Millions of tons of lignin—a biopolymer that strengthens the cell walls of plants—are produced each year by the pulp and paper industry. Although lignin production is widescale, lignin is considered a waste product with no commercial application due to its complexity as a non-uniform material. Incorporation of lignin into commercially important polymers remains a challenge in both pure research and applied industrial environments; yet if we could understand and use this material in a predictable manner, it would have a myriad of applications. Fortunately, a 2018 study in ACS Sustainable Chemistry & Engineering has revealed how to prepare and characterize different copolymers of lignin and polylactide (PLA).
Researchers uncover how to make better polymers from pulp and paper waste
Posted in Science Communication
Tagged biodegradable, biopolymers, chemistry, copolymer, copolymers, green, green chemistry, lignin, materials, Materials Chemistry, melt, Outreach Project, PLA, polymers, Public Engagement, UBC
Track Your Stress with Sweat
Do you hate having your blood drawn for your lab tests? Could there be a non-invasive way to obtain your lab results? Perhaps, sweat samples could be used to measure our health status instead.
Sweating is a naturally occurring process, whether it is from exercising or getting nervous on a test. Although sweat can be perceived as wet and smelly, sweat contains various types of biomarkers, such as the stress hormone, cortisol. Since excessive stress can contribute to various health problems, such as high blood pressure, could we use cortisol in our sweats to monitor our stress levels in real-time?
Molecular structure of cortisol. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported. Cortisol.png
In a recent study, Sekar et al. has developed a wearable electrochemical sensor that can measure cortisol in sweat. The researchers has integrated iron (III) oxide (Fe2O3) in conductive carbon yarn (CCY) to make a semiconductive platform. After that, the platform is coated with antibodies (anti-Cmab) in an electrochemical apparatus, which would make the sensor specific to cortisol. The final product would then become a Fe2O3/CCY immunosensor. The purpose of the study is to see if they can use CCY as a suitable platform for biosensors when monitoring sweats.
Adapted from Figure 1b in the Sekar et al (2019) paper. The black rectangle is the CCY with iron (III) oxide (orange spots). The green cylinder is the electrochemical apparatus. Licensed under a Creative Commons Attribution 4.0 International License
The researchers were able to test the sensor’s detection ability with different concentrations of cortisol. According to Figure 8b below, the line graph shows a linear relationship between the electrical current response from the Fe2O3/CCY immunosensor and the logarithm of cortisol concentration.
Adapted from Figure 8b in the Sekar et al (2019) paper. Each data point with error bar is the result from three successive experiments. Licensed under a Creative Commons Attribution 4.0 International License
The researchers also tested the sensor with real sweat samples from participants after performing cardio exercise. In the bar graph below, the error bars in the pink bar gives the RSD or relative standard deviation of 3.403%, 3.874%, and 4.064% from sweat sample 1, 2, and 3 respectively. These RSDs show small variations in averaged results from three successive experiments when testing with the Fe2O3/CCY immunosensor. According to the paper, the bar graph below shows a correlation between the two methods: the CLIA (chemiluminescence immunoassay) and their Fe2O3/CCY immunosensor. As a results, using CCY may be a possible choice for designing a biosensor that monitors cortisol in sweats.
Adapted from Figure 11 in the Sekar et al (2019) paper. Each pink bar with error bar is the result from three successive experiments. Licensed under a Creative Commons Attribution 4.0 International License
In addition, there are other similar studies that focus on wearable sweat sensors, such that they can transmit data to your phone, and diagnose cystic fibrosis. Therefore, sweat sensors are potential non-invasive diagnostic tools, which may lessen the burden on more invasive blood samples to measure our health status.
References
Stress and Heart Health. https://www.heart.org/en/healthy-living/healthy-lifestyle/stress-management/stress-and-heart-health (accessed Mar 26, 2019).
Sekar, M.; Pandiaraj, M.; Bhansali, S.; Ponpandian, N.; Viswanathan, C. Carbon fiber based electrochemical sensor for sweat cortisol measurement. Scientific Reports 2019, 9, 1-14. https://doi.org/10.1038/s41598-018-37243-w.
Stephanie, Relative Standard Deviation: Definition & Formula. https://www.statisticshowto.datasciencecentral.com/relative-standard-deviation/ (accessed Mar 26, 2019).
Geddes, L. Wearable sweat sensor paves way for real-time analysis of body chemistry. http://www.nature.com/news/wearable-sweat-sensor-paves-way-for-real-time-analysis-of-body-chemistry-1.19254 (accessed Mar 26, 2019).
Dusheck, J. Wearable sweat sensor can diagnose cystic fibrosis, study finds. http://med.stanford.edu/news/all-news/2017/04/wearable-sweat-sensor-can-diagnose-cystic-fibrosis.html (accessed Mar 26, 2019).
Plastic replacements: some new conSQUIDerations
The amount of plastic that has been produced to date now exceeds 8300 million metric tonnes (Mt). To put this into perspective, the average blue whale weighs approximately 180 Mt, thus 46 million blue whale’s worth of plastic has been produced since humans started commercializing plastics in 1950. Our society had become extremely dependent on plastic products and synthetic (petroleum- based) textiles which cause serious consequences such as microplastic and microfiber pollution as I’ve discussed in previous blog posts.
Figure 1. Size reference for blue whales. Wikipedia Commons
Bioplastics have more recently taken the stage as a potential avenue for replacing petroleum-based plastics. Biologically based polymers have structural elements such as helices, β-turns, β-sheets and coils which provide structural integrity and resilience and can replicate the desirable polymeric interactions in plastics. Additionally, a lot of new material is being developed based on the protein polymers that are naturally occurring in biological systems (including ourselves).
Figure 2. Fibrous protein polymers have molecular architecture that can include (i) helices and coils, (ii) β-turns and β-spirals, and (iii) β-sheets. Source
Video 1. SRT- coated fabrics that self-heal in water.
Squid ring teeth (SRT) are an especially promising candidate for making functional fibres and films due to its strength, conductivity and self-healing properties. The SRT are located inside the suction cups of the tentacles of squids and are composed of a naturally occurring protein complex. Fortunately, it is not necessary to harvest squid to obtain the SRT proteins as they can be biosynthetically produced since having their genome sequenced. The SRT-inspired monomer is repeated to create a polymeric chain and the resulting protein that is produced is named accordingly as tandem repeat (TR) proteins.
Figure 3. The Squid ring teeth of a giant squid. Wikipedia Commons
Figure 4. Optical images of squid ring teeth (SRT) and the six common squid species they originate from. Source
Films produced with SRT proteins consist of disordered domains that provide elasticity and flexibility to the materials in addition to ordered domains such as β-sheets that provide mechanical strength. One study designed four TR proteins denoted as TR-nX where X was the number of repeat units within the molecule. They measured the mechanical force of these four TR proteins and found that the ultimate strength of the protein’s scale linearly, with TR-n25 reaching an ultimate strength of 40 MPa. As seen in Figure 4 below, there is a limitation of the study due to sample size. The error bars of the TR-n12 and TR-n25 overlap, so it is not possible to say there is a statistically significant difference from each other.
Figure 4. Mechanical testing of fully hydrated TR proteins (inset shows 1/n dependence) Source
Additionally, SRT protein films have been suggested as a potential solution to the issues related to the release of microfibers into the water from washing. A cloth made from polyester was coated with an SRT protein film and was found to dramatically increase the cloths resistance to abrasion (and microfiber release) compared to cloths that were not coated with SRT protein films.
While there is still a lot of further research to be done, SRT-based proteins are a promising avenue for making our world a little bit less plastic.
~Isla
Posted in Biological Sciences, Science Communication
Tagged biological chemistry, chemistry, microplastic, plastic, pollution, polymers, protein, squid, technology
Does climate change result in an increase of wildfires?
As the temperatures get warmer and the days start getting longer, you may be excited for the summer season to start. However, the arrival of summer also means dryer weather, water shortages, and wildfires.
Poor air quality in Vancouver due to the raging wildfires. Photo Source: flickr
Wildfires can occur anywhere, but are most prevalent in the forests of Canada, the United States, Europe, and throughout the vegetated areas of Australia and South Africa. These wildfires are capable of destroying entire areas of up to 2.5 million hectare per year in Canada and can travel at speeds of 23 kilometers per hour! The main causes of wildfires are lightning and humans (surprise!), with lightning caused fires making up 45% of all fires and 55% of all fires being connected to human activities.
Historical wildfires across Canada. Photo Source: Natural Resources Canada
Although lightning caused wildfires occur naturally every year and are essential for the environment, wildfires should still be a concern for all of us. The smog that visits Vancouver every summer seems more severe year after year, could climate change be increasing the occurrence of wildfires?
According to science, climate change does result in an increase of wildfires. Climate change is the result of human activities, such as, fossil fuel burning, which produces large quantities of carbon dioxide. Just like methane and ozone, carbon dioxide is also a heat-trapping molecule, which you might know as a greenhouse gas. With greenhouse gas concentrations increasing, the heat radiated from earth cannot leave earth’s atmosphere. Over 90 percent of this trapped heat accumulates in the ocean and as a consequence, ocean heat contents rise and cause increases in global ocean temperatures. The increase in global heat content also causes ice to melt and sea levels to rise.
Global ocean heat content (OHC) for the top 2000 m of the ocean. Uncertainty estimates are shown in pink. Source: Science Advances
Aside from an increase in global ocean temperatures and higher sea levels, temperatures on land are also raised due to the trapping of heat by greenhouse gases. This results in more droughts and dryer weather, which are perfect conditions for wildfires to pick up.
So, other than knowing the reason for an increase in wildfires, how can we do our best to prevent wildfires from occurring?
First of all, always obey fire bans and signs that indicate the wildfire danger ratings. Next, never leave a campfire unattended & completely extinguish the campfire when leaving the area. Furthermore, any smoking material should be properly disposed of and most importantly, be sure to report any signs of wildfires.
Drug Sponge: Absorbing up the problems
https://www.youtube.com/watch?v=fQsYw5brVw8&t=7s
Chemotherapy is a well-known treatment for cancer, using drugs to destroy cancer cells. However, doctors administrate these anticancer drugs with caution because they are also considered poisonous. After cancer treatments, excess drugs can stay in the human body, causing damage to healthy cells, resulting in unwanted toxic side effects. What if there was something that can absorb these drugs like a portable filter?
Various chemotherapy treatments on the growth of mesenchymal stem cells (MSC). MSC is found in bone marrow cells, that contribute to regenerating bone and muscle tissues. Source
Dr. Steven Hetts from the University of California Berkeley initially thought of an idea, to introduce a sponge-like polymer that can absorb excess chemotherapy drugs. Sponges have immensely grown in popularity in the pharmaceutical field, as the metabolites produced hold biologically active natural products. Approximately 5300 different natural products extracted from sponges have shown pharmaceutical properties, such as anticancer and antibacterial active properties.
Schematic diagram of the developed 3D printed porous absorber. Source
In early 2019, he shared this concept among researchers from other American universities, eventually publishing a paper that describes the development of a porous absorbent polymer. The researchers built the lattice structure using 3D printing that allows the blood to circulate through the bloodstream. In addition, they coated the polymer with a polystyrenesulfonate copolymer, essential for absorbing the chemotherapy drug, doxorubicin.
Doxorubicin: a chemotherapy medication used to treat cancer. Source: Wikimedia Commons
This innovative biomedical device showed great promise, as the polymer efficiently absorbed 64±6% of the drug. Even though this was tested on pigs with healthy livers, the understanding of this device allows researchers to focus on improvements. Lattice size, the type of coating, the thickness of the coating, and the number of absorbers are all possible approaches to a more effective drug sponge.
With this in mind, doctors can potentially administrate higher doses of drugs for more aggressive tumors. In addition, modifications to the drug sponge’s coating can absorb other types of powerful chemotherapy drugs. Although testings on humans are not yet approved by the FDA, the drug sponge is a huge step towards minimizing chemotherapy toxic side effects.
Posted in Issues in Science, Science in the News
Tagged Biochemistry, chemistry, drug sponge, Pharmaceuticals
Can Weather Affect Our Moods?
You wake up in the morning and get dressed for the day. But the sky’s overcast and you can’t even get a glimpse of the sun. It’s already pouring outside and you utter to yourself, “This day’s off to a great start.”
Picture of a Rainy Day; Source: Max Pixel
Living in a city like Vancouver, where it rains for nearly half the year, you may start to wonder whether the weather actually has an effect on your mood. Is this merely a myth? Or does the idea have some merit to it?
From this paper published in 2011, the researchers came to the conclusion that it depends. Their results show that some people’s state of mind can be influenced by the weather. While for others, there was little to no effect.
They quantified this influence by focusing on three distinct mood indicators: happiness, anxiety, and anger. To measure this, the Internet version of the Electronic Mood Device, the Daily Mood Scale was used. Klimstra, et al. defined four groups of people – each affected differently by weather. They labelled these groups as: Summer Lovers (SL), Unaffected (UA), Summer Haters (SH), and Rain Haters (RH).
Graph Showing percentage of each type of individual; adapted from Klimstra, et al.
From their results, they found that nearly half of the individuals tested were in the UA group – meaning that the weather’s influence was minimal. As suggested by the writers of the paper, this could explain why previous studies concluded that the weather had an insignificant effect. However, the rest of the participants displayed changes in happiness, anxiety, and anger in the weather conditions that were tested – weather did have an effect on them.
Correlation results from their study. Source: Klimstra, et al.
The table above shows the correlation between sunshine, temperature, and precipitation and their effects on the mood indicators. Positive numbers indicate a positive correlation, whereas negative numbers indicate the opposite. The correlation ranges from -1 to +1; a number closer to the extremities (±1) indicates a stronger link. The number of people (of each group) is indicated by n. The probability value (p) represents how statistically significant the results are – the smaller the p-value, the higher the level of significance.
Summer day in Biei, Hokkaido, Japan. Source: Reginald Pentinio
You can see why they decided on these labels for each group. For example, individuals of the Summer Lover group were characterized as being happier, being less anxious, and being less angry on higher temperature and sunny days. However, precipitation caused reduced levels of happiness and increased levels of anxiety and anger.
It’s safe to say that the weather does have an effect on at least half of us.
This blog post’s focus was mainly on the study by Dr. Klimstra. The following video mentions some other ways the weather can affect us.
Developments in Radiolabelling of Cancer: A Talk with Chris Orvig
Recently, Dr. Chris Orvig and his research group from the UBC Chemistry department published “H2hox: Dual-Channel Oxine-Derived Acyclic Chelating Ligand for 68Ga Radiopharmaceuticals” in Inorganic Chemistry on February 18, 2019. This involves the development of a new ligand, H2hox, for potential use in radiolabelling of cancer cells within the body. The video below describes the radiolabelling process and why it is useful (warning: footage of a surgery from 4:08 onwards):
In general, ligands are compounds that bind to metal ions. These compounds can be positively charged, negatively charged, or neutral. Ligands that bind to a metal through multiple sites are known as polydentate ligands and tend to be more stable. H2hox is a hexadentate ligand, which means it can bind to 68Ga at six different sites.
A main portion of ligand design is to prevent radioactive metal ions from being attracted to negative phosphate ions in bone. On the use of gallium, Dr. Orvig explained “68Ga has several useful radioactive properties, and many ligands to bind with it have been developed. However, those existing ligands have different degrees of limitations.” One such example given in this paper is the commonly used ligand DOTA, which requires longer time until imaging can occur and high temperatures. This presents a problem in living beings as high temperature is harmful.
The structure of DOTA. Source: Wikimedia Commons
H2hox, the centerpiece of this new publication by the Orvig research group, has many advantages over other existing ligands that can bind to 68Ga. For one, the synthesis of H2hox is easier and faster than other previously reported ligands. H2hox tightly binds to 68Ga, and rapidly achieves efficient and reproducible radiolabeling in living systems (in vivo). These properties mean H2hox is applicable to cancer diagnosis and radiotherapy treatment for cancer.
The structure of H2hox. Source: Wang et al., 2018
“We have looked at [H2hox] in mice, and we have successors of that ligand that work with bigger metal ions that also work in mice very well,” said Orvig. Given all the tests on in vivo systems succeeded, Orvig replied that “The idea would be that we could potentially use derivatives of hox that are functionalized for positron emission tomography (PET). We view hox mostly as a potentially diagnostic ligand since it and the metals it coordinates to are small.” On what’s next for hox, Dr. Orvig said, “The next step now is to add the targeting vector (helps target cancer cells), and we’re working on that right now, then we would test that on a tumor model with the BC Cancer Agency. If all of that works then we might talk about going to a higher animal model.”
PET images of Ga-hox in mice. Source: Wang et al., 2018
Here is a video giving a brief introduction to positron emission tomography:
“This paper is a new kind of ligand because it contains oxinate (oxine bonded to metal) moieties, because oxinates bond very, very strongly to metal ions,” said Dr. Orvig. This helps prevent the gallium separating from H2hox and depositing in the body. “We are trying to create a ligand that could be useful for gallium, hence the focus in the paper, or copper because both gallium and copper are potentially useful for cancer radiotherapy,” Dr. Orvig explained.
Caption: The structure of oxine. Two of this structure can be observed in the H2hox image above. Source: Wikimedia Commons
According to Dr. Orvig, this research is intended to help with cancer treatment and making the process more consistent. “Chemotherapy essentially beats up every cell in the body, but the cancer is a little more susceptible since it’s dividing faster. What we’re trying to do is target radioactive isotopes to the cancer so that you can both specifically detect it and then specifically treat it with different forms of radiation. If you can specifically target it, then you can deal a lot more damage to the cancer cells than the healthy cells and avoid chemically poisoning chemotherapy patients.” This video explains the concepts behind chemotherapy:
https://www.youtube.com/watch?v=wjaFhdOowAg
Dr. Orvig’s group is pushing forward on the development of targeting vectors as part of a large government funded project that involves collaborations with co-investigators. Through a team effort, scientists at TRIUMF develop and produce the required gallium radioisotopes, while researchers at the BC Cancer Agency are working with Dr. Orvig’s group on testing cancer models. Specific cancer types that the BC Cancer Agency uses as a starting point are prostate cancer and a form of breast cancer, which are two common forms of cancer that are responsible for roughly 9100 deaths in Canada every year. These models are transplanted onto mice and tested.
While this new ligand system is an important advance in the area of radiopharmaceutical drug development, Dr. Orvig was careful to note that this is not a panacea for all types of cancer. “I often liken cancer to the common cold. The common cold is caused by some 200 different viruses, so the common cold is essentially 200 different diseases. Cancer is also a collection of different diseases. What they have in common and why they’re cancers is because the cells are dividing more rapidly than healthy cells and in a toxic fashion. So I would definitely not say H2hox is useful for a broad spectrum but for some very specific applications.”
~ Nicholas Patterson, Danial Yazdan, Wenxin Zhao, Samuel Gong
Photoactivated Self-healing Copolymers- It’s Lit
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)
Posted in Science Communication
Tagged chemistry, Outreach Project, plastic, pollution, polymers, science, technology
What is acid rain and why is it an issue?
Acid rain has become an issue in many industrial parts of the world, and has several associated risks. Acid rain, as defined by the Government of Canada, is any precipitation that has collected acidic gases or particles to gain a pH less than 5.6. This causes it to be slightly corrosive, allowing for damage to rocks and minerals and damage to plant life and ecosystems. Even buildings can suffer damage from acid rain.
A gargoyle statue that has been corroded by acid rain. Source: Wikimedia Commons
Entire ecosystems can be ravaged by acid rain given enough exposure. The image below shows a forest in the Czech Republic in 2009, with a large patch of trees that were killed. Lakes are also vulnerable to acid rain damage, as too many rains will make the lake too acidic for wildlife and vegetation to survive. A case like this even poses risk to surrounding wildlife that depend on the lake, so consequences can be widespread.
Trees killed by acid rain in a Czech Republic forest. Source: Flickr
However, some areas are more resistant to acid rain than others. Soil composition can sometimes result in the acid being neutralized before it can do too much harm. In other cases, essential compounds can be removed from the soil and plants can no longer properly uptake water.
There are several natural processes that contribute to acid rain, such as a large effect from volcanoes and a smaller one from rotting vegetation. However, these pale in comparison to the contribution from humans; namely vehicles, factories, and the burning of coal. Sulfur dioxide and nitrogen oxides are the two products of industry that cause acid rain to exist, through the chemical reactions detailed below.
The chemical interactions in precipitation that lead to acids being formed
Incredibly rare as it is, an asteroid can even result in a massive amount of sulfur trioxide being released into the atmosphere. Japanese researchers have theorized that the asteroid that wiped out the dinosaurs 65.5 million years ago released so much sulfur trioxide into the atmosphere that a torrent of lethal acid rains directly followed its impact.
Of course, important monuments are not immune to corrosion. Limestone is one material that a lot of monuments were constructed out of, and it is also one of the most vulnerable to acid. This is significant enough that a lot of research has been done trying to develop protections for limestone structures.
If you want a visual, here is a video from Discovery with one of their staff members looking around in Washington D.C. and observing acid rain damage in some notable locations.
Scientists have done work trying to lower sulfur dioxide and nitrogen oxide release from industry, but what is the easiest solution to the threat of acid rain? Simple, cutting down on vehicle emissions and the burning of coal. Otherwise, acid rain will only continue to be a growing problem and will cause more harm to buildings, people, and ecosystems.
Painting the town colourful with stretchable cellulose nanocrystals!
Just a few months ago, Dr. MacLachlan and his research group from the University of British Columbia discovered some extraordinary new properties of an elastomer made with cellulose nanocrystals (CNCs), which is a biomass-derived substance. These CNCs are everywhere, and can even be obtained by “tak[ing] a piece of paper and treat[ing] [it] with sulfuric acid for 45 minutes,” as Dr. MacLachlan explained. When this abundant and environmentally friendly material was added to the elastomer, it gave the elastomer its optical properties. In other words, when it is stretched under cross-polarizers, the CNC-elastomer changed colour, depending on how much it was stretched!
Stretching the CNC-elastomer under cross-polarizers. Source: Nature Communications
The MacLachlan group started working with CNCs for their optical properties by accident, or as Dr.MacLachlan said, “Serendipity in Science.” When they were looking into cellulose nanocrystals for storing hydrogen, one of the hundreds of samples came out with a red colour, which initiated Dr. Maclachlan’s invested research on cellulose nanocrystals.
Colourful thin films made with cellulose nanocrystals. Source: Chemistry World
The research group was interested in incorporating CNCs into elastomers since previous studies demonstrated that CNC-incorporated materials, such as silica and resins, proved to be inflexible and fragile when stretched. Therefore, the research team decided to investigate different methods that could synthesize a uniform CNC/elastomer structure, which can be stretched and returned to its original form once removing the applied force. The CNCs were successfully incorporated into the elastomer with the help of a sugar additive that helps stabilize the elastomer through evaporation of the solvent. With the success of incorporating elastomer with CNC, this CNC elastomeric material can be further studied for its optical properties.
The MacLachlan group was able to see fascinating optical properties when putting the elastomer under crossed-polarizers. These crossed polarizers permit only one plane of light to hit the elastomer. This is what allows you to see the birefringent optical properties. Birefringence can occur when light enters a material with a very ordered structure. Due to this order, the light is bent into a different plane, while travelling at a variety of speeds. This is the reason why we see the light scattering off from the highly ordered structures in the stretched CNC-elastomer.
Under a high-powered scanning electron microscope, they were able to determine that the cellulose nanocrystals were arranged in a helical shape in the unstretched elastomer, and would start to unwind when the elastomer was stretched. This unwinding elastomer gives rise to unique optical properties.
When light interacts with the elastomeric material, it gets reflected and bent in different directions, depending on how much the cellulose nanocrystals helical structure unwinds. The extent to which the structure is unwound determines what new colours are visible in the material. In other words, the amount the material is stretched directly related to the colour that we see!
A simple depiction of how the elastomer was made by EISA (evaporation induced self-assembly) and how the cellulose nanocrystals change when stretched in the material. Source: Nature Communications
When the light interacts with the material, it gets reflected and bent in different directions, depending on how much the cellulose nanocrystals helical structure unwinds. The different degrees of unwound structure results in a new colour that we can see in the material. This means that the amount the material is stretched is directly related to the colour that we see!
The observed spectrum of colour we see in inversed when the analyzer is parallel with the polarizers. We see the complementary colours. Source: Nature Communications
The discovery of the optical properties in CNC-elastomer is a significant step in the right direction, which can later be used in many applications. The MacLachlan group is currently making a CNC-elastomer that does not require crossed polarizers so we would be able to see the colour change with our naked eye! This new optical property would open up new possibilities for how this material can be used in our daily lives.
Some future applications include applying a thin layer of CNC-elastomer onto bridge supports and buildings. This would be a major benefit for the residents in Vancouver, as we are in a high-risk earthquake zone. As a result, the thin film could help us determine if our buildings are structurally intact with a simple colour change.
Vancouver’s Lions Gate Bridge. Source: Flickr
Another high impact example would be to coat the shipping boxes with this CNC-elastomer. Ideally, any tampering or damage done to the shipping boxes would be indicated by a colour change in the CNC-elastomer. So say good-bye to damaged Amazon deliveries and hello to a whole new world of satisfied internet customers.
Source: Flickr
This CNC-elastomer and future generations of it will result in endless applications, ranging from sensors in smartphones to incorporating it into helmets for impact sensing – it can do it all! In the 21st century, we live in a very visual society and respond strongly to visual changes like a colour. The impact of a material can have on your life by telling you a lot of information in an eye-catching way, which can bring home the important messages that it may be telling you. Imagine a future world where a simple colour change contains so many information like we see in a sci-fi movie. It is somewhere we want to live, and we believe that CNCs-elastomer’s have the potential to bring us there!
~ Alan, Amanda, Emily and Isabelle
Posted in Science in the News
Tagged Cellulose Nanocrystals, CNCs, Colour Changing, Elastomer, Materials Chemistry
