Anisotropic mechanical responses of composites having water microchannels

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>The combination of extremely different materials could result in composites with unique properties, although their different properties make the combination challenging. If water-swellable phases are combined with water-insoluble rubbery phases, the resulting composites can act as water-swellable and mechanically durable rubbers. Herein, novel composites of hydrophilic poly(<I>N</I>-isopropylacrylamide) (PNIPAM) or poly(ethylene glycol) and hydrophobic polyurethane (PU) or poly(dimethylsiloxane) were prepared by directional melt crystallization and a subsequent infiltration process. When the composites were compressed parallel to their microchannel direction, much higher moduli were obtained, and their unique deflection and plateau regions existed due to irreversible deformations such as buckling. The moduli of water-swollen PU/PNIPAM were higher than those of porous PU. The hysteresis of cyclic compression was maximal in the cases of parallel compression with a low swelling ratio (SR), which could effectively absorb mechanical energy input. On the other hand, perpendicular compression with a high SR produced reversible mechanical behavior. These results demonstrate that the pore-filling properties of hydrogels by swelling enhance the mechanical properties of composites. We also found that the deswelling kinetics of composites were surprisingly fast. These unique properties of water-swellable composites could be advantageous for various applications in future industries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The mechanical properties of novel composites having two separate and distinct phases were studies. </LI> <LI> The two phases, a water-swellable and a hydrophobic rubber phases, were combined into 3D co-continuous composites. </LI> <LI> Surprisingly fast deswelling kinetics and unique anisotropic mechanical responses were found. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Novel composites having two separate and distinct phases of extremely different properties showed surprisingly fast deswelling kinetics and unique anisotropic mechanical responses.</P> <P>[DISPLAY OMISSION]</P>