Hyperbranched Organosilicon Polymer-Based Transparent Hybrid Antifouling Coating with Active–Passive Synergistic Antibacterial Action

Abstract

Polydimethylsiloxane (PDMS)-based fouling-release coatings perform poorly in static conditions due to their lack of antifouling mechanisms like biocidal activity or surface repellence. The high melt viscosity, limited chain-end functional groups, and lack of intermolecular interactions of linear PDMS chains lead to challenges such as impaired processability, reduced adhesion to substrates, and diminished toughness and tear resistance. To overcome these drawbacks, this study strategically integrates hyperbranched polymers with relatively long branches and rigid adamantane skeletons into a hybrid network via a sol–gel process, successfully developing a series of synergistic amphiphilic silicone composite coatings (x-HSiN+-Ad) that combine both flexible and rigid characteristics. The material synthesis involves co-hydrolysis condensation of hyperbranched prepolymers rich in polyethylene glycol (PEG) and quaternary ammonium salt (QAS) groups (HSiN+), isocyanate-modified adamantane monomers, and silane coupling agents, followed by secondary crosslinking through the introduction of polyether amine (PEA). Experimental results show that the coatings exhibit an extremely low surface free energy of 29.34 mJ·m–2 and high transparency (>90%), along with substantially improved mechanical properties. This performance enhancement is attributed to the synergistic strain energy dissipation effect arising from the flexible buffering and energy dissipation of the hyperbranched silicone and PEG soft segments, combined with the rigid reinforcement of the adamantane hard segments. Consequently, the optimized coating achieves a hardness of 68 MPa, an elastic modulus of 1.63 GPa, and a substrate adhesion strength as high as 2.97 MPa, while also demonstrating excellent bending fatigue resistance. Furthermore, the coating surface provides multiple action mechanisms, including contact inhibition and hydration barrier formation, which significantly enhance resistance against static bacterial colonization: bacterial anti-adhesion rates reach 94.9% against Pseudomonas aeruginosa, 96.4% against Escherichia coli, and 92.5% against Staphylococcus aureus. After 14 days of static immersion, the Chlorella attachment on the coating remains at an extremely low level of 0.20%; in a 60-day marine field test, the coating exhibits outstanding antifouling performance with negligible fouling adhesion. Zone of inhibition tests further confirm that the material belongs to the category of structurally non-leaching antibacterial materials. This study elucidates how topological network regulation synergistically enhances the mechanical strength of silicone coatings and constructs interfacial amphiphilicity, providing an innovative design strategy for developing durable and environmentally friendly marine antifouling materials.