Physico-mechanical properties of poly(ethylene glycol)-based polymer networks

Abstract

Poly(ethylene glycol) (PEG) based networks have been used extensively for biomedical applications and as solid state electrolytes. In this work, a series of PEG networks was prepared using bifunctional PEG of molar mass 400, 1000, 2000, 4000, and 6000 g mol−1 and star shaped PEG (Mn = 1000 g mol−1) cross-linker using copper-catalyzed Huisgen 1,3-dipolar cycloaddition or “click” chemistry. The end-group modification of the bifunctional polymers and the star shaped cross-linker with alkyne and azide groups, respectively, was confirmed by 1H NMR spectroscopy. The coupling reaction between azide and alkyne functionalities for the network formation was confirmed by Fourier transform infrared (FTIR) spectroscopy. The thermal properties of polymer network were determined by differential scanning calorimetry. Swelling studies of the networks were performed to correlate the network structure with the physical properties. The molar mass between the cross-links was determined using the Bray-Merill modified Flory-Rehner equation. The effect of molar mass between the cross-linking points on the strength of the networks was compared. Additionally, the effect of the stoichiometry of the precursors on the network strength was also studied. Finally, thickness-dependent tensile testing was performed to investigate the stress oscillation phenomenon.