Potentiometric titrations of polymethacrylic acid

Wiley - Tập 2 Số 4 - Trang 432-446 - 1947
Aharon Katchalsky1, Pnina Spitnik1
1Laboratory of Macromolecular Chemistry, Hebrew University, Jerusalem

Tóm tắt

AbstractPotentiometric titrations of polymethacrylic acid were performed at different concentrations, different molecular weights, and in the presence of neutral salts, as well as in dioxane‐water mixtures. It was shown that the pH of the solutions fulfills the relation, pH = pK — n log [(1 — α)/α]. pK and n are independent of the molecular weight and concentration if a suitable activity factor is introduced. The equation is applicable to free acid solutions as well as acid mixtures. Copolymers of the type, polyallyl acetate‐maleic acid, show a more complicated curve. The curve is of the “polydibasic” type. Each branch of it fits equation (2) well. The formula is analyzed and is proposed to be the result of the action of the Maxwell‐Partington statistical factor, as well as of the decrease in entropy accompanying the stretch of the randomly kinked molecule. This stretch is caused by the repulsive forces between the ionized carboxyl groups. The distribution curves of the various degrees of ionization present, for any pH, are given. The activity correction implies small units of the size of one or two carboxyl groups. The behavior in salt solutions is dependent not only on the activity correction, but also on the salting‐out factor. This factor is high in polyvalent salts. The titration curves in dioxane‐water mixtures are satisfactorily accounted for by the change in the activity factor with the dielectric constant.

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Tài liệu tham khảo

Cohn E. J., 1943, Proteins, Amino Acids, and Peptides

Kern W., 1938, Z. physik. Chem., 181, 249

Speiser R., 1945, J. Phys. Colloid Chem., 49, 334

Branch G. E. K., 1941, The Theory of Organic Chemistry, 221

10.1021/ja01212a033

10.1021/ja01266a051

10.1021/ja01267a002

Van Slyke D. D., 1922, J. Biol. Chem., 42, 525, 10.1016/S0021-9258(18)85845-8

10.1101/SQB.1938.006.01.001

Linderstrøm‐Lang K., 1924, Compt. rend. trav. lab. Carlsberg, Sér. chim., 15

10.1111/j.1749-6632.1941.tb35241.x

Wyman J., 1943, Proteins, Amino Acids, and Peptides, 451

10.1021/ja01416a018

Weber H. H., 1927, Biochem. Z., 189, 381

10.1021/ja01372a006

10.1039/tf9373300670

10.1007/BF01451681

10.1007/BF01451143

10.1007/BF01522052

10.1039/tf9433900241

10.1002/pol.1946.120010306

Dole M., 1941, The Glass Electrode, 243

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Wiley

Tập 2 Số 4

432-446

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