Polymerization kinetics of acrylamide in micelles and microemulsions

Gels and microgels for nanotechnological applications

In recent years, "smart" materials have been the focus of considerable interest, from both fundamental and applied perspectives. Polymer gels are within this category; they respond to specific environmental stimuli by changing their size. Thus, the internal structure, the refractive index, and the mechanical properties of the polymer network change. They are considered super absorbent materials, as they can absorb solvent up to several hundred times their own weight. They respond rapidly to local environmental variations, an important fact in device miniaturization and microsensor developments. As size changes are accompanied by changes in internal dimensions, microgels have found application as carriers of therapeutic drugs and as diagnostic agents. They have also been used as microreactors, optically active materials, for template synthesis of nanoparticles or fabrication of artificial muscle. In this paper we review a set of application based on the special features associated to this systems. Basic concepts on the physical-chemistry of gel swelling is first described, followed by different applications covering drug delivery, composite materials using polymer gels to modulate optical or magnetic and electrical properties, molecular imprinting, gel-based biosensors and polymer sensors and actuators used in the field of artificial muscles.

Microstructural modifications induced by the entrapped glucose oxidase in cross-linked polyacrylamide microgels used as glucose sensors

Glucose oxidase (GO(x)) has been immobilized in cross-linked polyacrylamide microgels using the concentrated emulsion polymerization method. The immobilization of the enzyme is effective when the number of cross-links is equal or greater than 0.021mol/g. The swelling of the microgels is not affected by the entrapped enzyme but decreases with increasing the number of cross-links. The glass transition temperature of microgels with GO(x) presents considerable differences with that of the empty microgels, which are explained on base of the competition between the plasticizer effect of the encapsulated enzyme and the chain mobility restrictions imposed by the microgel cross-linking content. Immobilization of GO(x) slightly modifies the X-ray diffraction patterns of the microgels; however, the diffraction profiles of cross-linked microgels suggest the formation of bis(acrylamide) aggregates in the outer layers of the microgel particles.