Self-healing amino acid-bearing acrylamides/n-butyl acrylate copolymers via multiple noncovalent bonds

Four amino acid-bearing acrylamides, N-acryloyl-l-threonine (AThrOH), N-acryloyl-l-glutamic acid (AGluOH), N-acryloyl-l-phenylalanine (APheOH), and N-acryloyl-l, l-diphenylalanine (APhePheOH), were selected for copolymerization with n-butyl acrylate (nBA) to develop amino acid-based self-healable copolymers. A series of copolymers comprising amino acid-bearing acrylamides and nBA with tunable comonomer compositions and molecular weights were synthesized by free radical and reversible addition-fragmentation chain-transfer copolymerization. Self-healing and mechanical properties originated from the noncovalent bonds between the carboxyl, hydroxyl, and amide groups, and π-π stacking interactions among the amino acid residues in the side chains were evaluated. Among these copolymers, P(nBA-co-AGluOH) with suitable comonomer compositions and molecular weights (nBA : AGluOH = 82 : 18, Mn = 18 300, Mw/Mn = 2.58) exhibited good mechanical properties (modulus of toughness = 17.3 MJ m-3) and self-healing under ambient conditions. The multiple noncovalent bonds of P(nBA-co-AGluOH)s were also efficient in improving the optical properties with an enhanced refractive index and good transparency.

Biochar from palm fiber wastes as an activator of different oxidants for the elimination of pharmaceuticals from diverse classes in aqueous samples

Biochar (BP) obtained from palm fiber wastes was combined with H₂O₂, peroxymonosulfate (PMS), or persulfate (PDS) to treat valsartan, acetaminophen, and cephalexin in water. BP activated PMS and PDS but no H₂O₂. Computational calculations indicated that interactions of PMS and PDS with BP are more favored than those with HP. The highest synergistic effect was obtained for the removal of valsartan by BP + PMS. This carbocatalytic process was optimized, evaluating the effects of pH, BP dose, and peroxymonosulfate concentration, and minimizing the oxidant quantity to decrease costs and environmental impacts of the process. SO₄•^-, HO•, ¹O₂, and O₂•^- were the agents involved in the degradation of the pharmaceuticals. The reusability of BP was tested, showing that the carbocatalytic process removed ∼80% of target pollutants after 120 min of treatment even at the fourth reuse cycle. Also, the process decreased the phytotoxicity of the treated sample. Simulated hospital wastewater was treated and its components induced competing effects, but the system achieved the target pharmaceuticals removal in this matrix. Additionally, the analysis of environmental impact using a life cycle assessment unraveled that the carbocatalytic process had a carbon footprint of 2.87 Kg CO₂-Eq, with the biochar preparation (which involves the use of ZnCl₂ and electric energy consumption) as the main hotspot in the process.

Recyclable & highly porous organo-aerogel adsorbents from biowaste for organic contaminants' removal

Selective aerogel has become an attractive adsorbent for removing oil and organic contaminants due to its low density and excellent adsorption capacity. However, aerogels usually use non-sustainable or expensive nanomaterials and require complicated fabrication processes. Herein, using low-cost lignin reclaimed from the biorefinery waste stream as the starting material, we fabricated a highly porous, mechanically strong, and stable aerogel via a simple and one-step method under mild conditions. This aerogel exhibits a controllable micropore structure and achieves quick and efficient adsorption for oil (435% g/g), as well as toxic solvents such as THF (365% g/g). The selective and stable adsorbent can be reused multiple times and the oil adsorption capacity after 5 cycles remained at 89%. This highly efficient, mechanically strong, stable, and regenerable aerogel is a potential candidate for multiple applications such as cleaning up organic contaminants, oil remediation, and oil/water separation. Meanwhile, it also employs a "waste-treat-waste" concept by adding extra value to the biorefinery process for high-efficiency circular bioeconomy.

ROS-Scavenging Therapeutic Hydrogels for Modulation of the Inflammatory Response

Although reactive oxygen species (ROS) are essential for cellular processes, excessive ROS could be a major cause of various inflammatory diseases because of the oxidation of proteins, DNA, and membrane lipids. It has recently been suggested that the amount of ROS could thus be regulated to treat such physiological disorders. A ROS-scavenging hydrogel is a promising candidate for therapeutic applications because of its high biocompatibility, 3D matrix, and ability to be modified. Approaches to conferring antioxidant properties to normal hydrogels include embedding ROS-scavenging catalytic nanoparticles, modifying hydrogel polymer chains with ROS-adsorbing organic moieties, and incorporating ROS-labile linkers in polymer backbones. Such therapeutic hydrogels can be used for wound healing, cardiovascular diseases, bone repair, ocular diseases, and neurodegenerative disorders. ROS-scavenging hydrogels could eliminate oxidative stress, accelerate the regeneration process, and show synergetic effects with other drugs or therapeutic molecules. In this review, the mechanisms by which ROS are generated and scavenged in the body are outlined, and the effects of high levels of ROS and the resulting oxidative stress on inflammatory diseases are described. Next, the mechanism of ROS scavenging by hydrogels is explained depending on the ROS-scavenging agents embedded within the hydrogel. Lastly, the recent achievements in the development of ROS-scavenging hydrogels to treat various inflammation-associated diseases are presented.

Engineering the Surface Pattern of Microparticles: From Raspberry-like to Golf Ball-like

Control of the shape and uniformity of colloid particles is essential for realizing their functionality in various applications. Herein, we report a facile approach for the synthesis of narrowly dispersed anisotropic microparticles with well-defined raspberry-like and golf ball-like surface patterns. First, we demonstrate that hybrid raspberry-like particles can be achieved through a one-pot polymerization method using glycidyl polyhedral oligomeric silsesquioxane (GPOSS) and pentaerythritol tetra(3-mercaptopropionate) (PETMP) as monomers. Varying the polymerization parameters such as catalyst loading, monomer concentration, and the molar ratio of monomers, we are able to regulate the sizes and surface protrusion numbers of these raspberry-like microparticles. The formation mechanism is attributed to a competition balance between thiol-epoxy reaction and thiol-thiol coupling reaction. The former promotes rapid formation of large core particles between PETMP and GPOSS droplets (which can serve as core particles), while the latter allows for generation of surface protrusions by PETMP self-polymerization, leading to the formation of raspberry-like surface patterns. Based on the different POSS contents in the surface protrusions and cores of the raspberry-like microparticles, we demonstrate that they can be used as precursors to produce microporous silica (sub)microparticles with golf ball-like morphology via pyrolysis subsequently. Overall, this work provides a facile yet controllable approach to synthesize narrowly dispersed anisotropic microparticles with diverse surface patterns.

Sulfoxide-functionalized nanogels inspired by the skin penetration properties of DMSO

Among polymeric nanocarriers, nanogels are especially promising non-irritating delivery vehicles to increase dermal bioavailability of therapeutics. However, accurately tailoring defined interactions with the amphiphilic skin barrier is still challenging. To address this limited specificity, we herein present a new strategy to combine biocompatible nanogels with the outstanding skin interaction properties of sulfoxide moieties. These chemical motifs are known from dimethyl sulfoxide (DMSO), a potent chemical penetration enhancer, which can often cause undesired skin damage upon long-term usage. By covalently functionalizing the nanogels' polymer network with such methyl sulfoxide side groups, tailor-made dermal delivery vehicles are developed to circumvent the skin disrupting properties of the small molecules. Key to an effective nanogel-skin interaction is assumed to be the specific nanogel amphiphilicity. This is examined by comparing the delivery efficiency of sulfoxide-based nanogels (NG-SOMe) with their corresponding thioether (NG-SMe) and sulfone-functionalized (NG-SO2Me) analogues. We demonstrate that the amphiphilic sulfoxide-based NG-SOMe nanogels are superior in their interaction with the likewise amphipathic stratum corneum (SC) showing an increased topical delivery efficacy of Nile red (NR) to the viable epidermis (VE) of excised human skin. In addition, toxicological studies on keratinocytes and fibroblasts show good biocompatibility while no perturbation of the complex protein and lipid distribution is observed via stimulated Raman microscopy. Thus, our NG-SOMe nanogels show high potential to effectively emulate the skin penetration enhancing properties of DMSO without its negative side effects.

Recyclable High-Performance Epoxy-Anhydride Resins with DMP-30 as the Catalyst of Transesterification Reactions

Epoxy-anhydride resins are widely used in engineering fields due to their excellent performance. However, the insolubility and infusibility make the recycling of epoxy resins challenging. The development of degradable epoxy resins with stable covalent networks provides an efficient solution to the recycling of thermosets. In this paper, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) is incorporated into the epoxy-glutaric anhydride (GA) system to prepare high-performance epoxy resins that can be recycled below 200 °C at ordinary pressure via ethylene glycol (EG) participated transesterification. The tertiary amine groups in DMP-30 can catalyze the curing reaction of epoxy and anhydride, as well as the transesterification between ester bonds and alcoholic hydroxyl groups. Compared with early recyclable anhydride-cured epoxy resins, the preparation and recycling of diglycidyl ether of bisphenol A (DGEBA)/GA/DMP-30 systems do not need any special catalysts such as TBD, Zn(Ac)2, etc., which are usually expensive, toxic, and have poor compatibility with other compounds. The resulting resins have glass transition temperatures and strengths similar to those of conventional epoxy resins. The influences of GA content, DMP-30 content, and temperature on the dissolution rate were studied. The decomposed epoxy oligomer (DEO) is further used as a reaction ingredient to prepare new resins. It is found that the DEO can improve the toughness of epoxy resins significantly. This work provides a simple method to prepare readily recyclable epoxy resins, which is of low-cost and easy to implement.

Anomalously Shaped Functional Particles Prepared by Thiol-Isocyanate Off-Stoichiometric Click Dispersion Polymerization

Anomalously shaped microparticles have attractive advantages in applications. They are usually prepared by chain-growth polymerizations in heterogeneous systems. Recently, thiol-X step-growth polymerizations have been used to produce functional particles with a regular shape but rarely anomalous shapes. Herein, we report the preparation of anomalously shaped particles by thiol-isocyanate dispersion polymerization (Dis.P) in ethanol using polyvinylpyrrolidone (PVP) as a stabilizer and catalyst. Papillae-shaped, raspberry-like, and multibulged particles are prepared by tuning monomer combinations, contents, and feed ratios. Particle morphology evolutions during polymerization are observed by scanning electron microscopy (SEM). Distinct from previous works, particles with residual -SH groups are obtained even with equal moles of monomers added initially. The residue of -SH groups is revealed by Fourier transform infrared spectroscopy (FT-IR) analyses and confirmed by detection with a fluorescent probe containing disulfide linkage. Moreover, fluorescent particle probes are formed by the reaction of excess -NCO groups on particles with fluorescein isothiocyanate isomer I (FITC) and dithioacetal-functionalized perylenediimide (DTPDI). The probes are sensitive in detection of glutathione (GSH) and Hg²⁺ in water. Hg²⁺ as low as 1-0.1 ppb is detected using a raspberry-like particle probe with DTPDI.

Synthesis of poly(amide-thioether) with tunable hydrophilicity via thiolactone chemistry and its application in oil-in-oil emulsions

Oil-in-oil emulsions are ideal systems for water-sensitive reactions such as polymerizations and catalytic reactions, which has received extensive attention in recent years. The application of oil-in-oil emulsions has been developed slowly due to the limited types of surfactants and complicated synthesis process. Herein, we proposed a simple method to prepare poly(amide-thioether)-based surfactant for oil-in-oil emulsions via taking advantage of single-pot multicomponent and click characters of thiolactone chemistry. Using a combination of alkyl amine and acrylamide thiolactone, the aminolysis of thiolctone occurred first, generating thiol group in-situ, and then the generated thiol group would sequentially react with the double bonds of acrylamide to form polythioether in the presence of amine. The hydrophobicity of the surfactant could be effectively adjusted by the chain length of the alkyl amine and thus this polymer could serve as a promising surfactant for oil-in-oil emulsion. Notably, the emulsion types could be switched by changing the chain length of the alkyl amine. In addition, the effects of surfactant loading, volume ratio of oil phases, oil types on the size and stability of oil-in-oil emulsions were further investigated. It was demonstrated that the oil-in-oil emulsion stabilized by poly(amide-thioether)s kept stable after more than five months. Besides, we preliminarily explored the application of the oil-in-oil emulsion to prepare closed cell foam and porous particles via photo-initiated thiol-ene polymerization. It is believed that this super-stable oil-in-oil emulsion could offer more possibilities for highly potential water-sensitive systems.

TO/TMMP-TMTGE Double-Healing Composite Containing a Transesterification Reversible Matrix and Tung Oil-Loaded Microcapsules for Active Self-Healing

Thermoset epoxies are widely used due to their excellent properties, but conventional epoxies require a complicated and time-consuming curing process, and they cannot self-healed, which limits their applications in self-healing materials. Extrinsic and intrinsic self-healing materials are applied in various fields due to their respective characteristics, but there is a lack of comparison between the two types of healing systems. Based on this, a thiol-epoxide click reaction catalyzed by an organic base was introduced to achieve the efficient preparation of thiol-epoxy. Furthermore, tung oil (TO)-loaded microcapsules were introduced into the thiol-epoxy matrix of dynamic transesterification to obtain a TO/TMMP-TMTGE self-healing composite with an intrinsic-extrinsic double-healing system. For comparison, a TMMP-TMTGE self-healing material with an intrinsic healing system was also prepared, which contained only thiol and epoxy curing chemistries. The effect of the core/shell ratio on the morphology, average particle size, and core content of TO-loaded microcapsules was studied. It was found that when the core/shell ratio was 3:1, the average particle size of the microcapsules was about 99.8 μm, and the microcapsules showed good monodispersity, as well as a core content of about 58.91%. The differential scanning calorimetry (DSC) results showed that the TO core was successfully encapsulated and remained effective after encapsulation. Furthermore, scanning electron microscopy (SEM), atomic force microscopy (AFM), tensile tests, and electrochemical tests were carried out for the two types of self-healing materials. The results showed that the TO/TMMP-TMTGE composite and TMMP-TMTGE material both had self-healing properties. In addition, the TO/TMMP-TMTGE composite was superior to the TMMP-TMTGE material due to its better self-healing performance, mechanical strength, and corrosion protection performance.

TEMPO Driven Mild and Modular Route to Functionalized Microparticles

The synthesis of crosslinked polymeric microspheres (3.8-15.0 µm) via (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) initiated thiol-ene dispersion polymerization under ambient conditions is reported for the first time. The initiating ability of TEMPO for the thiol-ene reaction is validated by electron paramagnetic resonance (EPR) and ¹ H nuclear magnetic resonance (NMR) spectroscopy on model reactions between 1-octadecanethiol and two electron deficient enes, n-butylacrylate and divinyl sulfone. Critically, the TEMPO resonance observed in the EPR spectra decreases with time when TEMPO is mixed with thiol and an electron deficient ene. The ¹ H NMR spectra demonstrate formation of up to 90% of thioether under ambient conditions. Based on these model reactions, a variety of crosslinked polymeric microspheres are synthesized with excellent morphological stability using poly(vinyl pyrrolidone) as surfactant. The ability of the microspheres for a second TEMPO initiated thiol-ene reaction is demonstrated by the ligation of fluorescein-5-maleimide (an ene) to the microspheres' surface containing excess of thiol functionality and by ligation of cysteine (containing a thiol group) to the microspheres' surface containing an excess of ene functionality. The synthesized polymeric microspheres are characterized using scanning electron microscopy, differential scanning calorimetry, Fourier-transform infrared spectroscopy, zeta potential, and X-ray photoelectron spectroscopy.