Sunday, 29 April 2012

Just what are these "polymers"?

I’ve already said on my blog that I got into science marvelling about spaceships, stars and planets. I then said that I'm a specialist in polymers. So if I'm a logically consistent human being I must obviously think that polymers are as cool as spaceships. To tell you the truth, without polymers I doubt there would be any spaceships at all, but that's another story. This post is a primer on polymers and a very shallow attempt at showing what is so interesting about them.
A brief look around any vaguely man-made environment and we can quickly see that polymers, in their multitudinous forms, are everywhere in our daily lives. From mobile phones to computers, cars, clothes, carpets, stationery, packaging, paint, and even the very fabric of the human body, polymers are a huge part of everyday life whether we know (or care) or not. So what’s so special about a load of old plastic?
The key is in the architecture. Polymers in their simplest form are chain-like molecules formed of molecular repeat units, monomers. The number of repeat units can range from a few (oligomers) up to several million. The size and flexibility of polymer molecules give them their unique properties.
Here is an example. I take my inspiration here from Grosberg and Khoklov's excellent book Giant Molecules. If one were to make a scaled up version of a polymer molecule, say with monomer units the size of a football (soccer ball), that is a sphere with diameter 20cm. Let’s give our polymer  1 million repeat units. If we rolled our polymer up into a ball, nice and tight, it would look like a giant ball of wool with a diameter of about 20 metres, the size of a large detached house. If it behaved like a real polymer molecule dissolved in a good solvent, e.g. polystyrene dissolved in toluene, it would be an extended random structure around 400 metres in diameter. If we stretched it out end-to-end, it would have a length of 200km. 

This hierarchy of length scales gives polymers very interesting physical properties. In general, depending the molecular neighbourhood surrounding it, a polymer chains wants to be as disordered as it can possibly be (a manifestation of entropy and the laws of thermodynamics) and this gives it a structure like a messy coil of rope in three dimensions. Pull on the ends of a polymer molecule and you will feel a force resisting you. Straightening the polymer imposes order upon it. The elastic restoring force that pulls an elastic band back to its original shape is just the result of all those individual polymer molecules wanting to be messy coils rather than to be aligned. Add to that the fact that these long, spaghetti-like structures entangle with one another and you have a complex picture of a not-quite-solid, not-quite-liquid.

Another interesting property that some polymers possess is glassiness. You may think of a glass as a liquid that is unable to flow. Above the so-called "glass transition temperature" a polymer is molten - its molecules have enough energy to constantly rearrange themselves since the thermal energy all things possess above absolute zero causes molecules to be in perpetual motion, and this energy in this case is enough for the polymer molecules to move past one another (and if they are able, to flow). Cool a polymer below its glass transition temperature though, and the chains no longer have enough energy to move past one another - they are jammed, each chain blocking the motion of its neighbour and so on. This produces a tough material, such as perspex (poly[methyl methacrylate]) which is glassy at room temperature.

That's enough hand-wavy polymer physics. Now for some hand-wavy polymer chemistry. 

I think its increasingly fair to say that the chemists are really winning the race to drive polymers forward in the 21st century. Polymer chemistry is the incredibly creative art of playing Lego with molecules. In a typical polymerisation reaction, monomers are added together in a simple chain. A polymer chain does not have to be made up of identical monomers though; monomers with different physical properties (size, shape, etc.) and chemical functionalities (electrically charged, acidic, basic, etc.) may be added to build up a polymer with precisely defined properties. Polymers also do not have to be simple chains. Branched polymers are formed by using special monomers like molecular T-pieces, and are limited only by the imagination (and a little bit by chemistry, but that's somebody else's problem). Mindblowingly complex and large structures may be formed even with a single monomer and a single type of branching point. So I hope I have convinced you that chemists are really good at making lots of different types of polymers. The ingenuity and creativity of polymer chemists is truly second to none.

So put it all together and what have you got? Polymers by their very nature are complex - in some states disordered and engtangled, in other states glassy and unable to rearrange (not to mention crystalline polymers which are a whole other ball game). In all cases the physics of what is going on a the molecular level is responsible for the macroscopic behaviour of a polymeric material. Couple this with the incredible skills of polymer chemists at building polymers practically to order, with tailored properties and architectures, and we have the key to designing and making an abundance of advanced functional materials. The sky's the limit. 

I will heartily admit that I have barely scratched the surface of polymer science in this post, not even close. I hope however that you are a little bit wiser about what polymers are and what they do.

Sunday, 22 April 2012

The best rainbow of my life

You know that moment when you really wish you had your good camera?

I missed a (high definition) photo of the eeriest and most beautiful sight I have seen for a long, long time. I was out walking at about 5.30 pm this evening in Cronulla, New South Wales, and to a Pom relatively inexperienced with the Australian weather, it seemed unseasonably warm and humid for Autumn. The ocean waves were roaring into Cronulla beach, and making huge breakers, even for here, and although it wasn't particularly windy, for some reason a thick soupy ocean mist was all around. I'm sure some of the surf-savvy locals could have explained these conditions much better than I can, but everything about the scene, including a rising tide, contributed to the filmic atmosphere. Colours appeared particularly deep and vivid and the horizon over the ocean was barely visible, the sky and the ocean the same deep, rich grey, blended together.

As it has a habit of doing on planet Earth, the Sun was setting to the west (from Cronulla this means inland, in the direction of the Sutherland Shire). As its rays found a gap through the clouds, they lit the whole scene with a golden light and before my eyes the sliver of a rainbow appeared, from my vantage point appearing to come from the headland of South Cronulla. The sliver grew and grew into the fullest, brightest rainbow I have ever seen. Each individual colour in the rainbow was clearly visible, as was the dark band and the second ring of colours, much fainter than the inner. The rainbow stretched all the way from the headland, over the Bate Bay sky and down to Kurnell. I'm lucky I even had it with me on this stroll, but my phone camera picked up at least some of the detail of the rainbow (the full arc was way to big to capture).

I'm sure that somebody out there has taken an even better photo, because almost everyone I could see in the surprisingly lively Cronulla Park had stopped what they were doing to admire the view, and for the risk of sounding cheesy, it was one of those events that makes strangers begin to talk to one another.

What had made the rainbow so beautifully bright was the sheer volume of water vapour in the sky from the ocean mist, coupled with the low angle to the Sun and the fact that from my vantage point, the rainbow was cast onto the entire empty ocean sky that reaches out east in the direction of New Zealand, so nothing got in the way. The whole thing lasted about 10 minutes before the Sun went behind a cloud again. I can't say everything went back to normal after that though, because of the mist and the churning sea (and the grin plastered across my face).

I am now contemplating making it compulsory to take at least my compact camera with me on walks down to the sea, if not my chunky one. I'm off now to read about the physics of rainbows and I might start here (Wikipedia at its brilliant best).

Monday, 16 April 2012

Into cyberspace

The beginnings of my science blogging have taken me on a whirlwind tour of internet science communication, and I've a feeling I'm not in Kansas anymore. If I'm going to write a blog, I need to know what's already out there. Here is what I have seen on the first steps of my journey into the world of Cyber Science...

First and foremost, I am overwhelmed by the sheer volume and quality of the science communication that is available on the web. The dedication of scientists and science communicators out there today can be in no doubt.

Twitter is by far the chirpiest source of science chat, and even the smallest dabble in the twittersphere can lead to a quick reward. There is a particularly strong presence from journals and scientific publishers, who tweet headlines of their latest research papers, making for an excellent way to keep up to date with the latest breakthroughs. These feeds are not exactly pop science though, basically linking to proper full blown research articles. However, the frequent editorials and blog posts are of more general interest.

Organisations such as CERN (@cern) and NASA (@nasa) give regular updates on their big science projects, often with high-budget and well-thought-out multimedia content to browse. For general roundups, there are several dedicated science news feeds which do exactly what they say on the tin. Probably my favourite twitter feed so far is "Astro Pic Of The Day" (@apod,, which showcases daily images from around the cosmos to get the mind truly boggling. Below is today's image of the Eagle Nebula.
If you like twitter, you can follow this blog in stream-of-consciousness form at @scienceontoast. Hey, you can even follow the adventures of a zucchini who lives in space (@Astro_Zuc, or a courgette if you prefer).

There are quite literally thousands of science blogs out there, from dedicated individual bloggers to full time journal and publishers' blogs. There is no way I can do them justice so I'll just mention a couple. Guardian Science (twitter @guardianscience) has a range of blogs, including John Butterworth's Life and Physics, which has eloquent insights into the deepest questions of fundamental physics, explaining experiments taking place at the Large Hadron Collider amongst other things. At the other end of the length scale lies In The Dark, a blog by cosmologist (and, it would appear, poet and romanticist) Peter Coles. This blog has fascinating insights into the large scales structures of the universe interspersed with poetry, music and biographical pieces about the creator (of the blog, that is, not of the cosmos).

I'm sure I have given somewhat a physical bent to this small sample so I should also mention that the Royal Society of Chemistry and Nature Chemistry have very good chemistry blogs/sites. And I'm sure there are good biology blogs out there too......

This foray into online science has reminded me of the world of wonder that I remember as a young boy. In fact, come to think of it, I distinctly remember feeling that thrill in the lecture theatre as an undergraduate (though Peter Coles probably won't remember teaching me cosmology, I remember his lectures). So perhaps while a journey into the grown-up world of specialised research has given me a career and a roof over my head, perhaps it is good every now and then to sit back and appreciate the true magnitude of the science that is on offer to our fingertips, for free.

Friday, 6 April 2012

The wrong end of the telescope

Hello, and welcome to my new blog, Science On Toast. If you are reading this post, then you are one of my first visitors. Welcome! For what it's worth, let me offer you a little of my perspective on the world of science, and I hope you check back in the coming weeks when I will start my science blogging in earnest.

Like many young scientists, I was initially wowed into the field by big science - planets, stars and galaxies. I was lucky enough as a kid to have glossy books showing cutaway pictures of the Earth and its hot, dense innards, or diagrams of the Sun dwarfing the other planets in the solar system. I was fascinated by the huge forces and unimaginable distances involved, and of course this fitted seamlessly with the science fiction we grew up with; starships, lasers, phasers and warp drive.

Throughout high school physics we came somewhat back down to Earth as we went through the necessary learning of forces, distances and times that were somewhat more on a human scale. Biology taught us to look down microscopes to find the teeny tiny scale teeming with life, and coughs and colds put us beyond any doubt that the lowly germ could wreak havoc (but could also grant us days in bed playing computer games).

A physics student at university, I was caught out at first by the large leap in effort it required to perform at undergraduate level. At the same time though, I was amazed at the depth and variety of courses available and the diverse range of interests and personalities that were all thriving in this vast institution of learning. In the later years of my undergraduate degree the fine strands of science began to pull together. Especially as I began to read my first papers from scientific journals, a bigger picture began to emerge that was pieced together from all the isolated nuts and bolts, but now in sharp context. With the help of excellent academic tutors (to whom I am ever indebted) the way forward crystallised and a Ph.D. scholarship in polymers beckoned.

The study of these very small wiggly things led me to need some very specialist techniques - the scattering of neutrons and x-rays off materials to build up a picture of the atoms and molecules within. These instruments are large (tens of metres in size) and run inside major facilities, requiring of course a source of neutrons or x-rays. And so here I am: the little boy interested in planets, stars and galaxies is a now a grown man gazing deep down into the world of atoms and molecules!

So did I take a wrong turn? I am I looking down the wrong end of the telescope? No! In such a vast field as science, one can have many interests and take many twists. Of course, we must still make good choices, and that is down to following our interests, keeping our knowledge up to date, and, it would seem, a little bit of luck. To quote a sticker stuck on the office door of an Astrophysicist I met somewhere along the way... we are all in the gutter, but some of us are looking at the stars!