Polyacrylic acid (polycarboxyethylene) is a polymer of acrylic acid . A polymer is obtained by radical polymerization of acrylic acid in an aqueous solution or in an organic solvent medium ( exothermic process).
| Polyacrylic acid | |
|---|---|
 | |
| Are common | |
| Systematic name | Polyacrylic acid |
| Chem. formula | (C 2 H 3 COOH) n |
| Rac formula | (CH 2 -CH-COOH) n |
| Classification | |
| Reg. CAS number | [9003-01-4] |
| Reg. EINECS number | |
| CHEBI | |
Content
Properties
Polyacrylic acid and its salts are glassy fragile colorless polymers. For an acid, the glass transition temperature is 106 ° C, for its sodium salt, 230 ° C (for comparison, the glass transition temperature of polymethacrylic acid is 228 ° C, its sodium salt is 310 ° C). When the acid is heated, anhydride occurs with the formation of predominantly cyclic anhydride units, if the temperature is above 250 ° C - decarboxylation and crosslinking.
Solubility
Polyacrylic acid is well soluble in water , dioxane , methanol , ethanol , formamide , DMF ; not soluble in its monomer, acetone , diethyl ether , hydrocarbons .
Polyacrylic acid is a weak polyelectrolyte ; in a salt-free aqueous solution, pK a = 4.8 and almost linearly increases with an increase in the degree of neutralization , at the point of semi-neutralization pK a = 6.8 . The viscosity of an aqueous solution of polyacrylic acid increases with increasing degree of neutralization. For aqueous solutions of acid and its salts, a polyelectrolyte effect is characteristic.
When mixing aqueous solutions of polyacrylic acid with solutions of cationic polymers, surfactants and some drugs, the formation of insoluble complexes is possible. These complexes, as a rule, are formed by the forces of electrostatic attraction. Polyacrylic acid also forms complexes with non-ionic polymers through hydrogen bonds. [one]
Application
In dry form, polyacrylic acid is used as a very strong desiccant, including in baby diapers. In the form of aqueous solutions, the acid and its salts are used in the form of aqueous solutions as:
- stabilizers and flocculants of colloidal systems in technological processes;
- builders and thickeners ;
- binders when creating, for example, filling materials in medicine;
- antistatic agents for fibers and leathers;
- to obtain polymer-polymer complexes.
- as a binder in LIA.
Polyacrylic acid is a carrier of physiologically active substances, enzymes; its iron salts have hemostatic ability . Cross-linked polymers and copolymers of acrylic acid are ion exchange resins , including complexing ones.
See also
- Polymethacrylic acid
Literature
- A. B. Zezin. Encyclopedia of Polymers - vol. 1, M., 1972, p. 39; Polymer handbook, 2 ed., NY, 1975.
Notes
- ↑ VV Khutoryanskiy, G Staikos. Hydrogen-bonded interpolymer groups: formation, structure and applications. - 1. - World Scientific Pub Co Inc, 2009. - 377 p.