Synthesis and properties of ABA and ABC triblock copolymers with glassy (A), elastomeric (B), and crystalline (C) blocks

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Schmalz, Holger ; Böker, Alexander ; Lange, Ronald ; Krausch, Georg ; Abetz, Volker:
Synthesis and properties of ABA and ABC triblock copolymers with glassy (A), elastomeric (B), and crystalline (C) blocks.
In: Macromolecules. Bd. 34 (2001) Heft 25 . - S. 8720-8729.
ISSN 1520-5835
DOI: https://doi.org/10.1021/ma010875d

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Abstract

We describe the synthesis, characterization, and properties of polystyrene-block-poly(ethylene-alt-propylene)-block-polyethylene (PS-b-PEP-b-PE) and polystyrene-block-poly(ethylene-alt-propylene)-block-polystyrene (PS-b-PEP-b-PS) triblock copolymers. Morphological investigations using TEM, SEM, and SFM reveal for the PS-b-PEP-b-PE triblock copolymers a morphology consisting of PS cylinders and PE crystallites within a matrix of the PEP block, whereas the PS-b-PEP-b-PS triblock copolymer shows interconnected, distorted PS cylinders in the PEP matrix. Mechanical characterization of these triblock copolymers demonstrated that for small strains the PS-b-PEP-b-PE triblock copolymers exhibit the aimed smaller plastic deformations, i.e. better elastic properties, compared to the polystyrene-based ABA type thermoplastic elastomer. However, at high strains the PS-b-PEP-b-PS triblock copolymer shows a significantly better elastic recovery. The high plastic set at high elongations in PS-b-PEP-b-PE triblock copolymers is attributed to the weaker resistance of the PE crystallites compared to amorphous PS domains in the PS-b-PEP-b-PS triblock copolymer.