The chemistry that delighted us in 2018

This isn’t the bunny you’re looking for

A team of researchers in China fashioned a silk-based cloak that appears to fool night-vision technology. The cloak was woven from fibers that were at once porous and strong, thanks to a protocol of freezing, and then freeze-drying, a mixture of fibroin (a silk protein) and chitosan (a sugar). The inspiration was polar bear hairs, which are hollow, allowing them to reflect infrared emissions from a bear’s body back toward the animal to keep it warm. To test the fibers, the team made a little cape that it placed on a rabbit. Behind the lens of a thermal-imaging camera, the ninja bunny all but disappeared (Adv. Mater. 2018, DOI: 10.1002/adma.201706807). The process to make this fiber is still slow, but the researchers hope it can be used in some commercial product. Let your lettuce be warned.

Resin from the dead

By using gas chromatography and mass spectrometry, researchers figured out in 2018 what went into the fluid used by Egyptians in the second and third millennia BCE. The mixture, gathered from the wrist of the oldest-known mummy in the world, included plant oils, phenolic acids, and plant sugars, plus dehydroabietic acid and diterpenoids from conifer resin (J. Archaeol. Sci. 2018, DOI: 10.1016/j.jas.2018.07.011). The recipe was a surprise to some experts, who thought that during that era, people turned to the dry sands of the desert to mummify corpses. The study’s authors noted that these chemicals were common at later times in the mummification rites of ancient Egypt. The findings suggest that mummification was part of Egyptian cultural identity well before the time of the pharaohs, with whom it is most identified. Mummy mia!

If it’s yellow, let it mellow

Feed a cow only mango leaves and water, and the cow will give you urine that you can turn into paint. And that paint has made artists swoon. In 2018, researchers confirmed that Indian yellow, a brilliant golden pigment prized by artists in the 1800s, was likely manufactured from dried cakes of cow pee (Dyes Pigm. 2018, DOI: 10.1016/j.dyepig.2018.08.014). For years, people pooh-poohed this idea, documented by only one person in 1883, but by using gas and liquid chromatography and mass spectrometry on unrefined samples of the pigment, researchers teased out a chemical called hippuric acid, which is found, you guessed it, in cow urine.

A fizzy splash of color

In the quest for more ecofriendly coatings that can withstand heavy-duty use came this bubbly idea from a research team in Canada during 2018: a paint made with carbonated water. The paint consists of a polymer with charged side chains that dissolves in carbonation. But after it’s applied to a surface, the water and carbon dioxide evaporate, leaving behind a neutral polymer film. The coating withstood submersion and appeared to be durable in testing (Green Chem.2018, DOI: 10.1039/c8gc00130h). But there’s one downside to this low-pressure, Perrier-like paint: it doesn’t pop and hiss when you open the can.

I frizz you not

Could bad hair days be a thing of the past? Researchers in Chicago think so, thanks to a graphene-based hair dye that lends locks a variety of dark hues, tamps down flyaways, and lasts for up to 30 washes (Chem 2018, DOI: 10.1016/j.chempr.2018.02.021). Most hair dyes disrupt the hair shaft, allowing chemicals to meddle with melanin pigments, but lead researcher Jiaxing Huang explained that his team’s hair dye, formulated with the biopolymer chitosan and vitamin C, binds to the surface of hair. It does so through hydrogen bonds and interactions between chitosan and the hair’s keratin. And it seems to stop the electrostatic interactions that lead to the enemy of all good hairdos: frizz.

It’s all in the bag

They may not hold a laptop, wallet, and keys, but tiny cargo bags made in 2018 may work for targeted delivery of reagents or as mini flasks for reactions. The US-based research team that made them dropped a hydrophobic liquid onto an ultrathin polymer disk floating on top of a water-based solution. As the hydrophobic droplet hit the surface and plunged into the solution, the polymer disk wrapped around the water-hating liquid, forming a capsule (Science2018, DOI: 10.1126/science.aao1290). This action, which creates tiny polymer-coated vesicles, takes just a fraction of a second.