Multi-nuclear liquid state NMR investigation of the effects of pH and addition of polyethyleneglycol on the long-term hydrolysis and condensation of tetraethoxysilane

Wu, Cheng-Hsien; Jeng, Jiann-Shing; Chia, Jie-Lun; Ding, Shangwu

doi:10.1016/j.jcis.2010.09.024

Cited by 19 publications

(8 citation statements)

References 28 publications

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“…The overall process involves hydrolysis and condensation reactions that lead to the growth of clusters that eventually collide and link together to form a gel. The structure of the gel and the aggregation kinetics have been 17,18 . The temperature and time of the heat treatment depend on the kind of precursors and solvents used to produce the coating, but economically it is more interesting to work at lower temperatures and shorter times.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Siloxane-poly(methyl methacrylate) Hybrid Films Obtained on a Tinplate Substrate Modified by the Addition of Organic and Inorganic Acids

et al. 2015

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Tinplate is used to food packaging and other types of packages. The corrosion resistance of the tinplate has been study due the necessity of an alternative to high environmental impact of chromatization process. Therefore protective coatings as hybrid films base elaborations with different acids are studied to improve the barrier effect against corrosion. The objective of this work is characterize hybrid films deposited on a tinplate from a sol made up of the alkoxide precursors 3-(trimethoxysilylpropyl) methacrylate (TMSM), tetraethoxysilane (TEOS) and poly(methyl methacrylate) (PMMA) together with one of three acids (acetic, hydrochloric or nitric acid) and to verify their action against the corrosion of the substrate. The films were obtained by a dip-coating process and cured for 3 hours at 160 °C. The film hydrophobicity was determined by contact angle measurements, and the morphology was evaluated by SEM. FTIR measurements were performed to characterize the chemical structures of the films. The electrochemical behavior of the coatings was evaluated by techniques open circuit potential monitoring (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results demonstrate that the siloxane-PMMA films improve the protective properties of the tinplate, with the films obtained by acetic acid addition exhibiting the greatest improvement.

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Section: Introductionmentioning

confidence: 99%

Characterization of Siloxane-poly(methyl methacrylate) Hybrid Films Obtained on a Tinplate Substrate Modified by the Addition of Organic and Inorganic Acids

et al. 2015

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“…[20] Moreover, 29 Si NMR spectroscopy was employed widely to investigate the reaction kinetics and the quantitative study of organosilicate hydrolysis and condensation. [21][22][23][24][25][26][27][28][29][30][31][32] With regard to theoretical studies on the hydrolysis and oligomerization of silica, in 2005 Mora-Fonz et al [33] investigated the oligomerization and cyclization processes in the nucleation of microporous orthosilicic acid, Si(OH) 4 , by using DMOL3 with a numeric DNP basis set; in 2006 Trinh et al [34] studied the anionic and neutral mechanisms of oligomerization reactions of silica by using DFT calculations for various structures of silicate oligomers with the continuum solvation (COSMO) method and the activation energies for di-and trimer formation were estimated. In 2009 Trinh and co-workers [35][36][37] reported a DFTbased molecular dynamics simulation of silica oligomerization, providing thermodynamics, kinetics, and the mechanism of the reaction pathway for the anionic bond formation of siliceous oligomers.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Silicon Alkoxide Hydrolysis–Oligomerization Reactions: A DFT Investigation

2012

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Silica aerogels possess a variety of unique and remarkable properties, but the mechanisms of silicon alkoxide, Si(OR)(4), hydrolyses and oligomerization in the initial stage of sol-gel processes are still not well understood. On the basis of density functional theory calculations at the B3LYP/6-31G(d,p)//B3LYP/6-311++G(d,p) basis set level, the hydrolysis and oligomerization reactions of Si(OR)(4) in neutral, acidic, and alkaline solutions were systematically investigated and we found that in acidic solutions the precursor Si(OCH(3))(4) was inclined to hydrolyze rather than to condense and the hydrolysis processes were energetically more favorable than the neutral ones. In alkaline solutions, the hydrolysis products oligomerize through an S(N)1 dimerization mechanism and the condensation rates are fast to form denser colloidal aerogels. Our calculations also testify that the subsequent cyclization reactions are energetically unfavorable.

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“…Regarding the particle size control of non-mesoporous silica nanoparticles, the task is usually achieved by controlling the addition rate of the silicon source [ 31 ]. The control of the hydrolysis rate of the silicon precursor is the most important factor, and it can be achieved by varying the concentration of the catalyst, the pH of the reaction, adding alcohols as co-solvents, or by varying the nature of the alkoxysilanes used [ 32 , 33 , 34 ]. The particle size becomes larger when the rates of hydrolysis of alkoxysilanes are slowed [ 35 ].…”

Section: Introductionmentioning

confidence: 99%

Effects of Co-Solvent Nature and Acid Concentration in the Size and Morphology of Wrinkled Mesoporous Silica Nanoparticles for Drug Delivery Applications

Flood-Garibay

Méndez‐Rojas

2021

Molecules

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Hierarchically porous materials, such as wrinkled mesoporous silica (WMS), have gained interest in the last couple of decades, because of their wide range of applications in fields such as nanomedicine, energy, and catalysis. The mechanism of formation of these nanostructures is not fully understood, despite various groups reporting very comprehensive studies. Furthermore, achieving particle diameters of 100 nm or less has proven difficult. In this study, the effects on particle size, pore size, and particle morphology of several co-solvents were evaluated. Additionally, varying concentrations of acid during synthesis affected the particle sizes, yielding particles smaller than 100 nm. The morphology and physical properties of the nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and dynamic light scattering (DLS). Homogeneous and spherical WMS, with the desired radial wrinkle morphology and particle sizes smaller than 100 nm, were obtained. The effect of the nature of the co-solvents and the concentration of acid are explained within the frame of previously reported mechanisms of formation, to further elucidate this intricate process.

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Multi-nuclear liquid state NMR investigation of the effects of pH and addition of polyethyleneglycol on the long-term hydrolysis and condensation of tetraethoxysilane

Cited by 19 publications

References 28 publications

Characterization of Siloxane-poly(methyl methacrylate) Hybrid Films Obtained on a Tinplate Substrate Modified by the Addition of Organic and Inorganic Acids

Characterization of Siloxane-poly(methyl methacrylate) Hybrid Films Obtained on a Tinplate Substrate Modified by the Addition of Organic and Inorganic Acids

Mechanisms of Silicon Alkoxide Hydrolysis–Oligomerization Reactions: A DFT Investigation

Effects of Co-Solvent Nature and Acid Concentration in the Size and Morphology of Wrinkled Mesoporous Silica Nanoparticles for Drug Delivery Applications

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