Synthesis of Water-Dispersible Poly(dimethylsiloxane) and Its Potential Application in the Paper Coating Industry as an Alternative for PFAS-Coated Paper and Single-Use Plastics

Polyethylene-, polyvinylidene chloride-, and per- and polyfluoroalkyl substance-coated paper generate microplastics or fluorochemicals in the environment. Here, we report an approach for the development of oil-resistant papers using an environmentally friendly, fluorine-free, water-dispersible poly(dimethylsiloxane) (PDMS) coating on kraft paper. Carboxylic-functionalized PDMS (PDMS-COOH) was synthesized and subsequently neutralized with ammonium bicarbonate to obtain a waterborne emulsion, which was then coated onto kraft paper. The water resistance of the coated paper was determined via Cobb60 measurements. The Cobb60 value was reduced to 2.70 ± 0.14 g/m2 as compared to 87.6 ± 5.1 g/m2 for uncoated paper, suggesting a remarkable improvement in water resistance. Similarly, oil resistance was found to be 12/12 on the kit test scale versus 0/12 for uncoated paper. In addition, the coated paper retained 70-90% of its inherent mechanical properties, and more importantly, the coated paper was recycled via pulp recovery using a standard protocol with a 91.1% yield.

A comparative study of thallium(iii) and iodine(iii)-mediated ring contraction reactions for the synthesis of indane

Ring contraction reactions were carried out using HTIB and TTN to compare yields as well as the protection group tolerance.

Covalent Adaptable Network and Self-Healing Materials: Current Trends and Future Prospects in Sustainability

This work estimates that if the growth of polymer production continues at its current rate of 5% each year, the current annual production of 395 million tons of plastic will exceed 1000 million tons by 2039. Only 9% of the plastics that are currently produced are recycled while most of these materials end up in landfills or leak into oceans, thus creating severe environmental challenges. Covalent adaptable networks (CANs) materials can play a significant role in reducing the burden posed by plastics materials on the environment because CANs are reusable and recyclable. This review is focused on recent research related to CANs of polycarbonates, polyesters, polyamides, polyurethanes, and polyurea. In particular, trends in self-healing CANs systems, the market value of these materials, as well as mechanistic insights regarding polycarbonates, polyesters, polyamides, polyurethanes, and polyurea are highlighted in this review. Finally, the challenges and outlook for CANs are described herein.

Self-healing and self-cleaning clear coating

Coatings exhibiting both self-cleaning and self-healing properties are envisioned for a wide range of applications. Herein we report a simple fabrication approach toward poly(urea-urethane) (PU) coatings having self-healing and self-cleaning properties. The self-cleaning component is a poly(dimethylsiloxane) (PDMS), which is affordable in cost and also has a lower environmental footprint relative to its fluorinated counterpart. The self-healing properties are imparted by dynamic urea bonds of the matrix. The obtained surfaces are evaluated for their anti-smudge properties such as water-, oil- and ink-repellency, as well as optical properties. The self-healing properties of these coatings are evaluated by making scores with a doctor blade and monitoring the healing under different conditions using optical microscopy. The resultant coatings are also investigated for their good mechanical properties. The surface chemical compositions are determined x-ray photoelectron spectroscopy, while atomic force microscopy is used for microstructural analysis of these coatings.

Dual-Layer Approach toward Self-Healing and Self-Cleaning Polyurethane Thermosets

There is an urgent need for coatings that exhibit both self-healing as well as self-cleaning properties as they can be used for a wide range of applications. Herein we report a novel approach toward fabricating polyurethane thermosets possessing both self-cleaning and self-healing properties. The desired coating was achieved via casting a bottom layer of self-healable polyurethanes comprised of reversible phenolic urethane bonds followed by a subsequent dip-coating of the prepared layer in a solution of bis(3-aminopropyl)-terminated polydimethylsiloxane (PDMS-NH2). The PDMS was used to impart self-cleaning properties to the coating. While the self-healing behavior of the bottom polyurethane layer is achieved through phenolic urethane chemistry, via the exchange of phenolic urethane moieties. The prepared coatings were tested for their optical, mechanical, self-healing, and self-cleaning properties using a variety of characterization methods, which confirmed the successful fabrication of novel self-cleaning and self-healing clear urethane coatings.

A novel dual-layer approach towards omniphobic polyurethane coatings

Omniphobic surfaces have a plethora of applications ranging from household paints to sensors. The predominant practice of fabricating those materials/surfaces is to use fluorinated materials which are environmentally harmful, and thus have limited practical applications. In this study, we report a novel dual-layer approach of fabrication towards omniphobic surfaces using polyurethane (PU) as a matrix and polydimethylsiloxane (PDMS) as a self-cleaning ingredient. This approach was also used to produce omniphobic PU nanocomposites, where nanofillers (e.g., nanoclay, cellulose nanocrystals (CNCs) and graphene oxide (GO)) were incorporated. The resultant coatings were investigated for their performance, such as optical clarity, durability, and self-cleaning properties. In addition, scanning electron microscopy (SEM) was used for microstructural analysis of the obtained coatings. The facile nature of fabrication and the use of PDMS, an environmentally benign material relative to fluorinated chemicals, thus offer an eco-friendly sustainable scheme for practical applications aimed at omniphobic purposes.

Omniphobic surfaces have a plethora of applications ranging from household paints to sensors.

Synthesis of High Molecular Weight Polyester Using in Situ Drying Method and Assessment of Water Vapor and Oxygen Barrier Properties

The preparation of renewable polyesters with good barrier properties is highly desirable for the packaging industry. Herein we report the synthesis of high molecular weight polyesters via an innovative use of an in situ drying agent approach and the barrier properties of the films formed from these polyesters. High number average molecular weight (M_n) semiaromatic polyesters (PEs) were synthesized via alternating ring-opening copolymerization (ROCOP) of phthalic anhydride (PA) and cyclohexene oxide (CHO) using a salen chromium(III) complex in the presence of 4-(dimethylamino)pyridine (DMAP) cocatalyst. The use of a calcium hydride (drying agent) was found to enhance the number M_n of the synthesized PEs, which reached up to 31.2 ku. To test the barrier properties, PE films were prepared by solvent casting approach and their barrier properties were tested in comparison poly(lactic acid) films. The PE films showed significantly improved water vapor and oxygen barrier properties compared to the commercial poly(lactic acid) (PLA) film that suggests the potential use of these PEs in in the food packaging industry.

Fabrication of Food-Safe Water-Resistant Paper Coatings Using a Melamine Primer and Polysiloxane Outer Layer

Paper-based materials are highly desirable as packaging materials due to their numerous advantages that include low cost, renewability, and biodegradability. However, their hydrophilicity has limited their range of applications. Reported herein is a facile and economical approach for the preparation of biodegradable water-resistant paper for food-contact applications. Commercial printing paper and cup papers are coated with melamine, which is FDA approved for food-contact applications. Subsequently, a water-repellent outer layer is applied using poly(dimethylsiloxane) (PDMS)-isocyanate. A relationship between the PDMS concentration and water contact angles (WCAs) of the obtained coating was studied. Typically, the coated cup paper and printing paper had coating loadings of 1.61 ± 1.10 and 0.93 ± 0.74 wt %, respectively. After the coatings had been applied, the WCAs were very high (>125°), and water absorption had decreased by 70% for printing paper and by 35% for cup paper. Considering the facile fabrication method and the low-cost food-safe raw materials, herein, this approach will have great potential for the large-scale production of materials for use in food- and nonfood contact applications.

Encapsulation of catalyst in block copolymer micelles for the polymerization of ethylene in aqueous medium

The catalytic emulsion polymerization of ethylene has been a long-lasting technical challenge as current techniques still suffer some limitations. Here we report an alternative strategy for the production of semi-crystalline polyethylene latex. Our methodology consists of encapsulating a catalyst precursor within micelles composed of an amphiphilic block copolymer. These micelles act as nanoreactors for the polymerization of ethylene in water. Phosphinosulfonate palladium complexes were used to demonstrate the success of our approach as they were found to be active for hours when encapsulated in micelles. Despite this long stability, the activity of the catalysts in micelles remains significantly lower than in organic solvent, suggesting some catalyst inhibition. The inhibition strength of the different chemicals present in the micelle were determined and compared. The combination of the small volume of the micelles, and the coordination of PEG appear to be the culprits for the low activity observed in micelles.

Novel fluorene-based supramolecular sensor for selective detection of amoxicillin in water and blood

Synthesis, characterization and molecular recognition properties of fluorene based supramolecular cleft 1 is reported. The cleft molecule 1 was prepared in a single-step with good yield (85% yield), by linking Fluorene with 1-ethyl piperazine. The cleft molecule 1 was carefully characterized using various spectroscopic techniques such as NMR and mass spectrometry. The supramolecular interaction of cleft 1 with amoxicillin, 6APA, aspirin, captopril, cefotaxime, ceftriaxone, cefuroxime, diclofenac, penicillin, and cephradine was evaluated by fluorescent spectroscopy. The molecular recognition studies showed that amoxicillin selectively binds with cleft 1 in the presence of other drugs. The analytical method developed for the supramolecular interaction of molecular cleft 1 and amoxicillin was validated at varying pH, concentration and temperature during recognition process. Job's plots indicated that the stochiometry of the interactions between the cleft 1 and the amoxicillin was 1:1.

Synthesis, characterization and Cu(2+) triggered selective fluorescence quenching of Bis-calix[4]arene tetra-triazole macrocycle

A novel fluorescent bis-calix[4]arene macrocycle 9 incorporating metal-binding pockets was successfully prepared. The structure of macrocycle 9 and its precursors were characterized via EI-MS, MALDI-TOF-MS, ESI-MS, (1)H NMR, (13)CNMR, 2D NMR, and X-ray crystallography. The macrocycle 9 displayed selective fluorescence quenching after interacting with Cu(2+) in the presence competing metal cations including Mg(2+), Ca(2+), Ba(2+), Ag(+), Zn(2+), Ti(4+),Cd(2+), Hg(2+), Pb(2+), In(3+), La(3+), Cr(3+), Ni(2+), Sb(3+), V(5+), Fe(3+), Co(2+), Sn(2+), Sn(2+), and Tl(+). The Cu(2+) limit of detection was found to be 40 nM much lower than its threshold level (∼ 20 μM) in drinking water permitted by the U.S Environmental Protection Agency (EPA). Furthermore, drinking water samples from Karachi University (Pakistan) spiked with Cu(2+) were analysed with the sensing system and the results showed an excellent agreement with the fluorescence quenching phenomenon of macrocycle 9 examined in deionized water. Importantly, the chemosensor 9 could be used to detect Cu(2+) in living cells.

Fluorine-Free Anti-Smudge Polyurethane Coatings

Conventionally, low-surface-tension fluorinated reagents are incorporated into anti-smudge (oil- and water-repellent) coatings for oil repellency. However, fluorinated compounds are expensive and an environmental concern because of their high stability and bioaccumulation. These factors limit their widespread application. We report herein the development of fluorine-free anti-smudge polyurethane coatings that are clear at thicknesses up to tens of micrometers and are able to sustain extensive surface damage. We demonstrate that these coatings can be applied readily onto a diverse range of substrates.

Synthesis of poly(dimethylsiloxane)-block-poly[3-(triisopropyloxysilyl) propyl methacrylate] and its use in the facile coating of hydrophilically patterned superhydrophobic fabrics

We report the synthesis and applications of a novel poly(dimethylsiloxane-block-poly[3-(triisopropyloxysilyl)propyl methacrylate]) (PDMS-b-PIPSMA) diblock copolymer.

Quantification of residual liquid on repellent cotton fabrics after liquid roll off

A new method to detect and quantify any residual liquid left on coated cotton fabrics after liquid roll off using fluorescence microscopy.

Clear antismudge unimolecular coatings of diblock copolymers on glass plates

Two poly[3-(triisopropyloxysilyl)propyl methacrylate]-block-poly[2-(perfluorooctyl)ethyl methacrylate] (PIPSMA-b-PFOEMA) samples and one poly(perfluoropropylene oxide)-block-poly-[3-(triisopropyloxysilyl)propyl methacrylate] (PFPO-b-PIPSMA) sample were synthesized, characterized, and used to coat glass plates. These coatings were formed by evaporating a dilute polymer solution containing HCl, which catalyzed PIPSMA's sol-gel chemistry. Polymer usage was minimized by targeting at diblock copolymer unimolecular (brush) layers that consisted of a sol-gelled grafted PIPSMA layer and an oil- and water-repellant fluorinated surface layer. Investigated is the effect of varying the catalyst amount, polymer amount, as well as block copolymer type and composition on the structure, morphology, and oil- and water-repellency of the coatings. Under optimized conditions, the prepared coatings were optically clear and resistant to writing by a permanent marker. The marker's trace was the faintest on PFPO-b-PIPSMA coatings. In addition, the PFPO-b-PIPSMA coatings were far more wear-resistant than the PIPSMA-b-PFOEMA coatings.

Prussian blue nanocontainers: selectively permeable hollow metal-organic capsules from block ionomer emulsion-induced assembly

Hollow polymer-based particles are useful for the encapsulation, protection, and release of active compounds. Adding a metal-organic coordination framework shell to nanocontainers is an attractive goal because it should help control their stability and permeability while yielding new properties and functions. We have discovered that polymer capsules with a Prussian blue analogue inner shell can be synthesized by emulsion-induced assembly of a metal-containing amphiphilic block ionomer. The capsules are selectively permeable and were used as nanocontainers to encapsulate and release a model compound. Further, these nanomaterials are tunable in size and organize into 2-D close-packed arrays in the solid state. Potential applications for these materials include the encapsulation and nanopatterning of pharmaceutical, biological, and catalytic compounds.

2-(4-Chloro-phen-yl)-4-[1-(4-chloro-phen-yl)-3-methyl-1H-pyrazol-5-yl]-5-methyl-1H-pyrazol-3(2H)-one

The title compound, C₂₀H₁₆Cl₂N₄O, has two mol­ecules in the asymmetric unit. The two five-membered rings form a dihedral angle of 54.2 (3)° in one mol­ecule and 56.8 (3)° in the other independent mol­ecule. The amino group of the dihydro­pyrazolone unit of one mol­ecule acts as a hydrogen-bond donor to the carbonyl group of the dihydro­pyrazolone system of the other mol­ecule. The resulting N—H⋯O hydrogen bonds generate a chain running along the c axis. The crystal selected was a pseudo-merohedral twin with a 44.9 (3)% twin component.

Ethyl 2-(3-acetyl-6-methyl-2-oxo-2H-pyran-4-yl-oxy)acetate

The title compound, C(12)H(14)O(6), features a roughly planar mol-ecule (r.m.s. deviation for all non-H atoms = 0.287 Å). In the crystal, the mol-ecules are held together by C-H⋯O hydrogen bonds.

Methyl (2'-hydroxy-biphenyl-2-yl-oxy)acetate

The three independent mol­ecules of the title compound, C₁₅H₁₄O₄, have similar orientations of their aromatic rings, the dihedral angles between the rings being 57.0 (1), 58.1 (1) and 58.2 (1)°. In each mol­ecule, the hydr­oxy group forms an intra­molecular hydrogen bond to the carbonyl O atom, forming an S(10) ring motif.

2,2′-[Biphenyl-2,2′-diylbis(oxy)]diacetic acid monohydrate

In the crystal structure of the title compound, C₁₆H₁₄O₆·H₂O, the dihedral angle between the benzene rings is 60.8 (3)°. Mol­ecules are linked through a bifurcated O—H⋯O hydrogen bond, forming a zigzag chain along the b axis. The chains are further linked by O—H⋯O hydrogen bonds mediated by water mol­ecules.