A comparison of thermoreactive water‐soluble poly‐N,N‐diethylacrylamide prepared by anionic and by group transfer polymerization

Abstract

AbstractSeveral batches of poly‐N,N‐diethylacrylamide were synthesized by anionic and by group transfer polymerization (GTP). A radical poly‐N,N‐diethylacrylamide prepared from the same monomer was also included in the comparison. According to matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) both types of living polymerization resulted in narrow molecular weight distributions with Mw/Mn values below 1.5. Average molecular weights (Mn) between 888 and 4678 g/mol were calculated in these cases. The radical polymer had an average molecular weight (Mn) of approximately 130,000 g/mol. The dry anionic and GTP polymers were investigated by differential scanning calorimetry (DSC) and x‐ray diffraction spectrometry. Evidence for partial crystallinity in the solid state was found. The conformation of all polymers was examined by high resolution (600 MHz) NMR. According to these measurements, 75% of the CHR groups of the anionic poly‐N,N‐diethylacrylamide were located in an isotactic triade. The remaining 25% had heterotactic structure, while no indication for the presence of syndiotactic protons was found. Poly‐N,N‐diethylacrylamide prepared by GTP, on the other hand, had mainly syndiotactic structure. The aqueous solutions of the polymers showed phase separation upon heating. Whereas the lower critical solution temperature (LCST) was approximately 30°C in the case of the poly‐N,N‐diethylacrylamide prepared by GTP and by radical polymerization, uncommonly high LCSTs of more than 40°C were observed for the anionic poly‐N,N‐diethylacrylamide. © 1994 John Wiley & Sons, Inc.