Hybrid Thermoplastic Elastomers using Bottlebrush Block Copolymer Grafted Nanoparticles

Thermoplastic Elastomers (TPEs) are physically crosslinked polymer networks with extensive applications due to their unique mechanical properties and ease of processing. Current TPEs are limited by a narrow modulus range and low melting points, restricting the working range of processed parts. A potential method for overcoming such shortcomings is the use of bottlebrush polymers in which the polymer backbone is densely grafted with polymer chains, resulting in entanglement-free systems which aid in lowering the modulus of the material. An additional tuning parameter to increase elastomer functionality is to add inorganic nanoparticles, providing increased thermal stability and toughness, and from a structural standpoint, acting as “permanent” junction sites of the network. Here, the self-assembled structure and mechanical properties of a series of bottlebrush poly(dimethyl siloxane)-poly(styrene) (PDMS-PS) diblock copolymer grafted silica nanoparticles with varying polymer molecular weights and block volume fractions were investigated using a combination of X-ray scattering, transmission electron microscopy, and mechanical testing. It is found that the PDMS forms the soft deformable matrix while the microphase separated PS domains create network junctions. The synthesized bottlebrush block copolymer grafted nanoparticles demonstrate potential advantages over current thermoplastic elastomers by showing tunable mechanical and physical properties.