Amphiphilic block and random copolymers: aggregation and hydrophobic modification on metal-free tanned collagen fibers

Hydrophobicity enhancement of metal-free leather, which is crucial for improving its comprehensive performance, can be achieved by using amphiphilic copolymer retanning agents. However, the relationship between the sequential structure and the hydrophobic modification effect of amphiphilic copolymers remains unclear. Herein, an amphiphilic block copolymer was synthesized using stearyl methacrylate and 2-(dimethylamino)ethyl methacrylate via atom transfer radical polymerization, and the corresponding random copolymer with similar monomer compositions and molecular weights was prepared for comparison. The aggregation behavior of block and random copolymers was investigated. DLS and TEM results indicate that the block copolymer exhibits a larger aggregate size than the corresponding random copolymer. Molecular dynamics simulations suggest that the block copolymer aggregate exhibit a thicker hydrophilic shell and more concentrated distribution of cationic DMA block than the random copolymer aggregate. Subsequently, the block and random copolymers were used for the hydrophobic modification of metal-free tanned collagen fibers (CFs). The block copolymer shows superior binding capacity to CFs than the random one because of its larger size and more concentrated charge distribution. Hence, the block copolymer can form a dense and uniform hydrophobic film on the surface of collagen fibrils and endow CFs with higher hydrophobicity than the random one. This work provides theoretical guidance for modulating the hydrophobicity of CFs by tailoring the sequential structure of amphiphilic copolymers, which is expected to inspire the manufacturing of high-performance metal-free leather.

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