Dataset Information

Controlling Adsorption of Diblock Copolymer Nanoparticles onto an Aldehyde-Functionalized Hydrophilic Polymer Brush via pH Modulation.

ABSTRACT: Sterically stabilized diblock copolymer nanoparticles with a well-defined spherical morphology and tunable diameter were prepared by RAFT aqueous emulsion polymerization of benzyl methacrylate at 70 °C. The steric stabilizer precursor used for these syntheses contained pendent cis-diol groups, which means that such nanoparticles can react with a suitable aldehyde-functional surface via acetal bond formation. This principle is examined herein by growing an aldehyde-functionalized polymer brush from a planar silicon wafer and studying the extent of nanoparticle adsorption onto this model substrate from aqueous solution at 25 °C using a quartz crystal microbalance (QCM). The adsorbed amount, Γ, depends on both the nanoparticle diameter and the solution pH, with minimal adsorption observed at pH 7 or 10 and substantial adsorption achieved at pH 4. Variable-temperature QCM studies provide strong evidence for chemical adsorption, while scanning electron microscopy images recorded for the nanoparticle-coated brush surface after drying indicate mean surface coverages of up to 62%. This fundamental study extends our understanding of the chemical adsorption of nanoparticles on soft substrates.

SUBMITTER: Astier S

PROVIDER: S-EPMC10883040 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature

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Controlling Adsorption of Diblock Copolymer Nanoparticles onto an Aldehyde-Functionalized Hydrophilic Polymer Brush via pH Modulation.

Astier Samuel S Johnson Edwin C EC Norvilaite Oleta O Varlas Spyridon S Brotherton Emma E EE Sanderson George G Leggett Graham J GJ Armes Steven P SP

Langmuir : the ACS journal of surfaces and colloids 20240206

Sterically stabilized diblock copolymer nanoparticles with a well-defined spherical morphology and tunable diameter were prepared by RAFT aqueous emulsion polymerization of benzyl methacrylate at 70 °C. The steric stabilizer precursor used for these syntheses contained pendent <i>cis</i>-diol groups, which means that such nanoparticles can react with a suitable aldehyde-functional surface via acetal bond formation. This principle is examined herein by growing an aldehyde-functionalized polymer b ...[more]

PMID: 38320303

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Project description:Dynamic covalent chemistry has been exploited to prepare numerous examples of adaptable polymeric materials that exhibit unique properties. Herein, the chemical adsorption of aldehyde-functional diblock copolymer spherical nanoparticles onto amine-functionalized surface-grafted polymer brushes via dynamic Schiff base chemistry is demonstrated. Initially, a series of cis-diol-functional sterically-stabilized spheres of 30-250 nm diameter were prepared via reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization. The pendent cis-diol groups within the steric stabilizer chains of these precursor nanoparticles were then oxidized using sodium periodate to produce the corresponding aldehyde-functional spheres. Similarly, hydrophilic cis-diol-functionalized methacrylic brushes grafted from a planar silicon surface using activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) were selectively oxidized to generate the corresponding aldehyde-functional brushes. Ellipsometry and X-ray photoelectron spectroscopy were used to confirm brush oxidation, while scanning electron microscopy studies demonstrated that the nanoparticles did not adsorb onto a cis-diol-functional precursor brush. Subsequently, the aldehyde-functional brushes were treated with excess small-molecule diamine, and the resulting imine linkages were converted into secondary amine bonds via reductive amination. The resulting primary amine-functionalized brushes formed multiple dynamic imine bonds with the aldehyde-functional diblock copolymer spheres, leading to a mean surface coverage of approximately 0.33 on the upper brush layer surface, regardless of the nanoparticle size. Friction force microscopy studies of the resulting nanoparticle-decorated brushes enabled calculation of friction coefficients, which were compared to that measured for the bare aldehyde-functional brush. Friction coefficients were reasonably consistent across all surfaces except when particle size was comparable to the size of the probe tip. In this case, differences were ascribed to an increase in contact area between the tip and the brush-nanoparticle layer. This new model system enhances our understanding of nanoparticle adsorption onto hydrophilic brush layers.

Project description:Novel brush coatings were fabricated with glass surface-grafted chains copolymerized using surface-initiated atom transfer radical polymerization (SI-ATRP) from 2-(2-methoxyethoxy)ethyl methacrylate (OEGMA188) and acrylamide (AAm), taken in different proportions. P(OEGMA188-co-AAm) brushes with AAm mole fraction >44% (determined with XPS and TOF-SIMS spectroscopy) and nearly constant with the depth copolymer composition (TOF-SIMS profiling) exhibit unusual temperature-induced transformations: The contact angle of water droplets on P(OEGMA188-co-AAm) coatings increases by ∼45° with temperature, compared to 17-18° for POEGMA188 and PAAm. The thickness of coatings immersed in water and the morphology of coatings imaged in air show a temperature response for POEGMA188 (using reflectance spectroscopy and AFM, respectively), but this response is weak for P(OEGMA188-co-AAm) and absent for PAAm. This suggests mechanisms more complex than a simple transition between hydrated loose coils and hydrophobic collapsed chains. For POEGMA188, the hydrogen bonds between the ether oxygens of poly(ethylene glycol) and water hydrogens are formed below the transition temperature Tc and disrupted above Tc when polymer-polymer interactions are favored. Different hydrogen bond structures of PAAm include free amide groups, cis-trans-multimers, and trans-multimers of amide groups. Here, hydrogen bonds between free amide groups and water dominate at T < Tc but structures favored at T > Tc, such as cis-trans-multimers and trans-multimers of amide groups, can still be hydrated. The enhanced temperature-dependent response of wettability for P(OEGMA188-co-AAm) with a high mole fraction of AAm suggests the formation at Tc of more hydrophobic structures, realized by hydrogen bonding between the ether oxygens of OEGMA188 and the amide fragments of AAm, where water molecules are caged. Furthermore, P(OEGMA188-co-AAm) coatings immersed in pH buffer solutions exhibit a 'schizophrenic' behavior in wettability, with transitions that mimic LCST and UCST for pH = 3, LCST for pH = 5 and 7, and any transition blocked for pH = 9.

Dataset Information

Controlling Adsorption of Diblock Copolymer Nanoparticles onto an Aldehyde-Functionalized Hydrophilic Polymer Brush via pH Modulation.

Publications

Controlling Adsorption of Diblock Copolymer Nanoparticles onto an Aldehyde-Functionalized Hydrophilic Polymer Brush via pH Modulation.

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