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Chen, Qi'an, Zhanping Zhang, and Yuhong Qi. International Journal of Adhesion and Adhesives 128 (2024): 103532.
Bismuth neodecanoate (BiND) has emerged as an effective curing agent to optimize the interfacial adhesion between epoxy primers and silicone-based antifouling top-coatings, addressing a critical challenge in marine coating systems. Recent studies investigated the influence of BiND content on the curing kinetics, mechanical properties, surface morphology, and interlayer bonding performance of tie-coatings.
Tie-coatings with low or excessive BiND content exhibited prolonged curing times, insufficient for practical marine applications. Optimized BiND incorporation at 1 wt % achieved superior interlayer adhesion, balancing elongation, modulus, and hardness. Specifically, cross-linking density measurements revealed that increasing BiND led to higher molecular weight between cross-links (Mc) and lower network density (Ve), indicating a looser 3D network structure that enhances flexibility without compromising bonding integrity. Contact angle analysis with water and diiodomethane confirmed the influence of surface energy and roughness on adhesion performance.
Mechanically, BiND-modified tie-coatings demonstrated improved elongation and tensile strength at the optimal concentration, providing a robust interface with epoxy primers while maintaining compatibility with silicone top-coatings. The study highlights that careful tuning of BiND content is crucial: under-curing reduces application efficiency, while over-curing diminishes modulus and cross-link density, leading to weaker adhesion.
This case demonstrates BiND's multifunctional role as both a curing catalyst and performance modulator in marine coatings. By fine-tuning BiND concentration, durable, high-adhesion tie-coatings can be achieved, extending the service life of antifouling systems and providing a practical approach for advanced marine coating design.
Jansen, J. H., Mathews, D., Marrione, A., Roman-Matias, J., Al Abdulghani, A., Powell, A. B., ... & Hermans, I. (2024). ACS Sustainable Chemistry & Engineering, 12(26), 9612-9619.
Bismuth neodecanoate (BiNeo) has been demonstrated as a highly effective co-catalyst for polyesterification reactions, particularly when combined with titanium tetrabutoxide (TBT), offering a non-toxic alternative to traditional tin-based systems. In industrial polyester synthesis, TBT is highly reactive but suffers from hydrolytic instability, limiting its large-scale application. Prior attempts to improve stability involved mixing TBT with stannous octoate (SnOct), yet concerns over tin toxicity hindered long-term viability.
Recent studies reveal that BiNeo, when mixed with TBT in a 2:1 molar ratio, enhances both catalytic reactivity and hydrolytic stability under industrially relevant conditions. This synergistic interaction maintains the inherent catalytic activity of TBT while significantly increasing turnover numbers, suggesting that BiNeo stabilizes the reactive titanium species against moisture-induced deactivation. The resulting TBT/BiNeo catalyst mixture exhibits comparable polyesterification efficiency to monometallic TBT systems, with the added advantage of being environmentally benign.
Mechanistic investigations suggest that BiNeo interacts with the titanium center, reducing hydrolysis of the alkoxide groups while promoting esterification kinetics. This combination allows continuous high-yield polyester production without the need for toxic tin-based catalysts. The approach is particularly suitable for scalable industrial applications, where moisture sensitivity and environmental compliance are critical factors.
This case highlights BiNeo's multifunctional role as both a stabilizer and co-catalyst in polyester synthesis, providing a practical, eco-friendly strategy for improving catalyst performance while maintaining high reaction efficiency and operational safety.
Levent, Emre, et al. Green Chemistry 23.7 (2021): 2747-2755.
Bismuth neodecanoate (BiNeo) serves as a benchmark carboxylate in polyurethane (PU) synthesis due to its superior catalytic performance, stability, and solubility in both polar and nonpolar solvents. Its preparation via salt metathesis is often complicated by variable bismuth coordination numbers, which can lead to salt contamination; however, alternative methods employing BiPh₃ and stoichiometric carboxylic acids at 110 °C for extended heating times afford pure bismuth carboxylates in quantitative yield. Monitoring via ¹H NMR confirms complete conversion, indicated by benzene formation and disappearance of BiPh₃ signals.
Structurally, bismuth carboxylates, including BiNeo analogues, adopt high coordination geometries, typically nine-coordinate, with chelating and bridging (μ², μ³) binding modes that promote polymeric assemblies. Smaller carboxylate ligands tend to form extended polymeric frameworks, whereas sterically bulky ligands, such as neodecanoate, favor discrete oligomeric species. For example, the steric bulk of BiNeo likely supports tetrameric or dimeric motifs in the solid state, enhancing solubility and processability in organic media. X-ray diffraction studies of analogous bulky carboxylates, such as 2-phenylisobutyrate complexes, reveal dimeric assemblies bridged by tridentate ligands, forming Bi₂O₂ four-membered rings with long Bi-O bonds, suggesting similar structural stabilization for BiNeo.
These structural characteristics underpin BiNeo's effectiveness as a PU catalyst: its solubility, steric protection, and polymeric tendency facilitate uniform catalytic distribution, improved reactivity, and reduced aggregation. This makes BiNeo a highly versatile and environmentally benign additive for industrial-scale PU applications, combining high catalytic performance with favorable solid-state properties.
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