Complex new materials from simple chemistry: Combining an amino‐substituted polysiloxane and carboxylic acids

Changes in rheological, adhesive, and swelling properties of quaternary salts, made by adding one of eight mono- or six α,ω-alkanedioic acids (the latter with two to six or nine carbon atoms) to 6-7PSil (a polysiloxane with 6%–7% of the monomer units contain a 3-aminopropyl group) have been correlated with the salt structures. The simple acid-base chemistry initiates drastic changes in the bulk properties of the materials that depend on the amount and type of the added acid. Thus, the quaternized forms of the 6-7PSil have significantly enhanced viscoelastic and adhesive properties compared to those of the initial polysiloxane, and they can swell selectively liquids based on their polarity. Also, interpenetrating networks have been made in situ by photopolymerization of salts with vinylic carboxylic acids. DFT calculations on model systems consisting of dimethylammonium α,ω-alkanedioate salts with two to six carbon atoms provide insights into the interactions responsible for the unexpected dependence of the properties of the 6-7PSil salts on the chain lengths of the diacids. The potential for applying the methodologies described here to systems with other amino-substituted polymers and other acid types is noted. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017