how to silanise glass ??
J. Cranmer
group but do not remember any details. I would like to know how it is
done and if it is practicable to do this to a 3 inch diameter QVF
glass section. About 12 inches long.
Would this treatment be expected to prevent organics binding to the
glass surface.
Any pointers will be much appreciated.
John Cranmer
mge...@rocketmail.com
1) Dry the glass well either with a bunsen burner or in a very hot oven.
2) When sufficiently cool, plug both ends with desicant as appropriate
(a pledget of very dry cotton might work) or cool in a desicator.
3) Close one of the ends and fill the tube with a solution of
trichlorosilane in methylene chloride.
4) Close the other end and allow the tube to stand at room temperature
for 12-14 hours.
5) Empty the contents of the tube and allow to air dry. Clean
carefully and avoid any source of fluoride ion (e.g. tap water)
The trick is getting the glass as dry as possible before treating. Any
chlorosilane will work but trichloro-X-silanes seem to be the best.
You can do this on a vacuum line by boiling some trichloro silane
through the line a couple of times. We used to silanize NMR tubes this
way.
Good luck!
In article <cIMgOG7uIebNjz...@4ax.com>,
Sent via Deja.com http://www.deja.com/
Before you buy.
Uncle Al
"J. Cranmer" wrote:
>
> I have seen reference to silanised (spelling ?) glass in this news
> group but do not remember any details. I would like to know how it is
> done and if it is practicable to do this to a 3 inch diameter QVF
> glass section. About 12 inches long.
>
> Would this treatment be expected to prevent organics binding to the
> glass surface.
>
> Any pointers will be much appreciated.
You can modify the surface of glass to be almost anything you want -
polydimethylsiloxane, hydrocarbon, cationics, anionics, epoxides,
alcohols, PEG... - using silane coupling agents.
A quick and dirty for silanization would be Rain-X at your overpriced
auto parts supplier. Dilute it with additional anhydrous isopropanol,
soak the clean part for a few minutes, drain, dry, cure at 100 C for
an hour. Hematology supply including scientific supply catalogs has
overpiced silanizers. The champ for my money is Glasclad 6C. I've
had tens of pounds of polymer not stick to glass molds twenty grams at
a time.
http://www.unitedchem.com/ Fancy slane coupling agents are under
their Petrarch label.
To get a really clean glass surface dissolve a pound of KOH in 4
gallons of ethanol in a covered plastic pail, soak the glass
overnight. Retrieve (rubber gloves or tongs - dissolves flesh), wash
with water, 5% HCl, distilled water, drain, dry.
--
Uncle Al
http://www.mazepath.com/uncleal/
http://www.ultra.net.au/~wisby/uncleal/
http://www.guyy.demon.co.uk/uncleal/
(Toxic URLs! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Uncle Al
mge...@rocketmail.com wrote:
>
> Try this (used to work for me).
>
> 1) Dry the glass well either with a bunsen burner or in a very hot oven.
[snip]
NO! Silanization depends upon the presence of surface hydroxyls. You
are passivating the surface (reacting trace hydroxyl), not densely
silanizing it. And if you do that to NMR tubes you can droop them out
of round or out of camber, and will see it in line broadening in a
good spectrometer.
Open up the surface in KOH/EtOH followed by water rinsing, 5% HCl to
protonate, and more rinsing. Then air dry - certainly not above 100
C. Then silanize with an oligomeric reactive chloro or alkoxysilane.
In any case, TMSCl would not do a good job by its lonesome.
TMSCl/hexamethyldisilazane is vastly better.
To silanize RPC phases you want a trichlorosilyl reactive oligomer of
rather long chain length plus one of shorter chain length to create an
anchored crosslinked surface web with fingers desnely outstretched.
Then you cap anything that escaped with a TMS-based silanization like
TMS-imidazole or TMSCl/HMDS.
Steve
to have said
>Try this (used to work for me).
>
>1) Dry the glass well either with a bunsen burner or in a very hot oven.
>2) When sufficiently cool, plug both ends with desicant as appropriate
>(a pledget of very dry cotton might work) or cool in a desicator.
>3) Close one of the ends and fill the tube with a solution of
>trichlorosilane in methylene chloride.
>4) Close the other end and allow the tube to stand at room temperature
>for 12-14 hours.
>5) Empty the contents of the tube and allow to air dry. Clean
>carefully and avoid any source of fluoride ion (e.g. tap water)
>
>The trick is getting the glass as dry as possible before treating. Any
>chlorosilane will work but trichloro-X-silanes seem to be the best.
>
>You can do this on a vacuum line by boiling some trichloro silane
>through the line a couple of times. We used to silanize NMR tubes this
>way.
>
Very interesting - I was told dichlorodimethylsilane was the best -
you're saying Cl3SiH is the best? Is trichlorosilane commercially
avaliable?
This is exactly the technique I was taught except we used ClSi(CH3)2Cl
in toluene - it seemed to give a good coating and was cheap & easy to
get. I always meant to try coating my windshield with it but never got
around to it.....
Steve
>In any case, TMSCl would not do a good job by its lonesome.
>TMSCl/hexamethyldisilazane is vastly better.
>
>
What does the HMDS do that improves the situation?? Thanks....
marq
already found the answer at
http://fig.cox.miami.edu/~cmallery/255/255tech/tech800.htm
thanks anyway, and i learned to better consult the library and the
internet than ask in newsgroup. though reply is really fast here i guess
with the living references like you.
marq
Uncle Al
HCl acceptor and silanizing agent.
mge...@rocketmail.com
> Uncle Al <Uncl...@hate.spam.net> wrote:
> NO! Silanization depends upon the presence of surface hydroxyls. You
> are passivating the surface (reacting trace hydroxyl), not densely
> silanizing it. And if you do that to NMR tubes you can droop them out
> of round or out of camber, and will see it in line broadening in a
> good spectrometer.
Oops. Sorry. Forgot to clarify the difference between drying and
annealing the glass. The objective of drying is to simply remove the
surface moisture of the glass which would react with the silanizing
agent (be it a mono or dihalo silane) which, when I was doing this, was
an expensive reagent.
As Mr. Al gently pointed out, your objective in drying/activating the
glass surface is just that - not to drive off the active surface
silanols.
I can claim no more expertise in the matter of treatment of NMR tubes
than the crudest of hacks but, not to toot my own horn, we did do not a
little to progress the understanding of the phenomena of spin
saturation transfer and the NOE.
Alpphonz
newsgroup is not that bad marq maybe it just happened that there
are some people in the group who assume that subjects they know
too much about are not worth discussing here.
If you don't have time to research in the library...take time.
Alp
J. Cranmer
wrote:
>A quick and dirty for silanization would be Rain-X at your overpriced
>auto parts supplier.
Al
I often wondered. Do you know what is in rainex. It certainly works
well.
The reason I want to silanise the QVF glass is that we have to do an
large scale aqueous / organic (water + salt + alkali / xylene + methyl
naphthylenes) separation at 20 to 60 C.
The product in the organic layer coats the glass and we cannot see the
interface. Would silianised glass stand these conditions.
John Cranmer
Uncle Al
Rain-X patent numbers are on the bottle as is a general description of
the contents. Patent search engines at my Web page. Silanization
does not survive hot aqueous alkali. That's how you clean it off.
Organic scum on windows is a perpetual problem, from sight glasses to
UV disinfection of water.
Have you considered a slidable ultrasonic pinger, looking at echo
change across the interface either by transmission or reflection?
herodotus
soluble (Aqua-Sil) and the other is organic soluble (Surfa-Sil).
* Sent from RemarQ http://www.remarq.com The Internet's Discussion Network *
The fastest and easiest way to search and participate in Usenet - Free!
J. Cranmer
wrote:
>Rain-X patent numbers are on the bottle as is a general description of
>the contents. Patent search engines at my Web page. Silanization
>does not survive hot aqueous alkali. That's how you clean it off.
>Organic scum on windows is a perpetual problem, from sight glasses to
>UV disinfection of water.
>
>Have you considered a slidable ultrasonic pinger, looking at echo
>change across the interface either by transmission or reflection?
It would need to be flame / explosion proof to go into the plant
intended. The bosses will probably not want to pay for that.
John
Uncle Al
Insulate the wires, cover joins and seams with silicone resin. Ground
the metallic case. Rub down the whole thing with a dryer anti-cling
rag every day to dissipate static on dielectrics. Not so bad.
I once suggested that a pilot plant wall of dials and gauges presided
over by a fellow with a clipboard have its outputs rotated so normal
operation had every pointer vertical. The human eye is exquisitely
sensitive to deviation in a parallel field. Not only was the change
safe and effective, it made sense.
Management toured the room a a week later and went ballistic. The
scales went back to registration and the pointers went every which
way. What the hell, they didn't have to work there.
Christopher R. Lee
Soak overnight in dilute HCl (about 1M) to make lots of silanols.
Rinse with water, then methanol, then toluene (or other non hydroxylic
solvent).
Rinse for a few secons or minutes with dichlorodimethylsilane (about 1% in
toluene etc).
Rinse with methanol (to block remaining chlorosilane functions).
Dry in warm air.
The reference dates from before computer databases and is therefore declared
lost :-).
If you have a lot of glassware to do, try a gas phase method that was
published in Analytical Chemistry sometime in 1976. You need a vacuum oven.
Silanised glass is a bit lipophilic, so it will adsorb small amounts of non
polar compounds dissolved in very polar solvants, as with reversed-phase
chromatography. Unsilanised glass adsorbs polar compounds, particularly
cations (by ion exchange).
Regards
J. Cranmer <jo...@jacy.demon.co.uk> a écrit dans le message :
cIMgOG7uIebNjz...@4ax.com...
> I have seen reference to silanised (spelling ?) glass in this news
> group but do not remember any details. I would like to know how it is
> done and if it is practicable to do this to a 3 inch diameter QVF
> glass section. About 12 inches long.
>
> Would this treatment be expected to prevent organics binding to the
> glass surface.
>
> Any pointers will be much appreciated.
>
> John Cranmer
goncalo...@my-deja.com
Deyhimi, Farzad; Coles, Jonathan A. (1982) Rapid Silylation of a Glass
Surface: Choice of Reagent and Effect of Experimental Parameters on
Hydrophobicity Helv.Chim.Acta, 65 : 6 1752-1759.
Regards,
Goncalo Gamboa da Costa
zigo...@my-deja.com
Hi John,
> I have seen reference to silanised (spelling ?) glass in this news
> group but do not remember any details. I would like to know how it is
> done and if it is practicable to do this to a 3 inch diameter QVF
> glass section. About 12 inches long.
Try looking up Goncalo's reference, it looks OK.
And perhaps you will find my experience useful.
I find that bi- or tri-functional silanes
(dichlorodimethyl silane, trichloromethyl silane)
are disastrous. They always lead to the formation of
some silicone polymer on your glass surface, which is
difficult to remove. Only monofunctional silanes
give you a 'molecularly clean' surface.
The chlorosilanes react fast and make your surface
hyddrophobic within seconds or minutes. However they
produce HCl as a byproduct, and this occasionally attacks
other things you have put on your surface (e.g. metal).
Hexamethyldisilazane, HMDS, acts much more slowly
but its byproduct, ammonia, is much less agressive.
It is readily available. You can speed up its action
by heating the surface, say, to 60°.
While HMDS is a liquid, you can get effective silanization
by putting a few drops of liquid in the bottom of a container
and letting the vapor do the work. That way you avoid problems
of having to remove unreacted HMDS afterwards.
SiO2 surfaces go hydrophobic and stay that way,
at least if you don't etch the surface off with alkalis or
HF. However I find that many glass surfaces go back to
being hydrophilic after a while, at a rate which depends
on temperature. My theory, for which I have zero independent
evidence, is that it is related to the mobility of the metal
ions and counterbalancing SiO- sites in the glass creating
new silanol groups at the surface at a steady rate. Maybe someone
out there could comment?
One of the contributors to this thread - sorry I don't remember
who - recommended drying the surface. According to this observation
of mine it should give the same result, namely, to remove
silanol groups without completely covering the surface.
Heating a glass surface to 200°C for an hour does make it
markedly more hydrophobic, but not quite as hydrophobic as
a silanized glass surface. Barry Wood (University of Queensland)
reckons that you have to heat to 800°C to eliminate the last
silanol group.
>
> Would this treatment be expected to prevent organics binding to the
> glass surface.
>
'Prevent' is a big word. However yes, the binding energy of
organics to a silanized surface is much lower than to an untreated
surface, and it is much easier to clean off whatever contamination
you do have by mild procedures like solvents or rubbing with a
paper tissue. The cellulose lint which comes off the paper tissue
doesn't stick.
Cheers,
Zigoteau.
D Smith
The beaker I prepared by DCDMS solution in is of course also silanised, and after a minute or two exposure seems to be completely hydrophobic.
On Sunday, 7 November 1999 08:00:00 UTC, Christopher R. Lee wrote:
> The standard method used for decades by gas chromatographers is:
>
> Soak overnight in dilute HCl (about 1M) to make lots of silanols.
> Rinse with water, then methanol, then toluene (or other non hydroxylic
> solvent).
> Rinse for a few secons or minutes with dichlorodimethylsilane (about 1% in
> toluene etc).
> Rinse with methanol (to block remaining chlorosilane functions).
> Dry in warm air.
>
> The reference dates from before computer databases and is therefore declared
> lost :-).
>
> If you have a lot of glassware to do, try a gas phase method that was
> published in Analytical Chemistry sometime in 1976. You need a vacuum oven.
>
> Silanised glass is a bit lipophilic, so it will adsorb small amounts of non
> polar compounds dissolved in very polar solvants, as with reversed-phase
> chromatography. Unsilanised glass adsorbs polar compounds, particularly
> cations (by ion exchange).
>
> Regards
>
> J. Cranmer <jo...@jacy.demon.co.uk> a écrit dans le message :
> cIMgOG7uIebNjz...@4ax.com...
> > group but do not remember any details. I would like to know how it is
> > done and if it is practicable to do this to a 3 inch diameter QVF
> > glass section. About 12 inches long.
> >
> > glass surface.
> >
mira...@googlemail.com
Poutnik
to prevent inorganic or polar organic binding
to polar Si-OH groups.
For nonpolar organics, the effect may be the opposite,
binding organics to organic coating,
similar to a reverse phase chromatography.
For details how to, it may be preferred
to perform general internet search,
or get specialized literature.
What I heard, it is difficult
to reach professional quality in silanization
for critical application.
--
Poutnik ( The Pilgrim, Der Wanderer )
Knowledge makes great men humble, but small men arrogant.