Thermally switchable adhesion of photopolymerizable acrylate polymer networks

Switchable adhesion behavior of flat and structured photopolymerizable acrylate networks was investigated as a function of temperature. The molecular weight and the weight fraction of poly(ethylene glycol) dimethacrylate crosslinker was altered to maintain a constant glass transition temperature of approximately 57°C, but systematically vary the viscoelastic properties and the rubbery moduli (1.8-11.2 MPa). Dynamic mechanical analysis was performed to characterize the low-strain thermo-mechanical behavior of the materials. The flat samples tested with the spherical probe exhibited low pull-off forces at temperatures well above and well below the glass transition temperature of the material. A maximum pull-off force was observed in the vicinity of the glass transition temperature owing to the viscoelastic energy dissipative processes. The peak in pull-off force was observed to decrease with an increase in crosslinking density and modulus. The structured samples tested with spherical probe showed a decrease in adhesion with an increase in temperature up to the onset of glass transition, beyond which the adhesion was observed to increase due to the better contact formation allowed by the decrease in the material modulus. © 2013.