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Microcalorimetric detection of lower critical solution temperatures in aqueous polymer solutions

Schild, Howard G. and Tirrell, David A. (1990) Microcalorimetric detection of lower critical solution temperatures in aqueous polymer solutions. Journal of Physical Chemistry, 94 (10). pp. 4352-4356. ISSN 0022-3654 . https://resolver.caltech.edu/CaltechAUTHORS:SCHIjpc1990

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Abstract

A sensitive solution microcalorimeter was used to study lower critical solution temperatures (LCSTs) of aqueous polymer solutions. Endotherms with enthalpies on the order of the strength of hydrogen bonds were observed at temperatures concurring with LCSTs detected by classical cloud-point measurements for solutions of poly(N-isopropylacrylamide) (PNIPAAM), poly(vinyl methyl ether) (PVME), poly(propylene glycol) (PPG), and hydroxypropylcelluloe (HPC). The LCST of PNIPAAM was found to be dependent on the chain length, generally increasing with decreasing M-bar_n in the range M-bar_n = 1.6 X 10^5 to 5.4 X 10^3. Treatment of the calorimetric endotherm according to a two-state transiton model afforded cooperative unit sizes of the order of the chain length for PNIPAAM, PVME, and PPG. The apparent cooperative unit for the demixing transition of HPC was found to be larger than a single chain, consistent with previous observations of aggregation of HPC below the LCST. Depression of the LCST by added salts was observed.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/j100373a088DOIArticle
http://pubs.acs.org/doi/abs/10.1021/j100373a088PublisherArticle
ORCID:
AuthorORCID
Tirrell, David A.0000-0003-3175-4596
Additional Information:© 1990 American Chemical Society. (Received October 16, 1989) This work was supported by a National Science Foundation Predoctoral Fellowship to H.G.S. and by a grant from the US. Army Research Office (DAAL03-88-K-0038). Registry No. PVME, 9003-09-2; PPG, 25322-69-4; HPC, 9004-64-2; PNIPAAM, 25 189-55-3; Na2S04, 7757-82-6; NaBr, 7647-1 5-6; NaSCN, 540-72-7.
Funders:
Funding AgencyGrant Number
NSF Predoctoral FellowshipUNSPECIFIED
Army Research Office (ARO)DAAL03-88-K-0038
Issue or Number:10
Record Number:CaltechAUTHORS:SCHIjpc1990
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:SCHIjpc1990
Official Citation:Microcalorimetric detection of lower critical solution temperatures in aqueous polymer solutions Howard G. Schild and David A. Tirrell The Journal of Physical Chemistry 1990 94 (10), 4352-4356
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53527
Collection:CaltechAUTHORS
Deposited By: Anne Hormann
Deposited On:22 Jan 2015 21:46
Last Modified:03 Oct 2019 07:50

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