Mechanical property and dielectric spectra analysis of solvent-free poly(ionic liquid)/poly(ethyl acrylate) double network elastomers under tensile deformation

Solvent-free double network elastomers have excellent mechanical properties and stability. However, there are few studies on ion transport in solvent-free double network elastomers. In this paper, we prepared a kind of poly(ionic liquid) (PIL)-based solvent-free elastomer with double network structure by using crosslinked poly[2-(methacryloyloxy)ethyl] trimethyl ammonium bis(trifluoromethanesulfonyl) imine (P[VBTMA][TFSI]) network as brittle network and crosslinked poly(ethyl acrylate) (PEA) as stretchable network. The mechanical properties and the ion transport of samples as a function of elongation strain were investigated by stress-strain curves and broadband dielectric spectroscopy, respectively. The results show the double network elastomer has medium elastic modulus of 0.4–0.9 MPa, high elongation strain of 1700–2300% and ionic conductivity of 1.04 × 10⁻⁷ S·m⁻¹ at room temperature. When the sample does not yield, stretching almost does not affect the ion transport in the network. As the strain exceeds the yield point, the conductivity relaxation time of the samples with low crosslinking degree of PIL network increases little, while the conductivity relaxation time of the samples with high crosslinking degree increases significantly. This is because the former network breaks uniformly, while the latter appears phase separation when yielding. The result improves the understanding of ion transport in double network polyelectrolyte elastomers.