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Updated: May 30, 2026

Controlled Synthesis and Fluorescence Tracking of Highly Uniform Poly(N-isopropylacrylamide) Microgels
Published on: September 8, 2016
Single molecule tracking studies of lower critical solution temperature transition behavior in
Lindsay C C Elliott1, Moussa Barhoum, Joel M Harris
1Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA.
Abstract:
Spatial and temporal heterogeneities in expanded and collapsed surface bound poly(N-isopropylacrylamide), pNIPAAm, films are studied by single molecule tracking (SMT) experiments. Tracking data are analyzed using both radius of gyration (R(g)) evolution and confinement level calculations to elucidate the range of behaviors displayed by single Rhodamine6G (R6G) molecules. Confined diffusion that is dictated by the free volume within surface tethered chains is observed with considerable dispersion among individual R6G molecules. Thus, the distribution of probe behavior reflects nanometer-scale information about the behavior of the probe-polymer system at temperatures above (T > T(LCST)) and below (T < T(LCST)) the lower critical solution temperature (LCST). In this context, confinement-level analysis and R(g) evolution both show a larger degree of confinement of the probe in pNIPAAm at T > T(LCST). Temperature-dependent changes in confinement are evidenced at T > T(LCST) by a higher percentage of confined steps, longer periods of confined events, and smaller area of confined zones, as well as a shift in the overall distribution of R(g) evolution paths and final R(g) distributions.
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