Synthesis and characterisation of poly(2-hydroxyethyl methacrylate) polyelectrolyte complexes

Copolymerization of charged and neutral monomers is a well known methodology to introduce charged moieties in a polymeric chain to obtain polyelectrolytes. New polyelectrolyte complexes have been synthesized by radical copolymerization of neutral methacrylic monomer 2-hydroxyethyl methacrylate (HEMA) with cationic 2-methacryloyloxyethyltrimethyl ammonium chloride (METAC) and anionic 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) monomers in 10:1:1 and 10:1:2 stechiometric ratio. The chemical structure of the synthesized terpolymers was confirmed by FT-IR spectroscopy, moreover, X-ray photoelectron spectroscopy showed the presence of a cationic charge excess on the 10:1:2 terpolymer surface respect to 10:1:1 terpolymer. Swelling studies showed for 10:1:2 terpolymers a high water content in the swollen state and a “smart behaviour” upon changes in external stimuli such as pH, while, 10:1:1 terpolymer presented the behaviour of a neutral polymer.Mechanical and differential scanning calorimetry analysis confirmed that terpolymer networks were stabilised by ionic cooperative interactions. In fact, the inclusion of a oppositely ionic charges in polymeric network of p(HEMA) represent a way to achieve higher Elastic Modulus as they stabilise the terpolymer networks.Cytotoxicity and cytocompatibility studies demonstrated that all materials were not toxic, moreover, the presence of a cationic charge excess on 10:1:2 terpolymer surface are able to promote fibroblast adhesion.