A series of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAAm-co-PAA) copolymers were prepared by free radical copolymerization in MeOH solution. The incorporation of AA into PNIPAAm can enhance the glass transition temperature (Tg) values due to the strong intermolecular hydrogen bonding between the amide group of PNIPAAm and the carboxylic acid group of PAA based on 1H NMR and FTIR analyses. We found that the lower critical solution temperature (LCST) was increased with increasing pH in PNIPAAm-co-PAA aqueous solution. Further, high pressure DSC revealed that the LCST of all copolymer aqueous solutions were decreased with increasing CO2 pressure, an indication that the CO2 was able to displace H2O molecules around the polar CONH and COOH in PNIPAAm-co-PAA and promoted the hydrophobicity of the copolymers in aqueous solution leading to decreases in their LCST. We also found that the Tg of a film sample was increased by supercritical CO2 (scCO2) treatment, implying that intermolecular interactions in the copolymer were enhanced after the scCO2 treatment.

CO2-sensitive poly(N-isopropylacryl amide-co-acrylic acid) copolymers with high glass transition temperatures

253rd National Meeting (2017)

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