Synthesis of Chemically Grafted Polystyrene “Brushes” and Their Influence on the Dewetting in Thin Polystyrene Films

Voronov, Аndriy; Shafranska, Olena

doi:10.1021/la011489s

Cited by 42 publications

(48 citation statements)

References 47 publications

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“…Such "entropic dewetting" has been observed experimentally in polymer networks 9 and polymer brushes. 10,11 Autophobicity can be traced back to the formation of an interface between the strongly stretched chains in the polymer brush and the free chains of the melt. [4][5][6][7] The interface between brush and melt has many important applications: Such interfaces commonly occur between two immiscible homopolymers that have been reinforced by a diblock copolymer.…”

Section: Introductionmentioning

confidence: 99%

Static and dynamic properties of the interface between a polymer brush and a melt of identical chains

Pastorino

Binder

Kreer

et al. 2006

The Journal of Chemical Physics

133

180

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Molecular dynamics simulations of a short-chain polymer melt between two brush-covered surfaces under shear have been performed. The end-grafted polymers which constitute the brush have the same chemical properties as the free chains in the melt and provide a soft deformable substrate. Polymer chains are described by a coarse-grained bead-spring model with Lennard-Jones interactions between the beads and a FENE potential between nearest neighbors along the backbone of the chains. The grafting density of the brush layer offers a way of controlling the behavior of the surface without altering the molecular interactions. We perform equilibrium and non-equilibrium Molecular Dynamics simulations at constant temperature and volume using the Dissipative Particle Dynamics thermostat. The equilibrium density profiles and the behavior under shear are studied as well as the interdigitation of the melt into the brush, the orientation on different length scales (bond vectors, radius of gyration, and end-to-end vector) of free and grafted chains, and velocity profiles. The viscosity and slippage at the interface are calculated as functions of grafting density and shear velocity.

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Section: Introductionmentioning

confidence: 99%

Static and dynamic properties of the interface between a polymer brush and a melt of identical chains

Pastorino

Binder

Kreer

et al. 2006

The Journal of Chemical Physics

133

180

View full text Add to dashboard Cite

show abstract

“…Many properties such as structure, composition, or chain length may be varied during the synthesis providing control over the required wetting properties. [9][10][11]14 For smaller brush densities, however, suitably prepared brushes are known to enhance the wetting properties and reduce the contact angle of polymers that do not wet the bare substrate. 12 Although grafting polymers on a substrate is expected to increase the compatibility of polymer films because it adds attractive interactions to the substrate, it has been found that the brush's density plays an important role.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, polymers can also be adsorbed or irreversibly grafted onto substrates, [9][10][11] and the properties of the resulting brush may be further modified via the quality of the surrounding solvent. 11,15 The role of entropic factors in this wetting sequence has been emphasized, 13 and several self consistent field theoretical studies have been devoted to the study of the autophobic regime. 13 For too high grafting densities of the brush ͑or large crosslink density of polymer networks͒, polymers of the same material as the brush have been found to be autophobic, i.e., the chemically identical molecules in the brush and the melt repel each other and the melt dewets from the brush.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of polymers on a brush: Tuning the order of the wetting phase transition

MacDowell

Müller

2006

The Journal of Chemical Physics

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We develop a computational methodology for the direct measurement of a wetting transition and its order via the effective interface potential. The method also allows to estimate contact angles in the nonwet state and to study adsorption isotherms. The proposed methodology is employed in order to study the wetting behavior of polymers on top of a brush consisting of identical polymers. In the absence of long-range forces, the system shows a sequence of nonwet, wet, and nonwet states as the brush density is increased. Including attractive long-range interactions we can make the polymer liquid wet the bush at all grafting densities, and both first- and second-order wetting transitions are observed. The latter case is limited to a small interval of grafting densities where the melt wets the brush in the absence of long-range interactions. Second-order wetting transitions are preceded by a first-order surface transition from a thin to a thick adsorbed layer. The interval of second-order wetting transitions is limited at low grafting densities by a surface critical end point and at high grafting densities by a tricritical wetting point. Our study highlights the rich wetting behavior that results when competing adsorbent-substrate interactions of different scales are tuned over a broad range.

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“…More recently, experiments [105,106] on the wetting of PS on a PS brush indeed observe two wetting transitions: at small and very large grafting density the polymer film dewets the brush, while at moderate grafting density the PS film remains stable.…”

Section: Wetting On a Polymer Brushmentioning

confidence: 94%

Pulsed Laser Annealing of Thin Silicon Films

Sameshima¹,

Watakabe²,

Andoh³

et al. 2006

jjap

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Using Monte Carlo simulations and self-consistent field (SCF) theory we study the surface and interface properties of a coarse grained off-lattice model. In the simulations we employ the grand canonical ensemble together with a reweighting scheme in order to measure surface and interface free energies and discuss various methods for accurately locating the wetting transition. In the SCF theory, we use a partial enumeration scheme to incorporate singlechain properties on all length scales and use a weighted density functional for the excess free energy. The results of various forms of the density functional are compared quantitatively to the simulation results. For the theory to be accurate, it is important to decompose the free energy functional into a repulsive and an attractive part, with different approximations for the two parts.Measuring the effective interface potential for our coarse grained model we explore routes for controlling the equilibrium wetting properties. (i) Coating of the substrate by an oxide layer gives rise to a subtle interplay between shortrange and long-range forces,which may stabilize a film of mesoscopic thickness or result in the formation of nano-droplets. (ii) Coating the substrate with a polymer brush, we observe second-order wetting transitions at intermediate grafting densities, while the wetting transition is of first order at low and high grafting densities. In the latter limit, polymers of the same chemical structure as the brush do not wet the surface (autophobicity). (iii) Surface pattern (stripes) might give rise to unusual adsorption properties, which are related to morphological transitions. We relate our findings to experiments and discuss perspectives and limitations of the computational methods.

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Synthesis of Chemically Grafted Polystyrene “Brushes” and Their Influence on the Dewetting in Thin Polystyrene Films

Cited by 42 publications

References 47 publications

Static and dynamic properties of the interface between a polymer brush and a melt of identical chains

Static and dynamic properties of the interface between a polymer brush and a melt of identical chains

Adsorption of polymers on a brush: Tuning the order of the wetting phase transition

Pulsed Laser Annealing of Thin Silicon Films

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