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ABSTRACT: Many reactions in both chemistry and biology rely on the ability to precisely control and fix the solution concentrations of either protons or hydroxide ions. In this report, we describe the behavior of thermally programmable pH buffer systems based on the copolymerization of varying amounts of acrylic acid (AA) groups into N-isopropylacrylamide polymers. Because the copolymers undergo phase transitions upon heating and cooling, the local environment around the AA groups can be reversibly switched between hydrophobic and hydrophilic states affecting the ionization behavior of the acids. Results show that moderate temperature variations can be used to change the solution pH by two units. However, results also indicate that the nature of the transition and its impact on the pH values are highly dependent on the AA content and the degree of neutralization.
ACS Applied Materials & Interfaces 11/2012; · 4.53 Impact Factor
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ABSTRACT: A thermally responsive copolymer is designed to modulate the properties of an electrolyte solution. The copolymer is prepared using pNIPAM, which governs the thermal properties, and acrylic acid, which provides the electrolyte ions. As the polymer undergoes a thermally activated phase transition, the local environment around the acid groups is reversibly switched, decreasing ion concentration and conductivity. The responsive electrolyte is used to control the activity of redox electrodes with temperature.
Advanced Materials 02/2012; 24(7):886-9. · 13.88 Impact Factor
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ABSTRACT: Increased mass transport due to hemispherical diffusion is observed to occur in 3D porous carbon electrodes defined by interferometric lithography. Enhanced catalytic methanol oxidation, after modifying the porous carbon with palladium nanoparticles, and uncharacteristically uniform conducting polymer deposition into the structures are demonstrated. Both examples result in two regions of hierarchical porosity that can be created to maximize surface area, via nanostructuring, within the extended porous network, while taking advantage of hemispherical diffusion through the open pores.
ACS Applied Materials & Interfaces 10/2010; 2(11):3179-84. · 4.53 Impact Factor
