Copper-mediated synthesis of temperature-responsive poly(N-acryloyl glycinamide) polymers: a step towards greener and simple polymerisation

Stimuli-responsive materials with reversible supramolecular networks controlled by a change in temperature are of interest in medicine, biomedicine and analytical chemistry. For these materials to become more impactful, the development of greener synthetic practices with more sustainable solvents, lower energy consumption and a reduction in metallic catalysts is needed. In this work, we investigate the polymerisation of N-acryloyl glycinamide monomer by single-electron transfer reversible-deactivation radical polymerisation and its effect on the cloud point of the resulting PNAGA polymers. We accomplished 80% conversion within 5 min in water media using a copper wire catalyst. The material exhibited a sharp upper critical solution temperature (UCST) phase transition (10–80% transition within 6 K). These results indicate that UCST-exhibiting PNAGA can be synthesized at ambient temperatures and under non-inert conditions, eliminating the cost- and energy-consuming deoxygenation step. The choice of copper wire as the catalyst allows the possibility of catalyst recycling. Furthermore, we show that the reaction is feasible in a simple vial which would facilitate upscaling.

The 1 H NMR spectrum of the NAGA monomer with assigned protons to peaks is shown in Figure S1.
An example of the obtained DSC curve with labelled melting temperature is shown in Figure S2.After melting, NAGA undergoes polymerization indicated by the exothermic heat flow.Electronic Supplementary Material (ESI) for RSC Advances.This journal is © The Royal Society of Chemistry 2023

Further characterization of poly(N-acryloyl glycinamide)
Figure S4: 1 H NMR spectrum with assigned peaks to an impurified PNAGA polymer in DMSO-d 6 at 50 °C.Peaks between 6.5 and 5.5 ppm belong to the vinyl protons of an unreacted monomer.(1 wt.%).The lines represent five-parameter logistic fits of each set of data.

Figure
Figure S1: 1 H NMR spectrum of NAGA monomer in DMSO-d 6 at room temperature.

Figure S2 :
Figure S2: An example of the synthesized monomer NAGA DSC curve with highlighted melting temperature.

Figure S3 :
Figure S3: HPLC elugram of the NAGA monomer.By comparing the peak areas of the monomer and the impurities, the monomer purity was determined to be 93 %.

Figure S5 :
Figure S5: Comparison of different data processing.Left: Black connecting lines are for eye guidance only.Red dashed lines are linear regressions for the determination of k p app(a, c, e).Right: Data were plotted with a five-parameter logistic fit (Eq.1).k p app was calculated as the maximum of the first derivative of the five-parameter logistic fit curve(b, d, f).

Table S1 :
The theoretical and calculated degrees of polymerisation of the samples showing the presence of living chain ends.