Polymethylsiloxane alone and in composition with nanosilica under various conditions

Gun'ko, V.М.; Туров, В.В.; Krupska, Т.V.; Protsak, Iryna; Borysenko, M.V.; Pakhlov, E.M.

doi:10.1016/j.jcis.2019.01.102

Cited by 25 publications

(27 citation statements)

References 39 publications

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“…One of the main characteristics of these materials is their degree of hydrophobicity, which allows their interactions with various liquids, polymers, and solids to be controlled. PMS, as a 3D-cross-linked polymer with one CH 3 group attached to each Si atom and residual silanols [21,22,23], may be considered as an intermediate between PDMS and methylated nanosilica containing residual silanols [1,2,24,25,26,27,28]. In a series of nanostructured silicas with surface functionalities, such as –O) 3 SiCH 3 , –O) 2 Si(CH 3 ) 2 , and –O–Si(CH 3 ) 3 , the degree of hydrophobicity increases, i.e., PMS is less hydrophobic than PDMS.…”

Section: Introductionmentioning

confidence: 99%

“…Fumed nanosilica and PMS are soft-powder materials because their aggregates of nanoparticles and agglomerates of aggregates may be easily rearranged under any treatment [36]. The results of these treatments depend on several factors such as the (i) hydrational, thermal, and mechanical history of the components; (ii) the weight ratio of the components; (iii) the amounts of added water; (iv) the mechanical loading; (v) the time of treatment; and (vi) the temperature [1,2,24,25,26,36,37,38,39,40,41]. In this study, two important factors, namely, a small amount of added water and the type of mechanical loading upon stirring of the PMS/nanosilica blends, are analyzed to control the characteristics of the final blends.…”

Section: Introductionmentioning

confidence: 99%

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Nanostructured Polymethylsiloxane/Fumed Silica Blends

et al. 2019

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Polymethylsiloxane (PMS) and fumed silica, alone and in a blended form (1:1 w/w), differently pretreated, hydrated, and treated again, were studied using TEM and SEM, nitrogen adsorption–desorption, 1H MAS and 29Si CP/MAS NMR spectroscopy, infrared spectroscopy, and methods of quantum chemistry. Analysis of the effects of adding water (0–0.5 g of water per gram of solids) to the blends while they are undergoing different mechanical treatment (stirring with weak (~1–2 kg/cm2) and strong (~20 kg/cm2) loading) show that both dry and wetted PMS (as a soft material) can be grafted onto a silica surface, even with weak mechanical loading, and enhanced mechanical loading leads to enhanced homogenization of the blends. The main evidence of this effect is strong nonadditive changes in the textural characteristics, which are 2–3 times smaller than additive those expected. All PMS/nanosilica blends, demonstrating a good distribution of nanosilica nanoparticles and their small aggregates in the polymer matrix (according to TEM and SEM images), are rather meso/microporous, with the main pore-size distribution peaks at R > 10 nm in radius and average <RV> values of 18–25 nm. The contributions of nanopores (R < 1 nm), mesopores (1 nm < R < 25 nm), and macropores (25 nm < R < 100 nm), which are of importance for studied medical sorbents and drug carriers, depend strongly on the types of the materials and treatments, as well the amounts of water added. The developed technique (based on small additions of water and controlled mechanical loading) allows one to significantly change the morphological and textural characteristics of fumed silica (hydrocompaction), PMS (drying–wetting–drying), and PMS/A-300 blends (wetting–drying under mechanical loading), which is of importance from a practical point of view.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nanostructured Polymethylsiloxane/Fumed Silica Blends

et al. 2019

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“…The hydroxyl groups play an important role in the properties not only of nanooxides [1,2] but also of other nanostructured materials based on the siloxane bridges ≡Si-O-Si≡, ≡Si-OH, and functionalized groups. For example, commercial polymethylsiloxane (PMS) hydrogel, synthesized using methyltrichlorosilane as a precursor, contains 7-8 wt % of PMS and 93-92 wt % of water (Enterosgel, Kreoma-Pharm, Ukraine) [101]. It is characterized by incomplete crosslinking of residual silanols; therefore, it is hydrophilic and contains adsorbed water (see Figure S20).…”

Section: Resultsmentioning

confidence: 99%

“…Dried and stirred PMS rehydrated (h = 1 g/g) and stirred again is hydrophilic, but to a smaller degree than the initial hydrogel due to partial crosslinking of residual silanols. The bulk density of hydrocompacted wetted PMS powder is ρ b ≈ 0.5 g/cm 3 at V em ≈ 1.5 cm 3 /g, i.e., it remains as a disperse material, as well the blends with nanosilica A-300 [101]. Air-dried PMS and dry nanosilica A-300 (Pilot plant of Chuiko Institute of Surface Chemistry, Kalush, Ukraine) mixed in a porcelain mortar, and then with distilled water (h = 1 g/g) give a hydrophilic system.…”

Section: Resultsmentioning

confidence: 99%

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Polymer Adsorbents vs. Functionalized Oxides and Carbons: Particulate Morphology and Textural and SurfaceCharacteristics

Гунько

2021

Polymers

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Various methods for morphological, textural, and structural characterization of polymeric, carbon, and oxide adsorbents have been developed and well described. However, there are ways to improve the quantitative information extraction from experimental data for describing complex sorbents and polymer fillers. This could be based not only on probe adsorption and electron microscopies (TEM, SEM) but also on small-angle X-ray scattering (SAXS), cryoporometry, relaxometry, thermoporometry, quasi-elastic light scattering, Raman and infrared spectroscopies, and other methods. To effectively extract information on complex materials, it is important to use appropriate methods to treat the data with adequate physicomathematical models that accurately describe the dependences of these data on pressure, concentration, temperature, and other parameters, and effective computational programs. It is shown that maximum accurate characterization of complex materials is possible if several complemented methods are used in parallel, e.g., adsorption and SAXS with self-consistent regularization procedures (giving pore size (PSD), pore wall thickness (PWTD) or chord length (CLD), and particle size (PaSD) distribution functions, the specific surface area of open and closed pores, etc.), TEM/SEM images with quantitative treatments (giving the PaSD, PSD, and PWTD functions), as well as cryo- and thermoporometry, relaxometry, X-ray diffraction, infrared and Raman spectroscopies (giving information on the behavior of the materials under different conditions).

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Interfacial Phenomena in Nanostructured Systems with Various Materials

Gun'ko,

Turov

2024

ChemPhysChem

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Interfacial phenomena linked to the behavior of bound water, organic solvents (co‐sorbates, dispersion media), hydrogen, methane, acids/bases, and salts bound to various silicas, polymers, and carbon materials were analyzed vs. temperature and concentrations using 1H NMR spectroscopy, differential scanning calorimetry (DSC) and other methods. The material characteristics were studied using microscopy, infrared spectroscopy (IR), small angle X‐ray scattering (SAXS), and nitrogen adsorption. Confined space effects (CSE) result in enhanced freezing point depression (FPD) and stronger diminution of solvent activity and colligative properties of liquid mixtures in narrower pores. Short hydrophobic functionalities (Si‐CH3, Si(CH3)2) at a silica surface and the presence of nanopores result in differentiation of bound water into weakly (WAW, δH=0.2‐2.0 ppm) and strongly (SAW, δH=4‐6 ppm) associated waters of smaller solvent activity in smaller clusters located in narrower pores and unfrozen below a bulk freezing point. These effects are enhanced in hydrophobic dispersion media. Hydrophobic liquids could displace bound water into narrower pores inaccessible for their molecules larger than water and/or into broader pores to reduce contact area between immiscible liquids. The observed phenomena depend on sorbent/sorbate kinds and play an important role on practical applications of various sorbents.

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Polymethylsiloxane alone and in composition with nanosilica under various conditions

Cited by 25 publications

References 39 publications

Nanostructured Polymethylsiloxane/Fumed Silica Blends

Nanostructured Polymethylsiloxane/Fumed Silica Blends

Polymer Adsorbents vs. Functionalized Oxides and Carbons: Particulate Morphology and Textural and SurfaceCharacteristics

Interfacial Phenomena in Nanostructured Systems with Various Materials

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