Conformation of poly(methacrylic acid) in acidic aqueous solution studied by small angle X-ray scattering |
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Authors: | Muroga Y Yoshida T Kawaguchi S |
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Affiliation: | Department of Applied Chemistry, School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan. ymuroga@apchem.nagoya-u.ac.jp |
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Abstract: | The nature of the contracted form of poly(methacrylic acid) PMA chain in salt-free acidic aqueous solution was studied by analyzing scattering curves registered by small-angle X-ray scattering, comparing it with those of PMA in methanol at 26 degrees C and of partially neutralized PMA in aqueous solution containing added salt (the concentration of added salt, Cs=0.1 M NaF). It is shown that the distribution of segments in the contracted form as well as that of PMA in methanol is that of a random-coil in a theta medium and that this distribution of segments is stable over a fair range of degrees of ionization alpha for Cs below 0.1 M. Moreover, the persistence length of PMA at Cs=0.1 M (4+/-0.5 A) is substantially constant throughout the entire range of alpha, indicating that the contracted form of PMA changes to an expanded random-coil in a higher pH region without a significant change in the chain flexibility. |
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