Kinetic traps in polymer adsorption: exchange of polystyrene between the adsorbed state and a good solvent

Abstract

The conformations of polystyrene (PS) adsorbed onto silicon oxide from carbon tetrachloride (CCI4) were investigated through measurements of exchange rates between the adsorbed state and free solution.Infrared spectroscopy in attenuated total reflection (FTIR-ATR) was used to measure PS adsorbed onto oxidized silicon from dilute carbon tetrachloride solution at 25.0 °C. Protiopolystyrene (PS-h; Afw = 575 000 or 96 400) was allowed to adsorb for a variable time from a solution of concentration 1 mg mL"1; then this solution was replaced by a solution of deuteriopolystyrene (PS-d; Afw = 550 000 or 85 000) at the same concentration. An initial rapid exchange was completed over periods of minutes. No subsequent exchange was detectable over periods up to 10 h, indicating that a major fraction of the adsorbed polymer was kinetically trapped. With increasing surface residence time before exchange, the rapid exchange rate slowed moderately and the trapped fraction (TV) increased. For exchange of chains of matched chain length, after a residence time of 16 h, TV = 0.6 (Af" ~550 000) and TV = 1.0 (M" = 90 000). However, TV extrapolated to zero for residence times less than 1 h. In addition, PS-h could be entirely displaced by CH2CI2, indicating for this reason also that the adsorption was reversible in spite of being kinetically metastable. The higher trapped fractions after increased equilibration are tentatively interpreted to reflect logjammed states induced by steric hindrance between intertwined adsorbed chains.

The origin and characterization of conformational heterogeneity in adsorbed polymer layers

“…The common occurrence of non-equilibrium dynamics of polymers at surfaces has recently become widely appreciated [27][28][29][30][31][32][33][34][35][36] but its conceptual understanding has remained unsatisfactory. Can useful generalizations be made regarding what determines the distribution of heterogeneity given the intrinsically history-dependent nature of these materials?…”

Adsorption and Exchange Dynamics in Aging Hydroxyethylcellulose Layers on Silica

“…In cases where the decay was due to displacement of labeled chains by unlabeled chains as part of the adsorption process, the decay was interrupted when DI water was injected (42). Second, in cases where the adsorption of unlabeled material was preferred over fluorescein-labeled material, the effect was ionic strength dependent (40). Figure 4 shows that over the ionic strength range from 0.02 to 0.3 M, there is negligible influence of ionic strength.…”

“…Then, k ex = k ex , and K HEC−FHEC = K FHEC−HEC = 1. This assumption is frequently violated, for instance, with deuterio and protiopolystryene adsorbing on silica from CCl 4 (40), and fluoresceintagged PEO adsorbing onto silica at low ionic strengths (41). For coumarin tagged (PEO) on silica, the label was minimally invasive, with K CPEO−PEO = 2.5 for molecular weights near 100,000 (10).…”

Adsorption of polyethylene oxide on surface modified silica - stability of bare and covered particles in suspension

“…Their are some references in the literature [39][40][41] that polymer layers change their conformation in several hours. Also the existent time-dependence flocculation by bridging is a hint for a change of the layer structure in a period of hours.…”