Re: teeth material

[Dr P Barker <P.Barker@surrey.ac.uk>]

> Does anyone know about or know a reference regarding a material which is
> soft until it has light of a particular wavelength shined on it, at which
> time it hardens?
Many polymers will cross link on uv curing.  I don't know too many details
since I was a polymer physicist and always tried to avoid material which
changed their chemical structure half way through an experiment.  Roughly
speaking you can consider a polymer to be  a chain of -C-C-C-C- (with
bits hanging on the side, or the occasional O or N in the chain - just
for variety).  UV light can break this chain, leaving two carbons
desperate to bond to something.  Sometimes they'll bond to part of
another chain, kicking out some other atom.  Once the chains start
cross linking you'll you'll go from a putty-like material to a rubbery
one, finally to a hard material (like ebonite, or bakelite).  It's possible
to choose polymer chains which are especially susceptible to UV cross
linking, I think a few double bonds (C-C=C-) in the chain help - but
like I say, I avoided them!

Phil
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Phil Barker                phone:  01483 259 329
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