Chengsha Wei,Mingming Chen,Jiaojiao Tao,Xibo Wu,Majid Khan,Dong Liu,Ningdong Huang,Liangbin Li
In this paper, we described a new and simple method to produce degradable core cross-linking (CCL) micellar clusters that utilized CdS nanorods to assist thermal oxidation of the polythiol segment of a diblock copolymer, polystyrene-b-polythiol (PS-b-polythiol), at high concentration (2.3 wt%) in a common organic solvent (toluene). The CdS nanorods acted not only as catalysts, but also as templates. The diblock copolymer, PS-b-polythiol, was obtained by aminolysis of polystyrene-b-poly(2-(ethyl-xanthate)ethylmethacrylate) (PS-b-P1), a block copolymer synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization using a macroRAFT transfer agent, PS-CTA, and a methacrylate monomer that possessed a protected thiol group, in the presence of n-butylamine and tributyl phosphine. The CdS nanorods were synthesized conveniently by thermolysis of an alkyl xanthate, Cd-HDX. The TEM image clearly showed the formation of micellar clusters and the oxidation procedure was investigated by 1H-NMR and XPS. The formation of core cross-linking (CCL) micelles was confirmed to be reversible by reduction utilizing DTT as the reducing agent.
Small molecule inhibitors only form thin films that are composed of a single molecule layer or multiple molecule layers. Polymer inhibitors also cannot form thick or stable films due to the lack of crosslinking. Thus, these inhibitors are unable to provide robust protection for copper against corrosion. Inspired by the “skinning” phenomenon that is often met during the use of polythiol curing agents, we developed a novel and facile strategy that involves the skinning of polythiols on copper to form super thick protective films. Three types of polythiols, named SPT, TPT and LTPT, were prepared via thiol-click chemistry. Upon immersing bare copper into the solutions of the polythiols, Cu–S bonds immediately form to anchor the polythiol chains firmly on the copper surface, and the following Cu2+ catalysed S–S bond formation reaction leads to crosslinking and film formation. For SPT, TPT and LTPT, the film thicknesses were 2.03, 1.16 and 2.88 μm, and a very high inhibition efficiency of 99.81%, 99.96% and 99.68%, respectively, was achieved in 60 min. Neutral salt spray experiments demonstrated that the polythiol films provide excellent protection for over one week, whereas the control copper samples employing benzotriazole and 1-dodecanethiol suffered from severe corrosion in only 4 h. SPT and TPT have a storage problem due to their instability in air, but this problem was solved by using stable LTPT containing latent thiol groups.
Jin Han,Cheng Chen,Qingquan Xue,Yaochen Zheng,Shu Tian,Zhixiong Liu,Jieze Shen,Mingqiang Zhong
A catalyst-free and thermal-induced S→O acetyl migration (SOAM) reaction was occasionally found and used to fabricate the polythiol corrosion inhibitor . The route to prepare the polythiols was free of catalyst and side products. Only intramolecular migration process existed, while intermolecular migration was not found. Temperature-dependent 1 H NMR experiment showed the conversion rate of the SOAM reaction was 83% at 160 °C. Further heating at higher temperature or for longer reaction time, the conversion rate did not increase. It was speculated that there was equilibrium between two reversible migrations. The prepared polythiol inhibitor contains a large amount of latent thiol groups after the SOAM reaction process. The strong Cu S bonds immediately formed and made the polythiol chains firmly anchored on the copper surface when the copper metal was coated with the polythiols. Also S S bond formation reaction leads to dense crosslinking and film formation. Raman spectrum and SEM were used to characterized the protective film. A smooth and defect-free film with thickness of 1.9 μm was achieved when the copper sample was immersed in the polythiol solution for 60 min. The corrosion performance of the film is obtained by potential and impedance measurements and Tafel curves by immersing in a 3.5 wt% NaCl solution. All of the coated samples exhibited significantly lower corrosion rates than the bare copper sample, and the corrosion rate decreased as the immersion time increased. The inhibtion efficiency of the polythiol inhibitor was up to 99.3%. Neutral salt spray experiments indicated that the polythiol films provided excellent protection for over one week. The polythiols were also very stable in storage and have application in designing various polyacrylate polythiols resins.
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