Hydroxy-derivatised emulsion templated porous polymers (PolyHIPEs): Versatile supports for solid and solution phase organic synthesis

Poly(vinylbenzyl chloride-co-divinyl benzene) polyHIPE monolith-supported o-hydroxynaphthaldehyde propylenediamine Schiff base ligand complex of copper(ii) ions as a catalyst for the epoxidation of cyclohexene

Poly(vinylbenzyl chloride-co-divinyl benzene)-based polyHIPE monoliths of different porosities were prepared using high-internal-phase emulsions (HIPEs) containing a fixed amount of vinylbenzyl chloride (VBC, 6.0 g, 0.0393 mol) and divinyl benzene (DVB 4.0 g, 0.0308 mol) as the oil phase and different volume ratios of aqueous calcium chloride as the internal phase. Span-80 (2.0 g (4.67 mmol))-stabilized HIPEs were polymerized at 60 °C using potassium persulfate (0.4 g, 1.48 mmol) as the initiator. Upon varying the volume ratio of aqueous calcium chloride from 80 to 90%, the prepared polyHIPE monoliths have shown significant variations in their surface morphology, specific surface area (SA), and pore volumes (V p) as confirmed by scanning electron microscopy (SEM) and a gas adsorption (BET) method. The prepared polyHIPE monoliths were anchored with o-hydroxynaphthaldehyde propylenediamine Schiff base ligand (HNPn) and then loaded with copper(ii) ions (HNPn-Cu) to act as a catalyst. The structural information of unsupported HNPn-Cu complexes was obtained by recording its FT-IR and UV-visible spectra. The amount of copper(ii) ions loaded onto HNPn ligand-anchored polyHIPE monoliths was determined by atomic absorption spectroscopic analysis. In comparison to unsupported HNPn-Cu catalyst, the polyHIPE monolith-supported HNPn-Cu catalyst has shown high catalytic activity (66.8%), product selectivity for epoxycyclohexane (ECH) (94.8%), high turn over number (0.028 mol mol-1 h-1) and low energy of activation (22.4 kJ mol-1) in the epoxidation of cyclohexene in the presence of hydrogen peroxide (H2O2) as an oxidant at 40 °C. The polyHIPE-supported HNPn-Cu catalyst also shows high reuse applications. Studies show that there is sufficient scope to develop polyHIPE monoliths with various properties for specific applications.

Bioceramic nanocomposite thiol-acrylate polyHIPE scaffolds for enhanced osteoblastic cell culture in 3D

Emulsion-templated (polyHIPE) scaffolds for bone tissue engineering were produced by photopolymerisation of a mixture of trimethylolpropane tris(3-mercaptopropionate) and dipentaerythritol penta-/hexa-acrylate in the presence of hydroxyapatite (HA) or strontium-modified hydroxyapatite (SrHA) nanoparticles. Porous and permeable polyHIPE materials were produced regardless of the type or incorporation level of the bioceramic, although higher loadings resulted in a larger average pore diameter. Inclusion of HA and SrHA into the scaffolds was confirmed by EDX-SEM, FTIR and XPS and quantified by thermogravimetry. Addition of HA to polyHIPE scaffolds significantly enhanced compressive strength (148-216 kPa) without affecting compressive modulus (2.34-2.58 MPa). The resulting materials were evaluated in vitro as scaffolds for the 3D culture of MG63 osteoblastic cells vs. a commercial 3D cell culture scaffold (Alvetex®). Cells were able to migrate throughout all scaffolds, achieving a high density by the end of the culture period (21 days). The presence of HA and in particular SrHA gave greatly enhanced cell proliferation, as determined by staining of histological sections and total protein assay (Bradford). Furthermore, Von Kossa and Alizarin Red staining demonstrated significant mineralisation from inclusion of bioceramics, even at the earliest time point (day 7). Production of alkaline phosphatase (ALP), an early osteogenic marker, was used to investigate the influence of HA and SrHA on cell function. ALP levels were significantly reduced on HA- and SrHA-modified scaffolds by day 7, which agrees with the observed early onset of mineralisation in the presence of the bioceramics. The presented data support our conclusions that HA and SrHA enhance osteoblastic cell proliferation on polyHIPE scaffolds and promote early mineralisation.

Preparation and recyclable catalysis performance of functional macroporous polyHIPE immobilized with gold nanoparticles on its surface

High internal phase emulsion polymerization was adopted for preparing macroporous polymeric monoliths, polyHIPE–Br (PHIPE–Br). Macroporous PHIPE–Br was used as the initiator to initiate the atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA), resulting in a dense coating of polymers on the PHIPE surface and PHIPE–PGMA was obtained. Through a ring-opening addition reaction with TETA, a surface amino-polymer modified functional macroporous PHIPE–PGMA–TETA, was prepared conveniently. Gold nanoparticles could be easily in situ prepared and immobilized on the surface of PHIPE–PGMA–TETA. Characterization by scanning electron microscopy (SEM), EDX-mapping and TGA showed that PHIPE–PGMA–TETA was immobilized by the gold nanoparticles, and presented good catalytic properties. Moreover, the macroporous catalytic material, PHIPE–PGMA–TETA/Au NPs, presented recyclable catalytic performance without any decrease in activity. The materials and methods to form the monoliths and immobilize metal nanoparticles were simple and efficient, thus, opening new possibilities for highly porous PHIPE in catalysis applications.

The macroporous material PHIPE–PGMA–TETA/Au NPs has an open-cell and porous structure, and can effectively catalyze the reduction of 4-nitrophenol.

Surface glycopolymer-modified functional macroporous polyHIPE obtained by ATRP for the removal of boron in water

Macroporous polymeric monoliths PHIPE-PGAMA were obtained from polyHIPE with surface modification of PGAMA and used for boron removal.

Macroporous materials: microfluidic fabrication, functionalization and applications

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields.

Synthesis of Biodegradable Macroporous Poly(l-lactide)/Poly(ε-caprolactone) Blend Using Oil-in-Eutectic-Mixture High-Internal-Phase Emulsions as Template

We have demonstrated that l-lactide (LLA) forms a eutectic mixture with ε-caprolactone (CL) in a 30:70 mol ratio with a melting point of -19 °C. Taking advantage of the liquid nature and polarity at the LLA-CL eutectic mixture, we have formulated oil-in-eutectic-mixture high-internal-phase emulsions (HIPEs) by stepwise addition of the oil phase (tetradecane) into the continuous phase (mixture of surfactant and LLA-CL eutectic mixture) at room temperature and under stirring. The oil-in-LLA-CL-eutectic-mixture HIPEs were polymerized in the presence of both the organocatalysts 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and methanesulfonic acid (MSA) and the initiator benzyl alcohol (BnOH) at 37 °C and without the addition of any extra reagent or solvent in one single pot. The catalytic selectivities of DBU and MSA for the ring-opening polymerizations of LLA and CL, respectively, allowed the synthesis of macroporous poly(l-lactide)/poly(ε-caprolactone) blend materials. The resulting materials exhibited a macroporous morphology that resembled that of the HIPE internal-phase droplets used as templates. These materials proved effective as oil absorbents for oil/water separation with not only a noticeable performance, similar to that of conventional sorbents in terms of both selectivity and recyclability, but also unprecedented safe disposability, certainly of interest for applications in the cleanup of industrial oily wastewaters and oil spills, thanks to the biodegradable features of both poly(ε-caprolactone) and poly(l-lactide).

Modulation of protein behavior through light responses of TiO2 nanodots films

In this work, the behavior of protein molecules adsorbed on TiO₂ nanodots films are modulated through the light responses of the nanodots. TiO₂ nanodots films are first prepared through phase separation induced self assembly. Then, bovine serum albumin (BSA) is adsorbed on TiO₂ nanodots films and exposed to ultraviolet (365 nm) illumination. It is found the conformation of surface-bound BSA molecules changes with ultraviolet illumination. Moreover, the BSA molecules conjugate to the surface-bound molecules, which are in the overlayer, are released. The reason is ascribed to that TiO₂ nanodots absorb ultraviolet and result in the increase of surface hydroxyl groups on nanodots. Such increase further leads to intensified attraction of -NH3 groups in the surface-bound BSA molecules. That not only changes the conformation of the surface-bound BSA molecules, but also weaken the conjugation between surface-bound molecules and other BSA molecules in the overlayer. Eventually, the overlayer of BSA molecules is released. It is believed that such protein conformation variation and release behavior induced through light responses of TiO₂ nanodots are crucial in understanding the biomedical performance of TiO₂ nanostructures. Also, it could be widely utilized in tailoring of the materials-protein interactions.

Porous monoliths synthesized via polymerization of styrene and divinyl benzene in nonaqueous deep-eutectic solvent-based HIPEs

Due to their viscosity and polarity, DESs represent a suitable internal phase for HIPEs containing styrenic monomers in addition to acrylates, thus expanding on the range of monomers forming polymerizable DES-based HIPEs.

Porous silica spheres in macroporous structures and on nanofibres

Porous nanospheres have a wide range of applications such as in catalysis, separation and controlled delivery. Among these nanospheres, syntheses and applications of porous silica nanospheres have been investigated extensively. Uniform porous silica nanospheres can be synthesized using a modified Stöber method. In the present study, porous silica spheres were prepared in the pre-formed emulsion-templated porous polyacrylamide (PAM). A hierarchical hybrid structure of mesoporous silica spheres was formed in the highly interconnected macroporous polymer. The polymer scaffold could be removed by calcination with porous silica spheres and the macroporous structures retained. This resulted from the close packing or aggregation of small silica nanospheres in the pores and on the surface of pores of PAM. The modified Stöber synthesis was further carried out in pre-formed polymer nanofibres (chitosan and sodium carboxymethyl cellulose). The structure of porous silica spheres on nanofibres was produced in the presence of the polymer or composite fibres. The corresponding inorganic structures were successfully obtained after calcination. The hierarchical structures of porous nanospheres within macroporous structures or on nanofibres are of potential interest to researchers in nanomaterials, porous polymers, supported catalysis and controlled delivery.

Nanoporous polymers for hydrogen storage

The design of hydrogen storage materials is one of the principal challenges that must be met before the development of a hydrogen economy. While hydrogen has a large specific energy, its volumetric energy density is so low as to require development of materials that can store and release it when needed. While much of the research on hydrogen storage focuses on metal hydrides, these materials are currently limited by slow kinetics and energy inefficiency. Nanostructured materials with high surface areas are actively being developed as another option. These materials avoid some of the kinetic and thermodynamic drawbacks of metal hydrides and other reactive methods of storing hydrogen. In this work, progress towards hydrogen storage with nanoporous materials in general and porous organic polymers in particular is critically reviewed. Mechanisms of formation for crosslinked polymers, hypercrosslinked polymers, polymers of intrinsic microporosity, and covalent organic frameworks are discussed. Strategies for controlling hydrogen storage capacity and adsorption enthalpy via manipulation of surface area, pore size, and pore volume are discussed in detail.

High internal phase emulsion templates solely stabilised by functionalised titania nanoparticles

Porous polymer foams (poly-Pickering-HIPEs) have been synthesised from stable high internal phase emulsion templates solely stabilised by low concentrations of functionalised titania nanoparticles.