Toward Strong Thermoplastic Elastomers with Asymmetric Miktoarm Block Copolymer Architectures

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• 作者：Weichao Shi ; Nathaniel A. Lynd ; Damien Montarnal ; Yingdong Luo ; Glenn H. Fredrickson ; Edward J. Kramer ; Christos Ntaras ; Apostolos Avgeropoulos ; Alexander Hexemer
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：March 25, 2014
• 年：2014
• 卷：47
• 期：6
• 页码：2037-2043
• 全文大小：462K
• 年卷期：v.47,no.6(March 25, 2014)
• ISSN：1520-5835

文摘

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鈥?_n miktoarm block copolymers with an approximately 8:1 ratio of the A to A鈥?block molecular weights and n 鈮?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鈥揚I) 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.