Oxygen plasma treatment is commonly used to impart hydrophilicity to inherently hydrophobic polydimethylsiloxane (PDMS). However, the effect of plasma treatment on PDMS prepared from the commercial kit, Sylgard 184, is short-lived as hydrophobic recovery is observed within hours. The rapid hydrophobic recovery is attributed to the migration of low molecular weight (LMW) species to the surface. The effect of LMW species was investigated by deliberately adding them to a simplified PDMS system fabricated using hydrosilylation of vinyl and -SiH functionalized PDMS prepolymers. Long exposure to high vacuum was also evaluated as a method to remove LMW species and to slow down recovery. After short vacuum exposure, the rate of recovery was proportional to the percentage of LMW species added and inversely proportional to the molecular weight of the species. After extended vacuum exposure, these trends were eliminated and hydrophobic recovery of all PDMS systems including Sylgard 184 was substantially reduced.

Hydrophobic recovery of polydimethylsiloxane surfaces after oxygen plasma treatment

245th National Meeting (2013)

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