ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The copolymerization behaviour of the systems (a) acrylic acid (AA)-acrylamide (AM) and (b) methacrylic acid (MA)-acrylamide was studied in aqueous solution at 30°C as a function of pH. The copolymerization was carried out to high conversion (〉10%) and the monomer reactivity ratios r1 for (AA or MA) and r2 (for AM) were computed using the Mayo-Lewis integrated equation. For the system (a), r1 reached its maximum value of 0,92 at pH 2, and its minimum of 0,33 at pH 6, thereafter increasing again. No systematic variation was found for r2. In system (b), r1 decreased sharply from a maximum of 2,8 at pH 4 to 0,19 at pH 6, then increasing to 0,39 as the pH was raised to 10. The r2 value showed a gradual increase from 0,2 at pH 4 to 0,57 at pH 9. Addition of NaCl (conc.: 1 mol/l) partially restored the value of r1 for both AA and MA to those at low pH. The variation of r1 of AA and MA nearly parallelled the homopolymerization rates of the respective monomers, with respect to pH. These variations were traced to the electrostatic repulsive interactions between the reactive species - ionized monomer and ionized polymeric radical - and hydrophobic interactions. Certain discrepancies in the trends of r1 and r2 were also noted.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1977.021780408
Permalink
