Photophysical and Rheological Studies of the Aqueous Solution Properties of Naphthalene-Pendent Acrylic Copolymers

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Polymers and High Performance Materials


The effects of pH and the addition of various additives on the photophysical solution properties of the amphiphilic polyelectrolyte poly(2-(1-naphtylyacetyl)ethylacrylate-co-methacrylic acid) (NAEA-MAA) have been investigated. Unlike previously reported systems, an almost four-fold increase in excimer emission relative to monomer emission (IE/IM) is observed upon increasing pH and, consequently, the degree of ionization. An increase in the dilute solution viscosity of NAEA-MAA solutions with increasing degree of ionization indicates a somewhat expected transition from a compact coil to a more expanded coil at pH 7.5. The hydrophobic character of both the naphthyl groups of NAEA and the pendent methyl groups of MAA and/or the effective decoupling of the naphthyl chromophores from the polymer backbone via a spacer linkage are believed to be responsible, at least in part, for this behavior. Experiments utilizing urea, a water-structure breaker, indicate that at high pH hydrophobic interactions between naphthyl chromophores stabilize the copolymer in an intramolecular "hypercoil". Finally, synthesis of a hydrolytically stable analog of NAEA, necessary for further investigations, is outlined, and initial photophysical studies of its copolymers with methacrylic and acrylic acid are presented.

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ACS Symposium Series



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