Elaboration and Morphology Investigation of Poly (styrene‐co‐acrylic acid)/Poly(styrene‐co‐N,N‐dimethylacrylamide) Interpolymer Complexes

Random copolymers of styrene with acrylic acid (SAA) and with N, N-dimethylacrylamide (SAD) of different compositions were prepared and characterized. Depending on the nature of the solvent and the densities of interacting species incorporated within these polystyrene matrices, novel materials as soluble interpolymer complexes in THF or precipitates from butan-2-one were elaborated when SAA and SAD copolymers are mixed together due to the presence of specific interpolymer interactions. These specific intermolecular interactions were evidenced by ATR/FTIR spectroscopy, qualitatively from the appearance of new bands in the 1800-1550 cm -1 region and quantitatively using adequate spectral curve fitting for the determination of the fraction of the different species. The DSC analysis showed that all these materials as soluble or precipitate interpolymer complexes exhibited one composition-dependence glass transition temperature Tg, indicating that they are homogenous on a 20-40 nm scale. Information about the mixing at a smaller scale obtained by solid state proton NMR, provided from measurements of proton spin relaxation times T 1 (H) and T 1 ρ (H) in the laboratory and rotatory frames carried out for SAA-27, SAD-17 and their (70/30 and 50/50) mixtures as cast from THF or butan-2-one, confirmed similar phase behaviour promoted by a solvatation effect. The single T 1 (H) observed in the pure components and their blends as cast from both THF and butan-2-one confirm that these blends are homogeneous on the scale of 20-40 nm. Furthermore, the T 1 ρ (H) recoveries indicate that the blends were homogeneous on the scale of 2-3 nm only when cast from THF, while composite recovery curves T 1 ρ (H) were however observed with SAA-27 and its mixtures of different ratios below 120 °C when butan-2-one is the casting medium.