Toward strong thermoplastic elastomers with asymmetric miktoarm block copolymer architectures

Abstract

Thermoplastic elastomers (TPEs) are designed by embedding discrete glassy or semicrystalline domains in an elastomeric matrix. Typical styrenic-based amorphous TPEs are made of linear ABA-type triblock copolymers, where the volume fraction f of the glassy domains A is typically less than 0.3. This limitation ultimately restricts the range of mechanical strength attainable with these materials. We had previously predicted using self-consistent field theory (SCFT) that A(BA′)n miktoarm block copolymers with an approximately 8:1 ratio of the A to A′ block molecular weights and n ≥ 3 should exhibit discrete A domains at considerably larger f and offer potential for the combination of high modulus, high recoverable elasticity, and high strength and toughness. Using transmission electron microscopy and small-angle X-ray scattering on model polystyrene-b-polyisoprene (PS–PI) miktoarm copolymers, we show that such polymers indeed possess discrete PS domains for f values considerably higher than 0.3. The hexagonal morphology with PS cylinders was achieved for f= 0.5 and n = 3. Mechanical testing indicates that these miktoarm materials are strong, tough, and elastic and thus may be potential candidates for a new generation of thermoplastic elastomers.

ICB Affiliated Authors

Authors
W. Shi, N. A. Lynd, D. Montarnal, Y. Luo, G. H. Fredrickson, E. J. Kramer, C. Ntaras, A. Avgeropoulos, and A. Hexemer
Date
Type
Peer-Reviewed Article
Journal
Macromolecules
Volume
47
Pages
2037–2043