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Nylon – a bit of a stretch

25 September, 2014 - 13:41

Guest post by Rowena Fletcher-Wood

I first heard the story of the discovery of nylon during a chemistry class in school – it was told as a serendipitous discovery. A young lab assistant, clearing up at the end of a long day, clumsily poured two mixtures in together and noticed a precipitate. Dipping in a stirring rod, he pulled out a thin string, which he stretched out into a tough, translucent fibre. He realised the potential of his discovery, reported it to his superiors and left them to the tiresome job of working out what he had done to make it.

The invention of nylon created a revolution in hosiery
©Shutterstock

It’s funny how we use accident to shape our understanding of discovery and achievement, as though we want to excuse hard work and apologise for years of learning. It’s somehow disappointing, unromantic: the story of research whisks away that tantalising fantasy of stumbling upon treasure, reserving discovery for the experts.

The real story of nylon, interesting though it may be, is a bit of stretch from serendipity.

There was a young lab assistant, and his name was Julian Hill. He was working in the DuPont research laboratory, led by the rigorous organic chemist Wallace Hume Carothers, who had taken on the challenging ‘synthetic fibre race’. At the time, synthetic polymers were a mysterious conception; what they were made of and how they related to simpler compounds was unknown. The DuPont team had studied complex natural products such as cellulose and silk and from their understanding had developed polyamides through the condensation of dicarboxylic acids with diamines – fantastically interesting but, at the time, not particularly useful.

Discovery of nylon, 1941 re-enactment. DuPont chemist Julian Hill (1904-1996) carrying out a re-enactment in 1941 of the discovery of nylon in 1935. A glass rod is being used to pull threads from the sample prepared in a glass tube. This discovery was made at DuPont’s Experimental Station near Wilmington, Delaware. Hill was a member of the team, along with other chemists. The molasses-like mass stuck to the glass stirring rod and was drawn out into a thin fibre. After more research and development, DuPont was able to commercialise the new material. Production started in 1939, twelve years after the research program had started in 1927. Credit: Hagley archive/Science Photo Library

Julian Hill had been working with polyester when, dipping in a stirring rod, he pulled out a thin string, which he stretched out into a tough, translucent fibre – just like in the story I was told. But this was not considered extraordinary. Often, discovery is not about observing properties, but recognising them. One day, when Carothers was absent from the lab, the chemists decided to go rogue with the polyester and have a competition to see how long they could stretch it. They raced down the hall, delicately extending the fibre. They had extended it to four times the original length when it stopped. It would not stretch any more.

Suddenly, Hill understood: as they stretched the fibre, chains of molecules snapped into position, orienting themselves into a chain of a discrete thickness. This would be the basis for the first fully synthetic fibres.

But nylon was far from invented. The melting points of the polyesters they had were far too low for any practical applications, and so they returned to polyamides and began stretching those instead. It took 9 months, a patent for the ’cold-drawing’ process of making fibres by removing them from the water of condensation, and 80 new polyamides before the most promising, nylon-6,6, was discovered in May 1934.

Nylon, a dyeable, durable, shiny thermoplastic first entered the market in 1938 as the bristles of a toothbrush, before being appropriated for women’s hosiery in 1940. DuPont declined to trademark the name ‘nylon’, instead allowing it to enter the lexicon as an alternative name for ‘stockings’. The new ‘nylons’ were a huge success. Nowadays, this fantastic fabric, which leaves a lower carbon footprint than wool, is used for meat wrappings, instrument strings and carpets, amongst many other things. Its only downside is its toxicity upon heating: it melts rather than burns, and breaks down to produce hydrogen cyanide.

This is ironic, actually, because Carothers never got to see his creation take hold. In 1937, just as his achievements were being celebrated and developed, he committed suicide with cyanide. He had suffered with depression and was grieving for the loss of his sister, but his suicide came as a shock. The suicide has been described as an ‘embarrassment’ for DuPont, and records relating to Carothers were lost or destroyed. This may help to explain why the discovery of nylon has since been wrapped in myth and mystery.

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Categories: Education

A short time ago in a journal not so far, far away…

18 September, 2014 - 13:16

Guest post from Tom Branson

Inside Back Cover: Selective Targeting of Tumor and Stromal Cells By a Nanocarrier System Displaying Lipidated Cathepsin B Inhibitor (Angew. Chem. Int. Ed. 38/2014)
Angewandte Chemie International Edition
Volume 53, Issue 38, pages 10251-10251, 22 JUL 2014
DOI: 10.1002/anie.201406845
http://onlinelibrary.wiley.com/doi/10.1002/anie.201406845/full#car1

Science fiction often predicts future advances and has even prompted the development of some technologies. So should we be taking advantage of this association? Can we use a science fiction setting to showcase science fact? That idea is exactly what the latest cover of Angewandte Chemie has attempted to do.

It’s a trap!

There may be some of you who don’t immediately recognise the image above. It’s an homage to a scene in the Star Wars movies, where the plucky rebel alliance (piloting the small x-wing fighters) mount an attack on the Death Star, a moon-sized weapon of mass destruction and flagship of the evil empire. Hijacking this iconic scene is a certain way to grab the attention (George Lucas himself used it twice), especially by tapping into the current hype for the forthcoming films. But there doesn’t immediately appear to be a solid link between the rebel’s cause and Angewandte’s publishing ideals. In this case I’m not sure if the cover image really works to enhance and explain the research or actually provides a distraction from the science within. It’s certainly a fun image and a good way to get instant recognition of an idea, especially with fans of the franchise. That idea being the destruction of the evil empire, or in this case, evil cells.

In this interpretation the x-wing fighters have their own force fields and are carrying pills towards the Death Star, which itself looks to be in a dire state probably due to the growths in its innards. It should be a straightforward mission as long as the ships watch out for rogue fluorescing cells and a giant-lipidated-space-peptide.

This cover is very similar to an example from 2012 that also showed up in Angewandte. In both cases the empire, represented by the Death Star, took a beating, suggesting that there’s no sympathy for the Sith in the scientific community. For balance, I’d like to see someone’s interpretation of a Death Star nanoparticle destroying the peaceful bacterial population of Alderaan (I will accept joint authorship).

Stay on target

I love all things Star Wars (excluding Jar Jar Binks, of course) but this latest tie in to the franchise does seem a little out of place with the expanded Star Wars universe. No mention of carbonite or even ion cannons. But it does hint at the true content of the article: a new targeted drug delivery method. The group led by Boris Turk and Olga Vasiljeva from the Jožef Stefan Institute in Slovenia, have developed lipid vesicles conjugated to peptides that target extracellular cathepsin B (CtsB). CtsB is a cysteine protease that only translocates to the cell surface during cancer progression and is therefore a cancer-specific target. The research showed fluorophores and anticancer drugs could be transported in their vesicles and target the tumour environment.

For more about targeting cancer and less about the rebel alliance’s struggle, have a look at Angewandte Chemie.

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Categories: Education

Fried eggs, frying pans and fluoropolymers

16 September, 2014 - 14:57

Guest post by Jen Dougan

Of all the components of a cooked breakfast, a perfectly fried egg is arguably the most important. It’s for that reason, despite the myriad of other factors to consider – size/weight/colour/celebrity chef endorsement – that a frying pan’s non-stick credentials are key.

Polytetrafluoroethylene (PTFE), the ‘big daddy’ of non-stick, was discovered by accident in 1938. While attempting to make a new CFC refrigerant, American industrial research chemist Roy J. Plunkett noticed that a cylinder of tetrafluoroethylene had stopped flowing but its weight suggested something still inside. In his own words, ‘more out of curiosity… than anything else,’ Plunkett and his assistant cut open the cylinder to discover it was packed at the bottom and sides with a white, waxy solid. Analysis showed that the material was chemically inert, thermally and electrically resistant, and had very low surface friction.

What they had discovered was PTFE, a linear fluoropolymer prepared by the free-radical polymerisation of tetrafluorethylene. The carbon–fluorine bond is the strongest single bond in organic chemistry and the fluorine substituents shield the carbon skeleton from attack, making it chemically inert. Because of its useful material properties (and far from thoughts of fried eggs) PTFE was branded as Teflon and found uses in the Manhattan project, aerospace industries and even gecko research (it is the only known material to which a gecko’s feet cannot stick). But how did Teflon make its way from nuclear research into our kitchens?

By the 1950s Teflon was being used in fishing lines and a French woman asked her husband, an engineer, to coat her aluminium cooking pans with the material. PTFE-coated non-stick cookware was created, and launched as TefAl (from Teflon Aluminium). By the 1960s PTFE–coated cookware was being used in kitchens on both sides of the Atlantic.

However, on searching recently for a new frying pan I found many instances of implied safety issues with PTFE, mostly from ‘eco pan’ manufacturers and advocates. Two main themes recurred in accusations against PTFE cookware: concerns over perfluorooctanoic acid (PFOA), a surfactant used in its production, and ‘polymer fume fever’ – symptoms caused by inhaling polymer decomposition products.

PFOA is an environmentally persistent chemical and, in the mid-2000s, was classified by the US Environmental Protection Agency (EPA) as ‘likely to be carcinogenic to humans’. DuPont, a major user and producer of PFOA, settled with the EPA in 2005 over its failure to report possible health risks associated with PFOA. While PFOA is not present in PTFE cookware itself (it is destroyed during the manufacturing process), it was an environmental concern and after EPA stewardship, PFOA is no longer manufactured nor used by the major global fluoropolymer manufacturers, including DuPont.

Aside from PFOA concerns, PTFE coatings do begin to degrade at 260 °C. The decomposition of the polymer coating produces fumes, which, if inhaled, can cause ‘polymer fume fever’ – temporary symptoms much like the flu virus (see Shusterman DJ, Occup Med. 1993 8(3) 519). But just how likely is this to occur? It is possible to rapidly heat a pan to >260 °C, but if you follow the manufacturer’s instructions and don’t heat an empty pan,you would likely avoid any instances. The most common fats used in cooking have a smoke point well below 260 °C, which should act as a sufficient indicator of pan temperature and kitchen safety. Obviously, heating the pan without fat as a temperature gauge is riskier and should be avoided.

Still not keen on PTFE? There are alternatives. Used for cookware since the Han Dynasty in China (206 BC – AD 260) and still popular with cooks today, cast iron pans have unquestionably stood the test of time. Cast iron frying pans come bare or with an enamelled coating. Bare cast iron pans are porous and to achieve a non-stick finish worthy of a fried egg, oil is polymerised to form a hydrophobic layer across the pan surface. This process, known as ‘seasoning,’ can be repeated as required (depending on treatment of the pan), though is usually recommended yearly.

I’m satisfied that with normal use, PTFE pans will produce perfectly fried eggs without adverse health effects (apart from a risk of increased cholesterol). The only remaining question is whether to have them over-easy or sunny side up?

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Categories: Education

Meet our guest bloggers – Jen Dougan

16 September, 2014 - 12:53

My name is Jen Dougan and I am a Field Applications Scientist with an SME, developing diagnostic tools for clinical analysis. My job involves working with our R&D teams and customers in the field to drive and support product and applications development.

I recently moved into this position after a PhD and two post-docs (and a brief stint in science policy) in bio-nano-analytical chemistry. What I’ve loved about the transition into this role is the chance to ask questions and provide answers in a fast-paced, rigorous environment. It’s been fantastic to see some of the techniques used through my PhD and post-docs in action in a clinical setting.

Real world applications of chemical research are a central theme of this blog. I’ll be contributing regular posts here, to explore the chemistry in our every day lives. From the clothes we wear to the goods we use, it really is a chemical world.

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Categories: Education

Academic family: Sir Harold Kroto

11 September, 2014 - 16:35

Guest post by JessTheChemist

‘Scientists have a responsibility, or at least I feel I have a responsibility, to ensure that what I do is for the benefit of the human race’ – Harry Kroto

Thank you for your nominations for this month’s blog post. It was great to see so many of you getting involved in this series, highlighting interesting Nobel laureates for me to cover. However, I could only pick one winner, so I decided to write about Harry Kroto, inspired by this tweet from Bolton School:

@ChemistryWorld @JessTheChemist How about Bolton School Old Boy ‘Sir Harry Kroto’?

— BoltonSchoolChem (@Chem_BoltonSch) August 20, 2014

 

Harry Kroto has a formidable CV. Not only is he a highly distinguished and talented chemist, but he does a great deal to improve the teaching of chemistry to future generations. This has included setting up the not-for-profit Vega Science Trust, which helps scientists communicate with the public at large, and even returning to his childhood school to build Buckyballs with students.

Kroto began his career at the University of Sheffield where he gained his PhD in high resolution electronic spectra of radicals. After time spent in Canada and the USA, he returned to the UK – to the University of Sussex – to begin his independent research career. His research concentrated on the identification of carbon chains in the interstellar medium, which included work at Rice University, where Kroto and colleagues, Richard Smalley and Robert Curl, discovered the existence of C60 or Buckminsterfullerene. The discovery itself has become a well known scientific story, recently retold by Rowena Fletcher-Wood here on the Chemistry World blog. After numerous publications on the subject, Curl, Kroto and Smalley were awarded the Nobel Prize in chemistry in 1996 ‘for their discovery of fullerenes’. As with many other Nobel laureates, there’s a detailed biography of Kroto published by the Nobel foundation here.

Kroto is related to a number of influential scientists. He is distantly related to Roger Kornberg, who won the Nobel prize in chemistry in 2006 for his work on the molecular basis of eukaryotic transcription. Kornberg was lucky enough to work for the Nobel prize winner, Francis Crick, who famously contributed to the proposal that DNA had a double helical structure, along with James Watson.

Kroto’s academic partners and fellow Nobel prize winners, Curl and Smalley also have impressive scientific pedigree. Curl’s academic father was E. Bright Wilson, a pioneer in spectroscopy, and grandfather was Linus Pauling, who won both the Nobel prize in chemistry and the Nobel peace prize. Curl is also academic brother to Dudley Herschbach, winner of the Nobel prize in chemistry in 1986 for contributions towards the molecular dynamics of elementary chemical processes. Hershbach shared the prize with the Hungarian-Canadian chemist John Polanyi and Yuan T. Lee, the first person from Taiwan to be awarded a Nobel prize. Smalley is academically descended from William Lipscomb, who took the 1976 Nobel prize in chemistry for his contributions to borane chemistry. Not shown in our family tree are Thomas Steitz and Ada Yonath, who both went on to win Nobel prizes after time spent in Lipscomb’s lab. Lipscomb also demonstrated his sense of humour by regularly presenting at the Ig Nobel awards. Curl is also connected to Peter Atkins, author of undergraduate students’ favourite physical chemistry textbook!

Sir Harry Kroto's academic family tree

As you can see, Kroto has an eclectic lineage, and rich academic family history, from chemical biologists to physical chemists. Do you want to know what your academic genealogy is? If so, head to academictree.org, where you can add yourself to the website and start creating your very own tree.

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Categories: Education

Funding for fiction’s favourite poison

9 September, 2014 - 12:46

‘As for monkshood and wolfsbane, they are the same plant, which also goes by the name of aconite.’ – Severus Snape, Harry Potter and the Philosophers Stone by J. K. Rowling

In Harry Potter’s very first potions lesson he learnt about the magical properties of aconite. Muggle chemists, it seems, are only one step behind the magical world.

©istock

Aconitine – spelt slightly differently by scientists – has a highly complex structure that has never before been synthesised in the lab. But now, Duncan Gill from the University of Huddersfield, UK, has been awarded a £133,481 grant to develop a synthetic route to obtain this illusive molecule.

Attempts to make aconitine began after Czech chemist Karel Wiesner revealed its chemical structure in 1959. Weisner went on to publish several papers on the synthesis of alkaloids and terpenoids, an important initial step towards making the molecule. However, it wasn’t until last year that a major milestone was reached, when a team of researchers from the Memorial Sloan Kettering Cancer Institute, New York, announced the total synthesis of the related compound, neofinaconitine. Building on the work of his predecessors, Gill will have to develop new chemical methods to reach his target molecule.

If successful, Gill, who has previously worked as a process chemist at AstraZeneca, will need to be particularly careful when handling this compound. Aconitine is a potent neurotoxin and has been dubbed the ‘Queen of poisons’. One of the most notable references to aconitine comes from William Shakespeare’s Romeo and Juliet: it is the main ingredient in the toxic potion drunk by Romeo with fatal consequences.

The grant has been provided by the Leverhulme Trust and will be enough to employ a full-time post-doctoral advisor. Only time will tell if they can bring this fictional favourite to life in a laboratory setting.

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Categories: Education

The ‘ooh, that’s interesting’ moment

4 September, 2014 - 15:29

Guest post by Heather Cassell

©Shutterstock

Sometimes it happens when I’m reading a research paper, sometimes when I’m doing an experiment, analysing data or learning a new technique; or more often when I’m reading Twitter. It’s that moment when you discover something new and interesting, or re-discover a fact that you used to know, and it makes you pause and think ‘ooh, that’s interesting’. For me the discovery usually leads to a massive detour into reading things other than those I was meant to be reading or working on, but I always learn something from it and sometimes it’s actually relevant to my work. Whether it directly affects research or not, the ‘ooh, that’s interesting’ moment is at the heart of scientific investigation.

It can be great when it happens during an experiment, but it can also be deeply frustrating. An unexpected result forces you to seriously consider what is happening and to plan more experiments to further examine the anomaly. This encourages you to combine techniques, make use of all of the resources at your disposal or even seek out new collaborators. If the anomalous result is reliably proved correct and reproducible, then you will need to do more research to explain it. At its best, this is a very exciting time as you will get to learn new skills, create new knowledge and develop partnerships. At its worst, it can shatter your previous assumptions or even show that your idea or product is not as good as you think.

Personally, I really enjoy the flurry of activity associated with learning something new, especially a new experimental technique. I was recently involved with some experiments using atomic force microscopy (AFM) – I had a vague idea of what it was but I had never used this technique before. The analysis produced some amazing pictures but I had no idea what they meant, so I spent an enjoyable afternoon learning all about how AFM works and comparing the results we produced with results already published. The next time we used the machine I could analyse the images as they were formed, which was really helpful for determining if it was showing what we wanted or not. The ‘ooh, that’s interesting’ moment had provided the push I needed to learn a new skill.

Outside the lab, I really love spending time on Twitter. With so many scientists (and non-scientists) from different fields providing links to articles and blogs, there’s always more than enough to read. Just 10 minutes reading tweets can leave me with countless browser tabs open and new favourites to read. It’s now easier than ever to share your ‘ooh, that’s interesting’ moments with the world, meaning a tweet from a researcher half way across the globe can inspire new ways to think about my own research.

It is this process of discovery and continuous learning that is one of the main things I love about science. Now, back to Twitter…

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Categories: Education

Oranges and Lemons

28 August, 2014 - 15:33

Guest post by Rowena Fletcher-Wood

Scurvy plagued early sailors, and although many treatments were tried and promoted, a simple cure was masked for centuries behind a series of mistakes and misunderstandings.

This story begins at sea, long into a voyage after the fresh food stock had long run out and the sailors were left with only grains, hardtack and cured meats to eat. The sailors would become desperate as scurvy began to set in. Sailors were lost to scurvy in vast numbers, with estimates as high as two million lives lost between 1500–1800 AD.

©Shutterstock

Scurvy is an unpleasant disease in every way. Although symptoms take weeks or months to develop, they get very nasty. First you become lethargic, anaemic and pale, and all of your joints and muscles ache. You lose your appetite and begin to develop spots on your thighs and legs. Soon you become feverish, sick, and weak; gums soften and bleed, legs swell, old wounds reopen. Depression sets in. Eventually, scurvy takes hold completely: your teeth fall out and gums turn blue, you bleed beneath your skin and from the follicles of hairs. You suffer cardiac arrest and die.

Scurvy is caused by a deficiency in vitamin C (ascorbic acid), which is present in many foods – including tomatoes, sweet peppers, strawberries and spinach – but in particular citrus fruits. Several pathways in the body rely on vitamin C; it is vital for building collagen in tissues. We also use it for lipid metabolism, neurotransmission and strengthening bone and blood vessels. Although many species are capable of synthesising their own vitamin C, humans and a few other animals cannot – it is an essential nutrient that must come from our diet. But until 1927, we didn’t even know it existed.

The ancient Greek physician Hippocrates knew that fresh fruit, especially citrus, had an antiscorbutic effect – it could prevented and cure scurvy. In 1747, James Lind systematically proved that the addition of citrus fruit to the diet both treated and prevented the disease, in a candidate for the first ever clinical trial. But the medical establishment were not convinced, and continued to promote other approaches, including good hygiene, exercise, avoiding tinned meat and improving morale. Some of these approaches were successful, including prescribing the peppery herb scurvy-grass, which is related to horseradish. Unknown at the time, scurvy-grass leaves are rich in vitamin C.

A common belief was that the acidic principle treated scurvy: doctors believed any acid would do and that citric acid in fresh fruits was merely the best. Accidental destruction of ascorbic acid in treatments that would otherwise have been effective was common. Although vitamin C is present in milk, this was destroyed by the new process of pasteurisation, leaving bottle-fed babies susceptible to scurvy. James Lind himself was guilty too, bottling and selling lime juice that promptly oxidised and became useless.

When the 1867 Merchant Shipping Act insisted that all ships carry citrus fruits, fresh lemons were substituted for cheap, abundant West Indian limes which were more acidic but had only a quarter of lemons’ ascorbic acid content. These fruits were juiced, stored in air and piped through copper tubing, oxidising the vitamin C. Later tests in 1918 showed the juice to be almost useless, but at the time this was masked by simultaneous advances in diet and marine travel that reduced the prevalence of scurvy.

We owe the discovery of vitamin C to guinea pigs. Two Norwegian physicians, Axel Holst and Theodor Frølich, decided in 1907 to induce in guinea pigs a disease called beriberi, now known to be cause by a deficiency of vitamin B1. They used the same dietary restrictions they had used to induce the disease in pigeons, but the guinea pigs developed scurvy instead. Pigeons produce their own vitamin C, but like us, guinea pigs cannot. This was an exciting moment in medical history: the diseased guinea pigs were the first examples of non-human scurvy sufferers.

In 1932, the Hungarian biochemist Albert Szent-Györgyi posted a sample of hexuronic acid – which he had isolated in 1927 – to the University of Pittsburgh, asking them to test it on guinea pigs with scurvy. The results would gain him the Nobel prize for medicine five years later, and hexuronic acid was renamed ascorbic acid to celebrate its antiscorbutic effect.

Decades of nutritional experiments and almost–correct hypotheses had seen scurvy become increasingly rare, but it took almost 200 years – from Lind’s nutritional trials to Szent-Györgyi’s experiments – to identify the secret in citrus fruits.

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Categories: Education

WebElements: the periodic table on the WWW [http://www.webelements.com/]

Copyright 1993-2011 Mark Winter [The University of Sheffield and WebElements Ltd, UK]. All rights reserved.