Adhesion Energy-Assisted Low Contact Thermal Resistance Epoxy Resin-Based Composite.

Although intense efforts have been devoted to the development of thermally conductive epoxy resin composites, most previous works ignore the importance of the contact thermal resistance between epoxy resin composites and mating surfaces. Here, we report on epoxy resin/hexagonal boron nitride (h-BN) composites, which show low contact thermal resistance with the contacting surface by tuning adhesion energy. We found that adhesion energy increases with increasing the ratio of soybean-based epoxy resin/amino silicone oil and h-BN contents. The adhesion energy has a negative correlation with the contact thermal resistance; that is, enhancing the adhesion energy will lead to reduced contact thermal resistance. The contact thermal conductance increases with the h-BN contents and is low to 0.025 mm2·K/W for the epoxy resin/60 wt % h-BN composites, which is consistent with the theoretically calculated value. By investigating the wettability and chain dynamics of the epoxy resin/h-BN composites, we confirm that the low contact thermal resistance stems from the increased intermolecular interaction between the epoxy resin chains. The present study provides a practical approach for the development of epoxy resin composites with enhanced thermal conductivity and reduced contact thermal resistance, aiming for effective thermal management of electronics.

Self-Healing, High-Strength, and Antimicrobial Polysiloxane Based on Amino Acid Hydrogen Bond.

Recent years have witnessed the rapid development of self-healing and recyclable materials because they can extend the life of the material. For polysiloxane materials, exploring polysiloxanes with high-strength and self-healing properties remains a challenge. In this work, a high-strength and self-healing polysiloxane containing N-acetyl-L-cysteine (NACL) side groups is prepared. The NACL is used to form strong hydrogen bonds to build a self-healing network. Molecular simulations help explain the reasons and processes for the repair of modified polysiloxanes. On the one hand, the obtained modified polysiloxanes have good self-healing properties. The self-healing efficiency of modified polysiloxane can reach 96.9%. As the number of NACL increases, the tensile strength of the modified polysiloxane increases. For PMVS-30%NACL, the tensile strength can reach 4.36 MPa, and the strain can reach 586%. On the other hand, modified polysiloxane has an apparent inhibitory effect on Staphylococcus aureus. With the increase in the number of NACL, the antibacterial effect of modified polysiloxane is more obvious. Furthermore, NACL is a bio-based amino acid with excellent biocompatibility. This work expands the idea of designing and synthesizing high-strength polysiloxanes with antibacterial properties. It has great potential in the field of polysiloxane antimicrobial coatings.

A low-shrinkage dental composite with epoxy-polyhedral oligomeric silsesquioxane.

Polymerization shrinkage and mechanical properties affect the service life of dental restorative composites. Polyhedral oligomeric silsesquioxanes (POSS) can be an efficient strategy to improve the shrinkage properties and mechanical properties simultaneously. In this work, epoxycyclohexyl POSS (E-POSS) was used to modify the Bis-GMA/TEGDMA dental resins. E-POSS were introduced into the acrylic resin system via ring-opening reaction, and a cationic/free radical hybrid system was obtained. Double bond conversion, glass transition temperature, heterogeneity, crosslink density of dental resins and volumetric shrinkage, water sorption/solubility, flexural strength/modulus of dental composites were investigated. As the introduction of E-POSS caused higher double bond conversion and lower crosslink density, the polymerization shrinkage was significantly reduced to 2.91% (p < 0.05) and the flexural strength increased to 117.19 MPa (p < 0.05) compared to the control sample (5.06%, 99.16 MPa, p<0.05). Lower water sorption and solubility were also observed in composites contained E-POSS (p < 0.05).

Facile Fabrication of Flexible, Robust, and Superhydrophobic Hybrid Aerogel.

Silica aerogels, which are constructed with silica nanoparticles and numerous nanoscale pores, have many outstanding attributes, but they are usually brittle and hydrophilic. For the construction of a robust aerogel, the novel polyhedral oligomeric silsesquioxane (POSS) was introduced to prepare a series of aerogels possessing particles covered with elastic cushion to improve the mechanical property. The multialkoxy POSS, which possessed stiff Si-O-Si nanocages and flexible alkyl chains, was synthesized via thiol-ene click chemistry. After a facile and efficient approach, a partially ordered structure of SiO2 nanoparticles and organic elastic cushion would form spontaneously within the aerogels. With the POSS as the only precursor, several outstanding attributes were achieved in a single aerogel such as high specific surface area (SSA), high compression strength, high compression modulus, and noticeable compression flexibility. Meanwhile, the aerogel was superhydrophobic of which the contact angle (CA) was higher than 153°. Moreover, the potential application of oil-water separation is also presented.