Temperature-responsive polymer brush constructed on a colloidal gold monolayer

Kitano, Hiromi; Kago, Hirokazu; Matsuura, Kazuhiro

doi:10.1016/j.jcis.2008.11.058

Cited by 12 publications

(9 citation statements)

References 68 publications

(95 reference statements)

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“…Aqueous solutions of P(NIPAAm) exhibit a lower critical solution temperature (LCST) of approximately 305 K (32 °C) with respect to water, , meaning that P(NIPAAm) is soluble in water below LCST and becomes less soluble and collapsed to form a separate phase from the water phase above LCST. Due to such characteristics of their phase behavior in water, P(NIPAAm) has been extensively studied for pharmaceutical applications such as drug delivery systems, , detachment of cultured cells, , surface-properties control, , and drug barrier membranes …”

Section: Introductionmentioning

confidence: 99%

Deswelling Mechanisms of Surface-Grafted Poly(NIPAAm) Brush: Molecular Dynamics Simulation Approach

et al. 2012

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Technologies ranging from solvent extraction and drug delivery to tissue engineering are beginning to benefit from the unique ability of “smart polymers” to undergo controllable structural changes in response to external stimuli. The prototype is poly(N-isopropylacrylamide) (P(NIPAAm)) which exhibits an abrupt and reversible hydrophilic to hydrophobic transition above its lower critical solution temperature (LCST) of ∼305 K. We report here molecular dynamics simulations to show the deswelling mechanisms of the hydrated surface-grafted P(NIPAAm) brush at various temperatures such as 275, 290, 320, 345, and 370 K. The deswelling of the P(NIPAAm) brush is clearly observed above the lower critical solution temperature below which the P(NIPAAm) brush is associated with water molecules stably. By simulating the poly(acrylamide) brush as a reference system having the upper critical solution temperature (UCST) behavior with the same conditions employed in the P(NIPAAm) brush simulations, we confirmed that the deswelling of P(NIPAAm) brush does not take place at a given range of temperatures, which validates our simulation procedure. By analyzing the pair correlation functions and the coordination numbers, we found that the dissociation of water from the P(NIPAAm) brush occurs mainly around the isopropyl group of the P(NIPAAm) above the LCST because of its hydrophobicity. We also found that the NH of the amide group in NIPAAm does not actively participate in the hydrogen bonding with water molecules because of the steric hindrance caused by the attached isopropyl group, and thereby the hydrogen bonding interactions between amide groups and water molecules are significantly weakened with increasing temperature, leading to deswelling of the hydrated P(NIPAAm) brush above the LCST through favorable entropic change. These results explain the experimental observations in terms of a simple molecular mechanism for polymer function.

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Section: Introductionmentioning

confidence: 99%

Deswelling Mechanisms of Surface-Grafted Poly(NIPAAm) Brush: Molecular Dynamics Simulation Approach

et al. 2012

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“…We therefore applied Steglich's esterification conditions [27] using 2-bromo-2-methyl-propionic acid, a catalytic amount of DMAP, and a slight excess of DCC (synthesis II, method A) in analogy to a previously reported synthesis [28] of structurally related polymerization initiator 2,2 0 -dithiobis[1-(2-bromo-2-methylpropionyloxy)ethane] (5) [29][30][31][32][33][34][35][36][37][38][39][40][41] (Scheme 2).…”

Section: Resultsmentioning

confidence: 99%

“…[32,33,36,40] 2-Bromo-2-methyl-propanoic acid reacted with DCC exothermically and afforded the corresponding isourea derivative in situ. A catalytic amount of DMAP smoothly catalyzed the esterification at 5 C but because it was difficult to assess the endpoint of the heterogeneous reaction, stirring at room temperature was continued overnight to assure complete conversion.…”

Section: Resultsmentioning

confidence: 99%

Efficient Two-Step Synthesis of 11,11′-Dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane], a Conventional Initiator for Grafting Polymer Brushes from Gold Surfaces via ATRP

Belegrinou

Malinova

Masciadri

et al. 2010

Synthetic Communications

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11,11 0 -Dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane], a conventional initiator for grafting polymers from gold surfaces, was synthesized in two steps from 11-mercapto-1-undecanol in 88-92% overall yield. Oxidative dimerization of 11-mercapto-1-undecanol with a catalytic amount of sodium iodide and 30% hydrogen peroxide in ethyl acetate proceeded in 96% yield. Esterification with 2-bromoisobutyryl bromide in dichloromethane was clean and almost quantitative (92% yield) with pyridine used as base, whereas triethylamine gave a messy reaction (64% yield). Alternatively, esterification with 2-bromo-2-methyl-propanoic acid in dichloromethane occurred readily under Steglich's conditions with N,N 0 -dicyclohexylcarbodiimide (DCC) and a catalytic amount of dimethylaminopyridine (DMAP; 88% yield).

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“…Gold colloids were prepared by the reduction of hydrogen tetrachloroaurate(III) trihydrate (HAuCl 4 ·3H 2 O) with sodium citrate in water at 100 °C as previously reported. ,, The hydrodynamic diameter of the gold colloids was determined to be 20 nm on average using the dynamic light scattering technique (DLS-7000, Otsuka Electronics, Hirakata, Osaka, Japan; light source, He−Ne laser at 632.8 nm). The gold colloids were modified with disulfide-carrying poly(2-methacryloyloxyethyl d -mannopyranoside) (DT-PMEMan) (12.5 μg/mL) and purified by centrifugation at 1.0 × 10 4 G for 60 min four times (Supporting Information Scheme S-6) …”

Section: Methodsmentioning

confidence: 99%

Molecular Recognition at the Exterior Surface of a Zwitterionic Telomer Brush

et al. 2010

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3-Sulfo-N,N-dimethyl-N-(2'-methacryloyloxyethyl)propanaminium inner salt (SPB) was polymerized on a glass plate with a surface-confined initiator of atom transfer radical polymerization (ATRP) having a 2-bromoisobutyryl group. The glass plate modified with a brush of sulfobetaine telomer (PSPB) was highly hydrophilic and showed a strong resistance against nonspecific adsorption of proteins such as lysozyme and albumin. Through the polymerization from the free surface of PSPB chain by ATRP, furthermore, N-methacryloyloxysuccinimide (MAOSu) residues were introduced, and the incubation of the telomer (PSPB-b-PMAOSu)-modified glass chip with a lectin (concanavalin A, Con A) gave a glass chip covered with the Con-A-modified PSPB brush. The Con A fixed to the zwitterionic telomer brush pursued specific binding of mannose residues accumulated on the surface of Au colloidal particles, resulting in the increase in absorbance at 550 nm ascribable to localized surface plasmon resonance, while the nonspecific adsorption of proteins to the surface of the glass chip was still largely suppressed. The present results indicate usefulness of the zwitterionic telomer surface with antibiofouling properties as a scaffold for specific sensing devices.

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Temperature-responsive polymer brush constructed on a colloidal gold monolayer

Cited by 12 publications

References 68 publications

Deswelling Mechanisms of Surface-Grafted Poly(NIPAAm) Brush: Molecular Dynamics Simulation Approach

Deswelling Mechanisms of Surface-Grafted Poly(NIPAAm) Brush: Molecular Dynamics Simulation Approach

Efficient Two-Step Synthesis of 11,11′-Dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane], a Conventional Initiator for Grafting Polymer Brushes from Gold Surfaces via ATRP

Molecular Recognition at the Exterior Surface of a Zwitterionic Telomer Brush

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