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Interaction of poly(N-isopropylacrylamide) with sodium n-alkyl sulfates in aqueous solution

Schild, Howard G. and Tirrell, David A. (1991) Interaction of poly(N-isopropylacrylamide) with sodium n-alkyl sulfates in aqueous solution. Langmuir, 7 (4). pp. 665-671. ISSN 0743-7463. doi:10.1021/la00052a013.

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Cloud point, calorimetric, and fluorescence probe methods have been combined to examine aqueous mixtures of poly(N-isopropylacrylamide) (PNIPAAM) and a series of sodium n-alkyl sulfates of alkyl chain lengths (n) in the range 1-16. Surfactants of chain lengths ≤ 4 depress the lower critical solution temperature (LCST) of PNIPAAM and exhibit no evidence of enhanced aggregation in PNIPAAM solutions. This pattern of behavior is characteristic of the simple salt Na_2SO_4 as well. Surfactants of intermediate chain lengths (n = 5-10) depress the LCST at low surfactant concentration but cause an increase in the LCST at concentrations that exceed the critical aggregation concentration (CAC). Sodium n-dodecyl sulfate (n = 12) elevates the LCST even at low concentrations and forms aggregates in PNIPAAM solutions at a concentration 10-fold lower than the critical micelle concentration (cmc). Sodium n-hexadecyl sulfate forms aggregates in PNIPAAM solutions at temperatures below its Krafft temperature in water. The formation of polymer-bound micelles below the cmc is reported by pyrene, 1-pyrenecarboxaldehyde, and sodium 2-(N-dodecylamino)naphthalene-6-sulfonate but not by 1-benzoylacetone. The theory of Nagarajan and Ruckenstein, and in particular the treatment of Ruckenstein and co-workers, serves to rationalize the observed aggregation behavior as a consequence of screening of surfactant-water interaction by PNIPAAM chain units at the micellar surface.

Item Type:Article
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Tirrell, David A.0000-0003-3175-4596
Additional Information:© 1991 American Chemical Society. Received August 24, 1990. This work was supported by a National Science Foundation Predoctoral Fellowship to Howard G. Schild and by a grant from the U.S. Army Research Office (DAAL03-88-K-0038). We thank Professor D. A. Hoagland for helpful suggestions and Professor R. Nagarajan for instructive correspondence.
Funding AgencyGrant Number
NSF Predoctoral FellowshipUNSPECIFIED
Army Research Office (ARO)DAAL03-88-K-0038
Issue or Number:4
Record Number:CaltechAUTHORS:SCHIl1991b
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Official Citation:Interaction of poly(N-isopropylacrylamide) with sodium n-alkyl sulfates in aqueous solution Howard G. Schild and David A. Tirrell Langmuir 1991 7 (4), 665-671
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53515
Deposited By: Anne Hormann
Deposited On:22 Jan 2015 22:38
Last Modified:10 Nov 2021 20:03

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