| Abstract
| - Microgel particles are cross-linked polymer particles. When dispersed in a good solvent for the polymer concerned,they are able to respond to a range of external stimuli by changing volume. Hence, microgel particles are suited tonumerous applications (for example, controlled uptake and release) in the pharmaceutical, coatings, and water treatmentindustries. In this work, pH-sensitive, 0.5 wt % cross-linked poly(2-vinylpyridine) (PVP) microgel particles have beenprepared and characterized. When the dispersion pH is decreased below 4.5, the pyridine groups become protonatedand the microgel network becomes positively charged, causing the particles to expand. To investigate the possibilityof using light as a trigger for effecting volume changes, the interaction of these microgel particles with a photodegradableanionic surfactant, 4-hexylphenylazosulfonate (C6PAS), has been investigated using dynamic light scattering andelectrophoretic mobility measurements. The electrostatic attraction between the positively charged microgel network(at solution pH 3) and the negatively charged headgroups on the surfactant molecules caused a dramatic decrease inparticle volume, and charge-reversal of the particles occurred with increasing surfactant concentration. The UVirradiation of phenylazosulfonate surfactants destroys the anionic headgroup of the molecules, and the microgelparticles re-swell. The irradiation of PVP dispersions in the presence of C6PAS, along with mixed surfactant systemsof sodium dodecyl sulfate plus C6PAS, has been investigated.
|
