Visualizing the lower critical solution temperature phase transition of individual poly(nipam)-based hydrogel particles using near-infrared multispectral imaging microscopy

Irena Mejac; Hye-Hun Park; William W Bryan; T Randall Lee; Chieu D Tran

doi:10.1021/ac902099d

Visualizing the lower critical solution temperature phase transition of individual poly(nipam)-based hydrogel particles using near-infrared multispectral imaging microscopy

Anal Chem. 2010 Mar 1;82(5):1698-704. doi: 10.1021/ac902099d.

Authors

Irena Mejac¹, Hye-Hun Park, William W Bryan, T Randall Lee, Chieu D Tran

Affiliation

¹ Department of Chemistry, Marquette University, P.O. Box 1881, Milwaukee, Wisconsin 53201, USA.

PMID: 20108923
DOI: 10.1021/ac902099d

Abstract

This manuscript reports the use of near-infrared multispectral imaging (NIR-MSI) microscopy to provide the first direct observation and spectral measurement of individual poly(n-isopropylacrylamide-co-acrylic acid) (NIPAM-co-AAc) hydrogel particles. The high sensitivity and high spatial resolution (approximately 0.9 microm/pixel) of the NIR-MSI microscope, coupled with its ability to measure images and spectra directly and simultaneously, allows the unprecedented in situ monitoring of the size, morphology, and spectroscopic properties of individual hydrogel particles, which respond strongly to external stimuli (e.g., changes in temperature and/or pH). Importantly, this novel technique allows, for the first time, the direct measurement of the lower critical solution temperature (LCST) phase transition of individual hydrogel particles rather than that of a collection of hydrogel particles. Furthermore, NIR-MSI measurements reveal that the LCST value is unique for each individual hydrogel particle, depending strongly on particle size, with larger particles exhibiting higher LCST values.