Tag: polymer

Exploration of polymer cononsolvency mechanism through soft X-ray absorption spectroscopy

Exploration of polymer cononsolvency mechanism through soft X-ray absorption spectroscopy

This study investigates the cononsolvency mechanism of poly(N-isopropylacrylamide) (PNIPAM), which is soluble in pure methanol (MeOH) and water but insoluble in aqueous MeOH solutions. Combining oxygen K-edge X-ray absorption spectroscopy (XAS) with theoretical calculations executed in molecular dynamics (MD) simulations and inner-shell calculations, it was found that hydrophobic interactions between PNIPAM and MeOH clusters play a key role in PNIPAM aggregation and cononsolvency emergence.

PNIPAM is a stimuli-responsive polymer showing sensitivity to various chemical environments such as temperature and pH. PNIPAM dissolves in pure MeOH and H2O at room temperature but is insoluble in mixtures of MeOH and H2O, a phenomenon known as cononsolvency. Understanding the mechanism of cononsolvency is important for comprehending the phase transition dynamics not only of polymers but also of biomolecules, which undergo dynamics such as protein folding, DNA packing, and interchain complexation. In this study, we investigated the cononsolvency mechanism of PNIPAM in aqueous MeOH solutions from the oxygen K-edge XAS of PNIPAM along with theoretical calculations implemented in MD simulations and inner-shell calculations.

The oxygen K-edge XAS spectra of PNIPAM were measured in a transmission-type liquid cell at the soft X-ray beamline BL-7A of the Photon Factory (KEK-PF). XAS enables the element-selective analysis of light elements such as carbon, nitrogen, and oxygen. However, XAS measurements in transmission mode are difficult because soft X-rays are strongly absorbed by air and liquids. Our developed liquid cell allows XAS measurements of liquid samples in transmission mode under precise thickness control. The C=O π* peaks in the PNIPAM spectrum were observed after separating the contributions of the MeOH and H2O solvents. Figure 1 plots the energy shift of the C=O π* peaks in PNIPAM as a function of MeOH molar fraction at 25°C. n the MeOH-rich region, the energy shifts of the C=O π* peaks are higher in the mixed solvent than in pure MeOH. This energy shift is assigned to simple substitution of the hydrogen bond (HB) structure of the PNIPAM C=O group from MeOH to H2O. In contrast, the energy shift of the C=O π* peak of PNIPAM is much higher in pure H2O than in pure MeOH. Although the dissolution behaviors of PNIPAM in H2O and MeOH are identical on the macroscopic scale, the molecular interactions of PNIPAM with H2O and MeOH are very different on the microscopic scale. For this reason, cononsolvency of PNIPAM emerges in aqueous MeOH solutions.

Read more on KEK website

New studies towards lignin valorisation

New studies towards lignin valorisation

A little known, yet ubiquitous polymer

In work recently published in PNAS an international team of researchers characterised an important degradation step, allowing the breakage of lignin that leads to the production of individual components, which can be further harvested. To do so, they utilise several Diamond Light Source instruments:  the I23, I03 and B21 beamlines.

Compared to animals, plants don’t have a bony skeleton. They rely on rigid cell walls that separate each plant cell. These cell walls are composed of cellulose, pectin and lignin, making these molecules among the most abundant on earth. Lignin is a hydrophobic compound and plays a crucial role in vascular tissue, making them impermeable and allowing the transport of water in the plant efficiently. Lignin is a huge and complex molecule composed of different precursors called monolignols. The composition of lignin varies among plants.

From an industrial perspective, lignin is well known in the paper industry because it represents a third of the mass of the paper precursor. Lignin is a coloured component that yellows in the air and needs to be removed to have white paper. Currently there is only limited use for lignin and it is burned as low value fuel in these industries. New research and development have improved the transformation of lignin into value added components (biofuels, chemical compounds…) but research is still needed to improve the degradation process of lignin. A way to harvest these components is through enzymatic degradation. In work recently published in PNAS an international team of researchers characterised an important degradation step, allowing the breakage of lignin that leads to the production of individual components, which can be further harvested. To do so, they utilise several Diamond Light Source instruments:  the I23, I03 and B21 beamlines.

Read more on the Diamond website

Image: Structural architecture of LdpA and substrate interactions. (A) Superposition of SpLdpA (magenta) with NaLdpA (teal). (B) Side view of the SpLdpA trimer. Two protein chains are shown as surfaces (yellow and green) and one protein chain is shown in cartoon mode (red) with bound substrate erythro-DGPD (light blue). (C) Top view of the SpLdpA trimer. (D) Pseudo-stereoscopic view of the interaction of SpLdpA with the erythro-DGPD enantiomers (αS, βR) (Left) and (αR, βS) (Right). When viewed in stereo, alternating eye switching results in an optimal impression of the binding modes of the two diastereomer substrates. (E) Omit electron density map for the (αS, βR)- and (αR, βS)-erythro-DGPD enantiomers bound to SpLdpA at 2.5 σ level. (see Diamond news piece for complete image)

Mind the gap – ESRF tracks defects triggered by composites in root fillings

Mind the gap – ESRF tracks defects triggered by composites in root fillings

Polymer composite fillings of root-canal treated teeth can fail over time. Scientists led by the Charité University in Berlin (Germany) have found that this is not because of the dentist’s lack of skills but rather because of stresses that build up and deform the biomaterial just after it is placed. The results are published in Acta Biomaterialia.

It is one of the most peculiar images that can come to mind: a dentist restoring severely destroyed teeth and placing fillings on a beamline at a synchrotron. It is, however, exactly what happened on beamline ID19 a while back, when a team from the Charité and TU Universities in Berlin and the ESRF examined how well composite fillings adapt to cavities in the tooth root canal orifice.

To treat cavities in teeth, dentists expose solid tooth tissue prior to “filling” the volume of missing structure with rigid biomaterials that sustain chewing forces. In the past, dentists used metals such as amalgam or gold, but today they mostly use composite materials, made of polymer and glass. Such materials, which are well resistant to damage and highly aesthetic, allow rapid recovery of tooth function. However, composites tend to fail in the long run, especially in root-canal filled teeth.

Read more on the ESRF website

Image: Kerstin Bitter placing a filling on a tooth on ID19’s experimental hutch.

Credit: P. Zaslansky.

Diamond celebrates 10,000th paper – A breakthrough in chiral polymer thin films research

Diamond celebrates 10,000th paper – A breakthrough in chiral polymer thin films research

This could fundamentally change the technology landscape by enabling a new generation of devices

A recent paper in Nature Communications by an international team of collaborative researchers marks the 10,000th published as a result of innovative research at Diamond Light Source, the UK’s national synchrotron. This study presents disruptive insights into chiral polymer films, which emit and absorb circularly polarised light, and offers the promise of achieving important technological advances, including high-performance displays, 3D imaging and quantum computing.https://player.vimeo.com/video/502596383

Chirality is a fundamental symmetry property of the universe. We see left-handed (LH) and right-handed (RH) mirror image pairs in everything from snails and small molecules to giant spiral galaxies. Light can also have chirality. As light is travelling, its internal electric field can rotate left or right creating LH or RH circular polarisation. The ability to control and manipulate this chiral, circularly-polarised light presents opportunities in next-generation optoelectronics (Figs 1a and 1b). However, the origin of the large chiroptical effects in polymer thin films (Figs 1c and 2) has remained elusive for almost three decades. In this study, a group of researchers from Imperial College London, the University of Nottingham, the University of Barcelona, the Diamond Light Source and the J.A. Woollam Company made use of Diamond’s Synchrotron Radiation Circular Dichroism beamline (B23) and the Advanced Light Source in California.

Read more on the Diamond website

Image: In situ chiroptical response of ACPCA and cholesteric chiral sidechain polymers (CSCP) thin films. In situ CD spectra recorded during heating and cooling of ACPCA (F8BT: aza[6]H) and CSCP (cPFBT) thin films (note blue represents low temperatures and red represents high temperatures), (c) and (d) the CD intensity recorded at 480nm as a function of temperature during heating (red) and cooling (blue), and (e) and (f) CD intensity of thin films held at 140°C as a function of time for [P] (turquoise) and [M] (purple) systems (note the different time on-axis).

Powering the future of clean energy

Powering the future of clean energy

Hydrogen gas can be used to power vehicles and has the potential to provide electricity to homes

The global quest for clean energy is championed by researchers in Canada who are focused on harnessing the potential of hydrogen.

The idea of the hydrogen economy was first proposed 50 years ago as a way to combat the negative effects of fossil fuels. Its future is the focus of new research from the University of Toronto’s Thermofluids for Energy and Advanced Materials (TEAM) lab, whose work relied on the Canadian Light Source (CLS) at the University of Saskatchewan to visualize performance.

Read more on the Canadian Light Source website

Image: Adam Webb (CLS), Sergey Gasilov (CLS), Manojkumar Balakrishnan (U of T), Jason Keonhag Lee (U of T), Denise Miller (CLS), Kieran Fahy (U of T) on the BMIT beamline at CLS.

A polymer coating makes Metal Organic Frameworks better at delivering drugs

A polymer coating makes Metal Organic Frameworks better at delivering drugs

Researchers use Synchrotron InfraRed microspectroscopy to study the dynamics of drug release from MOFs

How to efficiently deliver targeted, controlled and time-released doses of drugs is a significant challenge for biomedicine. Finding solutions to this challenge would result in substantial benefits for patients, including more effective drug therapy and fewer undesirable side effects. The porous nature of metal-organic frameworks (MOFs) makes them attractive candidates for drug-delivery systems as they can be tailored to hold and transport a variety of encapsulated guest molecules. To this end, employing MOFs as a drug delivery vehicle could offer potential solutions to accomplish the targeted and controlled release of anti-cancer drugs. However, understanding the precise chemical and physical transformations that MOFs undergo as these guest molecules are released is challenging. In work recently published in ACS Applied Materials & Interfaces, researchers from the University of Oxford, University of Turin, and Diamond Light Source used a combination of experimental and theoretical techniques to address this problem. They show how the combination of hydrophilic MOF-encapsulated drug with a hydrophobic polymeric matrix is a highly promising strategy to tune the drug release rate for optimal delivery. Their results demonstrate that high-resolution synchrotron InfraRed microspectroscopy is a powerful in situ technique for tracking the local chemical and physical transformations, revealing the dynamics underpinning the controlled release of drug molecules bound to the MOF pores.  

Read more on Diamond Light Source website

Image: Using synchrotron infrared radiation to track the drug release process from MOF/Polymer composites.

A highly promising sustainable battery for electric vehicles

A highly promising sustainable battery for electric vehicles

McGill University researchers show that affordable materials could prove key for improving the batteries used in electric vehicles. The breakthrough was analyzed and confirmed with the Canadian Light Source (CLS) at the University of Saskatchewan. The research was funded by NSERC and supported by Hydro-Quebec.

As we move to greener technologies, the need for affordable, safe and powerful batteries is increasing constantly.

Battery-powered electric vehicles, for example, have much higher safety standards than our phones, and to travel the long distances required in Canada, lighter weight, high-energy capacity batteries make a world of difference.

Current rechargeable batteries tend to use expensive non-abundant metals, like cobalt, that carry an environmental and human rights toll under the poor labour conditions in mines in Africa. All are barriers to wider adoption.

The battery’s cathode, or positive electrode, is one of the best candidates for Li-ion battery improvement. “Cathodes represent 40 per cent of the cost of the batteries that we are using in our phones right now. They are absolutely crucial to improve battery performance and reduce dependency on cobalt,” says Rasool.

Read more on the Canadian Light Source website

Image : Lithium ion silicate nanocrystals coated in a conducting polymer known as PEDOT enhance battery performance even after 50 cycles, paving the way for high energy density cathodes.