Abstract:

The multi-network material PDGI/PAAm-PAMPS-PAAm (PDGI/TN) was synthesized, starting from PDGI/PAAm (PDGI/SN). The PDGI/TN was subsequently deswelled to an equilibrium state in an ethanol/water mixture (6 : 4)(V/V) to generate a material termed PDGI/TN-0.6. The results indicate that the swelling radio of the PDGI/TN was increased to 1070% ± 50%, compared with a value of 850% ± 45% for the original PDGI/SN. In addition, the color of the gel changed from blue (λ_max=450 nm) to transparent and the Bragg diffraction peak transitioned to 670 nm. The Bragg diffraction peak could also be tuned over the range from 450 to 670 nm by adjusting triple network and the ethanol/water solution. Loading-unloading cycling in conjunction with tensile and compressive testing demonstrated that the PDGI/TN-0.6 possessed outstanding mechanical properties. The tensile and compressive stresses of PDGI/TN-0.6 were significantly improved from those of the initial PDGI/ SN, to 0.99 and 37.0 MPa, respectively. Loading-unloading cycling data showed that the PDGI/TN-0.6 exhibited excellent responsiveness even after repeated trials. As compressive strain (ε_c) was increased from 0 to 0.5, the Bragg diffraction peak underwent a blue shift under compression and eventually spanned the entire visible spectrum wavelength range at the same rate that compressive deformation was applied and released. The effect of the triple network on the inner layer distance in this material was also investigated using scanning electron microscopy (SEM).

Key words: Lamellar structure, Photonic hydrogel, Hydrogel, Mechanochromic