Raman Microspectroscopic Studies on Thermo-Responsive Polymer Rich Domains Formed by Optical Tweezers

Abstract

Poly ( N - isopropylacrylamide ) ( PNIPAM ) as a representative water - soluble thermo - responsive polymer exhibits a coil - to - globule phase transition followed by phase separation upon temperature increase, leading to the formation of polymer - rich domains in solution. Quantitative analysis of polymer concentration in polymer - rich domains is a challenging task for deeper understanding of the phenomena. Recently, we developed an analytical technique that combined optical tweezers with confocal Raman microspectroscopy to determine the concentration in the domain. Furthermore, optical tweezers enhanced by localized surface plasmon formed a micro - assembly of PNIPAM on plasmonic nanostructures, providing the platform for a highly sensitive detection technique for fl uorescent and non fl uorescent organic molecules dissolved in an aqueous solution. These trapping method combined with microspectroscopies are applicable for a variety of other thermos - responsive polymers.