Diels–Alder “click” reactions: recent applications in polymer and material science

The evolution of material design has mirrored advancements in the understanding of materials, nature, and the requirements of target applications. Originally, materials were only intended to play a passive role, but with a deepened understanding of material properties and design has come an improved ability to harness these properties to create materials with predetermined response mechanisms. This article has three aims: i) to briefly discuss the origin of and motivation for having materials that are capable of undergoing healing either extrinsically or intrinsically; ii) to present the most recent and promising advancements in the field of self-healing materials; and iii) to discuss important material design and property specifications that should be considered in order to promote the development of optimized self-healing materials. The development of self-healing materials has become of increasing interest to material scientists in the last 20 years, given the extraordinary advantages that such systems offer in a wide range of applications. The design of an optimal self-healing material depends on many factors, including material application, stability, and production cost. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Current trends in the field of self-healing materials

Inorganic nanoparticles for biomedicine: where materials scientists meet medical research

Self-healing polymer composites possess the inherent ability to heal the damage event autonomically or non-autonomically with external intervention. These advanced materials can be commercialized if the challenges and limitations of different self-healing mechanisms are well known and considered. These include capsule-based healing systems, vascular healing systems, and intrinsic healing systems. To date, most of the reviews have studied and reported on different self-healing mechanisms including their response to impact, fatigue, and corrosion tests. This review focuses mostly on extrinsic and intrinsic self-healing polymer composites which have been reported during the past five years by comparing their healing efficiency, advantages, and challenges in the prospect of their future development as well as their possible applications across various industries such as aerospace, automobile, coating, electronics, energy, etc.

Self-Healing Polymer Composites: Prospects, Challenges, and Applications

A quick recovery: A semitransparent composite conductor comprising a layer of silver nanowire percolation network inlaid in the surface layer of a Diels-Alder-based healable polymer film is fabricated. The composite is flexible and highly conductive, and is capable of both structural and electrical healing via heating. Cut samples that completely lose their conductivity can recover 97% of it within 5 minutes of heating at 110 °C. The cutting and healing can be repeated at the same location for multiple cycles.

A Healable, Semitransparent Silver Nanowire‐Polymer Composite Conductor

Carbon fiber reinforced polymer (CFRP) laminates with remendable cross-linked polymeric matrices were fabricated using a modified resin transfer mold (RTM) technique. The healable composite resin, bis-maleimide tetrafuran (2MEP4F), was synthesized by mixing two monomers, furan (4F) and maleimide (2MEP), at elevated temperatures. The fast kinetic rate of the reaction of polymer constituents requires a fast injection of the healable resin into the carbon fiber preform. The polymer viscosity as a function of time and temperature was experimentally quantified in order to optimize the fabrication of the composite material and to guarantee a uniform flow of the resin through the reinforcement. The method was validated by characterizing the thermo-mechanical properties of the polymerized 2MEP4F. Additionally, the thermo-mechanical properties of the remendable CFRP material were studied.

Development and Characterization of Healable Carbon Fiber Composites with a Reversibly Cross Linked Polymer

Embodiments of the present invention relate to a metastable silver nanoparticle composite, a process for its manufacture, and its use as a source for silver ions. In various embodiments, the composite comprises, consists essentially of, or consists of metastable silver nanoparticles that change shape when exposed to moisture, a stability modulant that controls the rate of the shape change, and a substrate to support the silver nanoparticles and the modulant.

Metastable silver nanoparticle composites

The prostate-specific membrane antigen (PSMA) is an established target for the delivery of cancer therapeutic and imaging agents due to its high expression on the surface of prostate cancer cells and within the neovasculature of other solid tumors. Here, we describe the synthesis and screening of antibody-conjugated silica-coated iron oxide nanoparticles for PSMA-specific cell targeting. The humanized anti-PSMA antibody, HuJ591, was conjugated to a series of nanoparticles with varying densities of polyethylene glycol and primary amine groups. Customized assays utilizing iron spectral absorbance and enzyme-linked immunoassay (ELISA) were developed to screen microgram quantities of nanoparticle formulations for immunoreactivity and cell targeting ability. Antibody and PSMA-specific targeting of the optimized nanoparticle was evaluated using an isogenic PSMA-positive and PSMA-negative cell line pair. Specific nanoparticle targeting was confirmed by iron quantification with inductively coupled plasma mass spectrometry (ICP-MS). These methods and nanoparticles support the promise of targeted theranostic agents for future treatment of prostate and other cancers.

Development and screening of a series of antibody-conjugated and silica-coated iron oxide nanoparticles for targeting the prostate-specific membrane antigen.

Embodiments of the present invention relate to a metastable silver nanoparticle composite, a process for its manufacture, and its use as a source for silver ions and/or colorimetric signaling. In various embodiments, the composite comprises, consists essentially of, or consists of metastable silver nanoparticles that change shape when exposed to moisture, a stability modulant that controls the rate of the shape change, and a substrate to support the silver nanoparticles and the modulant.

Metastable silver nanoparticle composites with color indicating properties

The addition of metal nanoparticles to coolants used in thermal control systems can dramatically increase the thermal conductivity of the base fluid. Such metal nanoparticle-fluid composite materials are referred to as nanofluids and their use as coolants has the potential to reduce the weight and power requirements of spacecraft thermal control systems. The thermal conductivity of nanofluids is dependent on the concentration, size, shape, surface chemistry, and aggregation state of the constituent nanoparticles. The effects of nanoparticle loading concentration and the aspect ratio of the nanoparticles on the thermal conductivity and viscosity of water and ethylene glycol based coolants were investigated. Silver nanorods with a diameter of 55 ± 12 nm and an average length of 12.8 ± 8.5 μm at a concentration of 0.5% by volume increased the thermal conductivity of water by 68%. The thermal conductivity of an ethylene glycol based coolant was increased by 98% with a silver nanorod loading concentration of 0.5% by volume. Longer nanorods had a greater effect on the thermal conductivity than shorter nanorods at the same loading density. However, longer nanorods also increased the viscosity of the base fluid to a greater extent than shorter nanorods.

Richard K. Baldwin

Papers

Development and Characterization of Healable Carbon Fiber Composites with a Reversibly Cross Linked Polymer

Metastable silver nanoparticle composites

Development and screening of a series of antibody-conjugated and silica-coated iron oxide nanoparticles for targeting the prostate-specific membrane antigen.

Metastable silver nanoparticle composites with color indicating properties

Optimized Nanofluid Coolants for Spacecraft Thermal Control Systems