Functional Porous Polymers by Emulsion Templating: Recent Advances

Porous materials are currently of great scientific as well as technological interest. A strategy that is increasingly employed to prepare highly porous and well defined macroporous polymers is emulsion templating, whereby the droplets of a high internal phase emulsion are used to create pores in a solid material by curing or polymerization of the emulsion continuous phase. This Feature Article covers recent work in this area, focusing on: the preparation of such materials from new precursors and via novel approaches; the chemical modification of existing materials; and the application of the resulting porous structures in diverse areas of science and technology.     

Lubricant‐Infused Nanoparticulate Coatings Assembled by Layer‐by‐Layer Deposition

Omniphobic coatings are designed to repel a wide range of liquids without leaving stains on the surface. A practical coating should exhibit stable repellency, show no interference with color or transparency of the underlying substrate and, ideally, be deposited in a simple process on arbitrarily shaped surfaces. We use layer‐by‐layer (LbL) deposition of negatively charged silica nanoparticles and positively charged polyelectrolytes to create nanoscale surface structures that are further surface‐functionalized with fluorinated silanes and infiltrated with fluorinated oil, forming a smooth, highly repellent coating on surfaces of different materials and shapes. We show that four or more LbL cycles introduce sufficient surface roughness to effectively immobilize the lubricant into the nanoporous coating and provide a stable liquid interface that repels water, low‐surface‐tension liquids and complex fluids. The absence of hierarchical structures and the small size of the silica nanoparticles enables complete transparency of the coating, with light transmittance exceeding that of normal glass. The coating is mechanically robust, maintains its repellency after exposure to continuous flow for several days and prevents adsorption of streptavidin as a model protein. The LbL process is conceptually simple, of low cost, environmentally benign, scalable, automatable and therefore may present an efficient synthetic route to non‐fouling materials.     

Observation of colloidal growth in coal-derived liquids

Heavy direct coal liquefaction products are known to exhibit rapidly increasing viscosities upon prolonged exposure to oxygen. Small-angle X-ray scattering has been used to monitor changes in the colloidal structure of a coal liquid subjected to accelerated aging under an oxygen atmosphere for a total period of 54 days. The data are consistent with an agglomeration model for the formation of large colloidal-size scattering centres which are partially responsible for the rapidly increasing viscosity of the coal liquid.     

SERS Substrate-Dependent Interaction of the Anticarcinogenic Drug 5-Fluorouracil with Silver

5-Fluorouracil, an extensively used anticarcinogenic drug, was found to undergo a soft adsorption (i.e., no significant structural changes) on the metal surface of different Ag island films (35, 11, 8.7, and 6.5 nm thick). The 35 nm thick film provided the best SERS signal. The resistance of the Ag-complexed species to washing demonstrates the films' advantage over colloids and makes them very attractive for potential bio-applications.

Both deprotonated forms, which were previously detected on colloidal nanoparticles (50 nm diameter) at neutral pH, are also present in this case. However, the interaction mechanism of 5-FU species appears to be substrate dependent. While on colloidal nanoparticles they are orientated perpendicular or significantly tilted from the surface normal, on the much larger Ag-clusters of the island films (20-200 nm) they lie flat, attached through the carbonyl groups and the π-electrons. The charge-transfer mechanism significantly contributes to the rich information SERS reports for this system.     

On the development of colloidal nanoparticles towards multifunctional structures and their possible use for biological applications

In this Review, we describe the synthesis of high-quality colloidal nanoparticles in organic solvents, the mechanisms by which they can be transferred into aqueous solution, and some of their applications in biology. In particular, we will place emphasis on the creation of multifunctional nanoparticles or nanoparticle assemblies.     

Influence of granulometry and organic treatment of a Brazilian montmorillonite on the properties of poly(styrene‐co‐n‐butyl acrylate)/layered silicate nanocomposites prepared by miniemulsion polymerization

The influence of granulometry and organic treatment of a Brazilian montmorillonite (MMT) clay on the synthesis and properties of poly(styrene‐co‐n‐butyl acrylate)/layered silicate nanocomposites was studied. Hybrid latexes of poly(styrene‐co‐butyl acrylate)/MMT were synthesized via miniemulsion polymerization using either sodium or organically modified MMT. Five clay granulometries ranging from clay particles smaller than 75 μm to colloidal size were selected. The size of the clay particles was evaluated by specific surface area measurements (BET). Cetyl trimethyl ammonium chloride was used as an organic modifier to enhance the clay compatibility with the monomer phase before polymerization and to improve the clay distribution and dispersion within the polymeric matrix after polymerization. The sodium and organically modified natural clays as well as the composites were characterized by X‐ray diffraction analysis. The latexes were characterized by dynamic light scattering. The mechanical, thermal, and rheological properties of the composites obtained were characterized by dynamical‐mechanical analysis, thermogravimetry, and small amplitude oscillatory shear tests, respectively. The results showed that smaller the size of the organically modified MMT, the higher the degree of exfoliation of nanoplatelets. Hybrid latexes in presence of Na‐MMT resulted in materials with intercalated structures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Surface modification and metallization of polyimide using gold colloids as a seed layer

Herein we report on metallization of Cu on to surface‐modified polyimide resin, the method of which relies on potassium hydroxide‐induced modification of the polyimide surface to introduce carboxylic acid groups and incorporation of gold colloids as a seed layer through reduction of chloroauric acid. The contact angle of modified polyimide surface with water changed from 70 to 35° due to the hydrolysis of polyimide. Secondary amine group on the surface was detected with attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectrophotometry, suggesting that tertiary amine group has turned into secondary group. In addition, on the basis of hydrophilic behavior, we succeeded in depositing gold colloids on the chemically modified surface. SEM image of copper electroless plated on polyimide surface indicated that copper particles were compact and about ～ 300 nm in diameter. It showed that gold colloids provide an excellent conductive layer to catalyze the electroless plating of Cu on polyimide surface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Colloidal synthesis of Au nanoparticles using polyelectrolytes with 1,3,4-thiadiazole as reducing agents

Heterocyclic compounds are well known for their biological activity and coordination properties. Some heterocyclic compounds have been employed in the stabilization against coalescence of metallic nanoparticles in colloidal solutions, for example, tetrazole, triazole, and pyrazole. The aim of this work is to design new polyelectrolytes with heterocyclic pendant groups useful as reducing agents of Au³⁺ and as stabilizing agents for the synthesis of colloidal Au nanoparticles. Thus, polyelectrolytes with thiosemicarbazone and 1,3,4-thiadiazole pendant groups were used as reducing agents of Au³⁺ ions and stabilizing agents of Au nanoparticles. The voltammetry study of the polyelectrolytes showed that one with thiosemicarbazone pendant groups is the better reducing agent than polyelectrolytes with heterocyclic pendant groups. The polyelectrolytes can control the growth of the nanoparticles, obtaining structures with an average size of 9 nm. In this study, it was concluded that the nature of the heterocyclic group does not have an effect on the shape of nanoparticles and quasi-spherical nanoparticles were obtained with all polyelectrolytes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47790.