Composite Materials of Thermo-responsive Polymer Networks and Inorganic Nanoparticles

The focus of this work is on composite materials of inorganic nanoparticles such as TiO2 embedded within microspheres of a responsive polymeric network. Microgels of N-isopropylacrylamide (NIPAM) with interpenetrating (IP) linear chains of poly(acrylic acid) (PAAc) were synthesized to promote the incorporation of TiO2. Dynamic light scattering measurements of the IP-microgels in aqueous environments show that even in the presence of significant amounts of the ionizable acrylic acid moieties the microgels possess a large swelling response from 300nm in size to approximately 600nm. Two types of nanoparticles of titanium dioxide were immobilized within the microgels commercially available Degussa particles and fine TiO2 nanoparticles synthesized by hydrolysis of titanium(IV)isopropoxide. Transmission electron microscopy (TEM) of the composite materials shows that TiO2 can be successfully incorporated within the microgels and the nanoparticles do not aggregate. Using a simple spectroscopic method based on UV-VIS absorption, the extent of loading of the TiO2 within the polymeric matrix was found to be as high as 74% by mass.