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The pH-responsive behaviour of poly(acrylic acid) in aqueous solution is dependent on molar mass
Thomas Swift1, Linda Swanson2, Mark Geoghegan3
1Department of Chemistry, Brook Hill, University of Sheffield, Sheffield S3 7HF, UK and School of Chemistry and Forensic Sciences, University of Bradford, Richmond Building, Bradford BD7 1DP, UK. s.rimmer@bradford.ac.uk.
Abstract:
Fluorescence spectroscopy on a series of aqueous solutions of poly(acrylic acid) containing a luminescent label showed that polymers with molar mass, Mn < 16.5 kDa did not exhibit a pH responsive conformational change, which is typical of higher molar mass poly(acrylic acid). Below this molar mass, polymers remained in an extended conformation, regardless of pH. Above this molar mass, a pH-dependent conformational change was observed. Diffusion-ordered nuclear magnetic resonance spectroscopy confirmed that low molar mass polymers did not undergo a conformational transition, although large molar mass polymers did exhibit pH-dependent diffusion.
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