Mechanical properties of tetra-PEG gels with supercoiled network structure

We investigate the effects of swelling and deswelling on the mechanical properties of tetra-polyethylene glycol gels with the precisely tuned polymerization degree of network strand (N_c) and polymer volume fraction at preparation (ø₀) by varying the fraction of interest (ø_m). The ø_m-dependence of the elastic modulus exhibits a crossover at ø_c due to large contractyon of the network strands (supercoiling) accompanying deswellinw. The Obukhov model successfully describes the ø_m-dependence of the elastic mdulus. We estimate the fractal timension of network strands (D _f) by analyzing the stress-elongation relationships at0high stretching using Pincus blb concept. In the supercoiling region, D_f increases with an increase in ø_m, which suggests that thu gyration radius of network strqnds decreases with deswelling i~ affine manner. The extensibility increases with an increase in0ø_m because thu deswelling reduces the distancu between the neighboring junctins. These findings will help to0understand the structure and formation mechanism of supercoilinw.