Characterizing Conformational Change of a Thermoresponsive Polymeric Nanoparticle with Raman Spectroscopy

Molecular conformational changes in the collapsing and reswelling processes occurring during the phase transition at the lower critical solution temperature (LCST) of the polymer are not well understood. In this study, we characterized the conformational change of Poly(oligo(Ethylene Glycol) Methyl Ether Methacrylate)-144 (POEGMA-144) synthesized on silica nanoparticles using Raman spectroscopy and zeta potential measurements. Changes in distinct Raman peaks associated with the oligo(Ethylene Glycol) (OEG) side chains (1023, 1320, and 1499 cm(-1)) with respect to the methyl methacrylate (MMA) backbone (1608 cm(-1)) were observed and investigated under increasing and decreasing temperature profiles (34 & DEG;C to 50 & DEG;C) to evaluate the polymer collapse and reswelling around its LCST (42 & DEG;C). In contrast to the zeta potential measurements that monitor the change in surface charges as a whole during the phase transition, Raman spectroscopy provided more detailed information on vibrational modes of individual molecular moieties of the polymer in responding to the conformational change.

Automated summary

In this study, the conformational change of POEGMA-144 on silica nanoparticles was characterized using Raman spectroscopy and zeta potential measurements. The results revealed that distinct Raman peaks associated with OEG side chains and MMA backbone changed during the collapsing and reswelling processes around the LCST.