Swelling of hydrophilic polymers. II

Abstract

SYNOPSISThe swelling of five types of Sephadex that are either nonionic ( G ) or possess one of four different ionic groups [sodium carboxymethyl (CM) , sodium sulfopropyl (SP) , diethylaminoethyl chloride (DEAE), diethyl-(2-hydroxypropyl) aminoethyl chloride (QAE) ] in the same skeleton of the molecule has been studied by picture analysis and by calorimetry. Inducing dissociation of the ionic group in the polymer skeleton increased the water swelling. By the addition of sodium chloride, the maximum swelling volume of nonionic Sephadex was only slightly decreased. However, that of ionic polymers was considerably decreased. The variation of the apparent first-order rate constant of the swelling and that of the maximum swelling volume show the same tendency. The maximum heats of swelling were 93.2 ? 7.1 J g-' for G, 128.8 ? 9.1 J g-' for CM, 92.3 -t 8.0 J g-' for SP, 68.8 k 10.5 J g-' for DEAE, and 67.0 +. 7.2 J g-' for QAE and did not depend on the concentration of sodium chloride. From the results obtained, we conclude that the nonionic Sephadex swells only by hydration but that ionic Sephadexes swell mainly by the osmotic pressure due to the counterions of the ionic groups and that the swelling ratio is not dependent on the kinds of ions but on the ionic concentration. Most of the water in the gels of ionic Sephadexes is free water that does not interact with the Sephadexes. 0

Swelling of dextran gel and osmotic pressure of soluble dextran in the presence of salts

“…16 Some work has also been done on the swelling of Sephadex in NaCl solutions. 2,19 These results are also in general agreement with our data. Figure 3 describes the results of equilibrium osmotic-pressure measurements as a function of the concentration of dextran in solutions of NaCl, Na 2 SO 4 , and NaSCN and in pure water.…”

“…Because of its growing importance, the topic of salt effects on gel swelling has been given considerable attention. This has mainly been with respect to polyelectrolyte gels, [1][2][3][4][5] but also with respect to nonionic hydrogels. In the latter group, studied gels range from hydrophobic polymers such as poly(N-isopropyl acrylamide) (PNIPA), 6 -9 poly(vinylmethylether), 10 and poly(2-hydroxyethyl methacrylate) (PHEMA), [11][12][13] to slightly hydrophobic ones such poly(ethylene oxide) (PEO) 14,15 and poly(vinyl pyrrolidone) (PVP), 16 to more hydrophilic, nonionic polymers such as poly-(acrylamide) (PAAm) 6,17,18 and dextran.…”

“…This has mainly been with respect to polyelectrolyte gels,1–5 but also with respect to nonionic hydrogels. In the latter group, studied gels range from hydrophobic polymers such as poly( N ‐isopropyl acrylamide) (PNIPA),6–9 poly(vinylmethylether),10 and poly(2‐hydroxyethyl methacrylate) (PHEMA),11–13 to slightly hydrophobic ones such poly(ethylene oxide) (PEO)14, 15 and poly(vinyl pyrrolidone) (PVP),16 to more hydrophilic, nonionic polymers such as poly(acrylamide) (PAAm)6, 17, 18 and dextran 2, 19. The study of salt effects on such hydrophilic homopolymers sheds light on the role of the interactions between the various ions and hydrophilic groups (e.g., amide or hydroxyl) as part of the general effect of salts on polymers in aqueous solutions.…”

Absorption and desorption of liquid water by a superabsorbent polyelectrolyte: Role of polymer on the capacity for absorption of a ground

“…The Na ϩ ions come to fit between the polymeric chains and hidingplace between the loads carried by the macromolecule what minimizes the electrostatic repulsion 11 thus involving a reduction in the maximum rate of absorption. 12,13 The presence of the mono-valent ions K ϩ and NH 4 ϩ induces (by effect shielding) a reduction in the capacity for absorption of polymer, as in the case of NaCl; only differs the of electrostatic forces ensuring the interaction ions-site charged. These forces of attraction depend not only on the load of the ion but also on its ray and its polarizing capacity.…”

Application of deaerated water in swelling of cellulose and amylose and cotton desizing with enzyme

“…[1][2][3][4][5] The degree of interaction between the polymer and water measured by dilatometry was different in air-present water from in deaerated water that was obtained by cooling in a sealed container after boiling. 3,4 Air-present water in equilibrium with air contains about 16 mg L Ϫ1 of nitrogen, 7-8 mg L Ϫ1 of oxygen, and some inert gases at room temperature.…”