Controlled growth of triblock polyelectrolyte brushes

Osborne, Vicky L.; Jones, David; Huck, Wilhelm T. S.

doi:10.1039/b204737c

Cited by 119 publications

(132 citation statements)

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“…[31][32][33] Additionally, because light is the activating agent, SI-PMP is well suited for the direct synthesis of polyelectrolytes (PMAA, in this study), alleviating problems with, for example, catalyst complexation, dissociation, or disproportionation that occurs during ATRP of electrolytic monomers in protic media. [34][35][36][37][38] The response characteristics of the constituent materials used in this study are well known. Because of the weakly ionizable carboxylate groups along the backbone, the degree of dissociation of PMAA can be changed by adjusting the pH and/ or the ionic strength of the solution.…”

Section: Introductionmentioning

confidence: 99%

Swelling Behavior of Multiresponsive Poly(methacrylic acid)‐block‐‐poly(N‐isopropylacrylamide) Brushes Synthesized Using Surface‐Initiated Photoiniferter‐Mediated Photopolymerization

Rahane

Floyd

Metters

et al. 2008

Adv Funct Materials

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Surface‐initiated photoiniferter‐mediated photopolymerization (SI‐PMP) in presence of tetraethylthiuram disulfide is used to directly synthesize surface‐grafted poly(methacrylic acid)‐block‐poly(N‐isopropylacrylamide) (PMAA‐b‐PNIPAM) layers. The response of these PMAA‐b‐PNIPAM bi‐level brushes to changes in pH, temperature and ionic strength is investigated by using in‐situ multi‐angle ellipsometry to measure changes in solvated layer thickness. As expected for a block copolymer architecture, PMAA blocks swell as pH is increased, with the maximum change in the thickness occurring near pH = 5, and PNIPAM blocks exhibit lower critical solution temperature (LCST) behavior, marked by a broad transition between swollen and collapsed states. The response of the bi‐level brushes to changes in added salt at constant pH is complex, as the swelling behaviors of both the weak polyelectrolyte, PMAA, and thermoresponsive PNIPAM are affected by changes in ionic strength. This work demonstrates not only the robustness of SI‐PMP for making novel, bi‐level stimuli‐responsive brushes, but also the complex links between synthesis, structure, and response of these materials.

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Section: Introductionmentioning

confidence: 99%

Swelling Behavior of Multiresponsive Poly(methacrylic acid)‐block‐‐poly(N‐isopropylacrylamide) Brushes Synthesized Using Surface‐Initiated Photoiniferter‐Mediated Photopolymerization

Rahane

Floyd

Metters

et al. 2008

Adv Funct Materials

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“…In addition, we aim to find a route toward a "fast switch" that reversibly alternates between different polymer brush conformations, and as a consequence gain control over surface properties [12,13] such as wettability, hydration, and stiffness. Reversibly manipulating the polymer-brush conformation in a chemically selective way (not only by changing the ionic strength) will be a crucial step toward the use of surface-confined polyelectrolytes as nanoactuators.Cationic brushes of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) [14] were grown from gold surfaces, patterned into regions containing either initiator or methyl-terminated monolayers (Figure 1 a, b), by atom-transfer radical polymerization (ATRP) in an oxygen-free methanol/water (4:1) mixture. [15,16] The responsive behavior of the METAC brushes in different electrolyte environments (NaCl and MgSO 4 ) was studied under liquids using atomic force microscopy (AFM) and a quartz crystal microbalance with dissipation (QCM-D).…”

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confidence: 99%

Locking and Unlocking of Polyelectrolyte Brushes: Toward the Fabrication of Chemically Controlled Nanoactuators

et al. 2005

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Polymers are ideal building blocks for nanofabrication and the engineering of surfaces because of their response in shape and size to environmental changes in polymer concentration, ionic strength, pH, temperature, and solvent. Furthermore, since they are easy to synthesize, as well as chemically and mechanically robust, polymers are ideal materials to bridge the gap between biological nanomachines and silicon-based devices. Of particular interest herein is the exploration of the use of polymer brushes as nanoactuators. [1] Polyelectrolytes, that is, polymers containing charged monomers, change from an extended conformation in a solution of low ionic strength to a coiled conformation in solutions of high ionic strength.[2] When polyelectrolytes are covalently attached to a surface to form a brush, the polymer chains show a strongly extended (stretched) conformation in pure water, as a result of both the repulsion between neighboring chains and the repulsion between the monomers. [3][4][5][6] In contrast, when polymer brushes are placed in electrolyte solutions, the charges of the pendant groups in the polymer chains are screened, and the minimization of the electrostatic repulsions leads to entropically more favorable collapsed conformations. [4][5][6][7][8] This collapse is comparable to transitions from extended to coil-like conformations commonly observed for polyelectrolytes in solution. [3,4] In the case of polymer brushes, there are constraints on the degrees of freedom related to conformational changes, and as a result the height and the amount of water on the inner brush environment are reduced. [5,8] Our aim is to use the ionic-strength-sensitive behavior of polyelectrolyte brushes [9][10][11] in combination with specific binding interactions and ion-size-exclusion effects to design smart polymer surfaces that can be switched between a permanently collapsed and an extended state, where both states have different surface properties. In addition, we aim to find a route toward a "fast switch" that reversibly alternates between different polymer brush conformations, and as a consequence gain control over surface properties [12,13] such as wettability, hydration, and stiffness. Reversibly manipulating the polymer-brush conformation in a chemically selective way (not only by changing the ionic strength) will be a crucial step toward the use of surface-confined polyelectrolytes as nanoactuators.Cationic brushes of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) [14] were grown from gold surfaces, patterned into regions containing either initiator or methyl-terminated monolayers (Figure 1 a, b), by atom-transfer radical polymerization (ATRP) in an oxygen-free methanol/water (4:1) mixture. [15,16] The responsive behavior of the METAC brushes in different electrolyte environments (NaCl and MgSO 4 ) was studied under liquids using atomic force microscopy (AFM) and a quartz crystal microbalance with dissipation (QCM-D). [17] The conformational changes in the METAC brush in the presence of 1m NaCl electr...

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“…Osborne et al [202] proposed a microcontact printing treatment on gold with undecanethiol to prepare an inert background. Then, the patterned monolayer surface was exposed to initiator thiol and poly((2-methacryloyloxy)ethyl)trimethylammonium chloride brushes were grown using ATRP process.…”

Section: Atrpmentioning

confidence: 99%

Surface treatment and characterization: Perspectives to electrophoresis and lab‐on‐chips

et al. 2006

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The control and modification of surface state is a major challenge in bioanalytical sciences, and in particular in electrokinetic separation methods, due to the importance of electroosmosis. This topic has gained recently a renewed interest, associated with the development of "lab-on-chips" systems that extend the range of materials in which separation channels are fabricated. The surface science community has developed through the years a large toolbox of characterization tools and surface modification protocols, which is not yet fully exploited in the bioanalytical world. In this paper, we try and present an overview of these tools, in order to stimulate new ideas for improved and more controlled surface treatment strategies for separations in capillaries and microchannels. We briefly describe some physical and chemical aspects of electroosmosis (global and spatially resolved), streaming current, and streaming potential. We also review the main strategies for surface coating, and compare the advantages of physisorption, well-organized thin self-assembled monolayers, or conversely thick polymer "brushes". Examples of existing applications to electrophoresis in microchannel are also given.

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Controlled growth of triblock polyelectrolyte brushes

Abstract: We have achieved a significant breakthrough in the synthesis of polyelectrolyte brushes of controlled thickness and density, which has been demonstrated by the synthesis of triblock copolymer brushes composed of cationic, neutral, and anionic segments.

Cited by 119 publications

References 23 publications

Swelling Behavior of Multiresponsive Poly(methacrylic acid)‐block‐‐poly(N‐isopropylacrylamide) Brushes Synthesized Using Surface‐Initiated Photoiniferter‐Mediated Photopolymerization

Swelling Behavior of Multiresponsive Poly(methacrylic acid)‐block‐‐poly(N‐isopropylacrylamide) Brushes Synthesized Using Surface‐Initiated Photoiniferter‐Mediated Photopolymerization

Locking and Unlocking of Polyelectrolyte Brushes: Toward the Fabrication of Chemically Controlled Nanoactuators

Surface treatment and characterization: Perspectives to electrophoresis and lab‐on‐chips

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