Borate driven heterogeneous networks for porous elastomers with improved tribological and mechanical performances

Article https://doi.org/10.1038/s41467-025-66156-2 Borate driven heterogeneous networks for porous elastomers with improved tribological and mechanical performances Yuhao Wu 1, Liguo Qin 1 , Zeyu Ma 1, Mingqing Sun1, Zheng Wang1, Shan Lu1, Xiaodong Huang1, Wentao Xia1, Hao Yang1, Jianbo Liu1, Ke Yan1, Xin Ge2 , Sen Yang 3 & Guangneng Dong1 Received: 24 July 2024 Check for updates 1234567890():,; 1234567890():,; Accepted: 31 October 2025 Porous polydimethylsiloxane (PDMS) elastomers produced using conventional phase separation methods often suffer from limited tribological and mechanical properties. In this study, we present a general approach for the fabrication of porous elastomers with borate-driven heterogeneous networks, which leverage the borate at the two-phase boundary to stabilize the phases, without the need for additives such as surfactants. Pure porous elastomers are created by removing the alcoholysis phases, with precisely controllable pore structure and mechanical performance. Interestingly, under saltwater lubrication, an atypical corrosion–lubrication phenomenon occurs on the porous elastomers, reducing the friction coefficient and wear rate by over 95 and 90%, respectively. Additionally, unique mechanical advantages, such as 1250% of stretch, were predictively imparted to the elastomers by various boric acid functional groups. Our method is generally applicable to various PDMS systems and offers a novel approach for designing pure porous materials for water-lubricated components and flexible sensors. Double emulsions are formed via a phase separation, when two types of oils are sheared in specific proportions1. For example, beef soup exhibits oil-in-water phase separation between oil and water. Phase separation represents the transition from disorder to order in heterogeneous systems. To minimize free energy, colloids transform into two or more coexisting phases to achieve equilibrium2. The phase separation equilibrium is influenced by factors such as polymer–substrate interactions3, temperature4,pressure5,6, and composition ratio7,8. In a system with a constant amount of two substances a and b, the changes in the Gibbs free energies (Ga and Gb) per mole are described as follows9:  ∂Ga ∂T   dT + P ∂Ga ∂P   dP = T ∂Gb ∂T   dT + P ∂Gb ∂P  dP T ð1Þ where T and P represent the temperature and pressure of the system, respectively. By varying T, P, and the starting point of phase separation of components a and b, a controlled phase separation can be achieved. This principle also allows for the regulation of the liquid–liquid phase separation in polymer networks. In colloid systems, phase separation and polymerization typically occur simultaneously, enabling the control of the network structures of the polymer via adjustments in temperature, pressure, and the polymer ratio. For centuries, corrosion has been regarded as one of the factors that exacerbate friction and wear. However, metal friction components, such as bearings, blades, and axes, have to be used in a corrosive environment10,11. Friction can destroy the passivation film on the metal surface and promote corrosion12. To avoid metal corrosion, nonmetallic materials such as poly(ether-ether-ketone), epoxy resin, 1 Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Institute of Design Science and Basic Components, School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an, PR China. 2Department of Materials-Oriented Chemical Engineering, School of Chemical Engineering, Fuzhou University, Fuzhou, PR China. 3School of Physics, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi’an Jiaotong e-mail: ; ; University, Xi’an, PR China. Nature Communications | (2025)16:11183 1 Article https://doi.org/10.1038/s41467-025-66156-2 carbon composites, and polydimethylsiloxane (PDMS) have been used to replace metal in moving parts13,14. PDMS elastomers are critical base materials used in applications such as sensing15–18, anti-icing19–21, antifouling22,23, and anti-wear24. Hydrophobic PDMS has a coefficient of friction (COF) of 0.8–1.2 when used with water-based lubricants, and the high COF limits the use of PDMS25. Porous PDMS can reduce wear because their pores can capture the wear debris, thus reducing wear. However, conventional methods for preparing porous elastomers, including emulsion templates26,27, chemical foaming28, and particle template methods29, often face challenges in process control and compromise the frictional and mechanical performance of elastomers because of the numerous defects and impurities from surfactants and particle templates. An alternative approach involves fabricating porous elastomers using interpenetrating polymer networks (IPNs) by selectively degrading non-crosslinked subchains or extracting them from semi-IPNs or IPN precursors30–32. Existing studies on this method are limited and predominantly focus on composition ratio adjustments for pore structure control, ignoring the influence of pressure and temperature33,34. In addition to the PDMS network, another network in PDMS IPNs, such as poly(methyl methacrylate)33,35, has significantly distinct chemical characteristics compared to those of PDMS, which may result in a significant decrease in the mechanical properties of the elastomer when removed. Therefore, limited research has been conducted on the use of this method to regulate the mechanical properties. However, manipulating the degree of phase separation, fabricating highly pure porous polymer elastomers, and regulating their tribological and mechanical properties are theoretically feasible1,34–38. Heterogeneous-network PDMS This study presents a method for preparing heterogeneousnetwork porous PDMS (HNP-PDMS) elastomers, as shown in Fig. 1A. (For all abbreviations and their expansions, see Supplementary Table 1). Two networks were used: the first network consisted of D-PDMS with hydroxyl-terminated PDMS and boric acid (BA)39–41, whereas the second network was derived from Sylgard 184 PDMS components (vinyl-terminated PDMS, silica-hydrogen bonded PDMS, platinum catalyst42, and S-PDMS). The two networks, featuring similar main-chain properties, were driven by borate to achieve the heterogeneous phase separation. Prior to curing, the liquid mixture of Sylgard 184A + Sylgard 184B and dynamically crosslinked PDMS (S- and D-PDMS) was stirred to form multiple emulsions without any surfactants or solvents. Borates were incorporated into the PDMS network to stabilize the phase separation boundary to prepare the HNP-PDMS elastomers. HNPPDMS@ boric acid (BA) could spontaneously form the corrosioninduced self-lubrication effect in saltwater (3.5% of NaCl solution), changing the lubrication state from boundary lubrication to mixed lubrication (Fig. 1B, C). The COF and wear rate were as low as approximately 0.05 and 2.72 × 10−5 mm/N m, respectively. Mechanical performance advantages coul (...truncated)