Formaldehyde formation during the preparation of dialdehyde carboxymethyl cellulose tanning agent.

Formaldehyde was detected in dialdehyde carboxymethyl cellulose (DCMC) tanning agent prepared through periodate oxidation of sodium carboxymethyl cellulose (CMC). Formaldehyde was then introduced into leather through DCMC tanning, which poses a potential risk to human health. The formation mechanism of formaldehyde in DCMC was investigated by composition analysis and intermediate identification of DCMC with different polymerization degrees and sugar unit structures. Formaldehyde was derived from the overoxidation of C-6 on the reducing glucose residue of CMC. Moreover, glucose was produced from the concomitant degradation of CMC during oxidation, and then oxidized to liberate formaldehyde. The low degradation degree and high degree of substitution of CMC reduced the possibility of the formation of reducing glucose residue and glucose during oxidation, thereby resulting in low formaldehyde content in DCMC and DCMC-tanned leather. These findings serve as a foundation for the minimization of formaldehyde in DCMC and the development of ecological tanning approach.

Influence of synthesis parameters on properties and characteristics of poly (urea-formaldehyde) microcapsules for self-healing applications.

Poly(urea-formaldehyde) (PUF) microcapsules filled with dicyclopentadiene (DCPD) were prepared by in situ polymerisation and the effect of synthesis parameters, such as pH of the solution and agitation rate, on microcapsules size and shell thickness was evaluated. Scanning electron microscopy (SEM) and Fourier transform infra-red spectroscopy (FTIR) were performed. Adjusted pH conditions (pH = 3.5) and agitation rate (1350 RPM) were found using a design of experiments (DOE). SEM results indicated that microcapsule size was directly affected by agitation rate, whereas shell thickness was mostly affected by pH. After obtaining adjusted synthesis conditions, microcapsules presenting mean size of 60 µm and mean shell thickness of 4 µm were embedded in an epoxy matrix for evaluating the self-healing effect. FTIR and SEM analyses in damaged samples suggested that a healing agent was delivered to the crack location.

Statistical screening analysis of the chemical composition and kinetic study of phenol-formaldehyde resins synthesized in the presence of polyamines as co-catalysts.

The physico-chemical and application properties of phenol-formaldehyde resins used in the production of laminated plastics depend on such factors as: type and amount of catalyst, formaldehyde-to-phenol mole ratio, temperature and time of the synthesis process. The special impact on the reaction mechanism and kinetics, e.g. on the formation of mono-, di- and trihydroxymethyl derivatives of phenol (PhOH) is a consequence of the type and amount of the catalyst. This paper presents the results of optimisation research of resol resin synthesis catalysed by trimethylamine (TEA) carried out according to 32 experimental design. The aim of the research was to determine the synthesis conditions under which it is possible to achieve products with reduced content of unconverted formaldehyde (CH2O), phenol and its hydroxymetyl derivatives, while maintaining the required physico-chemical properties. The process employing selected polyamines as well as TEA together with polyamine co-catalysts i.e. diethylenetriamine (DETA) and triethylenetetraamine (TETA) was also studied. The results were compared with those of the resins which were synthesised with the use of classic catalysts-ammonia (NH3) and triethylamine for which the content of CH2O, PhOH and its hydroxymethyl derivatives was respectively: NH3-5.13% and 46.27%, TEA-0.33% and 52.41%. In the case DETA was added, the content of phenol and its hydroxymethyl derivatives could be reduced by 52.49% in relation to the resin obtained with the use of TEA and by 46.19% in relation to the resin obtained with the use of ammonia. The formaldehyde content was reduced by 78.79% and 98.64%, respectively. When TETA was added as a co-catalyst, the content of phenol and its derivatives was reduced by 48.04% versus triethylamine-catalysed resin and by 41.15% versus ammonia-catalysed material. The reduction in formaldehyde content reached 84.85% and 99.03%, respectively. The results of kinetic study were also presented, the prediction accuracy of the proposed kinetic model is more than 98% for all the catalysts in the state variable space. Polyamine co-catalysts gave much higher rate constants (0.50 and 0.45 for TETA and DETA, respectively).

Tailored Design of Bicontinuous Gyroid Mesoporous Carbon and Nitrogen-Doped Carbon from Poly(ethylene oxide-b-caprolactone) Diblock Copolymers.

Highly ordered mesoporous resol-type phenolic resin and the corresponding mesoporous carbon materials were synthesized by using poly(ethylene oxide-b-caprolactone) (PEO-b-PCL) diblock copolymer as a soft template. The self-assembled mesoporous phenolic resin was found to form only in a specific resol concentration range of 40-70 wt % due to an intriguing balance of hydrogen-bonding interactions in the resol/PEO-b-PCL mixtures. Furthermore, morphological transitions of the mesostructures from disordered to gyroid to cylindrical and finally to disordered micelle structure were observed with increasing resol concentration. By calcination under nitrogen atmosphere at 800 °C, the bicontinuous mesostructured gyroid phenolic resin could be converted to mesoporous carbon with large pore size without collapse of the original mesostructure. Furthermore, post-treatment of the mesoporous gyroid phenolic resin with melamine gave rise to N-doped mesoporous carbon with unique electronic properties for realizing high CO2 adsorption capacity (6.72 mmol g-1 at 0 °C).

The Prospecting Shortcut to an Old Molecule: Formaldehyde Synthesis at Low Temperature in Solution.

Over 30 megatons of formaldehyde are required per year and industrially produced through three high-temperature gas-phase processes: i) natural gas reforming to syngas, ii) methanol synthesis, and iii) partial oxidation to formaldehyde with limited selectivity. In vast contrast to these energy-intensive oxidative and dehydrogenative methods, a reductive "top-down" methodology using CO2 and CO as carbon source would be desirable and is not very well present in the literature for more than 100 years. The key to success is the reaction performance in liquid solution in water or methanol at low temperature.

Synthesis of fluorescent and low cytotoxicity phenol formaldehyde resin (PFR)@Ag composites for cell imaging and antibacterial activity.

Ag nanoparticles (NPs) were loaded onto the surface of phenol formaldehyde resin (PFR) NPs without any reducing agent. The as-synthesized PFR@Ag composites have low cytotoxicity, which makes them promising antibacterial agents. Furthermore, the good fluorescence of PFR could be used for cell imaging.

Catalytic activation of carbohydrates as formaldehyde equivalents for Stetter reaction with enones.

We disclose the first catalytic activation of carbohydrates as formaldehyde equivalents to generate acyl anions as one-carbon nucleophilic units for a Stetter reaction. The activation involves N-heterocyclic carbene (NHC)-catalyzed C-C bond cleavage of carbohydrates via a retro-benzoin-type process to generate the acyl anion intermediates. This Stetter reaction constitutes the first success in generating formal formaldehyde-derived acyl anions as one-carbon nucleophiles for non-self-benzoin processes. The renewable nature of carbohydrates, accessible from biomass, further highlights the practical potential of this fundamentally interesting catalytic activation.

Formaldehyde and methanol formation from reaction of carbon monoxide and hydrogen on neutral Fe2S2 clusters in the gas phase.

Reaction of CO with H2 on neutral FemSn clusters in a fast flow reactor is investigated both experimentally and theoretically. Single photon ionization at 118 nm is used to detect neutral cluster distributions through time of flight mass spectrometry. FemSn clusters are generated through laser ablation of a mixed iron-sulfur target in the presence of a pure helium carrier gas. A strong size dependent reactivity of (FeS)m clusters toward CO is characterized. The reaction FeS + CO → Fe + OCS is found for the FeS cluster, and the association product Fe2S2CO is observed for the Fe2S2 cluster. Products Fe2S2(13)COH2 and Fe2S2(13)COH4 are identified for reactions of (13)CO and H2 on Fe2S2 clusters: this suggests that the Fe2S2 cluster has a high catalytic activity for hydrogenation reactions of CO to form formaldehyde and methanol. Density functional theory (DFT) calculations are performed to explore the potential energy surfaces for the two reactions: Fe2S2 + CO + 2H2 → Fe2S2 + CH3OH; and Fe2S2 + CO + H2 → Fe2S2 + CH2O. A barrierless, thermodynamically favorable pathway is obtained for both catalytic processes. Catalytic cycles for formaldehyde and methanol formation from CO and H2 on a Fe2S2 cluster are proposed based on our experimental and theoretical investigations. The various reaction mechanisms explored by DFT are in good agreement with the experimental results. Condensed phase iron sulfide, which contains exposed Fe2S2 units on its surface, is suggested to be a good catalyst for low temperature formaldehyde/methanol synthesis.

Synthesis of multifunctional Ag@Au@phenol formaldehyde resin particles loaded with folic acids for photothermal therapy.

Multifunctional Ag@Au@ phenol formaldehyde resin (PFR) particles loaded with folic acids (FA) have been designed for killing tumor cells through photothermy conversion under the irradiation of near-infrared (NIR) light. Possessing the virtue of good fluorescence, low toxicity, and good targeting, the nanocomposite consists of an Ag core, an Au layer, a PFR shell, and folic acids on the PFR shell. The Ag@PFR core-shell structure can be prepared with a simple hydrothermal method after preheating. We then filled the PFR shell with a layer of Au by heating and modified the shell with polyelectrolyte to change its surface charge state. To capture tumor cells actively, FA molecules were attached onto the surface of the Ag@Au@PFR particles in the presence of 1-ethyl-3-(3-dimethly aminopropyl) carbodiimide (EDAC) and N-hydroxysuccinimide (NHS). Owing to the excellent property of Au NPs and Ag NPs as photothermal conversion agents, the Ag@Au@ PFR@FA particles can be utilized to kill tumor cells when exposed to NIR light.

Synthesis, characterization and anti-microbial activity of phenylurea-formaldehyde resin (PUF) and its polymer metal complexes (PUF-Mn(II).

Phenylurea-formaldehyde polymer (PUF) was synthesized via polycondensation of phenylurea and formaldehyde in basic medium, its polymer-metal complexes [PUF-M(II)] were prepared with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) ions. PUF and PUF-M(II) were characterized with magnetic moment measurements, elemental and spectral (UV-visible, FTIR, 1H-NMR, 13C-NMR and ESR) analysis. The thermal behaviors of all the synthesized polymers were carried out using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The thermal data revealed that all of the PUF-M(II) showed higher thermal stabilities than the PUF and also ascribed that the PUF-Cu(II) showed better thermal stability than the other PUF-M(II). The kinetic parameters such as activation energy, pre-exponential factor etc., were evaluated for these polymer metal complexes using Coats-Redfern equation. In addition, the antimicrobial activity of the synthesized polymers was tested against several microorganisms using agar well diffusion methods. Among all of the PUF-M(II), the antimicrobial activity of the PUF-Cu(II) showed the highest zone of inhibition because of its higher stability constant and may be used in biomedical applications.