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Interpenetrating polymer network (IPN), random copolymer, and homopolymer nanoparticles of acrylamide and acrylic acid were prepared using an inverse emulsion polymerization technique. Differential scanning calorimetry and Fourier-transform infrared spectroscopy were used to examine the molecular structure of the prepared polymeric nanoparticles. The spherical morphology and size (∼250 nm diameter) of the nanoparticles was confirmed using scanning electron microscopy. Dynamic light scattering was used to determine the monodispersity of the particle size distribution and examine the thermally responsive swelling properties of the polymeric nanoparticle structures. Of the particle systems studied, only the IPN nanoparticles exhibited a unique, rapid sigmoidal swelling transition with temperature. These systems also achieved a much larger relative swelling volume compared to random copolymer and homopolymer particles comprised of acrylamide and acrylic acid. Increased cross-linker density resulted in an overall decrease in the maximum relative swelling volume that was obtained.

The objective of this study was to synthesize and characterize a thermally responsive polymer-metal nanocomposite system comprised of a solid gold nanoparticle core and thermally responsive interpenetrating polymer network (IPN) shell, which was surface functionalized or PEGylated with a covalently bound linear poly(ethylene glycol) chain layer. Gold nanoparticles (50 nm diameter) were prepared using standard gold chloride and citrate reduction method. These particles were then encapsulated inside of a polyacrylamide (PAAm)/poly(acrylic acid) (PAA) IPN shell via an in situ inverse emulsion polymerization. The surface of the nanocomposite system was then PEGylated via covalent grafting of a linear methoxy-PEG-N-hydroxysuccinimide (M.W. 3400) to the primary amine groups of the PAAm network. Scanning and transmission electron microscopy were used to confirm the successful synthesis and encapsulation of gold nanoparticles within the IPN shell. Dynamic light scattering was used to examine the temperature swelling response of the IPN particles. Zeta-potential analysis was used to confirm the successful PEGylation of the final nanocomposite system.

Pieroeiectrlc quartz crystals coated wlth PVP-TMEDA and PVBC-TMEDA were found to be sensltlve to DIMP in the parts-per-bllllon concentratlon range. These coatlngs have outstandlng advantages compared to those previously described: higher sensitlvlty, faster response, and longer llfetime. I n addition, the cailbratlon curves pass through the origin, and the reproducibility and base line stabllity are withln f2 Hr. Also, the response and recovery tlmes are on the order of mlnutes for the PVP-TMEDA coatlng and on the order of seconds for the PVBGTMEDA copper complex. No serious interferences were observed.

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