Synthesis of spin labeled ethylene glycol based polymers and study of their segmental motion

Abstract

Understanding segmental dynamics of polymer chains is important to decipher the microscopic behavior in order to modulate the bulk properties of polymers. Study of electron spin resonance (ESR) spectroscopy of polymer chain segments is useful to understand internal dynamics of polymer chains in solution. In this paper, poly(oligoethylene glycol methacrylate-co-2,2,6,6-tetramethyl piperidin-4-yl methacrylate)s, OEG-TMPMs, were synthesized. The synthesized OEG-TMPMs were characterized by nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermogravimetric (TG) techniques. The TMPM moiety in OEG-TMPMs was oxidized to 2,2,6,6-tetramethyl-1-piperinidyloxy-4-yl methacrylate (TMP) to generate nitroxide radicals. These nitroxide radical-containing OEG-TMPs were analyzed with Fourier transform-infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and ESR spectroscopy. The effect of side chain length on the segmental mobility of OEG-TMPs was studied. The results showed that the longer pendent chains as in OEG-TMP-4 imparted higher flexibility to the backbone of the polymer and increased rotational freedom of nitroxide radicals as compared to restricted mobility in the case of shorter polymer side chains.