Eur. Phys. J. E 5, 105-115
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
M. Mizusaki1, Y. Morishima1, B.B. Raju2 and F.M. Winnik21 Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
2 Department of Chemistry and Faculty of Pharmacy, Université de Montréal, C.P. 6128 succursale Centre-ville, Montréal QC H3C 3J7, Canada
francoise.winnik@umontreal.ca
(Received 7 August 2000 and Received in final form 26 October 2000)
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.
82.35.Rs - Polyelectrolytes.
65.40.Gr - Entropy and other thermodynamical quantities.
82.30.Nr - Association, addition, insertion, cluster formation.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001
