Novel Bismaleimide Porous Polymer Microsphere by Self-Stabilized Precipitation Polymerization and Its Application for Catalytic Microreactors

Porous poly(bismaleimide-co-divinylbenzene) microspheres as dispersive solid-phase extraction adsorbent coupled to high-performance liquid chromatography for the determination of triazine herbicide residues in vegetable samples

In this work, monodisperse and nano-porous poly(bismaleimide-co-divinylbenzene) microspheres with large specific surface area (427.6 m2 /g) and rich pore structure were prepared by one-pot self-stable precipitation polymerization of 2,2'-bis[4-(4-maleimidophenoxy) phenyl] propane and divinylbenzene. The prepared poly(bismaleimide-co-divinylbenzene) microspheres were employed as dispersive solid-phase extraction (DSPE) adsorbent for the extraction of triazine herbicides. Under optimized conditions, good linearities were obtained between the peak area and the concentration of triazine herbicides in the range of 1-400 µg/L (R2 ≥ 0.9987) with the limits of detection of 0.12-0.31 µg/L. Triazine herbicides were detected using the described approach in vegetable samples (i.e., cucumber, tomato, and maize) with recoveries of 93.6%-117.3% and relative standard deviations of 0.4%-3.5%. In addition, the recoveries of triazine herbicides remained above 80.7% after being used for nine DSPE cycles, showing excellent reusability of poly(bismaleimide-co-divinylbenzene) microspheres. The adsorption of poly(bismaleimide-co-divinylbenzene) microspheres toward triazine herbicides was a monolayer and chemical adsorption. The adsorption mechanism between triazine herbicides and adsorbents might be a combination of hydrogen bonding, electrostatic interaction, and π-π conjugation. The results confirmed the potential use of the poly(bismaleimide-co-divinylbenzene) microspheres-based DSPE coupled to the high-performance liquid chromatography method for the detection of triazine herbicide residues in vegetable samples.

Construction of Marigold-like Poly(vinyl alcohol) Microspheres for Catalytic Microreactors

It has long been pursued to develop polymer microspheres with various special morphologies and structures for better results in applications such as catalysis, drug delivery, and bioscaffolds. However, it remains a challenge to develop a facile method to produce poly(vinyl alcohol) (PVA) microspheres with special morphologies. Herein, a micron-sized marigold-like poly(vinyl alcohol) (CE-PVATPA) microsphere was engineered and fabricated by a feasible strategy, that is, emulsification-cross-linking, freeze-drying, and secondary acetal reaction steps. The morphological evolution of microspheres was systematically investigated under different conditions, and the procedure of constructing PVA microspheres with stabilizing marigold-like structures was proposed. More importantly, a specially structured PVA microsphere microreactor synergistically loading palladium metal nanoparticles (CE-PVATPA@Pd) for the heterogeneous catalyst 4-nitrophenol (4-NP) could be further demonstrated, which indicated high catalytic activity and excellent recyclability. The resultant stabilized fabricating method is promising to provide valuable guidance for the design and fabrication of a high-performance PVA microsphere microreactor.

Physicochemical, structural, and adsorption characteristics of DMSPS-co-DVB nanopolymers

The aim of this work is the synthesis and characterization of the series of S,S'-thiodi-4,1-phenylene bis(thio-methacrylate)-co-divinylbenzene (DMSPS-co-DVB) nanomaterials. The series of new nanopolymers including three mixed systems with different ratios of DMSPS and DVB components, DMSPS-co-DVB = 1:1, DMSPS-co-DVB = 1:2, and DMSPS-co-DVB = 1:3, was synthesized in the polymerization reaction. The research task is to investigate the influence of the reaction mixture composition on morphological, textural, and structural properties of final nanosystems including size, shape, and agglomeration effect. The advanced biphasic nanomaterials enriched with thiol groups were successfully synthesized as potential sorbents for binding organic substances, heavy metals, or biomolecules. To determine the impact of the DMSPS monomer on the final properties of DMSPS-co-DVB nanocomposites, several techniques were applied to reveal the nano-dimensional structure (SAXS), texture (low-temperature nitrogen sorption), general morphology (SEM), acid-base properties (potentiometric titration), and surface chemistry and phase bonding effectiveness (FTIR/ATR spectroscopy). Finally, kinetic studies of aniline sorption on polymeric materials were performed.

Super-adsorbent microspheres based on a triallyl isocyanurate-maleic anhydride copolymer for the removal of organic pollutants from water

Owing to the frequent occurrence of diclofenac sodium (DS) in fresh aquatic environments and its potential toxicity towards living organisms, the effective removal of DS has attracted worldwide attention. Herein, a green and efficient strategy to fabricate crosslinked microspheres with interconnected mesoporous structures and abundant adsorption active sites was developed. With this strategy, triallyl isocyanurate (TAIC)-maleic anhydride (MAH) copolymer microspheres (TMs) with a diameter of 1.19-1.35 μm were first prepared by self-stabilized precipitation (2SP) polymerization, and the TMs possess a large amount reactive anhydride groups (62.5-71.8 mol%), a specific surface area of 51.6-182.4 m² g^-1 and a mesoporous structure (average pore size: 3.4-3.8 nm). Then the TMs were further functionalized with polyethylenimine (PEI) to give rise to cationic microspheres (Cat-TMs), which showed excellent adsorption performance to DS with a rapid adsorption rate (reached equilibrium within 30 min), a very high equilibrium adsorption capacity (1421 mg g^-1) and excellent recyclability. The pseudo-second-order model and Langmuir model were a good fit for the adsorption kinetic and isotherm process, respectively. Furthermore, due to the high cation density (4.291 mmol g^-1) and excellent pH buffer capacity of Cat-TMs, the adsorption capacity can be maintained at a high level within the pH range of 6-10. The regenerated Cat-TMs showed only a slight loss (<5%) in the adsorption capacity even after 5 adsorption-desorption cycles. In short, Cat-TMs can be considered as a highly promising adsorbent for the rapid and ultra-efficient removal of anionic organic contaminants and have significant potential to be applied in wastewater treatment.

A facile one-pot strategy for the preparation of porous polymeric microspheres via UV irradiation-induced polymerization in emulsions

In this study, a facile one-pot strategy was developed to prepare porous polymeric microspheres via photopolymerization, where organic solvents functioned as porogens. In this strategy, an oil phase containing organic solvents and photopolymerizable materials was stabilized in water to form a stable oil-in-water emulsion. Upon UV irradiation, the photopolymerizable materials (photosensitive monomers/photosensitive prepolymers) underwent polymerization to form microspheres and the subsequent removal of organic solvents left pores in microspheres, leading to the generation of porous polymeric microspheres with high yielding. The effects of organic solvents and the chemical structure and concentration of photopolymerizable materials on the microsphere structure were systematically explored. It was found that the polarity of the organic solvents played a decisive role in the preparation of porous microspheres. In addition, the increases in the solvent content and functionalities of photopolymerizable materials were more favorable for the generation of porous microspheres. This strategy could be applicable for a wide selection of photopolymerizable materials, which endowed this strategy with good applicability. The preparation of porous microspheres by this method was facile and easy to handle, enabling the scalable preparation of porous microspheres. In addition, the whole process can be completed within a few minutes at ambient temperature, which was time-saving and energy-saving.