Optical flow cell reflectometry was used to study the adsorption of @entity4280 ( @entity12468 ) to a @entity3440 surface and the subsequent surfactant adsorption and polymer desorption upon exposure to the anionic surfactant @entity3208 ( @entity214 ). We have studied these effects as a function of pH and surfactant concentration, but also for two different methods of @entity3440 preparation, O2 plasma and piranha cleaning. As a function of pH, a plateau in the amount adsorbed of    0.6 mg/m(2) is observed below a critical pH, above which the adsorption decreases to zero within 2-3 pH units. An increase in pH leads to dissociation of surface @entity2145 groups and a decreased potential for @entity3884 bonding between the polymer and surface. For the plasma- and piranha-cleaned @entity3440 , the critical pH differs by 1-2 pH units, a reflection of the much larger amount of surface @entity2145 groups on piranha-cleaned @entity3440 (for a given pH). Subsequent rinsing of the adsorbed layer of @entity12468 with an @entity214 solution leads to total or partial desorption of the @entity12468 layer. Any remaining adsorbed @entity12468 then acts as an adsorption site for @entity214 . A large difference between plasma- and piranha-cleaned @entity3440 is observed, with the @entity12468 layer adsorbed to plasma-cleaned @entity3440 being much more susceptible to desorption by @entity214 . For a plasma-cleaned surface at pH 5.5, only 30% of the originally adsorbed @entity12468 is remaining, while for piranha-cleaned @entity3440 , the pH can be increased to 10 before a similar reduction in the amount of adsorbed @entity12468 is seen. For a given pH, piranha-cleaned @entity3440 has a higher surface charge, leading to a smaller amount of adsorbed @entity214 per @entity12468 chain on a piranha-cleaned surface compared to a plasma-cleaned surface under identical conditions. In that way, the high negative surface charge makes desorption by negatively charged @entity214 more difficult. The high surface charge thus protects the neutral polymer from surfactant-mediated desorption.

Adsorption and surfactant-mediated desorption of @entity4280 on plasma- and piranha-cleaned XXXX surfaces.

@entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity3208 :: ('MESH:D012967', 'Chemical') :: ['sodium dodecyl sulfate'] @entity12468 :: ('CHEBI:53245', 'Chemical') :: ['PVP'] @entity4280 :: ('MESH:D011205', 'Chemical') :: ['poly(vinylpyrrolidone)'] @entity3440 :: ('MESH:D012822', 'Chemical') :: ['silica'] @entity2145 :: ('MESH:C031356', 'Chemical') :: ['OH'] @entity214 :: ('CHEBI:8984', 'Chemical') :: ['SDS']
@entity3440 :: (MESH:D012822,Chemical) :: ['silica']
