Smart Aqueous Reaction Medium

Smart materials show a nonlinear response to a stimulus. In aqueous solution, the reactions between methyl p -tolyl sulfide and peroxomonosulfate or m -chloroperbenzoic acid show the expected linear dependence of the logarithm of the measured rate constant on the reciprocal temperature. This constitutes Arrhenius behavior. In the presence of 5 or 15 g L - 1 of the thermoresponsive poloxamer, P104, H(OCH 2 CH 2 ) 27 (OCH(CH 3 )CH 2 ) 61 (OCH 2 CH 2 ) 27 OH, which forms micelles as the temperature is increased, anti-Arrhenius behavior or hyper-Arrhenius behavior is observed. Anti-Arrhenius behavior occurs when the organic sulfide partitions into the thermally induced poloxamer micelles while the peroxomonosulfate anion remains in the bulk aqueous phase, causing a decrease in rate. Hyper-Arrhenius behavior occurs when both the organic sulfide and the m -chloroperbenzoic acid partition into the thermally induced micelles, causing a much greater increase in rate with temperature than in the absence of poloxomer. These two different types of smart behavior of aqueous P104 are discussed.