Changing Ref. Index of Silicone Rubber
J. B. Rowland
liquid silicone rubber. The rubber must be optically clear and must
have a fairly quick curing time (in oven <24 hrs). But, I need two
batches of this silicone one with a refractive index of 1.40 and another
with an R.I. of 1.51. I have already contacted most of the major
silicone manufacturers with no luck, and I have decided to try and alter
the R.I. myself. Any suggestions?
Alan "Uncle Al" Schwartz
Changing the refractive index of silicone rubber entails two problems -
preventing the altering species from exsolving (blooming), and preserving
the physical properties of the rubber. The former demands covalent
linkage. Few organic things which dissolve in silicone rubber stay put.
You will ahve to live with the latter.
Hey, fella, 1.51 is kinda high.
If you can tolerate a stiffer rubber, replace part of the -O-(SiMe2)-
with -O-(SiMePh)- or (stiffer still) -0-(SiPh2)-. If fluorescence is not
a problem and you have a vinyl cure, add extra Si-H component and sop it
up with vinyl carbazole. Nothing boosts polymer RI as well as that stuff
- I made 60% water high-RI hydrogels ("Invulneron") with extraordinary
physical and optical properties. If you can get reactive oligomers iwth
phenethyl or phenylpropyl side chains replacing SiMe, you will get good
RI boost with lessened stiffness increments.
If you are using/depositing thin layers (fiber optics, perhaps?) you
might consider mixing or diffusing in a photoreactive (nitrene, carbene)
precursor with a fat aromatic ballast, especially a diphenyl sulfoxide.
Hit it with a blast of UV to covalently link it within the cured
silicone rubber.
--
Alan "Uncle Al" Schwartz
Uncl...@ix.netcom.com ("zero" before "@")
http://vvv.com/adsint/freehand/uncleal/
"Quis custodiet ipsos custodes?" The Net!
(Uncle Al has been Officially convinced to "voluntarily" shut down his
homepage in February. You can own his complete 529 essay collection.
Surf by before it dies!)