Aqueous colloidal microgel particles prepared from N-isopropylacrylamide (NIPAM) co-polymerized with different ratios of the comonomer vinyl laurate have been investigated with respect to their physicochemical properties and colloid stability. The hydrodynamic diameters of microgel particles synthesized using 10% and 50% w/v vinyl laurate have been examined. The poly(NIPAM)-co-vinyl laurate microgel particles, suspended in water, show similar conformational behavior to poly(NIPAM) microgels in that they reversibly shrink and swell (undergo a reversible volume phase transition) in response to heating and cooling. Turbidity measurements have been used to study the colloid stability of poly(NIPAM) and poly(NIPAM)-co-vinyl laurate microgel particles as a function of electrolyte concentration. When heated to 40 °C in a NaCl electrolyte solution, the poly(NIPAM)-co-vinyl laurate microgels form irreversible flocs and macroscopic gels above a critical electrolyte concentration. This novel flocculation behavior is in contrast to poly(NIPAM) microgels that reversibly flocculate when heated/cooled in an electrolyte solution (above a critical electrolyte concentration). Photon correlation spectroscopy (PCS) and turbidity measurements have been used to study the swelling (volume phase transition) behavior of the poly(NIPAM)-covinyl laurate microgels and good agreement was observed between the data obtained from both these techniques.

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The nature and properties of “smart” colloidal microgels are reviewed. Detailed descriptions including mechanistic information are reported with respect to the preparation of a number of physically different microgel structures including homopolymers, copolymers, polyelectrolyte, and core–shell type materials. The principal techniques used for the characterization of microgels are described, including dynamic light scattering and differential scanning calorimetery. Microgel properties are reviewed with respect to temperature sensitivity, pH sensitivity, colloid stability, rheological behavior, osmotic deswelling, and the influence of copolymers on microgels. Applications of these types of materials are also discussed and, include drug delivery devices, binding/adsorption agents, and catalytic compounds.