Polymeric Silane Research Articles

Engineered thin coatings of cross-linked silane polymers with urea group onto polypropylene fabrics for controlled release of thymol against molds in hay

With world population on the rise, animal food source production has significantly increased. Susceptibility of hay and other sources to molds poses a serious threat to food quality and safety. This study proposes an innovative approach to address this issue – an anti-mold fungicide comprising thymol bound on silica urea thin coating of polypropylene fabrics. The coating enhances the thermal stability of thymol allowing prolonged release. Coating composition and morphology as well as thermal stability and release rates were investigated. The coating provided efficient protection against mold growth with no side effects on hay exposed to thymol fumes. The results underscore the potential of this fungicide as a safe and effective hay preservative.

Dispersing silica fume in cementitious materials by silane copolymerized polycarboxylate Superplasticizer: On the role of dispersion effectiveness as a function of silane concentration

In this paper, a commonly used vinyl based silane coupling agent (SC), namely γ-methacryloxy propyl trimethoxyl silane (MAPTMS) was designed to co-polymerize with polycarboxylate superplasticizer (PCE) to increase the compatibility of PCE with silica fume (SF). The role of dispersion effectiveness as a function of silane concentration was systematically analyzed. It was found that at lower MAPTMS concentration, the prepared SC-PCE showed better SF dispersion capability than the control PCE with increasing MAPTMS concentration. The increased particle dispersion effectiveness was confirmed by minimized volume average particle size of SF by two orders of magnitude (from 27.507 μm to 0.275 μm), as well as a much slower SF particles settlement speed in a model cement solution. Increment of cement compressive strength reconfirmed the positive effect of SC-PCE on particle dispersion. When the mole substitution of AA by MAPTMS overran to 40%, however, SC-PCE behaved like polymeric silane silica sol and gelled as indicated by increase of viscosity overtime. The dispersion ability of SC-PCE ceased to be in effect. A maximum substitution ratio of MAPTMS was therefore need to be considered when designing a more effective SC-PCE for SF, as well as for other siliceous SCM.

Identifying the mechanism of formation of chlorinated silane polymer by‐products during chemical vapor infiltration of SiC from CH3SiCl3/H2

AbstractPolymerization by‐products with the formula (SiCl2)n or SinHxCl2n–x are accumulated at the reactor exhaust of SiC chemical vapor infiltration (CVI) from CH3SiCl3/H2, which occur as an explosive hazard. Thermodynamic constants of the chlorinated silane polymers (SiCl2)n and Cl(SiCl2)mCl (n ≤ 5, m ≤ 4) were obtained by quantum chemical calculations using the CBS‐QB3 method. Polymerization reaction pathways of SiCl2 to (SiCl2)n and Cl(SiCl2)mCl (n ≤ 3, m ≤ 3) were also determined using the CBS‐QB3 method, with higher accuracy than in previous reports. The thermodynamic and kinetic constants were incorporated into an existing elementary reaction model of CH3SiCl3 (methyltrichlorosilane; MTS) reacting with H2 to derive the UT2019 model. This enabled the decomposition of MTS into SiCl2 to be studied. Chemical equilibrium calculations and gas‐phase kinetic simulations were performed. The chemical equilibrium calculations revealed that the chlorinated silane polymers, which are explosive by‐products of CVI of SiC, are unstable in the gas phase at any temperature under reduced pressure conditions, suggesting that their formation could be inhibited by controlling the gas‐phase reactions. The gas‐phase kinetic simulations showed that by‐products with a polymerization degree of 3 are not produced above 400°C, but are rapidly produced in the gas phase below 400°C. These findings also apply to the chemical vapor deposition of Si from chlorinated silane precursors.

Super-structural 2D ultrathin carbon nitride/acrylate boron silane polymer with multi-function for enhancing antifouling performance

Haunted by marine biofouling and the ecological crisis caused by toxic antifouling paints, the demand for environmental coatings has become more and more pressing. In this work, a series of super-structural 2D ultrathin carbon nitride/acrylate boron silane polymers (CNPs) was prepared by incorporating C3N4 into a self-polishing acrylate boron silane polymer (ABSP). The antifouling, environmental performances were evaluated, and the antifouling mechanism was investigated. The results showed that when the content of C3N4 was 3–7 wt%, the coatings showed the best resistance to diatoms, Staphylococcus aureus and Escherichia coli in visible light. It was noted that the coatings showed weak antibacterial properties in the dark. In addition, the CNPs and ABSP were shown to expel mussels by photocatalytic active species, self-renewal and amphiphilic surfaces. The chemical oxygen demand (COD) values showed that the addition of C3N4 made the CNPs become environmental coatings.

Improved Adhesion of Nonfluorinated ZnO Nanotriangle Superhydrophobic Layer on Glass Surface by Spray-Coating Method

In this present work, a superhydrophobic glass surface comprising zinc oxide nanotriangles (ZnO-nt) and nontoxic silylating agent was developed via a cost-effective spray-coating technology. ZnO-nt was synthesized by a hydrothermal method. Poly(dimethylsiloxane) (PDMS) and dimethyldiethoxysilane (DMDEOS) were used as nontoxic (nonfluoro) silylating agents. The morphology and crystallinity of ZnO-nt were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. ZnO-nt with polymeric silane (PDMS) exhibited maximum wettability as compared to nonpolymeric silane (DMDEOS). The water contact angle (WCA), sliding angle (SA), and surface roughness of ZnO-nt/PDMS-coated glass substrate under UV treatment were 165 ± 1°, 3 ± 1°, and 791 nm, respectively. The WCA of ZnO-nt/PDMS was higher (165°) than that of commercial ZnO/PDMS (ZnO-C/PDMS). ZnO-nt/PDMS was strongly attached to the glass substrate with good stability and adhesion. The reasons for improved hydrophobicity, adhesion, and mechanism of hierarchical microstructure formation on the glass substrate were explained in detail. PDMS was attached to the glass substrate via hydrogen bonds from solvated zinc acetate.

Dual purpose hafnium oxide nanoparticles offer imaging Streptococcus mutans dental biofilm and fight it In vivo via a drug free approach

The removal of tenacious dental plaque is of paramount importance; however, early diagnosis can be a challenging task in dental clinics due to the limitations of current approaches, specifically X-ray-based techniques. We have approached this problem by integrating antibacterial properties and X-ray contrast enhancement in a single probe specific to colonies of Streptococcus mutans as the most predominant and carious oral bacteria. We report the synthesis of an inherently therapeutic polymeric silane conjugated hafnium oxide nanoparticles (Hf PS NPs). Using a high-affinity pathogen-selective peptide, the concept of molecularly targeted X-ray imaging of cariogenic pathogen S. mutans was demonstrated. Ex vivo studies using extracted human tooth demonstrated striking X-ray attenuation of NPs vs. tooth. Additionally, Hf PS NPs exhibited significant bactericidal properties against cariogenic pathogen. Electron microscopy revealed that the antibacterial activity occurred via a ‘latch and kill’ mechanism. Mechanistic studies determined that these NPs fragmented bacterial DNA components to exert their antimicrobial effect. Importantly, Hf PS NPs effectively inhibited the growth of a mature biofilm on an ex vivo human tooth model. Finally, the NPs were applied to the rodent model of dental biofilm. Topical administration of the Hf PS NPs for 8 days (1X daily) could effectively attenuate the S. mutans biofilm challenge. This report is the first of its kind to demonstrate that HfO2-based NPs can be used for simultaneous diagnosis and antibacterial treatment without requiring an additional drug.

Weathering behavior investigations and treatment of Kom Ombo temple sandstone, Egypt – Based on their sedimentological and petrogaphical information

The Temple of Kom Ombo is a huge ancient Egyptian temple in Upper Egypt. It was built by Ptolemy VI Philometor (180-145 BC) and added to by subsequent Ptolemys. The structure of the temple is built of local sandstone attributed to the Quseir Formation of “Nubian Sandstone” group at Gebel el-Silsila. Sandstone samples from Kom Ombo temple were taken to verify the source rock of the quarried material. Optical Polarizing Microscope (OPM) and Scanning Electron Microscope (SEM) were used to determine the microstructure and physical properties of the sandstone. X-Ray diffraction (XRD) was carried out for the Sandstone samples to identify its mineralogical composition. The sandstone samples were treated with six polymeric products to determine changes in their physical and mechanical properties after penetration, consolidation of polymers within them. This sandstone is composed mainly of three quartz arenite microfacies (feldspathic, sublithic and calcareous) that are interpreted to have been deposited in fluvial to fluvial-marine environment. Silane polymers is showing a good penetration and filling pores between grains and recommended for treatment and conservation of the sandstone. Acrylic polymer shows random penetration of polymer and formation of a film of polymer on the surface of sandstone. Silo11 gave the best result in consolidation of sandstone samples then primal AC33. Wacker BS29 gave the best result in isolating process of sandstone samples, then wacker BS 290.

Mild and Selective Et2Zn-Catalyzed Reduction of Tertiary Amides under Hydrosilylation Conditions

Diethylzinc (Et2Zn) can be used as an efficient and chemoselective catalyst for the reduction of tertiary amides under mild reaction conditions employing cost-effective polymeric silane (PMHS) as the hydride source. Crucial for the catalytic activity was the addition of a substoichiometric amount of lithium chloride to the reaction mixture. A series of amides containing different additional functional groups were reduced to their corresponding amines, and the products were isolated in good-to-excellent yields.

Direct Hydrosilylation of Tertiary Amides to Amines by an In Situ Formed Iron/N‐Heterocyclic Carbene Catalyst

AbstractTertiary amides were efficiently reduced to their corresponding tertiary amines in high isolated yields by using the commercially available and inexpensive polymeric silane polymethylhydrosiloxane (PMHS) as the reducing agent. The reaction is efficiently catalyzed by an in situ generated iron/N‐heterocyclic carbene complex (1 mol‐%) obtained from iron(II) acetate and 1‐(2‐hydroxy‐2‐phenylethyl)‐3‐methylimidazolium triflate ([PhHEMIM][OTF]). A catalytic amount of lithium chloride (1 mol‐%) present in the reaction mixture significantly reduced the reaction time and increased the chemoselectivity of the reduction process.

Effect of Polymeric Coupling Agent on Mechanical Properties of Kenaf Fiber / Polystyrene Composites

In order to improve the properties and the processability of kenaf fiber (KF) / polystyrene (PS) composites, the newly synthesized polymeric silane coupling agent (CA) was utilized and evaluated. KFs were reacted with CA in the melt system and in the solvent system. The composites reinforced by the modified KF showed enhanced mechanical properties compared with those reinforced by the unmodified KF. The effect was especially remarkable when the KF was modified with CA in the solvent system. As the CA content increases, the surface of KF recovered from the composites showed the higher Si / C ratio indicating the good reaction between KF and CA. The modified composites also showed a remarkable reduction in water uptake rate.

Efficient and Selective Hydrosilylation of Carbonyl Compounds Catalyzed by Iron Acetate and N‐Hydroxyethylimidazolium Salts

AbstractAromatic aldehydes, along with aryl alkyl, heteroaryl alkyl, and dialkyl ketones were efficiently reduced to their corresponding primary and secondary alcohols, respectively, in high yields, using the commercially available and inexpensive polymeric silane, polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by in situ generated iron complexes containing hydroxyethyl‐functionalized NHC ligands. Turnover frequencies up to 600 h−1 were obtained.

Selective hydrosilylation of ketones catalyzed by in situ‐generated iron NHC complexes

AbstractAryl alkyl‐, heteroaryl alkyl‐ and dialkyl ketones were readily reduced to their corresponding secondary alcohols in high yields, using the commercially available and inexpensive polymeric silane polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by an in situ‐generated iron complex, conveniently generated from iron(II) acetate and the commercially available N‐heterocyclic carbene (NHC) precursor IPr·HCl. Copyright © 2011 John Wiley & Sons, Ltd.

Photofunctional Eu3+/Tb3+ hybrid material with inorganic silica covalently linking polymer chain through their double functionalization

In the context, 2-thiosalicylic acid (TSA) is modified with two crosslinking reagents (3-chloropropyltrimethoxysilane (CTPMS), 3-(triethoxysilyl)-propyl isocyanate (TESPIC)) to achieve two kinds of sulfide bridges (abbreviated as TSA-CSi and TSA-TSi, respectively). And two organic polymers (poly acrylamide (PAM) and poly ethylene glycol (PEG)) are also functionalized with TESPIC to form their polymeric silane derivatives PAMSi and PEGSi. Then series of multi-component Eu3+/Tb3+ hybrid material have been assembled with inorganic silica covalently linking organic polymer through the sulfide bridges after co-hydrolysis and co-polycondensation with the above inorganic or organic alkoxyl compounds (TSA-CSi(TSi), PAMSi(PEGSi)) and tetraethoxysilane (TEOS). These hybrid material are characterized in details to compare with the binary hybrid material without organic polymer unit, whose results reveal that the photoluminescence properties of the hybrid system are improved with the introduction of the polymer unit.

Phonon Dispersion Analysis as an Indispensable Tool for Predictions of Solid State Polymorphism and Dynamic Metastability: Case of Compressed Silane

Diamond anvil cell experiments suggest that upon compression above 26.5 GPa silane (SiH4) forms a polymeric phase VI, whose crystal structure has not yet been solved. Here we present DFT calculations showing how phonon-guided optimization leads to a polymeric Fdd2 structure which is the lowest-enthalpy polymorph of SiH4 above 26.8 GPa, and which most probably can be identified as the experimentally observed polymeric phase. The new algorithm of predicting the lowest-energy structures enables simultaneous inspection of the potential energy surface of a given system, calculation of its vibrational properties, and assessment of chances for obtaining a metastable ambient-pressure structure via decompression. Our calculations indicate that at room temperature the differences in the vibrational and entropy terms contributing to the Gibbs free energy of different polymorphs of silane are negligible in comparison with corresponding differences in the zero-point energy corrections, in contrast to earlier suggestions. We also show that the Fdd2 polymorph should be metastable upon decompression up to 5 GPa, which suggests the possibility of obtaining a polymeric ambient-pressure form of SiH4. Polymeric silane should exhibit facile thermal decomposition with evolution of molecular hydrogen and thus constitute an efficient (12.5 wt%) material for hydrogen storage.

Spin coating and plasma process for 2.5D integrated photonics on multilayer polymers

Polymer spin coating, surface plasma treatment and selective UV-lithography processes have been developed to realize 2.5D photonic micro-resonators, made of disk- or ring-shaped upper rib waveguides, using common polymers such as SU8 (biphenol A ether glycidyl), PS233 (polymeric silane) and SOG (siloxane Spin on Glass). Both oxygen and argon plasma treatments, applied to PS233 and SOG before spin-coating the SU8, improve substantially the grip of multilayer devices (SU8 / PS233 or SU8 / SOG). Surface energy components derived from contact angle measurements have been used to optimize the processing conditions. In such integrated photonic devices, the both single-electromagnetic-modes called transverse electric (TE 00) and transverse magnetic (TM 00) have been excited in a SU8 micro-disk, with a single mode propagation strongly localized near the edge of the disk (i.e. the so called whispering gallery modes).

A practical concept for the kinetic resolution of a chiral secondary alcohol based on a polymeric silane

The paper describes our preliminary studies on the use of PMHS as a functionalizable polymer and hydride source for the kinetic resolution of secondary alcohols via chiral Cu(I)-catalyzed dehydrogenative silylating process. The chiral phosphine that chelates the Cu metal center has little influence on the selectivity factor of the kinetic resolution. The use of a stereogenic silane appears to be a key requirement to reach enantiodifferentiation in such a process.

Two-dimensional gel permeation chromatography (2-D GPC) correlation studies of the aggregate–aggregate interactions in acid-catalyzed triethoxysilyl-terminated polystyrene systems: weak catalysis by HNO3

Time-resolved gel-permeation chromatography (GPC) profiles were measured over a long period of time (t=0–768 h) for the HNO3-catalyzed reaction mixture of a well-defined polymeric silane coupling agent, triethoxysilyl-terminated polystyrene. The results showed that HNO3 catalyzes the rate of polymerization, but only to a small extent. Two-dimensional (2-D) GPC correlation spectra were calculated from time-resolved GPC profiles and were used to examine the mechanism of polymerization. The resolution enhancement obtained by 2-D correlation provided ample evidence for existence of four monomeric components. It has been demonstrated that dynamic variation in the population of these components occurs over a long reaction time, reflecting the mechanism of a slow polymerization process.

Two-dimensional Correlation Gel Permeation Chromatography (2D GPC) Study of Aggregate–Aggregate Interactions during Polymerization of 3-(Triethoxysilyl)propyl-terminated Polystyrene

The three-step polymerization process of a well-defined polymeric silane coupling agent, 3-(triethoxysilyl)propyl-terminated polystyrene, catalyzed by 1 mol/kg KOH–H2O, was traced as a function of reaction time using a gel-permeation chromatography (GPC) technique. A set of GPC traces collected during the polymerization was then converted to two-dimensional (2D) correlation maps, by using generalized 2D correlation analysis. The 2D correlation GPC maps reflected the details of the aggregational behavior (in particular, the aggregate–aggregate correlations) in each step of the polymerization, thus demonstrating the promising potential of this technique.

Two-dimensional gel permeation chromatography (2D GPC) correlation studies of the aggregate-aggregate interactions in acid-catalyzed triethoxysilyl-terminated polystyrene systems. The effect of specific catalysts on growth process

A set of time resolved gel-permeation chromatography (GPC) profiles, for the reaction mixture of a well-defined polymeric silane coupling agent, triethoxysilyl-terminated polystyrene with molecular weight equal to 8000 (TESi-PS (8000)), catalyzed by HCl (0.1 mol/kg) in tetrahydrofuran (THF), was measured over a long time scale (1–768 h). The GPC profiles were then converted to two-dimensional (2D) correlation spectra. The 2D GPC correlation spectra were compared with those for the CH3SO3H (0.1 mol/kg)-catalyzed TESi-PS (8000)-THF system. It has been demonstrated that predominant production of less-reactive oligomers in the HCl-catalyzed system hinders further growth of the oligomer, while formation of reactive oligomers leads to further growth of polymeric precursors in the CH3SO3H-catalyzed system.

Two‐dimensional correlation gel permeation chromatography study of aggregate–aggregate interactions during acid‐catalyzed polymerization of triethoxysilyl‐terminated polystyrene

AbstractThe three‐step polymerization of a well‐defined polymeric silane coupling agent, triethoxysilyl‐terminated polystyrene, catalyzed by acid (H3PO4), was traced as a function of the reaction time with gel permeation chromatography (GPC). Time‐resolved GPC traces collected during the polymerization process were then used to construct two‐dimensional (2D) correlation maps via generalized 2D correlation analysis. The results demonstrated that the synchronous and asynchronous 2D correlation GPC spectra directly reflected the dynamic variation of aggregate–aggregate interactions during each step of the polymerization. In particular, it was found that the formation of aggregates among the cyclic trimers (or tetramers) and monomers was critical for the preferential production of pentamers in the reaction system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3447–3460, 2004