Tag Archives: science

Photoactivated Self-healing Copolymers- It’s Lit

Posted on March 25, 2019 by | Leave a comment

A scratch on your car may no longer need a trip to the auto-shop. Simply applying heat or light could remedy this issue. This idea could soon be a reality using vitrimers, a new class of plastics that have thermal and chemical stability, but can also be self-healing on a small scale and fully recyclable on a larger scale.

Taylor Wright from Dr. Wolf’s group at UBC. Source

In 2018, at the University of British Columbia, Taylor Wright under the supervision of Dr. Michael Wolf investigated the photoactive self-healing properties of vitrimeric copolymers.

Photoactive materials undergo physical and chemical changes in response to illumination. The development of responsive materials to both heat and light were explored for the first time through the incorporation of functional molecular groups into the polymeric backbone of these systems.

Wright and Wolf’s focus on the molecule’s response to light also offered a new aspect into vitrimeric research compared to the previous studies, that exclusively focused on the vitrimers’ response to heat.

Figure 1. Comparison of thermoplastics and thermosets upon heating. Source

So what exactly are vitrimers? Vitrimers are a new class of polymeric material that was first created in 2011 by a Polish physicist, Dr. Ludwik Leibler. By combining characteristics of thermosets and thermoplastics, Leibler was able to develop a material that is strong and durable, yet moldable and recyclable.

Thermoplastics are made of plastics linked by intermolecular forces. They can be easily molded and shaped under heat, then cooled down to produce the final structure. This allows for ease when it comes to processing. Additionally, this property allows them to be recycled to produce new products.

Conversely, thermosets involve irreversible cross-linking, connecting the backbones of the polymer chains with molecular bridges. This results in enhanced chemical and heat resistance, making the material less susceptible to stress-cracking. However, due to their cross-linked bonds, these materials do not melt upon exposure to heat,  unable to remold and recycle.

Vitrimers combine the best properties of both materials; structural integrity is improved through cross-linking, as well as self-healing and fully recyclable properties.

Figure 2. The molecular structure of the photoactivated vitrimeric copolymer created by Wright and Wolf. Source

As seen above in Figure 2, the vertical wiggly line splits the system into the two unique parts that make this a copolymer. The left side shows the aromatic anthracene molecule that crosslinks into a dimer in response to UV radiation.  The amine on the right side behaves like a more traditional vitrimer and responds to heat to form reversible exchanges.

Originally, their aim was to create a single polymeric system that responds to both heat and light simultaneously. However, during their research, they found that amines directly bonded to the anthracene molecules simply do not engage in the bond exchange process. They believed the electronics of the ring alters the behaviour of the molecule in comparison with non-aromatic amines.

Studying the photodimerization and thermally exchangeable functionalities of the copolymer based on the vinylogous urethane vitrimer, the self-healable properties can be seen in the video above. Self- healing polymers are a class of materials that enable the repair of micro-scale damage in the coating, ultimately restoring the passive state of the metal substance.  This enables reprocessability or longer lifetimes in cross-linked polymeric materials. The systems containing anthracene undergo self-healing through reversible reactions, allowing monomers and polymer chains to link and unlink.

Figure 3. Polymer sample, P2, mounted on a glass slide. A scratch from a razor blade can be observed. Source

Wright and Wolf tested the modification of surface properties by using a razor blade to scratch a polymer sample (that Wright denoted as P2), that was mounted on a glass slide. By using optical microscopy, the scratches were observed as dark lines crossing the sample, as seen below in Figure 4. The scratches were seen to decrease in width and ultimately close during heating through a series of expansions and contractions of the material, which can be seen in the video above.

Figure 4. Optical microscope image of (a) sample P2a initial scratch, (b) P2a after heating (c) sample P2b initial scratch, (d) and (e) P2b after heating. Black scale bar is 300 μm. Source

These specific Wright and Wolf vitrimeric copolymers will not be scaled up for commercial use, due to the difficulties of incorporating the two components of the copolymer together. However, the general idea of vitrimeric materials has “almost limitless applications”. For example, they can be incorporated into products that have a long lifetime, such as shipping materials and plastic stadium seats which can be recycled into new products once they start to deteriorate.

Additionally, Wright is currently working on vitrimers that start as a viscous liquid, much like thermoplastics, that can be easily molded and processed. This possible advancement will provide more flexibility with processing the starting material and ease in the synthesis process.

~Brina, Isla and Taiki (Group 4)

Leave a comment

Posted in Science Communication

Tagged , , , , , ,

Gravitational constant G, the one value that behind “everything”

Posted on March 22, 2019 by | 1 comment

New equipment for the measuring the gravitational constant G is reported by Li on Nature using two techniques TOS and AFF.

As we all have studied in High school science class or physics class, the reason that an apple will fall from trees, a rocket needs to thrust hot air to the ground to take off and even how can astronauts can ‘fly’ in the middle of air all have to do with gravitational constant G.  The gravitational acceleration is often been mistaken as gravitational constant just as mistaking gravity as the only gravitational force. The gravitational force is the attractive force between any two objects and the force is proportional to the weights of the two objects(assume the distance is a constant) and this proportion is the G. Just like the most common noticed gravitational force we are experiencing, gravity, is actually the attraction between us or an object with earth.

Nowadays, even though there are still some strong arguments on G should not be treated as a constant, it is generally been accepted that Newton’s law of universal gravitation is ‘true’ and gravitational constant can be measured.  Starting from this point of view, getting an accurate gravitational value is crucial since this value has been used for lots of daily life technology and precise aerospace calculations in astronomy.

Uncertainties of current and previous experiments. Made by Stephan Schlamminger

This passage will compare the traditional way of measuring G and a new improved way of doing it developed by a research group lead by Qing Li. The measurement of G is affected by lots of factors such as air, magnetic field and more importantly other objects that are near the equipment. For the reason of presenting so much factors, the uncertainty of the results is very large as reported by Mohr the uncertainty is 47 parts per million. While in Li’s group, they achieved recorded the smallest uncertainty of 14 parts per million while the largest uncertainty is 550 parts per million larger.

In the early days, the first successful measurement of G was done by Cavendish in 1798 and the part that is hanged by string is two connected spheres in a dumb-bell shape as you can see from the video below.

But in Li’s group, they built a “two plate-containing torsion balances” which uses two plates to replace the spheres to improve the precision. Also what worth mention is they used a fused silicon dioxide (silica) fibers with high-quality factor of the torsional oscillation mode (Q) to reduce the anelastic effect. And with all the other improvements together they managed to obtain the smallest uncertainty.

The instruments made by Li’s team. Source

This experiment can potentially benefit a lot of area of work by providing a more accurate fundamental constant value. The accuracy of work and research from the benefited field can also be improved.

1 Comment

Posted in Issues in Science, Science in the News

Tagged , , ,

The Search for Exoplanets: A New Frontier in Astronomy

Posted on March 22, 2019 by | 2 comments

Have you ever wondered how many stars there are in our universe? The number is anywhere between ten thousand trillion (1022) to one quadrillion (1024). The fraction that fall within the same classification as our sun, a G type star, is about 7.6%. Additionally, it is estimated by NASA that 1 in 6 stars will contain an Earth-Sized planet. Further, detecting Earth-sized planets hundreds of trillions of miles away is a non-trivial feat to say the least, leading to possible underestimates and uncertainty. Human curiosity of space and the intrinsic challenge of finding these seemingly hidden planets in the vastness of space has led astronomy to a new frontier.

The discovery of new exoplanets canidates by the Kepler Space Telescope as of June 2017. Source: Wikimedia commons

Astronomy is constantly reminding us that earth and our solar system is minute. While much is known about our immediate solar neighborhood, gaps in knowledge and improved technology has driven a strong surge in detection of astronomically small objects. In particular, there has been a growing interest in exoplanet detection. Exoplanets are simply planets outside of our solar system. So far, we have discovered 3926 exoplanets, with the Kepler space telescope launched in 2009 claiming 2338 with another 2423 living in limbo yet to be confirmed. While stars emitting immense amounts of light may occasionally be detected directly, exoplanet detection often relies on indirect techniques.

Artist depiction of Pegasi 51 b. Source: Wikimedia commons

The first exoplanet detection was made in 1992 by astronomer Aleksander Wolszczan orbiting around an exotic type of star called a pulsar at 2300 ± 100 light years away. Another breakthrough occurred in 1995 when the exoplanet 51 Pegasi b was discovered orbiting around a star more comparable to our sun. 51 Pegasi b since has been extensively studied alongside it’s star Pegasi b. Using the radial velocity technique which takes advantage of changes in the wavelength of light by a phenomenon called the doppler effect and the gravity of an orbiting planet, 51 Pegasi b was determined to have an orbital period of 4.230785 ± 0.000036 day. In addition to the accuracy in which these measurements could be made, the detection changed planetary astronomy according to Didier Queloz who at University of Geneva alongside Michel Mayor made the discovery: “The shock was so profound that 51 Peg completely changed our perspective of how we could look for planets.”

Radial velocity measurements of 51 Pegasi from 1995 where the exoplanet 51 Pegasi b was detected with error bars at each point. Source: Harvard, with original publication from Nature, 1995, Vol 273, pp. 355. 

At the University of British Columbia, Professor Jaymie Matthews of the Physics and Astronomy department is seeking to improve exoplanet detection by increasing the accuracy of gravitational field measurements. In a paper published by Matthews in 2016, a new way to measure the surface gravity of stars with accuracies of 4% is presented. Matthews said: “If you don’t know the star, you don’t know the planet.” Another group of Scientist at the University of Washington as of 2014 measured the diameter of a “super-earth” with an accuracy of 1%, or about 148 miles at 300 light years away.

https://www.youtube.com/watch?v=9vNcWCwwSbs&frags=pl%2Cwn

– Dr. Jaymie Matthews on The Rush on Shaw TV discussing the birthday of the Hubble Space Telescope. Source: The Rush on Shaw TV, Youtube 2012

While stars like Pegasi 51 and it’s exoplanet might be 50.45±0.10 light years away and far from reachable, the star and planet are an endless source of curiosity for astronomers. With exoplanet detection growing as a field, the discovery of more nearby Earth-like planets might be worth watching out for.

—- Jonah A

References:

  1. NASA Exoplanet Science Institute: NASA Exoplanet Archive.  https://exoplanetarchive.ipac.caltech.edu/docs/counts_detail.html

2 Comments

Posted in Issues in Science

Tagged , , , , , , , , , , , , , ,

Is Machine Learning the Future of Technology Development and Chemistry Research?

Posted on March 1, 2019 by | 4 comments

The ability for scientist to develop new drugs for everything from rare diseases to headaches is often reliant on precedent and systematic investigations. These methods are often costly and time consuming. Similar problems arise in development of new materials that may enhance our energy production. Our limited ability to rationally design materials  hampers their development. This leads to reliance on our ability to recognize the trends and behavior of already existing materials. However, what if we could amplify the ability to recognize patterns beyond human limits? Machine learning answers this problem.

A graph depicting the general algorithm machine learning follows. Source: Wikimedia Commons

While machine learning is a form artificial intelligence, our jobs are safe. Machine learning is the use of statistics and the power of computers to predict results or identify trends in data. The general method relies on the input of “training” data which is analyzed using statistics. After developing a model, information may be inferred from new data the computer encounters.

-Video Source: Google Cloud Platform educational AI Adventures Series on YouTube by Yufeng Guo in 2017.

Large technology companies have recognized the advantage of integrating machine learning into technology development. Google is one example that has successfully introduced it. Gmail uses machine learning to service 1.5 billion active accounts. They claim to detect 99.9% of phishing and spam mail from entering the user’s inbox. However, machine learning is not limited to technology companies. Chemistry researchers have quickly adopted it.

Total Number of Chemistry Publications with “Machine Learning” in Title

Starting in 1969, the first chemistry journal article with “machine learning” in the title was published. By combining machine learning with a common technique called mass spectrometry, Peter Jurs at the University of Washington was able to determine chemical composition of “unknown” chemicals using the input of 348 unique patterns as “training” data.

More recently there has been an almost exponential increase in the number of chemistry publications applying machine learning. In the last two years approximately 6 times as many publications were made than in the past 48 years. Tommi Jaakkola, a Professor of Electrical Engineering and Computer Science at MIT said at a consortium about implementing machine learning in the pharmaceutical industry: “by marrying chemical insights with modern machine learning concepts and methods, we are opening new avenues for designing, understanding, optimizing, and synthesizing drugs.” The materials science community has also seen integration with the development of novel long chained molecules called polymers for photovoltaics by scientist at Osaka University. Shinji Nagasawa, the lead author explained the importance: “there’s no easy way to design polymers with improved properties. Traditional chemical knowledge isn’t enough. Instead, we used artificial intelligence to guide the design process.”

Solar cell efficiency over years showing a substantial increase. Source: Wikimedia Commons

While machine learning is not the solution to all chemical problems or spam mail, it is being widely accepted by the scientific community and technology industry for good reasons. Even with limitations, it’s effectiveness across a wide array of industry and research emphasizes the role it may play in the future of research and development.

—Jonah

References

  1. Graph-powerd Machine Learning at Google. Google AI Blog. https://ai.googleblog.com/2016/10/graph-powered-machine-learning-at-google.html (Accessed Feb 28, 2019).
  2. Jurs, P.C.; Kowalski, B.R.; Isenhour, T.L. Computerized Learning Machines Applied to Chemical Problems: Molecular Formula Determination From Low Resolution Mass Spectrometry. Chem. 1967, 41, 21-27.
  3. Machine Learning, Materials Science and the New Imperial MOOC. Imperial College London. https://www.imperial.ac.uk/news/187054/machine-learning-materials-science-imperial-mooc/ (Accessed Feb 28, 2019).
  4. UBC Summons. University of British Columbia.

4 Comments

Posted in Uncategorized

Tagged , , , , , , , , , , , , ,

Record Breaking Temperatures in Superconductive Materials

Posted on January 22, 2019 by | Leave a comment

More than 100 years ago a Dutch scientist named Heike Kamerlingh Onnes at Leiden University discovered a phenomenon in mercury know as superconductivity. When cooled to -269°C the mercury exhibited zero electrical resistance unlike conventional materials that release heat when transporting electricity.

Why is this important if it requires such a cold temperature? Over the past 100 years scientist and engineers have incorporated this phenomenon into our daily lives. This allowed for dramatic advancements in medicine such as the development of the MRI. Our power grid also takes advantage of this weird property. However, only select materials exhibit superconductivity when cooled below a temperature referred to as the critical temperature.

An example of a superconducting radio frequency cavity on display at Fermilab made of Niobium, a common metal in superconductivity applications. Source: Wikimedia Commons

In 1987 the technology was revolutionized when a material called yttrium barium cuprate was found to exhibit superconductivity below -181°C. This temperature is easily reached with liquid nitrogen, a widely accessible coolant. This marvelous material has found itself applied at the Large Hadron Collider in Geneva and most hospitals. While materials with higher critical temperatures have been slowly discovered, recent advancements have been shattering the records.

Timeline of Superconductive Materials
Source: Wikimedia Commons

Among these superconductors are a class which only exist at extremely high pressures. The smelly gas that comes from volcanos and is reminiscent of rotten eggs, Hydrogen sulfide (H2S), is one of these. When cooled to -70°C at 1.5 million atmospheres, hydrogen sulfide exhibits an exotic form of high pressure superconductivity. This discovery in 2015 by Mikhail Eremets and Alexander Drozdov at the Max Plank Institute for Chemistry in Mainz, Germany toppled previous records by 39°C, a significant breakthrough in the search for room temperature superconducting materials. Mikhail Eremets said: “Our research into hydrogen sulfide has however shown that many hydrogen-rich materials can have a high transition temperature.”

This has held true with a recently published paper by the same team in December of 2018. Lanthanum superhydride (LaH10) was found to be superconducting at -23°C, however it was at similar pressures to the previous discovery. This value was found to be even higher at -13°C when pressurized up to 2 million atmospheres as published by scientist at George Washington University in January of 2018. Maddury Somayazuli, an associate professor at The George Washington School of Engineering and Applied Science said: “Room temperature superconductivity has been the proverbial ‘holy grail’ waiting to be found, and achieving it-albeit at 2 million atmospheres-is a paradigm-changing moment in the history of science.” Future experiments are expected to provide more breakthroughs in the field.

An engineer at the Advanced Photon Source, part of Argonne National Laboratory where GW University experiments were preformed. Source: Advanced Photon Source Flicker (CC BY-NC-SA 2.0)

While high pressure superconductors lack application, understanding this  property may allow for the development of new materials. With continued research and the recent breakthroughs, the phenomenon of superconductivity may further be propelled into future technology that will have a significant impact on our quality of life.

-Jonah

References:

1.Drozdov et al, “Superconductivity at 250K in Lanthanum Hydride Under High Pressure,” arXiv:1812.0156 [cond-mat], Dec. 2018.                                        2.Somayazuli et al. (2019). Evidence for Superconductivity above 260K in Lanthanum Superhydride at Megabar Pressures. Physics Review Letters, (122), 027001-6.                                                                                                              3.Researchers Discover New Evidence of Superconductivity at Near Room Temperature. (2019, January 15). Phys.org. Retrieved from https://phys.org/news/2019-01-evidence-superconductivity-room-temperature.html                                                                                      4.Superconductivity: No Resistance at Record Temperatures. (2015, August 18). Max-Planck-Gesellschaft. Retriever from https://www.mpg.de/9366213/superconductivity-hydrogen-sulfide                  5.Eck, J. (2018). The History of Superconductors. Retrieved from http://www.superconductors.org/History.htm

 

 

 

Leave a comment

Posted in Uncategorized

Tagged , , , , , , , , , ,