Thermal insulative 2D-oriented bimodal micro-foams and high strength photonic thermoplastic elastomers by assembling olefin multiblock copolymers

Hierarchical 2D-oriented micro-foams and photonic elastomers are produced by assembling the mesophase separated and crystallized superstructures of olefin multiblock copolymers (OBCs). Highly 2D-oriented mono -modal and bimodal micro-foams are prepared via compression molding of as-received nascent OBC pellets, irradiation crosslinking, and a subsequent moderate-to-high-pressure supercritical CO2 foaming. Randomly short range ordered bimodal micro-foams are generated from the sheared counterparts. These micro-foams show excellent lightweight properties with foam density of 0.061-0.188 g cm(-3) and outstanding thermal conductivity of 20-36 mW m(-1) K-1 by laser flash analysis. Moreover, the order-disorder and order-order transitions of nascent and sheared bulk OBCs are characterized by a sequential annealing and subsequent crystallization procedure. The self-seeded nascent and sheared OBCs show hierarchical mesophase separation with domain spacings of 80-258 nm, measured by ultra-small X-ray scattering. The selective visible-light transmitted, transparent, and high-strength thermoplastic elastomers are then made via solvent-free compression molding of these OBC pellets. Meanwhile, low-temperature Sc-CO2 foaming shows that 2D lamellar crystals and 2D, 3D-growing spherulitic crystals with sharp interfaces are individually organized within 2D-oriented lamellar domains of photonic and opaque sheets, which account for their high tensile strength and low strain hardening properties, respectively. The 2D-oriented bimodal micro-foams and assembled photonic elastomers possess potential applications in lightweight sound and thermal insulation, auto-parts, shape memory light actuators, and soft sensors.

Automated summary

In this study, hierarchical 2D-oriented micro-foams and photonic elastomers were successfully produced by assembling the superstructures of olefin multiblock copolymers (OBCs). These materials demonstrate lightweight properties and excellent thermal conductivity, and have potential applications in sound and thermal insulation, auto-parts, shape memory light actuators, and soft sensors.