Conformation of Adsorbed Random Copolymers:  A Solid-State NMR and FTIR-PAS Study

The properties of bulk and adsorbed polyethylene-co-acrylic acid (PEA) random copolymers were characterized by solid-state NMR and vibrational spectroscopy. FTIR-PAS (Fourier transform infrared photoacoustic spectroscopy) measurements show that the copolymers are chemisorbed to zirconia surfaces via the carboxylic acid sticker groups. The chain mobility, conformation, and morphology of bulk and adsorbed PEA were studied by 13C CP-MAS, 2D WISE, and 1H spin diffusion NMR experiments. The effect of the copolymer loading and acrylic acid content on these properties was examined. Whereas adsorbed PEA with a 5% w/w acrylic acid content contain transoid chain segments at all loadings, samples with higher acrylic acid contents (15 % w/w) only display an all-trans component at higher loadings where unbound acid groups are present.