Trimethylammonium-Based Polymethacrylate Ionic Liquids with Tunable Hydrophilicity and Charge Distribution as Carriers of Salicylate Anions

Copolymers of [2-(methacryloyloxy)ethyl]trimethylammonium chloride, salicylate or bis(trifluoromethanesulfonate)imide (Cl–, Sal– or Tf2N–), and methyl methacrylate (MMA) were synthesized by atom transfer radical polymerization (ATRP). The effect of different molar fractions of ionic monomer (0.05–1.0) on physicochemical properties was investigated. The relative reactivity ratios of MMA and ionic monomer with the chloride anion (0.88 and 1.13, respectively) were determined by the linearization Jaacks method. The particles formed in water by copolymers with trimethylammonium chloride (≥50 mol %) reached sizes below 10 nm, whereas salicylate-containing copolymers supported strong self-assembly, yielding 200 nm superstructures. The copolymers, after modification by the exchange of Cl– and Sal– with Tf2N–, demonstrated the influence of the anion on solubility, glass transition temperature, and morphology. The anion-modified trimethylammonium copolymers, compared with those directly synthesized from Tf2N-containing monomer, indicated different properties. Both the chloride monomer (Cl– replaced by Sal– or Tf2N–) and its copolymers are able to exchange anions, including biologically active ones, which extends their future applications as poly(ionic liquid)s with therapeutic properties for controlled drug delivery.