Publications

Covalent bonds mediated interfaces are generally favorable for transferring interfacial stress and hence rationalizing the mechanical properties of the filled elastomeric composites. Aiming at reprocessable yet robust elastomeric composites, in this contribution, exchangeable interfacial crosslinks are introduced into the interfaces between epoxidized natural rubber (ENR) and multi-walled carbon nanotubes (MWCNTs). This is accomplished by functionalizing MWCNTs with carboxyl groups through diazo-coupling reaction and then incorporating the modified MWCNTs into diacid-cured ENR. Accordingly, covalent β-hydroxy ester bonds result in the interfaces between ENR and MWCNTs. The formation of covalent interfaces enables much uniform dispersion of MWCNTs and stronger interfacial adhesion. Comparing to the ENR filled with pristine MWCNTs, the modified composites exhibit much improved mechanical performance. Importantly, the exchangeable nature of interfacial β-hydroxy ester bonds has promoted effect on the reprocessibility of epoxy-MWCNTs vitrimers. Overall, we envision this interfacial strategy can provide an alternative avenue towards reprocessable yet robust elastomeric composites.

Polypropylene (PP)/organo-montmorillonite (OMMT) nanocomposites were prepared by using a highly effective PP solid-phase graft as compatibilizer. As a very low amount of PP graft was used, the properties of the PP matrix were maintained. The effects of the OMMT on the structure and properties of PP were studied fully. The intercalated structure of the nanocomposites was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD and TEM results showed that a typical intercalated structure was formed in the composites. The results of mechanical properties showed that the impact strength and the modulus of the nanocomposites were improved significantly compared with those of the neat PP. The thermal stability and crystallization of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The thermal stability of the nanocomposites, characterized by the initial decomposition temperatures, was substantially improved compared with that of the neat PP. The DSC results showed that the crystallization temperature of nanocomposites was increased compared with the neat PP. The viscoelasticity of the nanocomposites was studies by dynamic mechanical thermal analysis (DMTA). The DMTA results showed that the OMMT could improve the modulus of PP substantially. The T g of PP was lowered by the incorporation of the OMMT. The changes of the properties were correlated with the formation of the PP/OMMT nanocomposites.

Naturally occurring nanotubular halloysite exhibits a number of interesting characteristics, which make it a promising candidate for fabricating polymer-based nanocomposites for engineering and functional applications. The main attractive features of halloysite include its high mechanical strength/modulus, special lumen structure, essential noncytotoxicity and ability to regulate crystallization and enhance thermal stability. In this chapter, the processing methods, interfacial modifications and multiple effects of halloysite for halloysite polymer nanocomposites are discussed. The structural benefits of halloysite and distinctions of halloysite polymer nanocomposites are also highlighted.

Electrically and thermally conductive polymer composites are extensively used in our daily life. It is of great significance to fulfill the conductivity requirement while maintaining desirable mechanical performance. An efficient solution to achieve this goal is to construct segregated structures in polymer composites by confining fillers into the interstitial areas among polymer domains. Thus far, it still remains a challenge to create segregated structures in cross-linked polymeric networks. Herein, we report a facile methodology to construct segregated structures in sulfur-cured rubbers using an industrially accessible process toward robust, flexible, highly conductive elastomer composites. Specifically, natural rubber granules (NR-RGs) with reactive di- and polysulfides on the surface are fabricated and then mixed with NR gum, carbon nanotubes (CNTs), and curing additives, followed by compression molding to yield two-phase separate composites. In the composites, CNTs are selectively dispersed in the continuous NR phase due to the volume exclusion effect caused by the separate NR-RG phase, leading to overwhelming electrical conductivity compared to the counterparts with randomly dispersed CNTs. In addition, NR-RGs can serve as novel reinforcement for NR, imparting the composites with remarkably improved modulus and retained stretchability. The simultaneously improved electrical conductivity and mechanical properties are due to the strong interfacial adhesion between the NR matrix and NR-RGs, as the di- and polysulfides on the surface of NR-RGs can participate in the cross-linking reactions of NR gum and enable the establishment of covalent bonding across the interfaces. The universality of this approach in preparing segregated composites with a combination of high conductivities and robust mechanical properties is demonstrated using other diene rubbers as the matrix and boron nitride as the filler.

It remains challenging to simultaneously realize mechanical robustness, malleability, and functionality in elastomers via facile yet efficient methods. Herein, a simple strategy for the biomimetic heterogeneous design is proposed to achieve mechanically strong, malleable, and functionalized elastomers. We demonstrate the strategy by straightforward mechanical mixing of a highly cross-linked vitrimeric elastomer with a homogeneous gum and subsequent curing, resulting in heterogeneous vitrimeric elastomers (hetero-VEs). The hetero-VEs comprise two phases: a hard phase with dense cross-links and a soft matrix with few cross-links, with excellent interface between the two phases. The hard phases can be deformed upon loading, dissipating energy, which significantly improves the overall mechanical performance of the hetero-VEs. When conductive fillers are incorporated into the soft matrix, due to the volume exclusion effect of the hard phases, the resultant hetero-VEs exhibit high conductivity with a small fraction of fillers. In view of the facile and generic preparation process, this strategy should be a promising way to reinforce and functionalize many vitrimeric elastomer systems.

The increasing demand for hydrogen peroxide (H₂O₂) necessitates greener production methods. In response, we developed an iodine-nitrogen-codoped metal-free carbon catalyst using the coordination microstructure regulation strategy, combined with rapid Joule heating for precise iodine and nitrogen doping. This approach allows precise control over the formation of active iodine-nitrogen coordination sites, significantly enhancing the catalytic performance for H₂O₂ production via the two-electron oxygen reduction reaction. Among the synthesized catalysts, I-N₄ demonstrated superior catalytic activity, achieving a high H₂O₂ selectivity of 90-96% and a production rate of 1265 mg L^-1 h^-1 at -0.4 V vs reversible hydrogen electrode. Operando Raman spectroscopy confirmed the dynamic evolution of intermediates during the reaction, while chronoamperometric tests showed long-term stability. This scalable, energy-efficient synthesis method offers significant potential for sustainable energy and environmental applications.

As a kind of bio‐derived feedstock, vegetable oil (VO) shows great potential to replace petroleum‐based monomers to develop sustainable polymer materials because of its easy availability, low cost, bio‐renewable, and environmentally friendly nature. However, due to the high cross‐linking density and amorphous nature, directly cured VOs generally tend to be brittle and weak. To date, it is still difficult to adopt VOs and their derivatives as structural materials to prepare high‐performance elastomers. To address this important issue, a multi‐scale topology design strategy was proposed in this work. First, topology regulation and functionalization of VO‐based networks were realized by managing functional groups proportion during the bulk polymerization of epoxidized soybean oil with dimer fatty acids. Furthermore, a second polymer (SN) network was introduced into the VO‐based network as a protective layer via interfacial cross‐links. The generated VO‐based elastomers (VOEs) exhibit unprecedented comprehensive properties (VO content ≥70 wt.%, T g as low as −24.4°C, toughness up to 6.8 MJ/m 3 ). Besides, the VOEs also exhibit excellent reprocessability and self‐healing capability. Overall, this work developed a novel kind of VOEs with significant comprehensive advantages and provided important inspiration for the preparation of high‐performance elastomers through multi‐scale topology regulation.

In silica-filled rubber composites, the silanization modification of silica plays a vital role in enhancing the compatibility between silica and a rubber matrix and hence the properties of the composites. In the present study, with the goal of promoting silanization reactivity and extent, we utilize a phosphonium ionic liquid (PIL) as a novel catalyst for the silanization reaction between silica and bis(3-triethoxysilylpropyl)-tetrasulfide (TESPT), a commonly used silane in the tire industry, in the styrene–butadiene rubber (SBR) matrix. Dynamic rheological measurement, bound rubber measurement, freezing point depression, and heat capacity increment together show that the addition of a small amount of PIL into a TESPT-modified SBR/silica composite gives rise to significant improvement in the interfacial adhesion between silica and the rubber matrix, which is on account of the promoted silanization extent of silica with the catalyst of PIL. Consequently, the resulting composite prepared at room temperature with fewer parts of TESPT exhibits superior overall performance in comparison with the composites prepared by adding excessive TESPT and compounding at an elevated temperature. In particular, the energy loss during rolling of the rubber wheel is drastically decreased as a result of the improved interfacial silanization, which shows great potential in energy-saving green tires.

The use of silica to partially replace carbon black is a common practice in the fabrication of “green tires.” Although some degree of consensus has been approached concerning the improved performance conferred by silica substitution, such as the improved dispersion of carbon black, a quantitative understanding of the relationship between filler networking and the performance of rubber composites has not been established. Thus, an investigation focusing on filler network structure and the correlation between the network structure and the reinforcement of rubber composites was conducted. We prepared solution-polymerized styrene–butadiene rubber (SSBR) reinforced by carbon black and carbon black/silica in different ratios. To exclude as much of the effect from changed crosslinking, and figure out how filler blending influences filler dispersion and filler network structure, the silane generally used in the tire industry was not adopted. The quantitative predictor, the mass fractal dimension df, was derived from the Kraus model and the Huber–Vilgis model. We found that when the amount of substituted silica increases, the filler cluster branching decreases, accompanied by increased reinforcement efficiency. The depressed filler networking induced by silica substitution at an appropriate proportion leads to improved dynamic properties, including lower rolling resistance and better wet skid. When the silica proportion in the filler is too high, severe filler networking is observed, resulting in decreased reinforcing efficiency and impaired dynamic properties.

Imine bond crosslinked networks with tunable mechanical and dynamic properties are prepared by varying the precursor molecular weight and network crosslinking degree.

In this work, tea polyphenols (TPs) were employed as an environmentally friendly and highly efficient reducer and stabilizer for graphene oxide (GO). The results from XPS, Raman, and conductivity studies of reduced graphene indicated the efficient deoxidization of GO. The adsorption of oxidized TPs onto graphene supplies steric hindrance among graphene sheets to keep them individually dispersed in water and some solvents. To investigate the reduction mechanism, epigallocatechin gallate (EGCG), the primary component of TPs, was used as a model. Characterization by 1H NMR and FTIR spectroscopies indicated that the gallic units in EGCG were converted to galloyl-derived orthoquinone and the flavonoid structure survived during the reduction. To further enhance the organosolubility of the resultant graphene, derivatization of the graphene was conducted by galloyl-derived orthoquinone–thiol chemistry. The successful derivatization was found to greatly improve the organosolubility of graphene in solvents with low boiling points.

Reinforcement is a fundamental issue in rubber science and engineering. Traditionally, rubber reinforcement relies on the incorporation of rigid particles into rubber network or creation of the rubber network with dual-crosslink. However, all these methods inevitably sacrifice the unique elasticity of rubber, which is a shackle toward some crucial applications such as energy-saving tires. In this contribution, a novel strategy of rubber-reinforced rubber (3R) with the combination of significant reinforcement and high elasticity is proposed. With experimental/simulating integrated method, a brand-new reinforcing mechanism for rubber is disclosed, called soft matrix-induced large extensionability of hard rubber (“SMILE-HR”). The soft matrix endows the highly-crosslinked rubber particles (HPs) with the capacity of large extensionablity, so the molecular chains in HPs can be highly oriented and thus obtain high strength during stretching, which are primarily responsible for the dramatic reinforcement of 3R. This skillful combination of these two elastic constituents conquers the stubborn contradiction between reinforcement and elasticity, which is very promising for the engineering rubbers served in dynamic environment.