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Unveiling the Effects of the Molecular Structural Characteristics of SEBS on the Phase-Separation Morphology and Electrical/Mechanical Properties of PCDTPT/SEBS Blends
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DOI：10.1021/acs.macromol.6c00929.png)
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Abstract
En 中文
Polystyrene-b-poly(ethylene-r-butylene)-b-polystyrene (SEBS) is an elastomer commonly blended with conjugated polymers (CPs) to enhance their electrical and mechanical performance. However, rational elastomer selection remains challenging, as the effects of the molecular structure of SEBS on blend structures and performance are poorly understood. In this work, we systematically investigate how the molecular structural characteristics of SEBS govern the microstructures and properties of CP/SEBS blend films by blending a brittle CP, poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b′]dithiophen-2-yl)-alt-[1,2,5]thiadiazolo[3,4-c]pyridine] (PCDTPT), with five SEBS elastomers that differ in terms of polystyrene/poly(ethylene-r-butylene) (PS/PEB) ratio, polar grafting, and molecular weight. Our findings reveal that the PS/PEB ratio determines the lateral phase-separation morphology types, such as continuous network/island-like domains, and vertical phase-separation morphology types, such as sandwich, gradient distribution, and inverse sandwich structures, in PCDTPT/SEBS blends. Compared with the crystalline microstructure, phase-separation, particularly lateral phase-separation, has more dominant effects on the electrical and mechanical performance of PCDTPT. An optimal PS content of approximately 30% in SEBS produces a favorable phase-separated morphology of the PCDTPT/SEBS blend, which holds potential for achieving good overall performance. Introducing carboxyl groups into SEBS results in the formation of noncovalent intermolecular hydrogen bonds with PCDTPT, thereby tuning the blend morphology and properties without altering the lateral and vertical phase-separated morphology types. Blending with low-molecular-weight carboxyl-grafted SEBS facilitates the formation of ordered PCDTPT nanofibers, thereby yielding the highest conductivity but the lowest crack onset strain (COS) among the blends. In contrast, blending with high-molecular-weight carboxyl-grafted SEBS improves PCDTPT/SEBS miscibility, reduces phase domain size, and prevents brittle nanofiber formation. This blend has the second-highest conductivity and the highest stretchability of all five blends studied. In this study, a clear relationship between the phase-separation morphology of PCDTPT/SEBS blends and the molecular structure characteristics of SEBS is established. These findings provide rational criteria for selecting SEBS elastomers for stretchable CP films with balanced electrical and mechanical performance.
Keywords:
Electrical conductivity
Molecular properties
Morphology
Noncovalent interactions
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5.2
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3.6W
Citations:
9.4W
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