Bidimensional Response Maps of Adaptive Thermo- and pH-Responsive Polymer Brushes

Laloyaux, Xavier; Mathy, Bertrand; Nysten, Bernard; Jonas, Alain M.

doi:10.1021/ma1009484

Cited by 30 publications

(29 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[14][15][16][17][18][19] Polyacid and polybase brushes dissociate in aqueous solution as a function of pH to yield a charged polymer as dictated by the brush pK a . 16,[20][21][22] The inherent confinement of polymer chains in a polymer brush has been reported by some authors to modify the pK a , with the solution ionic strength, brush thickness, grafting density and even position within the brush identified as factors that can affect the apparent local pK a of polymer brushes. 17,[23][24][25][26] Charging of the polyelectrolyte brush causes intra-and inter-chain repulsion between neighbouring functional groups, resulting in absorption of solvent and counterions into the brush and significant swelling of the brush layer.…”

Section: Introductionmentioning

confidence: 99%

Polyelectrolyte brush pH-response at the silica–aqueous solution interface: a kinetic and equilibrium investigation

Cheesman

Smith

Murdoch

et al. 2013

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Polymer brushes are commonly used to modify the properties of solid surfaces. Here a family of polybasic poly(2-(diethylamino)ethyl methacrylate) brushes have been grown using ARGET ATRP from a cationic macroinitiator adsorbed on two types of silica surfaces: QCM crystals and oxidised silicon wafers. The pH-response of these brushes is investigated as a function of brush thickness in a constant flow environment in order to focus on the intrinsic dynamics of the polymer brushes. Independent QCM-D and in situ ellipsometry kinetic studies demonstrate the swelling process of protonation and solvent uptake is typically eight times faster than the corresponding neutralisation and solvent expulsion from the collapsing brush. However, the maximum rate of these processes is independent of brush thickness. The initial pH response of the brushes is hysteretic due to brush entanglement, which once overcome allows highly reversible pH-induced conformational changes. Multiple pH cycles demonstrate that the viscoelastic nature of the swollen state relative to the collapsed brush is independent of brush thickness.

show abstract

Section: Introductionmentioning

confidence: 99%

Polyelectrolyte brush pH-response at the silica–aqueous solution interface: a kinetic and equilibrium investigation

Cheesman

Smith

Murdoch

et al. 2013

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…32 At at substrates, dual temperature and pH control of brush swelling has recently been demonstrated for copolymers of ethylene glycol methyl ether methacrylate and MAA. 33 However, when hydrophilic ionic monomers are used in copolymerization, temperature response becomes suppressed at even moderate fractions of ionic units in copolymers. 34 Therefore, dual response could only be realized at only very low content of ionic monomers, 29 while at high fractions of an ionic monomer, the brush became predominantly pH-, rather than dually pH-and temperature-responsive.…”

Section: Introductionmentioning

confidence: 99%

Tunable pH and temperature response of weak polyelectrolyte brushes: role of hydrogen bonding and monomer hydrophobicity

Zhuk

et al. 2013

Soft Matter

View full text Add to dashboard Cite

We report on weak polyacid brushes with highly tunable pH and temperature response characteristics. This was achieved by synthesizing a series of homo-and copolymers which contain 2-alkylacrylic acids (aAAs) of increased hydrophobicity, i.e. acrylic acid (AA), methacrylic acid (MAA), or 2-ethylacrylic acid (EAA), using surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization. As revealed by contact angle measurements, in situ ellipsometry and AFM studies of brush swelling, the pH-response of PAA and PMAA brushes was similar, with brushes remaining highly swollen (swelling ratio 2.5-3.0) at low pH values. The PEAA brush, however, was unique as it showed low degrees of water uptake (<10%) at pH < 5 due to insolubility of this polyelectrolyte in acidic solutions, moderate swelling at high pH and relatively high (>70 ) contact angles in the entire pH region from 2 to 8. Copolymer brushes of aAAs with N-isopropylacrylamide (NIPAM), denoted as P(AA-co-NIPAM), P(MAA-co-NIPAM) and P(EAA-co-NIPAM), demonstrated dual pH and temperature response, which was strongly dependent on the type of aAA co-monomer. P(AA-co-NIPAM) and P(MAA-co-NIPAM) brushes underwent large-amplitude pHinduced changes in brush swelling and water contact angle in the range of pH from 3 to 6, and were only weakly responsive to temperature in the transition region. In contrast, more hydrophobic P(EAA-co-NIPAM) brushes demonstrated both pH and temperature responses at physiologically relevant neutral/ basic pH values even when the content of EAA units in the copolymer was as high as $50%. We discuss the role of inter-and intra-molecular hydrogen bonding and monomer hydrophobicity and ionization (quantified by FTIR) in determining pH ranges for brush response. These findings might enable control of molecular/cellular adhesion and flow at interfaces potentially useful in microfluidic and biomedical applications.

show abstract

“…However, it shows a nonmonotonic behavior for ρ̅ g > 0.2. Multiple experimental studies − have reported that the swelling ratio of a PNIPAm brush smoothly decreases with increasing temperature up to ∼33 °C and plateaus after that and increases with decreasing graft density. Devaux et al have reported a maximum swelling ratio of 0.2–0.4 for polystyrene brushes with a maximum volume fraction in the brush up to 0.85.…”

Section: Stimuli-dependent Pnipam Brush Propertiesmentioning

confidence: 99%

Stress in a Stimuli-Responsive Polymer Brush

2020

View full text Add to dashboard Cite

The application of a polymer brush in sensing, actuation, self-folding, among others acutely depends on the tuneable bending of a brush-grafted substrate caused by the stress in the brush. However, the stress in a stimuli-responsive brush has not been investigated. In this work, we study the stress in the stimuli-responsive planar polymer brushes of neutral water-soluble polymers with low to very high graft densities using strong stretching theory (SST). First, SST with the Langevin force-extension relation for a polymer chain is extended to the study of stimuli-responsive brushes. Stress profile and other properties of a Poly(N-isopropylacrylamide) (PNIPAm) brush are then obtained using the extended SST and an empirical Flory-Huggins parameter. The model predicts that the stress in a PNIPAm brush is inhomogeneous and compressive at all temperatures and graft densities. The resultant stress is predicted to increase in magnitude with increasing graft density. Moreover, it decreases in magnitude with an increase in temperature before plateauing in low graft density brushes. In contrast, its magnitude increases weakly with increasing temperature in high density brushes. This contrasting behavior is traced to the minimum in interaction free energy density vs polymer volume fraction curve for PNIPAm solution at a large volume fraction, and stiffening of chains due to finite extensibility. Furthermore, our results indicate that the ability to tune the resultant stress by changing temperature diminishes with increasing graft density.

show abstract

Bidimensional Response Maps of Adaptive Thermo- and pH-Responsive Polymer Brushes

Cited by 30 publications

References 53 publications

Polyelectrolyte brush pH-response at the silica–aqueous solution interface: a kinetic and equilibrium investigation

Polyelectrolyte brush pH-response at the silica–aqueous solution interface: a kinetic and equilibrium investigation

Tunable pH and temperature response of weak polyelectrolyte brushes: role of hydrogen bonding and monomer hydrophobicity

Stress in a Stimuli-Responsive Polymer Brush

Contact Info

Product

Resources

About