Single Molecule Rod−Globule Phase Transition for Brush Molecules at a Flat Interface

Sheiko, Sergei S.; Prokhorova, S. A.; Beers, Kathryn L.; Matyjaszewski, Krzysztof; Khokhlov, and Alexei R.; Möller, Martin

doi:10.1021/ma010746x

Cited by 201 publications

(278 citation statements)

References 24 publications

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“…It allows the precision synthesis of a variety of novel well-defined polymer architectures having exciting structure-property-function relationships (such as block and graft copolymers, stars, brushes and bottle-brush structures) starting from a vast array of commercial functional monomers. Thus, controlled radical polymerization has been investigated extensively for poly(N-alkyl)acrylamides by using atom transfer radical polymerization (ATRP) [2][3][4][5][6][7][8][9][10][11][12][13][14][15], reversible addition fragmentation chain transfer (RAFT) [16][17][18][19][20][21][22], nitroxide-mediated polymerization (NMP) [23][24][25][26] and degenerative chain transfer polymerization (DTP) [19,[27][28][29]. In this review, discussion of polymer synthesis has been kept to a minimum.…”

Section: Synthesismentioning

confidence: 99%

Non-ionic Thermoresponsive Polymers in Water

Aseyev

Tenhu

Winnik

2010

Advances in Polymer Science

457

511

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Numerous non-ionic thermally responsive homopolymers phase separate from their aqueous solutions upon heating. Far fewer neutral homopolymers are known to phase separate upon cooling. A systematic compilation of the polymers reported to exhibit thermoresponsive behaviour is presented in this review, including N-substituted poly[(meth)acrylamide]s, poly(N-vinylamide)s, poly(oxazoline)s, protein-related polymers, poly(ether)s, polymers based on amphiphilic balance, and elastin-like synthetic polymers. Basic properties of aqueous solutions of these polymers are briefly described.

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Section: Synthesismentioning

confidence: 99%

Non-ionic Thermoresponsive Polymers in Water

Aseyev

Tenhu

Winnik

2010

Advances in Polymer Science

457

511

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“…[1] Thus, SFM has been successfully employed to study DNA, [2] RNA, [3] and their complexes with proteins, [4] surfactants [5] and other compounds. The ex situ visualization of conformational changes of DNA molecules has been carried out for the effect imposed by interaction with oppositely charged silanes, [6] with polymer nanoparticles, [7] surfactants, [8] Mg 2 + ions (in ethanol), [9] spermidine, [10,11] polylysine, [12,13] poly(ethylene glycol)-poly(amidoamine) copolymer, [14] lipospermine and polyethylenimine.…”

Section: Introductionmentioning

confidence: 99%

“…In recent studies we had focused on brushlike macromolecules [1,[24][25][26] that consist of a macromolecular backbone densely grafted by macromolecular side chains. The steric repulsion between the side chains imposes an effective rigidity of the brushlike macromolecule.…”

Section: Introductionmentioning

confidence: 99%

Reversible Collapse of Brushlike Macromolecules in Ethanol and Water Vapours as Revealed by Real‐Time Scanning Force Microscopy

Gallyamov

Tartsch

Khokhlov

et al. 2004

Chemistry A European J

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Environment-controlled scanning force microscopy allowed us to study adsorption and desorption of single poly(methacrylate)-graft-poly(n-butyl acrylate) brush molecules on mica in real time. The molecules transform reversibly from a two-dimensional, extended wormlike state to a compact globular state. The dynamics of the conformational transition was sufficiently slow in order to allow its observation by scanning force microscope in real time. The reversible transformation is effected by coadsorption of water or ethanol, the latter introduces the collapse. Adsorbing ethanol and water from the vapour atmosphere results in a change of the surface properties of mica, either favouring adsorption or desorption of the graft polymer. When the extended, tightly adsorbed poly(n-butyl acrylate) brush molecules are exposed to ethanol vapour, the macromolecules swell and contract to form compact globules. Exchanging the ethanol vapour to a humid atmosphere caused the molecules to extend again to a wormlike two-dimensional conformation. Coexistence of collapsed and extended strands within the same molecule indicates a single-molecule first-order transition in agreement with observations on Langmuir films previously reported.

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“…The characteristic property of these macromolecules is their ability to change shape upon lateral compression on a substrate. [16][17][18] If the film pressure increases, the number of side chains adsorbed to the surface decreases allowing the backbone to coil. This causes the macromolecules to become more compact and occupy less area on the substrate.…”

mentioning

confidence: 99%

Molecular Pressure Sensors

Sun

Shirvanyants

et al. 2007

Advanced Materials

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Flow properties of molecularly thin films are at the foundation of many practical applications such as lithography, microfluidics, coatings, and lubrication. [1][2][3][4][5][6][7][8][9][10] Further advances in these fields depend on understanding the mechanisms that control the kinetics of flow. [11][12][13][14] However, one of the problems in flowing monolayers is the independent characterization of the driving and frictional forces that are intimately coupled through the molecular interactions between the fluid and the substrate. In this regard, the visualization of compressible macromolecules during flow provides an exceptional opportunity to study these forces.[15] Here we report on the monitoring of brush-like macromolecules as they change their shape in response to variations in the film pressure during flow. After appropriate calibration, these molecular sensors can be used to gauge both the pressure gradient and the friction coefficient at the substrate. We anticipate the utilization of such miniature sensors for probing flow properties on nanometer length scales. The design of the pressure-responsive macromolecules is based on brush-like polymer architectures comprised of a flexible backbone surrounded by a dense shell of side chains (Fig. 1a). The characteristic property of these macromolecules is their ability to change shape upon lateral compression on a substrate. [16][17][18] If the film pressure increases, the number of side chains adsorbed to the surface decreases allowing the backbone to coil. This causes the macromolecules to become more compact and occupy less area on the substrate. Therefore, the area per molecule can be used as a pressure sensitive parameter to gauge the variations of film pressure within flowing monolayers. Molecular brushes (Fig. 1a) with the same degree of polymerization of a poly(2-hydroxyethyl methacrylate) backbone (n = 570 ± 50) and different degrees of polymerization of poly(n-butyl acrylate) (pBA) side chains (n = 35 ± 5 and n = 51 ± 5) were synthesized by atom transfer radical polymerization. [19,20] At room temperature, the materials are fluid melts that spontaneously spread when placed on higher surface energy substrates such as mica and graphite.[21] Small drops of molecular brushes (volume ∼ 1 nl, radius ∼ 100 lm) were deposited on a substrate inside an environmental chamber under controlled temperature (T = 25°C) and relative humidity (RH = 30-99 %). Like many other fluids, the drops first spread by generating a molecularly thin precursor film moving ahead of the macroscopic drop (Fig. 1b). [22] Using an atomic force microscope (Multimode, Nanoscope 3A, Veeco Metrology Group), we monitored the spreading process over a broad range of length scales ranging from the motion of the film front all the way down to the movements of the individual molecules within the film.[15,23] Figure 1c shows the time dependence of the film length L= R -R 0 observed on mica at a high relative humidity (RH = 99 %), where R 0 = 63 lm is the initial drop radius and R is the total radiu...

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Single Molecule Rod−Globule Phase Transition for Brush Molecules at a Flat Interface

Cited by 201 publications

References 24 publications

Non-ionic Thermoresponsive Polymers in Water

Non-ionic Thermoresponsive Polymers in Water

Reversible Collapse of Brushlike Macromolecules in Ethanol and Water Vapours as Revealed by Real‐Time Scanning Force Microscopy

Molecular Pressure Sensors

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