Gold nanoparticles are encapsulatedwithin thermoresponsive pNIPAMmigrogels through an easy two‐stepprotocol. The core/shell structure ofthe composite is characterized by TEM,AFM, PCS, and UV‐vis spectroscopy. The restricted environment and thehigh porosity of the microgel shell arestudied through the overgrowth of thegold core.

Small-angle neutron scattering and dynamic light scattering have been used to study the thermodynamics of swelling and the associated structure modifications of highly cross-linked temperature-sensitive poly (N-isopropylacrylamide) [poly(NIPAM)] microgels in D2O. A particle core-shell model is proposed, with the core containing most of the cross-linker molecules. The Flory-Rehner theory, with the inclusion of a concentration dependent Flory solvency parameter, successfully describes the experimental swelling, despite the inhomogeneous character of the particles. Interestingly, the shell evolution with temperature controls the whole particle swelling, exerting an external pressure over the core, which in turn influences its size during the swelling process. Scaling laws for the correlation lengths were found with respect to temperature and polymer concentration. Finally, it has been encountered that for the collapsed microgel states, the particle surface seems to have a fractal character.

The swelling of cationic microgel particles has been studied experimentally, in the weak screening regime. The solution pH was selected as the external variable triggering the swelling, which was followed by dynamic light scattering. The particle charge was determined by conductometric and potentiometric titrations, leading to a good correlation between the charge of the microgel network and its size. This leads to the conclusion that the swelling is mainly charge controlled. The Flory-Huggins thermodynamic theory for gels, including a term accounting for the counterion distribution within the microgel, has been used to interpret the experimental data. The osmotic term associated with the counterions explains fairly well the observed behavior, and additional contributions due to the internal microgel microscopic structure are not necessary, as Pincus et al. have suggested.

Thermoresponsive nanocomposites comprising a gold nanoparticle core and a poly(N‐isopropylacrylamide) (pNIPAM) shell are synthesized by grafting the gold nanoparticle surface with polystyrene, which allows the coating of an inorganic core with an organic shell. Through careful control of the experimental conditions, the pNIPAM shell cross‐linking density can be varied, and in turn its porosity and stiffness, as well as shell thickness from a few to a few hundred nanometers is tuned. The characterization of these core–shell systems is carried out by photon‐correlation spectroscopy, transmission electron microscopy, and atomic force microscopy. Additionally, the porous pNIPAM shells are found to modulate the catalytic activity, which is demonstrated through the seeded growth of gold cores, either retaining the initial spherical shape or developing a branched morphology. The nanocomposites also present thermally modulated optical properties because of temperature‐induced local changes of the refractive index surrounding the gold cores.