Surface and interfacial energetic analysis of amphiphilic copolymers

Abstract

A series of hydrophilic-hydrophobic copolymeric surfaces of 2-hydroxyethyl methacrylate and various alkylmethacrylate have been prepared by in-situ solution copolymerization using a redox radical initiator. Contact angles of various appropriate probing fluids on the polymeric surfaces were determined in air (hydrophobic environment) and under water (hydrophilic environment). From contact angle data, the dispersive interaction contribution ($\gamma_s^d$) and the polar contribution ($\gamma_s^p$) to the total surface free energy ($\gamma_s$) and interfacial energetic quantities (e.g., water-polymer, liquid-polymer interface, etc.) were estimated by surface and interface physicochemical theory using various approximated interfacial interaction terms. In particular, we investigated both the experimental and analytical methodologies of contact angle study in two approaches (i.e., computational and graphical method). In air measurement, the estimated results have some difference in magnitude but the energetic trends are similar and reasonable while under water measurement, the analyzed results are very similar and good agreements between the computational and graphical method were observed. From comparisons of surface energetic components between hydrophobic medium and hydrophilic one, it is found that surface and interface energetic components of polymeric surface as a representative low-energy surface are highly dependent on environmental fluid. Also, from the correlation between interfacial energetic results and recently proposed surface energetic criterion of biocompatibility, we find that HEMA/BMA, HEMA/HMA copolymer systems are in the region of biocompatibility.