Who Knew Plastic Could Be So Clever?

I was wrong, my next post isn't on the reactivity series.

I chose to do Polymers and Smart Materials instead, because they kinda fit together, and now I can tick two items off my list :P

Okay then, so lets go.

Plastics are a long chain of molecules (usually monomers that are alkenes). They're often carbon based too. Polymers have double covalent bonds, which look like- C=C. These double bonds (or unsaturated bonds) open up and 'join hands'.

The easiest example is apparently Ethene becoming Polythene.

Yeah, can you believe it. That's the EASIEST. WJEC are having a laugh in my opinion.

But anyway. That diagram and everything I just discussed is polymerisation, which put simply, is the act of one thing being broken up, stuck back together and with the prefix 'poly' whacked in front. Simples.

Next thing I need to talk about is the properties of plastics and how the forces between their bonds determines those properties.

It's pretty simple.

Week forces between the bonds means the atoms can slide over each other, hence making it stretchy and have a how melting point. Which all makes sense.

And molecules with strong bonds is the exact opposite, so high melting points and no stretchiness.

Alas, I'm not finished. Smart materials, because we've all been dying to get to those, haven't we?

Basically, a smart material is aptly named. It's a clever material because it responds to changes in its environment, like light, temperature and pH. Different smart materials react in different ways, so they all have different names, and here's every little dirty secret on each of them.

Shape-memory polymers - When you heat them up, you can stretch or deform them into any shape you fancy. When it cools off, it'll stay in that shape. But if it gets knocked out of shape (in a car accident, for example), you can take it home, heat it up (with a hair-drier, for example) and it'll go back to the original shape. Which is why they'd be mighty useful to use as car bumpers.

Thermochromatic paints - Are exactly what it says on the tin. They change colour according to temperature change, so we can use them on those baby-forehead-thermometers, black-mugs-that-turn-into-a-picture and those cool sheets they show us in school.

Photochromatic materials - Are also what they say they are. (If you're an idiot, the word 'photo' is in 'photograph' and 'photosynthesis' because they both involve light), so you can correctly assume that photochromatic means that these materials will change colour according to light change. When the light hits the molecules, it breaks a bond, so the material will rearrange itself to form a different type of molecule, which just happens to be a different colour. When the light is taken away, the molecules will go back to the original formation. This is the stuff they use in the fancy varifocal sunglasses for people going blind.

Shape-memory alloys - Surprise surprise, these also do what they claim to do. They seem pretty elastic, and always return to their original shape after being heated. Scientists think these could be useful to replace tendons, and they've already been used to make bendy glasses, and to make springs that widen peoples arteries.

Hydrogels - This one kinda does what it says it does. The hydro bit is fair enough, because these substances are really absorbent and used in nappies. But last time I checked (which, fair enough, was about seven years ago when my brother was born), nappies don't have gel in them. But anyway, these hydrogels can also change according to changes in pH, temperature and infra-red radiation, which would make them useful in replacing damaged muscle tissue.

Wooo. That's the end.

Kthnxbi.