PDMS - NanoLabStaff/nanolab GitHub Wiki
PDMS is a silicon-based organic elastomer with repeating monomer unit SiO(CH3)_2. The elastomer can conform to structures smaller than 100 nm during replica molding. PDMS is typically supplied in a two component kit with a base (vinyl-terminated PDMS) and a curing agent (copolymers of methylhydrosiloxane and dimethylsiloxane mixed with a platinum complex). The low glass transition temperature keeps it liquid at room temperature. Upon mixing, a hydrosilylation reactions takes place between vinyl (SiCH=CH2) and hydrosilane (SiH) groups, cross-linking the polymer.
Cross-linking increases the viscosity until a solid elastomer is formed. The cross-linking is very dependent on temperature. Sylgard 184, a commercially available PDMS-kit from Dow Corning, cures completely in >48h at room temperature, but in 10 min at 150°C. At room temperature it is typically possible to work with PDMS for 2h after mixing, but the viscosity will increase during this time.