A method for an approximate determination of a polymer-rich-domain concentration in phase-separated poly(N-isopropylacrylamide) aqueous solution by means of confocal Raman microspectroscopy combined with optical tweezers

Tatsuya Shoji; Riku Nohara; Noboru Kitamura; Yasuyuki Tsuboi

doi:10.1016/j.aca.2014.11.001

A method for an approximate determination of a polymer-rich-domain concentration in phase-separated poly(N-isopropylacrylamide) aqueous solution by means of confocal Raman microspectroscopy combined with optical tweezers

Anal Chim Acta. 2015 Jan 7:854:118-21. doi: 10.1016/j.aca.2014.11.001. Epub 2014 Nov 6.

Authors

Tatsuya Shoji¹, Riku Nohara², Noboru Kitamura³, Yasuyuki Tsuboi⁴

Affiliations

¹ Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka 558-8585, Japan. Electronic address: t-shoji@sci.osaka-cu.ac.jp.
² Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Japan.
³ Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo 060-0810, Japan; Department of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
⁴ Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, Osaka 558-8585, Japan.

PMID: 25479874
DOI: 10.1016/j.aca.2014.11.001

Abstract

The paper demonstrates that a confocal Raman microspectroscope combined with optical tweezers is a promising technique to estimate polymer concentration in polymer-rich domain in phase-separated-aqueous polymer solution. The sample polymer is poly-(N-isopropylacrylamide) (PNIPAM) that is well-known as a representative thermo-responsive polymer. Optical tweezers can selectively trap the polymer-rich domain at the focal point in non-contact and non-intrusive modes. Such situation allows us to determine polymer concentration in the domain, which has been unclear due to a lack of appropriate analytical technique. It is applicable for a variety of other thermo-responsive polymers.

Keywords: Confocal Raman microspectroscopy; Near-infrared laser beam; Optical trapping; Optical tweezers; Photothermal effect; Poly-(N-isopropylacrylamide); Radiation force; Thermo-responsive polymer.