Solid–Liquid Self-Adaptive Polymeric Composite

Abstract

A solid-liquid self-adaptive composite (SAC) is synthesized using a simple mixing-evaporation protocol, with poly(dimethylsiloxane) (PDMS) and poly(vinylidene fluoride) (PVDF) as active constituents. SAC exists as a porous solid containing a near equivalent distribution of the solid (PVDF)-liquid (PDMS) phases, with the liquid encapsulated and stabilized within a continuous solid network percolating throughout the structure. The pores, liquid, and solid phases form a complex hierarchical structure, which offers both mechanical robustness and a significant structural adaptability under external forces. SAC exhibits attractive self-healing properties during tension, and demonstrates reversible self-stiffening properties under compression with a maximum of 7-fold increase seen in the storage modulus. In a comparison to existing self-healing and self-stiffening materials, SAC offers distinct advantages in the ease of fabrication, high achievable storage modulus, and reversibility. Such materials could provide a new class of adaptive materials system with multifunctionality, tunability, and scale-up potentials.

Structural Reinforcement through Liquid Encapsulation

“…Synthesis of Spherical Composite : To synthesize the polymer encapsulated liquid shells, the authors followed a similar procedure to the one reported by Dong et al The authors took PVDF (Alfa Aesar, 23 500–29 500 P) and dissolved into tetrahydrofuran (THF) while under magnetic stirring. The solution was monitored until it reached homogenization (≈3 h).…”

“…The material was cycled constantly at 5 Hz and a difference in the stiffness behavior is clear. As more spheres are added the material begins to exhibit increased stiffening, or self‐stiffening as described by others . Self‐stiffening has generally been seen when performing isothermal tests with a multitude of cycles over time.…”

“…This new approach represents a shift in the concepts about structural reinforcement and expands on the work of Style et al by using a much stiffer matrix and a modified liquid filler which gives rise to novel pathways and materials that would previously be disregarded. Recently, work from our group showed how mobile and liquid interfaces can help a material adapt to stresses . This mechanism can be exploited more broadly to create stronger and more resilient materials.…”

“…The simulations showed that mixing these two polymers lead to the formation of a structurally rigid PVDF outer shell encapsulating a liquid phase (PDMS), which is in good agreement with the experimental data. The elemental analysis by Dong et al on similar materials revealed that fluorine atoms are preferentially located on the shell of the microspheres while silicon atoms are found within the microspheres. This further supports the expected core–shell structure with a fluid core of PDMS and a solid external shell of PVDF.…”

Toughening by Nanodroplets: Polymer–Droplet Biocomposite with Anomalous Toughness

“…Consequently, scientific and technical studies of PDC with liquid droplets are new and have seldom been reported. 27,28 In sections 2 and 3, we will demonstrate weak droplets as a flexible, powerful, and kinetics-favored second phase for design of PDCs with unusual and novel mechanical properties.…”