Reprogrammable Hydroplastic Latex Films and Water-Driven Phase Separation

Thermoplastics are a class of plastic polymers that can be remolded repeatedly by heating and cooling. Recently, inspired by the concept of thermoplastics, hydroplastic materials, a type of materials that can be reshaped with the aid of water, have aroused great interest. In this research, a simple and versatile approach to the preparation of hydroplastic latex film is developed and water-driven phase separation in the film is studied. Core-shell latex particles with protonated poly(2-(dimethylamino)ethyl methacrylate) (p-PDMAEMA) shells and poly(n-butyl acrylate-co-methyl methacrylate) P(nBA-co-MMA) cores are synthesized, and latex films are prepared by solution casting. After water treatment, the films can be molded into various shapes and fixed into three dimensional shapes in dry state. The hydroplastic behavior is dependant on the phase structure. In the latex film there exist hydrophobic P(nBA-co-MMA) phases surrounded by continuous hydrophilic p-PDMAEMA phases. In aqueous solution, water molecules diffuse into the hydrophilic phases, resulting in an increase in the volume ratio of the hydrophilic phases and a decrease in the mechanical properties; and the latex films are endowed with the hydroplasticity. The swollen of the hydrophilic phases by water allows the boundary interdiffusion of P(nBA-co-MMA) chains and the coalescence of the hydrophobic phases.