I've been wanting to use 3D printed mold (resin) for curing PDMS for micro-contact printing. I figured that PDMS wouldn't come off that easily so silanization would be required however, I do not have a vacuum chamber so, will it be possible to use Trichloro(1H,1H,2H,2H-perfluorooctyl)silane at lower concentration dissolved in appropriate solvent and dip coat it?
Any suggestions would be helpful!
📷 📷Anhydrous liquid phase deposition of chlorosilanes, methoxysilanes, aminosilanes and cyclic azasilanes is preferred for small particles and nano-featured substrates . Toluene, tetrahy- drofuran or hydrocarbon solutions are prepared containing 5% silane . The mixture is refluxed for 12-24 hours with the substrate to be treated . It is washed with the solvent . The solvent is then removed by air or explosion-proof oven drying . No further cure is necessary . This reac- tion involves a direct nucleophilic displacement of the silane chlorines by the surface silanol . If monolayer deposition is desired, substrates should be predried at 150°C for 4 hours . Bulk deposition results if adsorbed water is present on the substrate . This method is cumbersome for large scale preparations and rigorous controls must be established to ensure reproducible results . More reproducible coverage is obtained with monochlorosilanes .Chlorosilanes can also be deposited from alcohol solution . Anhydrous alcohols, particularly ethanol or isopropanol are preferred . The chlorosilane is added to the alcohol to yield a 2-5% solution . The chlorosilane reacts with the alcohol producing an alkoxysilane and HCl . Progress of the reaction is observed by halt of HCl evolution . Mild warming of the solution (30-40°C) promotes completion of the reaction . Part of the HCl reacts with the alcohol to produce small quantities of alkyl halide and water . The water causes formation of silanols from alkoxysilanes . The silanols condense on the substrate . Treated substrates are cured for 5-10 mins . at 110°C or allowed to stand 24 hours at room temperature .📷Fig. 2 Vacuum tumble dryers can be used for slurry treatment of powders.Fig. 1 Reactor for slurry treatment of powders. Separate filtration and drying steps are required.
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Fig. 3 Twin-cone blenders with intensive mixing bars are used for bulk deposition of silanes onto powders.
Vapor Phase Deposition
Silanes can be applied to substrates under dry aprotic conditions by chemical vapor deposition methods . These methods favor mono- layer deposition . Although under proper conditions almost all silanes can be applied to substrates in the vapor phase, those with vapor pres- sures >5 torr at 100°C have achieved the greatest number of commer- cial applications . In closed chamber designs, substrates are supported above or adjacent to a silane reservoir and the reservoir is heated to sufficient temperature to achieve 5mm vapor pressure . Alternatively, vacuum can be applied until silane evaporation is observed . In still another variation the silane can be prepared as a solution in toluene, and the toluene brought to reflux allowing sufficient silane to enter the vapor phase through partial pressure contribution . In general, substrate temperature should be maintained above 50° and below 120° to promote reaction . Cyclic azasilanes deposit the quickest- usually less than 5 minutes . Amine functional silanes usually deposit rapidly (within 30 minutes) without a catalyst . The reaction of other silanes requires extended reaction times, usually 4-24 hours . The reaction can be promoted by addition of catalytic amounts of amines .
Spin-On
Spin-On applications can be made under hydrolytic conditions which favor maximum functionalization and polylayer deposition or dry conditions which favor monolayer deposition . For hydrolytic deposition 2-5% solutions are prepared (see deposition from aqueous alcohol) . Spin speed is low, typically 500 rpm . Following spin-depo- sition a hold period of 3-15 minutes is required before rinse solvent . Dry deposition employs solvent solutions such as methoxypropanol or ethyleneglycol monoacetate (EGMA) . Aprotic systems utilize toluene or THF . Silane solutions are applied at low speed under a nitrogen purge . If strict monolayer deposition is preferred, the substrate should be heated to 50° . In some protocols, limited polylayer formation is induced by spinning under an atmospheric ambient with 55% relative humidity .
Spray application
Formulations for spray applications vary widely depending on end-use . They involve alcohol solutions and continuously hydrolyzed aqueous solutions employed in architectural and masonry applica- tions . The continuous hydrolysis is effected by feeding mixtures of silane containing an acid catalyst such as acetic acid into a water stream by means of a venturi (aspirator) . Stable aqueous solutions (see water-borne silanes), mixtures of silanes with limited stability (4-8 hours) and emulsions are utilized in textile and fiberglass appli- cations . Complex mixtures with polyvinyl acetates or polyesters enter into the latter applications as sizing formulations .
This info is cut and past from an article posted on rebate below.
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