The role of the molecular weight of the adsorbed layer on a substrate in the suppressed dynamics of supported thin polystyrene films

Abstract

The adsorbed layer at a solid surface plays a crucial role in the dynamics of nanoconfinement polymer materials. However, the influence of the adsorbed layer is complex, and clarifying this...

Eliminating the Tg-Confinement Effect in Polystyrene Films: Extraordinary Impact of a 2 mol % 2-Ethylhexyl Acrylate Comonomer

“…This approach or very similar methods have been widely used in the characterization of T g by ellipsometry. 3,4,[6][7][8][9][10][11]13,24,27,[31][32][33][34][36][37][38][39][40][41]56,57,61,62 As shown in Figure 1A, the T g for a 15-nm-thick PS film is ∼90 °C, which is ∼10 °C lower than the T g of a bulk, 350-nm-thick PS film. This result is in reasonable accord with other ellipsometry-based determinations of PS T g -confinement effects 3,6,9,10,13,15,23,[31][32][33][34][36][37][38][39][40]45 and can be explained as originating with a free-surface effect.…”

“…The glass transition temperature, T g , is a key characteristic of polymer materials because many physical and mechanical properties change markedly when a polymer undergoes a glass transition from a rubbery state to a glassy state or vice versa. , For polymer films confined at the nanoscale, perturbations originating at the polymer/free surface and the polymer/solid interfaces often result in deviations of the measured T g from the bulk T g . − Such nanoconfinement behavior is important because it can affect the commercial application of ultrathin polymer films and may aid in understanding the underlying mechanisms of glass transition behavior, which has been a long-standing, unresolved challenge. − Indeed, the T g -confinement behavior of polymers has been the subject of intense research since 1994 when Keddie et al , first reported that, relative to bulk T g , the T g s of polystyrene (PS) and poly­(methyl methacrylate) ultrathin films supported on silicon decrease and increase, respectively, with decreasing nanoscale thickness.…”

Langevin dynamics simulation on optimal conditions for large and stable loops of adsorbed homopolymers on substrates

“…1,2,8,14 Moreover, experiments speculated that the adsorption layer affects the glass transition of the polymer thin film through entanglement between loops and non-adsorbed chains. 9–11 Molecular dynamics (MD) simulation proved that entanglement between the loop and free chains inhibits the motion of free chains. 15…”

“…The adsorption of polymers plays a very important role in the stability of colloidal particles, 1,2 nanoscale surface modification, 3,4 antifouling, 5,6 adhesiveness 7,8 and glass transition temperature of polymer films. [9][10][11] The adsorbed chains usually have three kinds of structures: train, loop, and tail, corresponding to continuously adsorbed segments, segments between two adsorbed trains, and non-adsorbed segments at chain's end, respectively. 12 In a substrate-supported polymer film, there is an adsorption layer which consists of a dense flat adsorption layer dominated by trains and an extended layer dominated by loops and tails.…”

“…1,2,8,14 Moreover, experiments speculated that the adsorption layer affects the glass transition of the polymer thin film through entanglement between loops and non-adsorbed chains. [9][10][11] Molecular dynamics (MD) simulation proved that entanglement between the loop and free chains inhibits the motion of free chains. 15 The conformation of the adsorption layer is affected by many factors, such as the chain length, 1,2,5,14,[16][17][18][19] attraction strength of the substrate [17][18][19][20] and polymer concentration, 6,16,[21][22][23][24] as reported in theoretical, experimental and simulation studies.…”