Phase Behavior of Poly(N-isopropylacrylamide) Nanogel Dispersions: Temperature Dependent Particle Size and Interactions
The phase behavior of poly(N-isopropylacrylamide) nanoparticles dispersed in aqueous medium is investigated as a function of temperature using static and dynamic light scattering techniques. The diameter, d of the particles, as determined by dynamic light scattering measurements
on dilute dispersion showed a decrease in size from 273 nm at 25 °C to 114 nm at 40 °C as function of temperature with a sudden collapse of particle volume (volume phase transition) at 32.4 °C. Further this nanoparticle dispersion is found to turn turbid beyond volume phase transition.
Static light scattering measurements on samples with intermediate concentration and high concentration showed liquid-like order and crystalline order respectively. The intensity of the Bragg peak of the crystallized sample when monitored as a function of temperature showed crystal to liquid
transition at 26.2 °C and a fluid to fluid transition at 31 °C. The occurrence of melting at a volume fraction of 0.85 and the absence of change in number density across the fluid-to-fluid transition suggest that interparticle interaction is repulsive soft-sphere below the volume phase
transition. The reported results on the phase behavior of poly(N-isopropylacrylamide) nanogel suspensions are discussed in the light of the present results.
Keywords: LIGHT SCATTERING; NANOGELS; POLY(N-ISOPROPYLACRYLAMIDE); THERMO-RESPONSIVE; VOLUME PHASE TRANSITION
Document Type: Research Article
Publication date: 01 September 2009
- Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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