Synthesis and Characterization of Silicone-Based Surfactants as Anti-Foaming Agents

Thermophysical properties of polyethylene glycol oligomers via molecular dynamics simulations

Polyethylene glycol (PEG) is a versatile chemical with numerous applications in various fields, including biomedical research, pharmaceutical development, and industrial manufacturing. Molecular dynamics (MD) is a powerful tool for investigating the thermophysical properties of PEG molecules. In this study, we employ the General AMBER force field (GAFF) to perform MD simulations on various PEG oligomers, focusing on the calculation of density, self-diffusion coefficients, shear viscosity, and thermal conductivity. The results demonstrate excellent agreement with experimental data, where GAFF outperforms other force fields in reproducing thermophysical properties. For a PEG tetramer, the GAFF force field reproduces experimental data within 5% for the density, 5% for the diffusion coefficient, and 10% for the viscosity. In comparison, the OPLS force field displays significant deviations exceeding 80% for the diffusion coefficient and 400% for the viscosity. A detailed analysis of partial charge distributions and dihedral angles reveals that they significantly impact the structural behavior of PEG oligomers. The findings highlight the GAFF force field as one of the most accurate and reliable options for simulating systems with PEGs.

One-step synthesis of amphiphilic copolymers PDMS-b-PEG using tris(pentafluorophenyl)borane and subsequent study of encapsulation and release of curcumin

A series of amphiphilic block copolymer (BCP) micelles based on poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEG) were synthesized by a one-step reaction in the presence of tris(pentafluorophenyl)borane (BCF) as a catalyst. The structural composition of PDMS-b-PEG (PR11) and PEG-b-PDMS-b-PEG (PR12) was corroborated by FTIR, 29Si NMR, and TGA. The BCPs were assembled in an aqueous solution, obtaining micelles between 57 and 87 nm in size. PR11 exhibited a higher (2.0 g L-1) critical micelle concentration (CMC) than PR12 (1.5 g L-1) due to the short chain length. The synthesized nano micelles were used to encapsulate curcumin, which is one of three compounds of turmeric plant 'Curcuma longa' with significant biological activities, including antioxidant, chemoprotective, antibacterial, anti-inflammatory, antiviral, and anti-depressant properties. The encapsulation efficiency of curcumin was 60% for PR11 and 45% for PR12. Regarding the release study, PR11 delivered 53% curcumin after five days under acidic conditions (pH of 1.2) compared to 43% at a pH of 7.4. The degradation products of curcumin were observed under basic conditions and were more stable at acidic pH. In both situations, the release process is carried out by breaking the silyl-ether bond, allowing the release of curcumin. PR11 showed prolonged release times, so it could be used to reduce ingestion times and simultaneously work as a nanocarrier for other hydrophobic drugs.

Silicone polyether surfactant enhances bacterial cellulose synthesis and water holding capacity

The versatility and unique properties of bacterial cellulose (BC) motivate research into enhancing its synthesis. Here a silicone polyether surfactant (SPS) was synthesized and tested as a non-nutritional additive to the cultivation media of Komagataeibacter xylinus. The addition of SPS to the Hestrin-Schramm (HS) medium resulted in a concentration-dependent decrease in surface tension from 59.57 ± 0.37 mN/m to 30.05 ± 0.41 mN/m (for 0.1% addition) that was correlated with an increased yield of BC, up to 37% wet mass for surfactant concentration close to its critical micelle concentration (0.008%). Physicochemical characterization of bacterial cellulose obtained in presence of SPS, showed that surfactant is not incorporated into BC structure and has a moderate effect on its crystallinity, thermal stability. Moreover, the water holding capacity was enhanced by over 40%. Importantly, obtained BC did not affect L929 murine fibroblast cell viability. We conclude that SPS provides an eco-friendly approach to increasing BC yield in static culture, enabling more widespread industrial and biomedical applications.

Physio-Chemical Analysis of Amide and Amine Poly(dimethylsiloxane)-Modified Defoamer for Efficient Oil-Water Separation

The formation of foam due to the injection of surfactant foam in FAWAG causes significant problems in the oil well production and separation facilities. The excessive foam can lead to the reduction of the separator capacity as well as its efficiency. A defoamer is needed to break and destroy the foam in the separator. There are many commercially available defoamer agents in the market, but not all defoamers are suitable for every application. For this reason, four modified silicone-based defoamers were successfully synthesized and characterized based on the data obtained from the screening process using various commercial defoamers. The performance of modified defoamers was evaluated using TECLIS FoamScan that imitate real conditions of treatment. The results show that all four of the modified silicone-based defoamers, especially amide-terminated-modified defoamers (S2) showed excellent performance as a defoaming agent to mitigate foam in specific conditions. The best-case condition for the modified defoamer to perform was at a high temperature (60 °C), gas flow rate of 1.0 L/min, and low ration concentration of the surfactant to brine (30:70). The study on the bubble count and distribution using a KRÜSS Dynamic Foam Analyzer revealed that S2 excellently contributes to the formation of unstable foam that can fasten foam destruction in the foaming system.

Increasing Silicone Mold Longevity: A Review of Surface Modification Techniques for PDMS-PDMS Double Casting

Polydimethyl siloxane (PDMS) has been used extensively for microfluidic devices due to its chemical properties allowing for rapid molding and versatile biological application. Soft lithography based PDMS fabrication primarily comprises casting from patterned photoresist on a silicon wafer. The patterned photoresist is often replaced with the cast PDMS as a more durable template mold for final PDMS fabrication that is less fragile and expensive. PDMS-PDMS double casting prolongs the longevity of soft lithography molds and reduces overall costs to microfuidic applications. A common end to the lifetime of PDMS negative masters is the risk of bonding between the replicate and mold and distorted topographrical features. This review examines common chemical and physical debonding approaches between PDMS-PDMS castings to exend the lifetime of PDMS masters.

Thermal, Catalytic Conversion of Alkanes to Linear Aldehydes and Linear Amines

Alkanes, the main constituents of petroleum, are attractive feedstocks for producing value-added chemicals. Linear aldehydes and amines are two of the most important building blocks in the chemical industry. To date, there have been no effective methods for directly converting n-alkanes to linear aldehydes and linear amines. Here, we report a molecular dual-catalyst system for production of linear aldehydes via regioselective carbonylation of n-alkanes. The system is comprised of a pincer iridium catalyst for transfer-dehydrogenation of the alkane using t-butylethylene or ethylene as a hydrogen acceptor working sequentially with a rhodium catalyst for olefin isomerization-hydroformylation with syngas. The system exhibits high regioselectivity for linear aldehydes and gives high catalytic turnover numbers when using ethylene as the acceptor. In addition, the direct conversion of light alkanes, n-pentane and n-hexane, to siloxy-terminated alkyl aldehydes through a sequence of Ir/Fe-catalyzed alkane silylation and Ir/Rh-catalyzed alkane carbonylation, is described. Finally, the Ir/Rh dual-catalyst strategy has been successfully applied to regioselective alkane aminomethylation to form linear alkyl amines.

Polymer-Free Electronic-Grade Aligned Semiconducting Carbon Nanotube Array

Conjugated polymers are used commonly to selectively sort semiconducting carbon nanotubes (S-CNTs) from their metallic counterparts in organic solvents. The polymer-wrapped S-CNTs can be easily processed from organic solvents into arrays of CNTs for scalable device fabrication. Though the conjugated polymers are essential for sorting and device fabrication, it is highly desirable to remove them completely as they limit the electronic properties of the device. Here, we use a commercially available polymer, namely, poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6'-(2,2'-bipyridine))] (PFO-BPy), to sort large-diameter S-CNTs with ultrahigh selectivity and fabricate CNT-array-based field effect transistors (FETs) via a floating evaporative self-assembly (FESA) process. We report quantitative removal of the polymer wrapper from the FESA aligned S-CNT arrays using a metal-chelation-assisted polymer removal (McAPR) process. The implementation of this process on FESA films requires the selective thermal degradation of the polymer into oligomers, combined with optimization of the solvent type and temperature of the metal complexation reaction. Resulting S-CNT array FET devices show that the electronic properties of pristine CNT are preserved through this process. Optical microscopy, UV-vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used to characterize the quantitative polymer removal. We quantitatively describe the FET devices to analyze the fundamental characteristics of FETs (mobility (μ), on-conductance (G_on), and contact resistance (2R_c)) by comparing before and after polymer removal. The ability to completely remove the polymer wrapper in aligned CNT arrays without adversely affecting the device properties opens up applications beyond FETs into photovoltaics and biosensing.

Monitoring structural evolution of organosilicate species during sol-gel processes by electrospray ionization mass spectrometry

RATIONALE

Electrospray ionization mass spectrometry (ESI-MS) has been employed to study species distribution in controlled acid-catalyzed hydrolysis and condensation of (3-chloropropyl)trimethoxysilane (CPTMS), which is frequently used in the synthesis of hybrid silica-based materials.

METHODS

The conditions of analysis for reaction products, i.e. organosilicate oligomers, were optimized by using various capillary temperatures and solute concentrations. The structures of organosilicate oligomers were shown to vary with reaction duration and the molar ratio of water to siloxane (r), with multiple types of oligomers attributed to linear, cyclic and hydroxylated species.

RESULTS

The evolution of oligomeric structures was elucidated from the ESI-MS spectra. The number and intensity of cyclic oligomers increase with an increase in the r-value or reaction length, at the expense of linear species, indicating the trend to formation of cross-linked polysiloxane structures.

CONCLUSIONS

Overall, this work demonstrates that ESI-MS is an indispensable tool for the comprehensive characterization of the correlation between properties and structure of hybrid silica-based materials.

Synthesis of a novel silicone based copolymeric surfactant and application in emulsion polymerization

A novel silicone-containing acrylic monomer, trimethylsiloxybutoxy dimethylsiloxybutyl acrylate (TSBA) and diethylene glycol monoallyl ether (DGME) was synthesized successfully. Then, a novel copolymeric surfactant was prepared by the free radical polymerization of TSBA and DGME in the presence of dioxane and azobisisobutyronitrile (AIBN) as a solvent and initiator, respectively. Next, a series of polyvinyl acetate (PVAc), 2-ethylhexyl acrylate (2-EHA) and polystyrene (PSt) latexes were successfully synthesized, each one throughout by the emulsion copolymerization in the presence of a copolymeric surfactant. This copolymeric surfactant exhibited excellent surface activity and the surface tension decreased with an increase in the concentration of the copolymeric surfactant.