Affinity of Polystyrene Films to Hydrogen-Passivated Silicon and Its Relevance to the <i>T</i><sub>g</sub> of the Films

Fujii, Yoshihisa; Yang, Zhaohui; Leach, Joan; Atarashi, Hironori; Tanaka, Keiji; Tsui, Ophelia Kwan Chui

doi:10.1021/ma901851w

Cited by 148 publications

(219 citation statements)

References 35 publications

(77 reference statements)

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“…The non-zero thickness of the irreversibly adsorbed layer after short annealing above the bulk T g is in agreement with values of ∆ε(t = 0) smaller than ∆ε BULK by 20 − 30%, and with previous investigations [31][32][33] . Annealing, in fact, provokes the thickening of an adsorbed layer already formed during solvent evaporation and during the preannealing step, that is, already formed during the most commonly used annealing conditions.…”

Section: Impact Of Chain Immobilization On the Dielectric Functionsupporting

confidence: 91%

“…Such a scaling is in line with our ideas on the impact of interfacial layers, as the thickness of the Guiselin brushes scales with R g itself 29,33 . Regardless of the extent of the distribution of conformations and the kinetics of adsorption, the trends in Figure 4 are in agreement with the idea that ∆T g is proportional to the polymer interface width 43 , that is, the thickness of the interfacial layer with non-bulk density.…”

supporting

confidence: 88%

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The lifetime of the deviations from bulk behaviour in polymers confined at the nanoscale

2011

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monitoring the impact of annealing on the dynamic glass transition of nanometres-thick polymer layers provides new insights into the mechanisms behind the tremendous changes in the performance of macromolecular materials in close proximity to an interface. Here we present results revealing a correlation between deviations from bulk behaviour, manifesting in changes to the glass transition temperature, the reduction of dielectric strength and the growth of an irreversibly adsorbed layer (Guiselin brushes). The non-universal behaviour of polymers under confinement could be explained in terms of a dimensionless number given by the ratio between the timescale of adsorption and the annealing time. In particular, in the case of slow adsorption kinetics, such as for polystyrene on aluminium, deviations from bulk behaviour correspond to metastable states with an extremely long lifetime.

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Section: Impact Of Chain Immobilization On the Dielectric Functionsupporting

confidence: 91%

supporting

confidence: 88%

The lifetime of the deviations from bulk behaviour in polymers confined at the nanoscale

2011

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“…0 (R g ranging from 3 nm to 18 nm) was obtained, close to the one obtained by Fujii et al 25 for native oxide covered Si (h ads ≈ 0.47×R g ) and confirm that the longer the PS chains, the thicker the adsorbed layer as reported also by Housmans 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 in agreement with the work of Fujii. 26 For longer times, differences only arise when films are preannealed or not. The value of h res for pre-annealed films is always greater than for unannealed films.…”

Section: Resultsmentioning

confidence: 99%

Stability of Polymer Ultrathin Films (<7 nm) Made by a Top-Down Approach

Bal

Beuvier

Unni³

et al. 2015

ACS Nano

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In polymer physics, the dewetting of spin-coated polystyrene ultrathin films on silicon remains mysterious. By adopting a simple top-down method based on good solvent rinsing, we are able to prepare flat polystyrene films with a controlled thickness ranging from 1.3 to 7.0 nm. Their stability was scrutinized after a classical annealing procedure above the glass transition temperature. Films were found to be stable on oxide-free silicon irrespective of film thickness, while they were unstable (<2.9 nm) and metastable (>2.9 nm) on 2 nm oxide-covered silicon substrates. The Lifshitz-van der Waals intermolecular theory that predicts the domains of stability as a function of the film thickness and of the substrate nature is now fully reconciled with our experimental observations. We surmise that this reconciliation is due to the good solvent rinsing procedure that removes the residual stress and/or the density variation of the polystyrene films inhibiting thermodynamically the dewetting on oxide-free silicon.

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“…We study the η eff of PS-HSi (hydrogen-terminated Si, it is more strongly adsorbed by PS than SiOx. 18 Figure 4 is the For the 3 nm films (circles), the data with M w below (above) 13.2 kg/ mol were taken at 90°C (120°C). The data of the 5 nm films (squares) were taken at 120°C.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Viscosity and Surface-Promoted Slippage of Thin Polymer Films Supported by a Solid Substrate

Chen¹,

Peng²,

Lam

et al. 2015

Macromolecules

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Thermally activated flow dynamics of polystyrene films supported by silicon is studied for a wide range of film thickness (h 0 ) and molecular weights (M w ). At low M w , the effective viscosity of the nanometer thin films is smaller than the bulk and decreases with decreasing h 0 . This is due to enhancement of the total shear flow by the augmented mobility at the free surface. As M w increases, with h 0 becoming smaller than the polymer radius of gyration (R g ), the effective viscosity switches from being substrate-independent to substrate-dependent. We propose that interfacial slippage then dominates and leads to plug flow. The friction coefficient is found to increase with h 0 providing h 0 /R g < ∼1, demonstrating a surface-promoted confinement effect. ■ INTRODUCTIONMany recent experiments reveal that polymer under confinement in the nanometer range often exhibits dynamics distinguishably different from the bulk. 1−5 While the mechanisms underpinning the new properties are still controversial, most results suggest that they originate from surface effects. Usually, the chain dynamics near the free (air) surface is faster than the bulk 6−11 but that near the substrate is slower. 12,13 By embracing analogous effects in a layer model, variations in the dynamic properties, including the glass transition temperature, T g , 10,14,15 and effective viscosity, η eff , 8,12,16 with the average polymer thickness, h 0 , were explained. At high molecular weights, M w , where the unperturbed radius of gyration, R g , exceeds ∼h 0 , de Gennes further proposed that the highmobility chain segments at the free surface can bring about mobility enhancement to the whole chain through chain connectivity. 17 Here, we report a comprehensive study on the η eff of polystyrene supported by oxide-coated Si (PS-SiOx; SiOx thickness = 102 ± 5 nm) with 13 ≤ M w ≤ 2300 kg/mol (∼3 < R g < ∼41 nm (Supporting Information)), polydispersity index 1.01−1.1, and h 0 /R g from ∼0.2 to ∼10. A new dynamic regime dominated by plug flow and instigated by a surface-promoted confinement effect is found. ■ EXPERIMENTAL METHODSPolystyrene (PS), with a weight-average molecular weight, M w , of 13.7−2300 kg/mol and polydispersity index of 1.01−1.1, was purchased from Scientific Polymer Products (Ontario, NY). In this experiment, we use as-cast films made from spin-coating. Methods of sample preparation and characterization have been reported before. 8,18 In brief, the as-purchased polymer granules are first dissolved in toluene, and then the solution is filtered through a PTFE membrane filter with pore size 0.1 μm (Fisher Scientific Co.) before being spincoated onto a substrate to form the films. The substrates, purchased from Siltronix (France), are single crystal (001) silicon wafers covered by a 102 ± 5 nm thick thermal oxide. Before use, the wafers are cut into 1.5 cm × 1.5 cm slides and submerged in a piranha solution at 130°C for 10 min, followed by thorough rinsing in deionized water and then drying by 99.99% nitrogen. Afterward, the slides are furt...

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Affinity of Polystyrene Films to Hydrogen-Passivated Silicon and Its Relevance to the T_g of the Films

Cited by 148 publications

References 35 publications

The lifetime of the deviations from bulk behaviour in polymers confined at the nanoscale

The lifetime of the deviations from bulk behaviour in polymers confined at the nanoscale

Stability of Polymer Ultrathin Films (<7 nm) Made by a Top-Down Approach

Viscosity and Surface-Promoted Slippage of Thin Polymer Films Supported by a Solid Substrate

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Affinity of Polystyrene Films to Hydrogen-Passivated Silicon and Its Relevance to the Tg of the Films

Cited by 148 publications

References 35 publications

The lifetime of the deviations from bulk behaviour in polymers confined at the nanoscale

The lifetime of the deviations from bulk behaviour in polymers confined at the nanoscale

Stability of Polymer Ultrathin Films (<7 nm) Made by a Top-Down Approach

Viscosity and Surface-Promoted Slippage of Thin Polymer Films Supported by a Solid Substrate

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Product

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Affinity of Polystyrene Films to Hydrogen-Passivated Silicon and Its Relevance to the T_g of the Films