Protein‐metal interactions—traditionally regarded for roles in metabolic processes—are now known to enhance the performance of certain biogenic materials, influencing properties such as hardness, toughness, adhesion, and self‐healing. Design principles elucidated through thorough study of such materials are yielding vital insights for the design of biomimetic metallopolymers with industrial and biomedical applications. Recent advances in the understanding of the biological structure–function relationships are highlighted here with a specific focus on materials such as arthropod biting parts, mussel byssal threads, and sandcastle worm cement. 相似文献
Designing the reversible interactions of biopolymers remains a grand challenge for an integral mimicry of mechanically superior biological composites. Yet, they are the key to synergistic combinations of stiffness and toughness by providing sacrificial bonds with hidden length scales. To address this challenge, dynamic polymers were designed with low glass‐transition temperature Tg and bonded by quadruple hydrogen‐bonding motifs, and subsequently assembled with high‐aspect‐ratio synthetic nanoclays to generate nacre‐mimetic films. The high dynamics and self‐healing of the polymers render transparent films with a near‐perfectly aligned structure. Varying the polymer composition allows molecular control over the mechanical properties up to very stiff and very strong films (E≈45 GPa, σUTS≈270 MPa). Stable crack propagation and multiple toughening mechanisms occur in situations of balanced dynamics, enabling synergistic combinations of stiffness and toughness. Excellent gas barrier properties complement the multifunctional property profile. 相似文献
It is a significant but challenging task to simultaneously reinforce and functionalize diene rubbers. Inspired by “sacrificial bonds”, the authors engineer sacrificial hydrogen bonds formed by pendent urazole groups in crosslinked solution‐polymerized styrene butadiene rubber (SSBR) via triazolinedione click chemistry. This post‐crosslinking modification reveals the effects of the sacrificial bonds based on a consistent covalent network. The “cage effect” of the pre‐crosslinked network facilitates the heterogeneous distribution of urazole groups, leading to the formation of hydrogen‐bonded multiplets. These multiplets further aggregate into clusters with vicinal trapped polymer segments that form microphase separation from the SSBR matrix with a low content of urazole groups. The clusters based on hydrogen bonds, serving as sacrificial bonds, promote energy dissipation, significantly improving the mechanical properties of the modified SSBR, and enable an additional wide transition temperature region above room temperature, which endows the modified SSBR with promising triple‐shape memory behavior.
Electrically conductive adhesive (ECA) is an alternative for the toxic lead-based solders. However, unstable electrical conductivity
has long been a haunting problem. Galvanic corrosion at the ECA/pad interface has recently been found to be the major mechanism
for this decay. Applying a more active metal or alloy on a dissimilar metal couple in contact can prohibit galvanic corrosion.
In this study, powders of aluminum, magnesium, zinc, and two aluminum alloys were added in an ECA and applied on five pad
surfaces. The aging of the bulk resistivity and contact resistance of the ECA/metal surface pairs were studied. The two alloys
significantly suppressed the increase of the contact resistance on all tested metal surfaces. 相似文献
The effects of solvent cleaning, hydrogen etching, and additional oxidation treatment of 4H-SiC off-axis surfaces were investigated.
The morphology of the resulting surfaces was observed by atomic force microscopy (AFM), and the chemical composition was studied
by x-ray photoelectron spectroscopy (XPS). It is confirmed that simple cleaning and hydrofluoric acid (HF) etching procedures
do not yield smooth surfaces, although the surfaces show mainly SiC-like bonds. High-temperature hydrogen etching can effectively
remove polishing scratches, leading to a very smooth morphology, but it leaves some residual graphitic-bound carbon behind.
It is shown that a subsequent oxidation step not only removes residual graphite on the hydrogen-etched surface but also produces
the same chemical composition on all treated surfaces. 相似文献
In pursuit of inexpensive and earth abundant photocatalysts for solar hydrogen production from water, conjugated polymers have shown potential to be a viable alternative to widely used inorganic counterparts. The photocatalytic performance of polymeric photocatalysts, however, is very poor in comparison to that of inorganic photocatalysts. Most of the organic photocatalysts are active in hydrogen production only when a sacrificial electron donor (SED) is added into the solution, and their high performances often rely on presence of noble metal co‐catalyst (e.g. Pt). For pursuing a carbon neutral and cost‐effective green hydrogen production, unassisted hydrogen production solely from water is one of the critical requirements to translate a mere bench‐top research interest into the real world applications. Although this is a generic problem for both inorganic and organic types of photocatalysts, organic photocatalysts are mostly investigated in the half‐reaction, and have so far shown limited success in hydrogen production from overall water‐splitting. To make progress, this article exclusively discusses critical factors that are limiting the overall water‐splitting in organic photocatalysts. Additionally, we also have extended the discussion to issues related to stability, accurate reporting of the hydrogen production as well as challenges to be resolved to reach 10 % STH (solar‐to‐hydrogen) conversion efficiency. 相似文献
