The association of octadecyl-end-capped poly-(sodium 2-acrylamido-2-methylpropanesulfonates) in water and salt solutions: A study by fluorescence spectroscopy and isothermal titration calorimetry |
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Authors: | M Mizusaki Y Morishima BB Raju FM Winnik |
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Institution: | (1) Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan, JP;(2) Department of Chemistry and Faculty of Pharmacy, Université de Montréal, C.P. 6128 succursale Centre-ville, Montréal QC H3C 3J7, Canada, CA |
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Abstract: | Steady-state fluorescence spectroscopy and isothermal titration calorimetry (ITC) have been used to study the aggregation
in aqueous solutions of poly-(2-acrylamido)-2-methylpropanesulfonic acids, sodium salt mono-endcapped with either N,N-di-n-octadecyl or N-4-(1-pyrenyl)butyl]-N-n-octadecyl which were prepared by free radical polymerization of 2-(acrylamido)-2-methylpropane sulfonic acid (AMPS) initiated
with the azo compounds, 4,4'-azobis{cyano-N,N-di-n-octadecyl}pentanamide and 4,4'-azobis{cyano-N,N-4-(1-pyrenyl)butyl]-n-octadecyl}pentanamide, respectively. Both techniques indicate the occurrence of multimolecular aggregates in solutions of
the polymers in water and in 0.2 M NaCl. The concentration range for aggregation is about 1-14 mmol AMPS l-1 (0.5-2.7 g l-1) in 0.2 M NaCl and the enthalpy of micellization, estimated from ITC data, is ∼100 J mol AMPS]-1. The accessibility of the chromophores to neutral molecules and to cationic species was assessed by quenching of fluorescence
with nitromethane and thallium nitrate, respectively. The association of the mono-endcapped polymers is compared to that of
PAMPS derivatives carrying hydrophobic groups randomly attached along the chain.
Received 7 August 2000 and Received in final form 26 October 2000 |
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Keywords: | PACS 82 35 Rs Polyelectrolytes – 65 40 Gr Entropy and other thermodynamical quantities – 82 30 Nr Association addition insertion cluster formation |
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