Influence of generation number on the dewetting of hypergraft poly(2-ethyl-2-oxazoline) films

Barnes, K A.; Douglas, Jack F.; Liu, Dawei; Bauer, Barry J.; Amis, Eric J.; Karim, Alamgir

doi:10.1002/(sici)1097-0126(200005)49:5<463::aid-pi434>3.0.co;2-5

Cited by 6 publications

(6 citation statements)

References 25 publications

(48 reference statements)

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“…The initial formation of holes in thin film is similar to the injection of air into a highly viscous fluid confined to near two dimensions. At a late stage of dewetting, there is a strong tendency for the holes to coalesce, and this coalescence process largely determines the morphology of the late‐stage dewetting pattern 43. When the rims of growing holes eventually contact each other, the opposing faces flatten out because of increased viscous resistance encountered by the polymer, and a thin liquid ribbon is formed between neighboring holes by a merger of these rims.…”

Section: Resultsmentioning

confidence: 99%

Hole‐growth instability in the dewetting of evaporating polymer solution films

Raghavan

Douglas

et al. 2002

J Polym Sci B Polym Phys

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We investigate the dewetting of aqueous, evaporating polymer [poly(acrylic acid)] solutions cast on glassy hydrophobic (polystyrene) substrates. As in ordinary dewetting, the evaporating films initially break up through the nucleation of holes that perforate the film, but the rapidly growing holes become unstable and form nonequilibrium patterns resembling fingering patterns that arise when injecting air into a liquid between two closely spaced plates (Hele-Shaw patterns). This is natural because the formation of holes in thin films is similar to air injection into a polymer film where the thermodynamic driving force of dewetting is the analogue of the applied pressure in the flow measurement. The patterns formed in the rapidly dewetting and evaporating polymer films become frozen into a stable glassy state after most of the solvent (water) has evaporated, leaving stationary patterns that can be examined by atomic force microscopy and optical microscopy. Similar patterns have been observed in water films evaporating from mica substrates, block copolymer films, and modest hole fingering has also been found in the dewetting of dry polymer films. From these varied observations, we expect this dewetting-induced fingering instability to occur generally when the dewetting rate and film viscosity are sufficiently large.

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Section: Resultsmentioning

confidence: 99%

Hole‐growth instability in the dewetting of evaporating polymer solution films

Raghavan

Douglas

et al. 2002

J Polym Sci B Polym Phys

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“…11 At present, these film stabilization effects are not well understood theoretically, but it seems clear that a combination of equilibrium (modification of polymersurface interactions) and kinetic stabilization effects (entanglement and changes in T g ) are generally involved. 12,13 In the present paper, we adopt a novel strategy to inhibit the dewetting of thin polymer films based on the introduction of C 60 fullerene nanoparticles into the spincasting polymer solution. This stabilization is contrary to the usual experience where film inhomogeneities often lead to "cratering" (hole formation).…”

Section: Introductionmentioning

confidence: 99%

“…Recent work has also shown that the tendency toward polymer film dewetting on inorganic substrates can be inhibited through grafting polymer layers onto the solid substrate with and without the addition of high molecular weight polymer, sulfonation and metal complexation of the polymer, and the introduction of specialized end groups onto the polymer with a high affinity for the inorganic substrate . At present, these film stabilization effects are not well understood theoretically, but it seems clear that a combination of equilibrium (modification of polymer−surface interactions) and kinetic stabilization effects (entanglement and changes in T g ) are generally involved. , …”

Section: Introductionmentioning

confidence: 99%

Suppression of Dewetting in Nanoparticle-Filled Polymer Films

et al. 2000

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The perturbing influence of nanosize filler particles on the dewetting of spun-cast polymer films is investigated. Previous studies have shown that spun-cast films of unentangled polystyrene (PS) and polybutadiene (PB) dewet acid-cleaned silicon wafers when the films are annealed above their bulk glass transition temperature T g. It is also known that "impurity" particles tend to promote dewetting in thin polymer films. Here we demonstrate that the addition of a small amount of C60 fullerene nanoparticles to the spin-casting polymer solution leads to an inhibition of dewetting in thin (L < 100 nm) PS and PB films cast on both acid-cleaned and carbon-coated silicon wafer substrates. Neutron reflection measurements indicate that this effect is associated with the formation of a diffuse fullerene layer near the solid substrate. Evidently, the immobilized fullerene particles form an enrichment layer at the solid boundary and "pin" the contact line of the growing dewetted ("dry") regions so that hole growth in the filled films becomes arrested at a scale which diminishes with increasing filler concentration. Above a relative fillerpolymer mass fraction of 1%, we no longer observe hole formation by atomic force microscopy on the time scales of our measurements (typically on the order of hours), suggesting the existence of a critical filler surface coverage for the suppression of dewetting. The roughness of the fullerene layer probably also contributes to the modification of the surface wetting properties through a change in the surface energy of the substrate, as suggested by recent measurements on substrates "roughened" by other means such as irradiation of polymer film substrates, grafting of polymer chains, etc.

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“…The ordered arrangement of nanoparticles is important not only in bulk but also on the surface since the surface topography influences the optical, mechanical, electrical, or thermal properties. Dewetting of thin films creates different kinds of structures on the surface depending on the molecular architecture, film thickness, interfacial energies, surface defects, fluid's viscosity, and external perturbation. − Although largely investigated, research related to dewetting is limited to polymer films and structure formation on surface based on homopolymers, polymer blends, and block copolymers without added nanoparticles. − Inorganic and organic particles can be used as fillers in the polymer matrix for suppression of dewetting. Both types of fillers give rise to different kinds of surface structures. − The inhibition of dewetting in thin filled polymer films might occur because of enrichment of filler particles at air−polymer or polymer−substrate interface.…”

Section: Introductionmentioning

confidence: 99%

“…Dewetting of thin films creates different kinds of structures on the surface depending on the molecular architecture, film thickness, interfacial energies, surface defects, fluid's viscosity, and external perturbation. [26][27][28][29] Although largely investigated, research related to dewetting is limited to polymer films and structure formation on surface based on homopolymers, polymer blends, and block copolymers without added nanoparticles. [26][27][28][29][30][31][32][33][34][35][36][37] Inorganic and organic particles can be used as fillers in the polymer matrix for suppression of dewetting.…”

Section: Introductionmentioning

confidence: 99%

Maghemite Nanoparticles on Supported Diblock Copolymer Nanostructures

et al. 2007

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Diblock copolymer nanostructures with metal oxide nanoparticles are prepared on solid supports by spin-coating. The maghemite nanoparticles (Fe 2 O 3 ) are masked with grafted polystyrene chains to allow a tailored positioning on top of nanostructures created by the symmetric polystyrene-block-polyisoprene diblock copolymer. Film thickness and lamellar thickness of the diblock copolymer are smaller than the nanoparticles diameter to prevent the particles from being embedded inside the polymer superstructure. Nanostructures without nanoparticles are compared with structures with up to 30% nanoparticles content. The structural analysis is based on atomic force microscopy and grazing incidence small-angle X-ray scattering. The observed structures are explained in the framework of a retarded dewetting process preceding microphase separation. With increasing nanoparticle concentration the structural type changes from droplets into a continuous structure and covers typical lengths between 50 and 195 nm. Above a critical concentration cluster formation out of nanoparticles is present in coexistence with isolated nanoparticles and dominates structure creation.

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Influence of generation number on the dewetting of hypergraft poly(2-ethyl-2-oxazoline) films

Cited by 6 publications

References 25 publications

Hole‐growth instability in the dewetting of evaporating polymer solution films

Hole‐growth instability in the dewetting of evaporating polymer solution films

Suppression of Dewetting in Nanoparticle-Filled Polymer Films

Maghemite Nanoparticles on Supported Diblock Copolymer Nanostructures

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