(713c) Role of Hofmeister Series of Salts On the Volume Phase Transition of Peptide Modified N-Isopropylacrylamide Networks

The addition of salts and amino acids to N-isopropylacrylamide (NIPAAm) based copolymers has been investigated with neutron reflection and FTIR. Poly(NIPAAm) is a well studied thermoresponsive polymer that undergoes a hydrophilic-hydrophobic transition at roughly 32oC in aqueous solutions. The addition of salts tends to interfere with the hydrophilic-hydrophobic moieties of poly(NIPAAm) manifesting a phase change by influencing the interaction of water with the polymer. Using standard Merrifield solid phase peptide synthesis, we engineered small peptide sequences in copolymers of poly(NIPAAm) polymerized with a lysine-like, amine terminated monomer, N-(3-aminopropyl)methacrylamide hydrochloride. We demonstrate how the volume-phase transition and isoelectric point of the networks can be fine-tuned with the addition of amino acids based on the type of charge and hydrogen-bonding moiety.