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Investigation of the LCST of polyacrylamides as a function of molecular parameters and the solvent composition

✍ Scribed by Thomas Baltes; Frédéric Garret-Flaudy; Ruth Freitag

Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
274 KB
Volume
37
Category
Article
ISSN
0887-624X

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✦ Synopsis

The paper investigates the thermoprecipitation of two macromolecule structures, poly(N-isopropylacrylamide) (poly-NIPA) and poly(N,N-diethylacrylamide) (poly-DEA) from aqueous solution. The majority of the data are collected for small (M w Ͻ 5000 g/mol) homogeneous (D Ͻ 1.3) molecules of the indicated type synthesized by anionic, group transfer, and radical polymerization in the presence of a chain transfer agent. Conventional radical polymers (M w Ͻ 200,000 g/mol) are also synthesized and used for comparison. Turbidity curves (photometry) and transition enthalpies (high sensitivity differential scanning calorimetry) are measured to investigate the phase transition as a function of the molecular size and the tacticity as well as the concentration of certain solution additives (simple salts, glucose, and the surfactant tetrabutylammonium acetate) and mixtures thereof. Where applicable, the results are interpreted on the basis of a two-state model to gain insight in the cooperativity of the transition.

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