Construction of stimuli-responsive and mechanically-adaptive thermoplastic elastomeric materials

Abstract

The stimuli-responsive systems present in nature have inspired scientists to develop new-generation synthetic mechano-adaptive materials for various technological applications. In this work, an effective strategy was adopted to construct a biomimetic mechano-adaptive thermoplastic elastomeric material, whose mechanical properties can be stimulated by water. The inherent ability of calcium sulphate (CaSO4) to reversibly alter its crystal structure by the hydration/dehydration process was exploited in a technologically compatible hydrophilic thermoplastic elastomeric (TPE) blend by dispersing it as a phase responsive filler. Significant enhancements in the mechanical properties were then achieved in the water-treated CaSO4 filled TPE composite. The improved mechanical properties of the water-treated composite originated with the creation of in-situ hydrated nanosized CaSO4 crystals were also correlated with the strong filler-filler interactions and higher aspect ratio of the filler. The storage modulus (dynamic stiffness) of the resulting TPE composite could be reversibly altered from ∼9.6 to ∼46.7 MPa. Most importantly, ∼92% mechanical adaptivity of the resulting TPE composite was achieved due to the reversible transformation of nanosized crystals into a hemihydrate mesocrystalline form by exploiting the hydration/dehydration process. The alteration of in-situ polymorphic CaSO4 phase morphological structures was verified using transmission electron microscopy, Raman spectroscopy and X-ray diffraction. This technique provides a unique pathway for the creation of next-generation stimuli-responsive TPE materials by controlling the polymorphic phase morphological structure of mineral filler.