Effects of Adsorbing-Block Molecular Weight on the Thickness of Adsorbed Diblock Copolymers

Webber, Richard M.; Anderson, John L.

doi:10.1021/la00021a044

Cited by 18 publications

(21 citation statements)

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“…To check the validity of this assumption, the final adsorbed amounts at the end of the kinetics experiments (from the plateau region) are compared with the adsorbed amounts obtained from the dry layer thickness measurements. 22 It should be noted that the ellipsometric thickness corresponds to an average thickness, which will be equal to the overall thickness only in the case of a perfectly homogeneous layer with a boxlike density profile. 9…”

Section: Methodsmentioning

confidence: 99%

Looped Polymer Brushes Formed by Self-Assembly of Poly(2-vinylpyridine)−Polystyrene−Poly(2-vinylpyridine) Triblock Copolymers at the Solid−Fluid Interface. Kinetics of Preferential Adsorption

et al. 2006

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The kinetics of assembly of a series of poly(2-vinylpyridine)-polystyrene-poly(2-vinylpyridine) (PVP-b-PS-b-PVP) triblock copolymers from the selective solvent toluene onto a silicon surface has been studied using phase-modulated ellipsometry. The adsorbed amount and thickness have been determined independently as functions of time. Even though the adsorbed amount as a function of time follows the traditional two-step process that is typical of the self-assembly of diblock copolymerssthere is an initial fast adsorption followed by a slow buildup of the layer (brush regime)sthe thickness shows an "overshoot" that corresponds to the brush regime. We attribute this phenomenon, not observed in the self-assembly of amphiphilic diblock copolymers, to having both ends of the chain tethered. The final ellipsometric thicknesses of the brush made from the triblocks are less than that expected for a single-end tethered brush made from a diblock copolymer with a buoy block of similar molecular weight. This result supports the conclusion that PVP-b-PS-b-PVP triblock copolymers adsorb mainly in a looplike conformation.

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Section: Methodsmentioning

confidence: 99%

Looped Polymer Brushes Formed by Self-Assembly of Poly(2-vinylpyridine)−Polystyrene−Poly(2-vinylpyridine) Triblock Copolymers at the Solid−Fluid Interface. Kinetics of Preferential Adsorption

et al. 2006

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“…The PVP/PS diblock copolymers were adsorbed from toluene to the pores of track-etched mica membranes. More details of this system are found in other references. ,, The membranes were thin (≈7 μm thick) disks of muscovite mica with capillary type pores formed by first irradiating the disk with a collimated beam of fission fragments and then etching the tracks into pores. The pores were uniform, straight capillaries with a cross section having the geometry of a 60° rhombus.…”

Section: Methodsmentioning

confidence: 99%

“…In this system the PVP preferentially adsorbs to the mica and the PS chains are solvated. The first three papers ,, deal with the relationship between the thickness of the adsorbed layers and the size of the PVP and PS blocks. Here we are concerned with changes in the thickness of the adsorbed polymer layer effected by changes in temperature about the ϑ point for the solvated (PS) chains.…”

Section: Introductionmentioning

confidence: 99%

Thermal Expansion and Contraction of Adsorbed Diblock Copolymers near ϑ Conditions

1996

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The hydrodynamic thickness of adsorbed layers of poly(2-vinylpyridine)/polystyrene (PVP/PS) diblock copolymers was measured as a function of temperature near the ϑ point of PS in cyclohexane. Adsorption occurred from a selective solvent, toluene, with the PVP block anchoring the PS chains to the pores of mica membranes. The ratio of block sizes, N PVP/N PS, was in the range 0.03−0.16. The hydrodynamic thickness (L H) was determined by measuring the flow rate of cyclohexane at the specified temperature as a function of applied pressure difference across the membrane. The variation of L H with temperature was linear and reversible. The expansion coefficient of the layers was defined as α = L H(T)/L H(ϑ). The experimental values of dα/dT were of order 10-2 (°C)-1, which is almost an order of magnitude greater than the temperature derivative of the expansion factor of PS chains in cyclohexane solution above ϑ. Predictions of L H based on Scheutjens−Fleer theory for terminally attached chains and a Brinkman model for viscous flow through polymer chains were made using literature-derived values for the fundamental system properties. The theory overpredicts L H(ϑ) and underpredicts dα/dT; one possible explanation for these discrepancies is a temperature dependent, reversible adsorption of PS segments to areas of the surface not covered by the PVP block.

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“…[13][14][15][16][17][18][19][20][21][22][23] Most of the work in this arena has focused on linear diblock copolymers, with limited work on triblock, 20,21 star-block, or more complicated structures, such as combs. 24 Interface-modifying layers made from these more complex macromolecules are interesting because the various architectures may provide the ability to alter surface properties in ways that are not feasible with linear copolymers.…”

Section: Introductionmentioning

confidence: 99%

Impact of Solvent Quality on the Density Profiles of Looped Triblock Copolymer Brushes by Neutron Reflectivity Measurements

et al. 2008

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Preferential adsorption of poly(2-vinylpyridine)-deuterated polystyrene-poly(2-vinylpyridine) (PVP-dPS-PVP) triblock copolymers from toluene onto silicon leads to the formation of dPS loops tethered by the PVP end blocks. Using neutron reflectometry, we have determined the segment density profiles of these looped polymer brushes in toluene, a good solvent for the dPS block, and in cyclohexane at 20°C (poor solvent), 32°C, (near-Θ solvent), and 50°C (marginal solvent). While the swelling behavior qualitatively agrees with that observed for singly grafted brushes, there are interesting differences in the local structural details: In a good solvent, the segment density profiles are composed of an inner parabolic region and a long, extended tail. In cyclohexane, the profiles are described by exponential decays. We ascribe these features to a novel polydispersity effect that arises due to tethering the PS loops by both ends. The results also show that the less dense layers undergo more significant changes in swollen height as solvent quality is changed and that the looped brushes of different molecular weight, asymmetry, and tethering density adhere to scaling relationships derived for lightly cross-linked polymer gels.

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Effects of Adsorbing-Block Molecular Weight on the Thickness of Adsorbed Diblock Copolymers

Cited by 18 publications

References 0 publications

Looped Polymer Brushes Formed by Self-Assembly of Poly(2-vinylpyridine)−Polystyrene−Poly(2-vinylpyridine) Triblock Copolymers at the Solid−Fluid Interface. Kinetics of Preferential Adsorption

Looped Polymer Brushes Formed by Self-Assembly of Poly(2-vinylpyridine)−Polystyrene−Poly(2-vinylpyridine) Triblock Copolymers at the Solid−Fluid Interface. Kinetics of Preferential Adsorption

Thermal Expansion and Contraction of Adsorbed Diblock Copolymers near ϑ Conditions

Impact of Solvent Quality on the Density Profiles of Looped Triblock Copolymer Brushes by Neutron Reflectivity Measurements

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