#copolymers

New method for creating biomimetic membranes offer solutions for energy, desalination and medicine

Researchers from the Adolphe Merkle Institute (AMI), together with international collaborators, have pioneered a novel method for creating thin, energy-converting membranes that mimic the structure and function of biological cell membranes. This discovery could have significant applications in fields ranging from implantable artificial electric organs to water desalination. The new technique leverages the interface of an aqueous two-phase system to form and stabilize these membranes. By carefully controlling the conditions under which two immiscible water-based solutions interact with the opposing sides of these membranes, the researchers created membranes that are just 35 nanometers thick but can cover areas larger than 10 square centimeters without defects. "This approach takes advantage of favorable interactions to stabilize ultra-thin self-assembled structures that are at least one thousand-fold larger than was previously possible," says Assistant Prof. Alessandro Ianiro, a former group leader in AMI's Biophysics lab.

Bright and tough: A material that heals itself and glows

A research team at the RIKEN Center for Sustainable Resource Science (CSRS) has succeeded in developing a self-healing material that is also capable of emitting a high amount of fluorescence when absorbing light. The research, published in the Journal of the American Chemical Society, could lead the way to the creation of new materials such as organic solar cells that are more durable than current types. In 2019, Zhaomin Hou and his team at RIKEN CSRS successfully copolymerized ethylene and anisylpropylene using a rare-earth metal catalyst. The resulting binary copolymer displayed remarkable self-healing properties against damage. The copolymer's soft components, alternating units of ethylene and anisylpropylene, coupled with hard crystalline units of ethylene-ethylene chains, acted as physical cross-linking points, forming a nano-phase-separated structure that proved crucial for self-healing. Building upon this success, they incorporated a luminescent unit, styrylpyrene, into a monomer and then formed polymers that also included anisylpropylene and ethylene. This process led to the synthesis, in a single step, of a self-healing material with fluorescence characteristics.

Plumber's nightmare structure presents itself as an assemblage where all exits seem to converge inward -- a plumber's nightmare but an anticipated uniqueness for researchers, suggesting distinctive traits divergent from traditional materials. Nonetheless, this intricate configuration was deemed unattainable, bordering on the realm of the impossible. Recently, a research team at Pohang University of Science and Technology (POSTECH) unearthed clues from neglected minuscule ends, transforming this dream into reality. The journal Science not only published this research but also spotlighted it as an article, sparking considerable interest within academic circles. Professor Moon Jeong Park and PhD candidate Hojun Lee from POSTECH's Department of Chemistry brought to life nanostructures of block copolymers (hereafter BCPs), which were previously only envisioned. This study was featured in Science and published on the fifth of January 2024.

Harnessing the building blocks of polymer recycling

Polymers are lightweight, durable, and easily processed into fabricated parts, features that promoted polymers to become the most relevant class of engineering materials by volume. However, recycling polymers is a challenge that materials scientists have been researching for decades.

An alternate route toward a more sustainable polymer industry is to increase the service lifetime of polymers. An intriguing new concept is to impart the ability to "self-heal" from structural damage. Michael Bockstaller, professor of materials science and engineering at Carnegie Mellon University Materials Science and Engineering, in collaboration with Krzysztof Matyjaszewski, professor of chemistry, has discovered that the binding of copolymers on the surface of nanoparticles that are already used in industrial manufacturing provides an economic and scalable route toward self-healing polymers with increased strength and toughness.

Normally when you think of the building blocks of materials, you think of atoms. In Bockstaller's research group, this concept inspired a new approach to fabricate functional materials by assembling nanoparticle building blocks using a form of atom transfer radical polymerization, a technique invented and developed by Matyjaszewski. The properties of the resulting materials can be varied by controlling the interactions between nanoparticle building blocks. This concept opens up new possibilities to vary properties of engineering materials without having to change their chemical composition—a feature that is highly beneficial in the context of recyclability.

Polymers, large molecules made up of repeating smaller molecules called monomers, are found in nearly everything we use in our day-to-day lives. Polymers can be natural or created synthetically. Natural polymers, also called biopolymers, include DNA, proteins, and materials like silk, gelatin, and collagen. Synthetic polymers make up many different kinds of materials, including plastic, that are used in constructing everything from toys to industrial fiber cables to brake pads.

As polymers are formed through a process called polymerization, the monomers are connected through a chain. As the chain develops, the structure of the polymer determines its unique physical and chemical properties. Researchers are continually studying polymers, how they form, how they are structured, and how they develop these unique properties. By understanding this information, scientists can develop new uses for polymers and create new materials that can be used in a wide variety of industries.

In a paper published in Nature Communications on May 4, researchers describe a new structure found in an aqueous solution of an amphiphilic copolymer, called a bilayer-folded lamellar mesophase, that has been discovered through a random copolymer sequence.

Controlling the length of supramolecular polymers

Systems made up of one supramolecular polymer are well understood, but much remains unknown for systems involving the combination of multiple supramolecular polymers, such as what affects the length of the resulting copolymers. For her Ph.D. research, Elisabeth Weyandt examined how the length of these copolymers change. Weyandt defended her thesis at the department of Chemical Engineering & Chemistry on September 17.

In conventional polymers, like those used in plastics, monomers are joined together by covalent bonds. However, in supramolecular polymers things are a little different as monomers are connected by a combination of weaker, non-covalent bonds like hydrogen bonding or π-π stacking.

Single component supramolecular polymer systems are well understood but moving from single to multi-component systems to obtain functional supramolecular materials and systems remains challenging. When mixing several supramolecular components, the aggregate length is affected, which in turn affects material properties.

New copolymer binder to extend the life of lithium ion batteries

Anyone who has owned a smartphone for over a year is most likely aware that its built-in lithium (Li)-ion battery does not hold as much charge as when the device was new. The degradation of Li-ion batteries is a serious issue that greatly limits the useful life of portable electronic devices, indirectly causing huge amounts of pollution and economic losses. In addition to this, the fact that Li-ion batteries are not very durable is a massive roadblock for the market of electric vehicles and renewable energy harvesting. Considering the severity of these issues, it is no surprise that researchers have been actively seeking ways to improve upon the state-of-the-art designs of Li-ion batteries.

One of the major causes for the drop in capacity over time in Li-ion batteries is the degradation of the widely used graphite anodes—the negative terminals in batteries. The anode, together with the cathode (or the positive terminal) and the electrolyte (or the medium that carries the charge between two terminals), provide an environment where the electrochemical reactions for the charging and discharging of the battery can take place. However, graphite requires a binder to prevent it from falling apart with use. The most widely adopted binder today, poly(vinylidene fluoride) (PVDF), has a series of drawbacks that render it far from an ideal material.