filters and those coated from alcohol-only systems. The haemocompatibility of the coated filters was equivalent for both coating solvent systems. employed, and far superior when compared to the uncoated control.