Nitroxide-Mediated Polymerization of <i>N</i>-Isopropylacrylamide: Electrospray Ionization Mass Spectrometry, Matrix-Assisted Laser Desorption Ionization Mass Spectrometry, and Multiple-Angle Laser Light Scattering Studies on Nitroxide-Terminated Poly-<i>N</i>-isopropylacrylamides

Abstract

Nitroxide-mediated controlled living free radical polymerization of N-isopropylacrylamide using highly sterically hindered 2,2,6,6-tetraethylpiperidin-4-on-N-oxyl 1 is described. In addition, an improved synthesis for nitroxide 1 is presented. Poly-N-isopropylacrylamides (PNIPAMs) prepared are analyzed by multiple-angle laser light scattering. Moreover, the nitroxide-terminated PNIPAMs are characterized using electrospray ionization mass spectrometry, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and Fourier transform ion cyclotron MALDI-MS. Careful MS analysis reveals that chain-end degradation of nitroxide-terminated PNIPAMs occurs during MALDI analysis. A mechanism for chain end degradation is presented.