Synthesis of Poly(styrene-co-methyl methacrylate)-Based Ionomers and Their Langmuir and Langmuir−Blodgett (LB) Film Formation

Poly(styrene- co -methyl methacrylate) (PS−PMMA) ionomers with several degrees of sulfonation were synthesized and characterized by infrared, UV−vis, and NMR spectroscopies, elemental analysis, and differential scanning calorimetry (DSC). Stable Langmuir films could be produced with PS−PMMA with 3 and 6 mol % of sulfonation, while PS−PMMA 8% exhibited material loss to the water subphase, probably due to its higher solubility. Surface pressure and surface potential isotherms with PS−PMMA 3% spread onto salt-containing subphases pointed to a film behavior characteristic of the polyelectrolyte effect, where charge repulsion governs the film properties. The Langmuir−Blodgett films of this ionomer were successfully transferred onto various substrates, as confirmed by UV−vis and FTIR spectroscopies. Using cycling voltammetry, we show that LB films from PS−PMMA 3% can be applied in selective sensing of dopamine, even in the presence of interferents such as ascorbic acid.