Sorption of polycyclic aromatic hydrocarbons to polystyrene nanoplastic

Microplastic has become an emerging contaminant of global concern. Bulk plastic can degrade to form smaller particles down to the nano-scale

Formation of micelles with complex coacervate cores.

Micelles are commonly regarded as colloidal structures spontaneously formed by amphiphilic molecules, that is, molecules consisting of two distinct parts of which one is soluble and the other is insoluble. This definition is too restrictive: other kinds of molecules can also form micelles. We report on the formation of micelles from a mixture of a (water-soluble) polyanion and a diblock copolymer with two entirely water-soluble blocks: one cationic and one neutral. The cationic block forms a complex coacervate with poly(acrylic acid); the neutral block serves as a stablizing block, prohibiting the growth of the complex coacervate droplets to macroscopic sizes. The formation of these micelles upon mixing is preceded by a macroscopic phase separation. The polymer-rich phase which initially forms rearranges into a stable micellar solution

Facile one-step synthesis of monodisperse micron-sized latex particles with highly carboxylated surfaces

A facile method for the aqueous synthesis of monodisperse and micronmeter-sized colloids with highly carboxylated surfaces is presented. The method is applied to three different monomers, styrene, methyl methacrylate, and 2,2,2-trifluoroethyl methacrylate, and illustrate tuning of the size and monodispersity in the reactions. High surface density of carboxylic acids of up to 10 COOH nm-2 from potentiometric titrations, is achieved through copolymerization with itaconic acid. The versatility of this system is highlighted by creating highly fluorescent and monodisperse particles that can be index matched in aqueous solution and through surface modification via the carboxylic acid groups using standard amidation chemistry

The adsorption of hydrophobically modified carboxymethylcellulose on a hydrophobic solid: effects of pH and ionic strength.

Abstract Carboxymethylcellulose with 1.2% dodecyl groups (per glucose unit) was prepared by amidation with dodecylamine. This polymer behaves as a hydrophobically modified polyelectrolyte with the following thickening properties which are determined from viscosity data. It adsorbs from aqueous solution on spin-coated polystyrene films to various extents, depending on pH and ionic strength. The adsorbed amount has a surprising minimum at around pH 6 which coincides with a maximum in viscosity of a dilute solution, and with a very pronounced maximum in the hydrodynamic radius as determined from dynamic light scattering. To our knowledge, such behavior has not been reported before. It suggests that at low pH the polymer is present in the form of small aggregates which upon increasing the pH first swell and then break up into single molecules

Self-assembly of poly(ferrocenyldimethylsilane-b-methyl methacrylate) block copolymers in a selective solvent

The self-assembly of poly(ferrocenyldimethylsilane-b-methyl methacrylate) block copolymers, with PFDMS contents of 9-61 wt % (block ratios 1:23-1:1.5), is described. PFDMS-b-PMMA block copolymers form remarkable cylindrical micelles with very narrow diameter distributions at block ratios in the range of 1:10-1:6 (18-26 wt % PFDMS) in the block-selective solvent acetone, which is a good solvent for PMMA and a nonsolvent for PFDMS. The micelles, with a PFDMS core and a PMMA corona, were studied in solution by means of dynamic light scattering, 1H NMR spectroscopy, and cryo-transmission electron microscopy. Micelles were also deposited on silicon substrates by dip-coating and characterized with atomic force microscopy and scanning electron microscopy. The micelles were over 3 m long and had an overall diameter of around 22 nm. Dynamic light scattering experiments confirmed the formation of rodlike micellar aggregates in acetone. The cylindrical micelles exhibited a rod-to-sphere transition around 60 C. When cooled below this transition temperature, the micelles reassembled back to their original aggregation state. Depolarized DLS experiments showed no rotational contribution to the measured decays of the autocorrelation functions. We ascribe this to the extreme length of the micelles, which arrests rotational movement. 1H NMR spectra recorded in acetone-d6 showed PFDMS signals, indicating that these blocks in the micellar cores have some mobility. This suggests that the cores are not in a crystalline state and that crystallization is not a driving force in the formation of these PFDMS-b-PMMA cylindrical micelles, but rather the contrast in solvophilicity between the blocks, which in the bulk are in the strong segregation limi

Complex coacervation core micelles as anti-fouling agents on silica and polystyrene surfaces

The adsorption of mixtures of a diblock-co-polymer with a negatively charged block and a neutral, hydrophilic block and an oppositely charged homopolymer on anionic and hydrophobic surfaces was studied with reflectometry. It turned out that the adsorbed mass is at a maximum when the number of cationic and anionic polyelectrolyte groups is equal. In bulk solution, the components form micelles at this composition. The thickness of the layers was in the order of the micellar radius in bulk solution, i.e. 25 nm. The adsorption kinetics are sensitive to block lengths of the diblock-co-polymer. The adsorbed layers were stable with respect to solvent exposure and even 1 M ionic strength could not completely erode the layers. The layers dramatically influenced the functionality of the surface, as they acted as excellent anti-fouling agents versus protein adsorption

Supramolecular assembly of self-healing nanocomposite hydrogels

Hierarchical self-assembly of transient composite hydrogels is demonstrated through a two-step, orthogonal strategy using nanoparticle tectons interconnected through metal–ligand coordination complexes. The resulting materials are highly tunable with moduli and viscosities spanning many orders of magnitude, and show promising self-healing properties, while maintaining complete optical transparency

Wormlike aggregates from a supramolecular coordination polymer and a diblock copolymer

The formation of wormlike micelles in mixed systems of a supramolecular coordination polymer Zn-L2EO4 and a diblock copolymer P2MVP41-b-PEO205 is investigated by light scattering and Cryo-TEM. By direct mixing at a stoichiometric charge ratio, the above mixtures proved to be capable of formation of spherical micelles with a radius of about 25 nm (Yan et al. Angew. Chem., Int. Ed.; 2007, 46, 1807-1809). Lately, we find wormlike micelles with a hydrodynamic radius >150 nm in a mixture with excess positive charge, that is, a negative charge fraction f- <0.5. The transformation between wormlike and spherical micelles can be realized by variation of the mixing ratio through different protocols. Upon addition of negatively charged Zn-L2EO4 to a mixture with excess positively charged P2MVP41-b-PEO205, most of the wormlike micelles are transformed into spherical ones; upon addition of positively charged P2MVP41-b-PEO205 to a mixture of pure spherical micelles, wormlike micelles can be produced again. The effect of sample preparation protocol, sample history, and concentration on this transformation process is systematically reported in this article. A possible mechanism for the formation of wormlike micelles is proposed

Enzyme-catalyzed modification of PES surfaces: Reduction in adsorption of BSA, dextrin and tannin

Poly(ethersulfone) (PES) can be modified in a flexible manner using mild, environmentally benign components such as 4-hydroxybenzoic acid and gallic acid, which can be attached to the surface via catalysis by the enzyme laccase. This leads to grafting of mostly linear polymeric chains (for 4-hydroxybenzoic acid, and for gallic acid at low concentration and short modification time) and of networks (for gallic acid at high concentration and long exposure time). The reaction is stopped at a specific time, and the modified surfaces are tested for adsorption of BSA, dextrin and tannin using in-situ reflectometry and AFM imaging. At short modification times, the adsorption of BSA, dextrin and tannin is significantly reduced. However, at longer modification times, the adsorption increases again for both substrates. As the contact angle on modified surfaces at short modification times is reduced (indicative of more hydrophilic surfaces), and keeps the same low values at longer modification times, hydrophilicity is not the only determining factor for the measured differences. At longer modification times, intra-layer reactivity will increase the amount of cross-linking (especially for gallic acid), branching (for 4-hydroxybenzoic acid) and/or collapse of the polymer chains. This leads to more compact layers, which leads to increased protein adsorption. The modifications were shown to have clear potential for reduction of fouling by proteins, polysaccharides, and polyphenols, which could be related to the surface morphology