Characterization of the network properties of poly(ethylene glycol)–acrylate hydrogels prepared by variations in the ethanol–water solvent composition during crosslinking copolymerization

Abstract

The characteristics of poly(ethylene glycol) (PEG)-acrylate hydrogel networks were investigated as a function of the ethanol-water solvent composition during freeradical crosslinking copolymerization. Macromonomer (88% -methoxy-PEG-acrylate and 10% -phenoxy-PEG-acrylate) and crosslinker (2% PEG-diacrylate) concentrations were kept constant. As the copolymerization progressed, the polymer solution in 100% ethanol became increasingly turbid, indicating the development of a heterogeneous network structure. In 100% water, however, the initially turbid polymer solution became increasingly transparent as the crosslinking copolymerization progressed. All the gels were optically clear upon equilibration in water. Kinetic studies, with attenuated total reflectance-infrared, showed a long induction period, along with a lowered reaction rate, in 100% ethanol, and a decrease in conversion with an increase in ethanol content. These results agree with the UV analysis of the sol fractions, which indicated an increase in the amounts of unreacted PEG-acrylates with an increase in the ethanol content. The gels which were formed with a high ethanol concentration exhibited lower Young's modulus and higher swelling ability, suggesting that the network structure was significantly affected by the solvent composition during free-radical crosslinking copolymerization. From the stressstrain and swelling experiments, the Flory-Huggins interaction parameter was evaluated. The creep characteristics of the hydrogels were modeled with two Kelvin elements.

Water uptake, transport and structure characterization in poly(ethylene glycol) diacrylate hydrogels

“…"XX", "YY" and "ZZ" represent the weight percent of PEGDA, water and PEGA in the prepolymerization solution, respectively. [31], 1412 cm −1 [32,33], and 1190 cm −1 [33] disappear due to polymerization. The spectra for other film compositions are similar to that of the 20/80 PEGDA/H 2 O and 10/10/80 PEGDA/PEGA/H 2 O films; they are not shown for the sake of brevity.…”

Analysis of poly(ethylene glycol)‐diacrylate macromer polymerization within a multicomponent semi‐interpenetrating polymer network system

“…ATR-FTIR has been shown to be a viable method for monitoring the chemical conversion and reaction kinetics of photopolymerized acrylate systems. 17,18 In this study, the conversion of PEGdA acrylate functional groups during free-radical photopolymeriztion was monitored in situ using a Brukker Equinox 55 ATR-FTIR spectrometer (single reflection, ZnSe crystal, eight scans per spectrum) and the effects of DMPA and PEGdA concentration, gelatin modification, and gelatin weight ratio were compared. Polymer mixture solutions containing DMPA initiator (0.02, 0.1, or 0.5 wt % in solution), modified gelatin (G, EG, mPG, or mP/EG), and PEGdA 600 (5, 10, or 15 wt % in solution) at specific gelatin/PEGdA 600 weight ratios (0:100, 30:70, 40:60, or 50:50, respectively) were prepared as described above.…”

Development of techniques to compare mechanical properties of reversible hydrogels with spherical, square columnar and ocular lens geometry

“…This might be due to the presence of ethanol in the cosolvent. Ethanol is known to significantly change the molecular kinetics, termination reaction, and network properties of similar systems [35]. If the copolymerization and crosslinking reaction were quantitative and the junctions were all tetra-functional, then the theoretical M c , based on the stoichiometry of the monomers and cross-linkers, would be 1631 Da (the average molecular weight between cross-linking was taken to be 77.3 Da).…”