Large Swelling Capacities of Crosslinked Poly(N-isopropylacrylamide) Gels in Organic Solvents

MARTINEZ, MARÍA V.; MOLINA, MARÍA A.; ABEL, SILVESTRE BONGIOVANNI; BARBERO, CESAR A.

MRS Advances

Cambridge University Press

Año: 2018

PNIPAM hydrogels are widely studied materials which swell in a great extent in water andwater like solvents (e.g. alcohols). The hydrophilic nature of PNIPAM networks is veryattractive however it is an important disadvantage at the moment of encapsulatinghydrophobic drugs, which minimize their use in other fields. In this work we studied theswelling in different solvent mixtures with water and also in pure nonaqueous solvents, someof them immiscible with water. Accordingly, PNIPAM gels swell strongly in highly polarsolvents (e.g. chloroform) but it does not swell in slightly polar solvents (e.g. toluene). Themain interaction between the solvent and the polymer chain seems to involve the hydrogenbonding with the amide group, according to the calculated Hansen parameters (h). It ispossible to swell the gel in binary or ternary mixtures containing toluene. In that way, nonpolarsubstances can be loaded inside the gel to change its properties. As a proof of concept,polyaniline (PANI) solubilized in chloroform using camphorsulfonate as solubilizingcounterion. The obtained nanocomposites become sensitive to pH changing color andconductivity when exposed to basic or acidic aqueous solutions.