High-Performance Dopamine-Based Supramolecular Bio-Adhesives.

The need for wound closure or surgical procedures has been commonly met by the application of sutures. Unfortunately, these are often invasive or subject to contamination. Alternative solutions are offered by surgical adhesives that can be applied and set without major disruption; a new class of supramolecular-based adhesives provides potential solutions to some of these challenges. In this study, a series of polymers utilizing dopamine as a self-assembling unit are synthesized. It is found that these motifs act as extremely effective adhesives, with control over the mechanical strength of the adhesion and materials' tensile properties enabled by changing monomer feed ratios and levels of cross-linking. These materials significantly outperform commercially available bio-adhesives, showing yield strengths after adhesion at least two times higher than that of BioGlue and Tisseel, as well as the ability to re-adhere with significant recovery of adhesion strength. Promisingly, the materials are shown to be non-cytotoxic, with cell viability > 90%, and able to perform in aqueous environments without significant loss in strength. Finally, the removal of the materials, is possible using benign organic solvents such as ethanol. These properties all demonstrate the effectiveness of the materials as potential bio-adhesives, with potential advantages for use in surgery.

Conjugated Microporous Polymers for Catalytic CO2 Conversion.

Rising carbon dioxide (CO2) levels in the atmosphere are recognized as a threat to atmospheric stability and life. Although this greenhouse gas is being produced on a large scale, there are solutions to reduction and indeed utilization of the gas. Many of these solutions involve costly or unstable technologies, such as air-sensitive metal-organic frameworks (MOFs) for CO2 capture or "non-green" systems such as amine scrubbing. Conjugated microporous polymers (CMPs) represent a simpler, cheaper, and greener solution to CO2 capture and utilization. They are often easy to synthesize at scale (a one pot reaction in many cases), chemically and thermally stable (especially in comparison with their MOF and covalent organic framework (COF) counterparts, owing to their amorphous nature), and, as a result, cheap to manufacture. Furthermore, their large surface areas, tunable porous frameworks and chemical structures mean they are reported as highly efficient CO2 capture motifs. In addition, they provide a dual pathway to utilize captured CO2 via chemical conversion or electrochemical reduction into industrially valuable products. Recent studies show that all these attractive properties can be realized in metal-free CMPs, presenting a truly green option. The promising results in these two fields of CMP applications are reviewed and explored here.

Chemically Driven Oscillating Soft Pneumatic Actuation.

Pneumatic actuators are widely studied in soft robotics as they are facile, low cost, scalable, and robust and exhibit compliance similar to many systems found in nature. The challenge is to harness high energy density chemical and biochemical reactions that can generate sufficient pneumatic pressure to actuate soft systems in a controlled and ecologically compatible manner. This investigation evaluates the potential of chemical reactions as both positive and negative pressure sources for use in soft robotic pneumatic actuators. Considering the pneumatic actuation demands, the chemical mechanisms of the pressure sources, and the safety of the system, several gas evolution/consumption reactions are evaluated and compared. Furthermore, the novel coupling of both gas evolution and gas consumption reactions is discussed and evaluated for the design of oscillating systems, driven by the complementary evolution and consumption of carbon dioxide. Control over the speed of gas generation and consumption is achieved by adjusting the initial ratios of feed materials. Coupling the appropriate reactions with pneumatic soft-matter actuators has delivered autonomous cyclic actuation. The reversibility of these systems is demonstrated in a range of displacement experiments, and practical application is shown through a soft gripper that can move, pick up, and let go of objects. Our approach presents a significant step toward more autonomous, versatile soft robots driven by chemo-pneumatic actuators.

Selective CO2 Electroreduction from Tuneable Naphthalene-Based Porous Polyimide Networks.

A series of porous polyimides (pPIs) are synthesized, and their surface areas and pore sizes are optimized by the previously reported Bristol-X'an-Jiatong (BXJ) approach. How this approach can be used to tune and optimize the porous network properties to target and tune their ability to capture CO2 is demonstrated. Once optimized, these porous organic frameworks are utilized, for the first time, as electrocatalysts for the conversion of CO2 . The excellent Faradaic efficiencies (FEs) for the conversion of CO2 to formate (91%) and methanol (85%) present exciting opportunities for the metal-free generation of useful fuels and feedstocks from CO2 . In addition, the ability to directly address and select the conversion products through tuning of the porous materials' properties highlights the potential of this approach, and more generally for a wide range of organic frameworks as future metal-free CO2 reduction catalysts.

Controlled Removal of Organic Dyes from Aqueous Systems Using Porous Cross-Linked Conjugated Polyanilines.

Porous organic materials, as a broad class of functional materials, offer a promising route for low-cost purification of contaminated wastewaters. We have synthesized a range of highly cross-linked conjugated porous polyanilines and optimized their porosity and water dispersibility by tuning reactant feed ratios, previously unreported in the synthesis of such networks. To demonstrate their ability to adsorb model dyes used in the textile industry, we exposed the networks to a range of cationic aromatic dyes, leading to absorption capacities of >100 mg/g, reported for the first time with respect to polyaniline networks. The versatility of the networks was further demonstrated by the preparation of gel composites, producing active gels for efficient and facile removal and recycling, ideal for real-world applications. Finally, chemical modifications of the networks were undertaken to target the removal of model anionic organic dye pollutants, showing the wide applicability of our approach.

Inducing hardening and healability in poly(ethylene-co-acrylic acid) via blending with complementary low molecular weight additives.

The design and synthesis of low molecular weight additives based on self-assembling nitroarylurea units, and their compatibility with poly(ethylene-co-acrylic acid) copolymers are reported. The self-assembly properties of the low molecular weight additives have been demonstrated in a series of gelation studies. Upon blending at low percentage weights (≤5%) with poly(ethylene-co-acrylic acid) the additives were capable of increasing the stress and strain to failure when compared to the parent copolymer. By varying the percentage weight of the additive as well as the type of additive the mechanical properties of poly(ethylene-co-acrylic acid) could be tailored. Finally, the healability characteristics of the blends were improved when compared to the original polymer via the introduction of a supramolecular 'network within a network'.