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Hydration of polyacids
Author(s) -
Ikegami Akira
Publication year - 1968
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1968.360060314
Subject(s) - chemistry , polyelectrolyte , methacrylic acid , acrylic acid , polymer chemistry , hydroxide , maleic acid , copolymer , polymer , ammonium , counterion , poly(methacrylic acid) , polyacrylic acid , ammonium hydroxide , inorganic chemistry , organic chemistry , ion
The hydration of several polyacids has been investigated with special attention to the effects of neighboring charged groups and hydrophobic groups on the hydration regions. The molar volume change due to the structural change of water by the hydration was obtained by the method of refractivity measurement. The polyacids employed were poly(acrylic acid), poly(methacrylic acid), poly( L ‐glutamic acid), and a copolymer of maleic acid and vinyl acetate. The measurement of the refractive index was performed for the solutions of these polymers neutralized to varying degrees by tetrabutyl‐ammonium hydroxide and sodium hydroxide. The results confirm the characteristics of the previous model of the hydration of polyelectrolytes, that is, the cooperative action of neighboring charged groups induce the second hydration region in addition to the intrinsic hydration region. The stiff structure of water in these regions restricts the mobility of counterions forced to enter into these regions by the strong electrostatic potential of polyions. The results indicate also that hydrophobic groups induce an additional hydration region around their neighboring charged groups. Small but negative volume changes were observed for conformational changes of poly( L ‐glutamic acid) and poly(methacrylic acid) induced by the neutralization of carboxyl groups.