Dihydroxy Indole-free Poly(catecholamine) for Smooth Surface Coating with Amine Functionality AITranslate

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DOI：https://doi.org/10.1021/acsapm.3c00803

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The catecholamine of polydopamine (PDA) is associated with adhesion and self-polymerization. However, 5,6-dihydroxyindole (DHI) of PDA inevitably consumes primary amine groups, which are helpful for the post-modification of PDA-coated surfaces. Furthermore, DHI leads to particle aggregation by causing π–π interaction and cation−π interaction. Here, we used 3,4-dihydroxybenzylamine hydrobromide to achieve DHI-free poly(catecholamine) (PCA) coating by self-polymerization. The DHI-free nature renders a smooth and uniform surface. Moreover, the suppressed indole ring formation preserves the primary amine groups after the DHI-free PCA coating, suggesting an alternative surface amine functionalization strategy to the conventional silane-based coating that is only applicable to hydroxyl-containing surfaces. Surface amine functionality of DHI-free poly(catecholamine) is confirmed by the fluorescence image of the tethered NHS ester-functionalized polydiacetylene liposome by the NHS ester-amine coupling reaction. Furthermore, DHI-free PCA was used to modify the surface properties of graphene to enhance the thermal conductivity of graphene-polymer composites. Graphene nanoplatelets (GnPs) coated with DHI-free PCA formed adequate intermolecular bonding with the poly(acrylic acid) matrix, which reduces interfacial thermal resistance. The resulting graphene-polymer composites achieved a sharp increase in thermal conductivity, reaching 2.9 W/mK at 15 wt % of graphene content, which is 87% larger than the thermal conductivity of control composites with untreated graphene.