29Si Solid-state NMR Spectroscopy Research Articles

Design Hybrid Porous Organic/Inorganic Polymers Containing Polyhedral Oligomeric Silsesquioxane/Pyrene/Anthracene Moieties as a High-Performance Electrode for Supercapacitor.

We synthesized two hybrid organic-inorganic porous polymers (HPP) through the Heck reaction of 9,10 dibromoanthracene (A-Br2) or 1,3,6,8-tetrabromopyrene (P-Br4)/A-Br2 as co-monomers with octavinylsilsesquioxane (OVS), in order to afford OVS-A HPP and OVS-P-A HPP, respectively. The chemical structures of these two hybrid porous polymers were validated through FTIR and solid-state 13C and 29Si NMR spectroscopy. The thermal stability and porosity of these materials were measured by TGA and N2 adsorption/desorption analyses, demonstrating that OVS-A HPP has higher thermal stability (Td10: 579 °C) and surface area (433 m2 g-1) than OVS-P-A HPP (Td10: 377 °C and 98 m2 g-1) due to its higher cross-linking density. Furthermore, the electrochemical analysis showed that OVS-P-A HPP has a higher specific capacitance (177 F g -1 at 0.5 A F g-1) when compared to OVS-A HPP (120 F g -1 at 0.5 A F g-1). The electron-rich phenyl rings and Faradaic reaction between the π-conjugated network and anthracene moiety may be attributed to their excellent electrochemical performance of OVS-P-A HPP.

Copper Complexes of Silicon Pyridine-2-olates RSi(pyO)3 (R = Me, Ph, Bn, Allyl) and Ph2Si(pyO)2

The organosilicon pyridine-2-olates 1a–1d (RSi(pyO)3, R = Me (a), Ph (b), Bn (c), Allyl (d); pyO = pyridine-2-olate) may serve as tripodal ligands toward CuCl with formation of complexes of the type RSi(μ2-pyO)3CuCl (2a–2d). In addition, for R = Allyl, formation of the more stable isomer 2d′ (κO-pyO)Si(μ2-pyO)2(μ2-Allyl)CuCl was observed. In the presence of dry air (as a source of oxygen), reactions of 1a–1d and CuCl afforded Cu(II) complexes RSi(μ2-pyO)4CuCl (3a–3d); 3a–3c in good yield, and 3d only as a side product. Reaction of Ph2Si(pyO)2 (4) and CuCl in equimolar ratio afforded, depending on reaction conditions, a series of (CuCl)n-ladder-type oligonuclear Cu(I) complexes Ph2Si(μ2-pyO)2(CuCl)n(μ2-pyO)2SiPh2 (n = 2 (52), 3 (53), 4 (54)). In all of the above compounds, the pyO group is Si–O bound and, in the case of μ2 coordination, Cu–N bound. All new compounds (1c, 1d, 2b, 2c, 2d, 2d′, 3b, 3c, 3d, 52, 53, 54) were characterized by single-crystal X-ray diffraction, and further characterization includes solution 1H, 13C, 29Si NMR spectroscopy (1c, 1d, 2b, 2c, 2d’, 53, 54), solid-state 29Si (2b, 2c, 2d′, 53, 54) and 63Cu NMR spectroscopy (2c, 2d′) as well as computational analyses of the isomerization of the couple 2d, 2d′.

<sup>29</sup>Si NMR Investigation of the Effect of Acetic and Oxalic Acids on Portland-Limestone Cement Hydration

The use of carboxylic acids in mix design alters the hydration process of cement, the resulting pore structure of the obtained cement paste, and, consequently, the mechanical properties of concrete. All these changes are directly related to the structure of the calcium silicate hydrate phase. In the present study, the effect of acetic acid and oxalic acid on the hydration of Portland-limestone cement was monitored using solid state 29Si NMR spectroscopy. The results showed that acetic acid facilitated alite and belite hydration, however, the formation of polymerized silicate chains, incorporating Q2p species, begun later than in pure cement paste. Oxalic acid accelerated the polymerization, but slowed down alite and belite hydration. Such behaviors may correspond to decreased porosity (acetic acid addition) and increased strength (oxalic acid addition). Both acids accelerated belite hydration, compared to the pure paste, likely due to an increased acidity of the pore solution. The findings provide structural information about C─S─H phase, to be considered for thaumasite sulfate attack investigations on Portland-limestone cement pastes containing carboxylic acids.

Influence of Addition of Antibiotics on Chemical and Surface Properties of Sol-Gel Coatings.

Infection is one of the most common causes that leads to joint prosthesis failure. In the present work, biodegradable sol-gel coatings were investigated as a promising controlled release of antibiotics for the local prevention of infection in joint prostheses. Accordingly, a sol-gel formulation was designed to be tested as a carrier for 8 different individually loaded antimicrobials. Sols were prepared from a mixture of MAPTMS and TMOS silanes, tris(tri-methylsilyl)phosphite, and the corresponding antimicrobial. In order to study the cross-linking and surface of the coatings, a battery of examinations (Fourier-transform infrared spectroscopy, solid-state 29Si-NMR spectroscopy, thermogravimetric analysis, SEM, EDS, AFM, and water contact angle, thickness, and roughness measurements) were conducted on the formulations loaded with Cefoxitin and Linezolid. A formulation loaded with both antibiotics was also explored. Results showed that the coatings had a microscale roughness attributed to the accumulation of antibiotics and organophosphites in the surface protrusions and that the existence of chemical bonds between antibiotics and the siloxane network was not evidenced.

Towards efficient ciprofloxacin adsorption using magnetic hybrid nanoparticles prepared with κ-, ι-, and λ-carrageenan

The efficient removal of the antibiotic ciprofloxacin (CIP) from aqueous samples using magnetic nanosorbents prepared using three sulfated polysaccharides, κ-, ι- and λ-carrageenan and an alkoxysilane agent containing a reactive epoxide ring is described. The prepared nanosorbents were characterized in detail using FTIR spectroscopy, solid-state 29Si and 13C NMR spectroscopy and elemental microanalysis. The synthesis method was more effective for incorporating higher amounts of κ-carrageenan in the siliceous shells. Although being less sulfated, κ-carrageenan is cheaper than the other carrageenan tested. The CIP adsorption was a cooperative process, well described by the Dubinin–Radushkevich isotherm, with maximum adsorption capacities of 878, 969 and 865 mg/g for κ-, ι- and λ-carrageenan sorbents, respectively. Overall, the produced magnetic nanosorbents are among the best magnetic systems with high adsorptive efficiency for CIP. It is suggested that protonated CIP molecules are exchanged with ester sulfate counterions of carrageenan at the particles’ surface as the main pathway for CIP adsorption. The adsorption process was exothermic and entropically favorable for the three sorbents. However, at 298 K, the adsorption was spontaneous for κ-carrageenan-based sorbents and non-spontaneous for ι- and λ-carrageenan particles. The magnetic sorbents could be reused and maintained their ability towards CIP removal up to four cycles. The removal efficiency in wastewater was enhanced with the sorbent dose. Magnetic carrageenan nanosorbents were prepared using three carrageenan polysaccharides (κ-, ι-, and λ-carrageenan). The resulting magnetic particles removed the antibiotic ciprofloxacin efficiently from ultra-pure water and wastewater samples. Magnetic features enabled the fast magnetic separation of the nanosorbents from water.

13C, 27Al and 29Si NMR Investigation of the Hydration Kinetics of Portland-Limestone Cement Pastes Containing CH3-COO--R+ (R=H or Na) Additives.

The hydration kinetics of Portland-limestone cement pastes with organic additives in the form of acetic acid and sodium acetate were studied by using solid-state 13C, 27Al and 29Si NMR spectroscopy. The evolution of the relative content of various phases was monitored over the period of one month: amorphous and crystalline calcite (in 13C spectra), ettringite, aluminum in C-S-H gel, calcium aluminates and calcium hydroaluminates (in 27Al spectra), as well as alite, belite and silicon in C-S-H gel (in 29Si spectra). The retarding effect of the additives on cement hydration at early age was demonstrated. We show that the kinetics of phase assemblage formation is influenced by the acetate ion adsorption on the surface of the anhydrous cement components and hydrated phases. The kinetics of formation of ettringite in the cement paste, depending on the addition of acetic and or sodium acetate, is discussed in the context of potential thaumasite sulfate attack.

Fast and Selective Aqueous-Phase Oxidation of Styrene to Acetophenone Using a Mesoporous Janus-Type Palladium Catalyst.

A heterogeneous Janus-type palladium interphase catalyst was obtained by selective surface modification of a hollow mesoporous silica material. The catalyst comprises hydrophobic octyl groups on one side of the silica nanosheets and single-site bis-imidazoline dichlorido palladium(II) complexes on the other. The structure of this composite material has been analyzed by means of elemental analysis, atomic absorption spectroscopy, BET surface analysis, TGA, SEM and solid-state CP-MAS 13C and 29Si NMR spectroscopy. The catalyst showed extraordinary activity for the aqueous-phase oxidation of styrene to acetophenone using 30% hydrogen peroxide as the oxidant. An 88% yield of acetophenone could be achieved after 60 min.

Enhanced Removal of Non-Steroidal Inflammatory Drugs from Water by Quaternary Chitosan-Based Magnetic Nanosorbents

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most common pharmaceuticals used worldwide. They are widely detected in natural waters due to their persistence in wastewater treatment, and their removal is desirable in wastewater management. As a contribution to tackle this challenge, this study explores magnetic quaternary chitosan-based nanosorbents for the effective magnetically assisted removal of three NSAIDs (diclofenac, naproxen, and ketoprofen) from water. Toward this goal, silane groups were grafted onto the backbone of trimethyl chitosan through the reaction with an epoxide functionalized silane. Once silanized, the modified chitosan was employed to coat Fe3O4 nanoparticles. The prepared materials were characterized using FTIR spectroscopy and solid-state 29Si and 13C NMR spectroscopy, which confirmed the encapsulation of Fe3O4 nanoparticles with a hybrid siliceous material enriched in trimethyl chitosan. The effect of the initial NSAIDs concentration, pH, and contact time in the adsorption behavior was investigated. The kinetic data were well described by the pseudo-second-order kinetic model, indicating a chemisorption mechanism. The maximum adsorption capacities estimated from the Langmuir model were 188.5 mg/g (0.5925 mmol/g), 438.1 mg/g (1.7371 mmol/g), and 221.5 mg/g (0.8710 mmol/g) for diclofenac, naproxen, and ketoprofen, respectively. These adsorption capacities are higher than those of most reported sorbents, indicating the potential of these biosorbents to remove the selected NSAIDs using low-energy magnetically assisted separation.

Linear/Ladder-Like Polysiloxane Block Copolymers with Methyl-, Trifluoropropyl- and Phenyl- Siloxane Units for Surface Modification.

Multiblock copolymers containing linear polydimethylsiloxane or polymethyltrifluoropropylsiloxane and ladder-like polyphenylsiloxane were synthesized in a one-step pathway. The functional homopolymer blocks and final multiblock copolymers were characterized using solution and solid-state multinuclear 1H, 13C, 19F, and 29Si NMR spectroscopy. It was shown that the ladder-like block contains silanol units, which influence the adhesion properties of multiblock copolymers and morphology of their casted films. The adhesion to metals and mechanical properties of multiblock copolymers were tested. The SEM study of casted films of multiblock copolymers shows the variety of formed morphologies, including long-strip-like or globular.

Synthesis of high surface area aluminophosphate and -phosphonate xerogels by non-hydrolytic sol-gel reactions

We disclose the preparation of high-surface-area mesoporous aluminophosphates and aluminophosphonates by the non-hydrolytic sol-gel reactions (NHSG) of Al(NMe 2 ) 3 with trimethylsilylated phosphate OP(OSiMe 3 ) 3 , phosphonates RP(O)(OSiMe 3 ) 2 (R = Me, t Bu, Ph), and bis-phosphonates (Me 3 SiO) 2 (O)P–X–P(O)(OSiMe 3 ) 2 (X = C 6 H 4 , (C 6 H 4 ) 2 ) in dry toluene. The reactions proceed by silylamine elimination of Me 3 SiNMe 2 to provide organic-inorganic hybrid xerogels with properties influenced by organic substituents and the Al:P ratio of the precursors. Dried xerogels exhibit large surface areas (up to 1000 m 2 g −1 ) and matrices based on condensed Al–O–P networks. They stay stable under relatively harsh thermal conditions. 27 Al, 13 C, and 29 Si solid-state NMR spectroscopy was employed to characterize the aluminum coordination and the residual amido and trimethylsilyl groups. The catalytic performance of NHSG prepared material was examined in gas-phase dehydration of ethanol to ethylene exhibiting conversion and selectivity comparable to weak solid acid benchmark catalysts. The number of unreacted surface groups was determined by gravimetric measurements and by thermal analysis (TG-DSC). These residual groups have the potential to be used in post-synthetic grafting of catalytically active metal centers. • Aluminophosphates and aluminophosphonates are prepared by non-hydrolytic sol-gel synthesis. • Mesoporous xerogels with large surface areas (1030 m 2 g -1 ). • Gas-phase dehydration of ethanol to ethylene with good conversion and selectivity.

The Effects of Alkaline Earth Metals on the Structure of Sodium Borosilicate Glasses: <sup>11</sup>B and <sup>29</sup>Si NMR Study

The effect of substitution of alkaline earth metals for sodium on the structure of alkali borosilicate glasses had been studied using the solid-state 11B and 29Si NMR spectroscopy. NMR spectra enable to evaluate the relative mole fractions of different silicon and boron structural units in studied samples. The obtained results demonstrate that alkaline earth metals increase the polymerization degree of the silicon structural units at the expense of de-polymerization of the boron units. The reason for these changes is preferential coordination of sodium and alkaline earth metals to the boron units, that increases strongly for the studied alkaline earth metals.

Efficient Conversion of Carbon Dioxide by Imidazolium-Based Cross-Linked Nanostructures Containing Polyhedral Oligomeric Silsesquioxane (POSS) Building Blocks.

Polyhedral oligomeric silsesquioxanes (POSS) have been employed as molecular building blocks for the synthesis of imidazolium cross-linked networks, to be used as heterogeneous catalysts for the conversion of carbon dioxide into cyclic carbonates. Two hybrid materials with different nucleophilic species (bromide and iodide) have been prepared and characterized by means of elemental analysis, 13 C and 29 Si solid-state NMR spectroscopy, thermogravimetric analysis and IR spectroscopy. The solids were tested as the sole catalyst under metal- and solvent-free reaction conditions showing full selectivity toward the formation of cyclic carbonates. High turnover number (TON) and productivity values, up to 5502 and 1081 respectively for glycidol conversion at 100 °C and up to 4942 and 1122 for epichlorohydrin conversion at 150 °C after 3 h, were obtained. Such outstanding productivity values were ascribed to the optimal organic/inorganic (i. e., imidazolium moiety/POSS support) weight ratio. The recyclability of the materials was successfully verified for five consecutive runs allowing their consideration as promising candidates for continuous flow technologies.

Acid functionalized coal fly ashes: New solid catalysts for levulinic acid esterification

Coal fly ash (CFA) from different sources (CFA 5, 10, 13) and different size fractions (> or < 75 μm) were characterized and used as inorganic supports for sulfonic acid functionalization by two methodologies including one-pot organosilylation (CFA_CSPTMS) and two-step benzyl alcohol condensation followed by sulfonation (CFA_BnSO3H). The as-prepared organosulfonic CFAs were characterized by solid-state 1H, 13C and 29Si NMR spectroscopy, XPS, S content was quantified by elemental analysis and the intrinsic acidity was determined by potentiometric titration; the highest –SO3H content was obtained for CFA13_BnSO3H. All the functionalized CFAs were tested for the first time as acid solid catalysts in the esterification of levulinic acid (LA) a biomass platform molecule, in the presence of n-butanol. n-Butyl levulinate was the only product with conversions of 100% after 40 min. reaction and using the CFA13_BnSO3H as catalyst. This catalyst also exhibited the highest TOFs (447 h−1) and showed to be the most stable and reusable for 5 consecutive catalytic cycles.

Pressure-Induced Geopolymerization in Alkali-Activated Fly Ash

The present study investigated geopolymerization in alkali-activated fly ash under elevated pressure conditions. The fly ash was activated using either sodium hydroxide or a combination of sodium silicate solution and sodium hydroxide, and was cured at 120 °C at a pressure of 0.22 MPa for the first 24 h. The pressure-induced evolution of the binder gel in the alkali-activated fly ash was investigated by employing synchrotron X-ray diffraction and solid-state 29Si and 27Al MAS NMR spectroscopy. The results showed that the reactivity of the raw fly ash and the growth of the zeolite crystals were significantly enhanced in the samples activated with sodium hydroxide. In contrast, the effects of the elevated pressure conditions were found to be less apparent in the samples activated with the sodium silicate solution. These results may have important implications for the binder design of geopolymers, since the crystallization of geopolymers relates highly to its long-term properties and functionality.

Compressible, Thermally Insulating, and Fire Retardant Aerogels through Self-Assembling Silk Fibroin Biopolymers Inside a Silica Structure-An Approach towards 3D Printing of Aerogels.

Thanks to the exceptional materials properties of silica aerogels, this fascinating highly porous material has found high-performance and real-life applications in various modern industries. However, a requirement for a broadening of these applications is based on the further improvement of the aerogel properties, especially with regard to mechanical strength and postsynthesis processability with minimum compromise to the other physical properties. Here, we report an entirely novel, simple, and aqueous-based synthesis approach to prepare mechanically robust aerogel hybrids by cogelation of silk fibroin (SF) biopolymer extracted from silkworm cocoons. The synthesis is based on sequential processes of acid catalyzed (physical) cross-linking of the SF biopolymer and simultaneous polycondensation of tetramethylorthosilicate (TMOS) in the presence of 5-(trimethoxysilyl)pentanoic acid (TMSPA) as a coupling agent and subsequent solvent exchange and supercritical drying. Extensive characterization by solid-state 1H NMR, 29Si NMR, and 2D 1H-29Si heteronuclear correlation (HETCOR) MAS NMR spectroscopy as well as various microscopic techniques (SEM, TEM) and mechanical assessment confirmed the molecular-level homogeneity of the hybrid nanostructure. The developed silica-SF aerogel hybrids contained an improved set of material properties, such as low density (ρb,average = 0.11-0.2 g cm-3), high porosity (∼90%), high specific surface area (∼400-800 m2 g-1), and excellent flexibility in compression (up to 80% of strain) with three orders of magnitude improvement in the Young's modulus over that of pristine silica aerogels. In addition, the silica-SF hybrid aerogels are fire retardant and demonstrated excellent thermal insulation performance with thermal conductivities (λ) of 0.033-0.039 W m-1 K-1. As a further advantage, the formulated hybrid silica-SF aerogel showed an excellent printability in the wet state using a microextrusion-based 3D printing approach. The printed structures had comparable properties to their monolith counterparts, improving postsynthesis processing or shaping of the silica aerogels significantly. Finally, the hybrid silica-SF aerogels reported here represent significant progress for a mechanically customized and robust aerogel for multipurpose applications, namely, as a customized thermal insulation material or as a dual porous open-cell biomaterial used in regenerative medicine.

Thermal evolution of hydrates in carbonation-cured Portland cement

The present study investigates the thermal evolution of hydrates in carbonation-cured Portland cement. Paste samples were placed in a carbonation chamber after the 24 h of initial curing, while reference samples were cured in a sealed condition until 28 days. Thermogravimetry, unconfined strength tests, X-ray diffractometry, and solid-state 29Si and 27Al MAS NMR spectroscopy were conducted. The results showed that the binder gel in carbonation-cured cement shares some structural similarities with aluminosilicate glass in terms of Si and Al analogues. This characteristic was also reflected by its thermogravimetric behavior, presenting much less weight loss associated with dehydration in comparison with hydrated cement. However, the binder gel in carbonation-cured cement underwent depolymerization into monomeric Si at 800 °C, similar to hydrated cement. Moreover, carbonation-cured cement underwent crystallization pathway identical to that of hydrated cement, displaying a hydrate-like thermal behavior.

Chitosan-silica hybrid nanosorbents for oil removal from water

Water pollution caused by oil spills is an environmental problem that raises concerns all over the world. Sorbent materials are of great importance for the removal of the remained oil after skimming operation. Nevertheless owing to reduced size, most sorbents are difficult to collect from water and therefore there is need to develop effective oil sorbents that could be easily separated from aquatic environments. Herein new magnetic nanosorbents composed of magnetite nanoparticles functionalized with chitosan hybrid siliceous shells were successfully prepared using a one-step sol–gel encapsulation method. As a proof of concept, these nanosorbents were tested in the magnetically assisted removal of non-polar organic solvents from water. The characterization of the materials using FTIR spectroscopy, solid-state 29Si and 13C NMR spectroscopy and elemental microanalysis confirmed the extensive modification of the particles’ shells with chitosan molecules covalently linked to the siliceous domains. These hybrid particles could efficiently adsorb various non-polar organic solvents from water, a behavior that was ascribed to the presence of chitosan macromolecules grafted at the surface of the particles. This is a new type of sorbent with potential application in the removal of oil from water using magnetic separation technologies.

Iron(II), Cobalt(II), Nickel(II), and Zinc(II) Silylene Complexes: Reaction of the Silylene [iPrNC(NiPr2 )NiPr]2 Si with FeBr2 , CoBr2 , NiBr2 ⋅MeOCH2 CH2 OMe, ZnCl2 , and ZnBr2.

Reaction of the donor-stabilized silylene [iPrNC(NiPr2 )NiPr]2 Si (1) with FeBr2 , CoBr2 , NiBr2 ⋅MeOCH2 CH2 OMe, ZnCl2 , and ZnBr2 afforded the respective transition-metal silylene complexes 4-8, the formation of which can be described in terms of a Lewis acid/base reaction (4, 5, 7, 8) or a nucleophilic substitution reaction (6). However, the reactivity profile of silylene 1 is not only based on its strong Lewis base character; the different coordination modes of the two guanidinato ligands (4-6 vs. 7 and 8) add an additional reactivity facet. The paramagnetic compounds 4 and 5 and the diamagnetic compounds 6⋅THF, 7, and 8⋅0.5 Et2 O were structurally characterized by single-crystal X-ray diffraction. In addition, compound 6⋅THF was studied by 15 N and 29 Si solid-state NMR spectroscopy, and 7 and 8 were characterized by NMR spectroscopic studies in the solid state (15 N, 29 Si) and in solution (1 H, 13 C, 29 Si). Compounds 4-8 represent very rare examples of FeII , CoII , NiII , and ZnII silylene complexes. Four-coordinate silicon(II) compounds with an SiN3 M skeleton (M=Fe, Co, Ni) and M in the formal oxidation state +2 (4-6) have not yet been reported, and five-coordinate silicon(II) compounds with an SiN4 Zn skeleton (7, 8) are also unprecedented.

NMR and EPR Studies of Free-Radical Intermediates from Experiments Mimicking the Winds on Mars: A Sink for Methane and Other Gases

A new kind of solid–gas chemical reactions has been investigated using solid-state powder 2H, 13C, and 29Si NMR and EPR spectroscopies. These studies involve reactions between a silicate-created Si free-radical intermediate and a few ordinary gases such as isotopically 2H-, 13C-, and 17O-enriched methane (13CH4 and CD4), carbon dioxide (13CO2), hydrogen (2H2), and oxygen (17O2). The solid-state Si free-radical intermediate and gas reaction and silicate products are formed in a specially designed rotating apparatus, which by mechanical tumbling mimics the winds and collision speed of the mineral particles on Mars. It is shown that the “hard” quartz (SiO2) or corundum (α-Al2O3) grain particles, used to simulate the collision particles in a rotating Pyrex (borosilicate) reaction flask, act as an abrasive on the “soft” Pyrex flask and thereby create a silicate Si free-radical intermediate. EPR studies show that this radical is identical to the silicate radical intensively investigated by EPR from γ-irradiatio...

Inorganic fillers influence on the radiation-induced ageing of a space-used silicone elastomer

A space-used filled silicone rubber (silica and iron oxide fillers) and its polysiloxane isolated matrix were exposed to high energy electrons in order to determine their ageing mechanisms from a structural point of view. Physicochemical analysis evidenced that both filled and unfilled materials predominantly crosslink under such irradiation. Solid-state 29Si NMR spectroscopy allowed the identification of T-type SiO3 units as the main new crosslinks formed in the polymer network. It also revealed an increase in Q-type SiO4 units in the irradiated filled sample. Thanks to the combination of NMR spectroscopy and ammonia-modified swelling tests, these Q-type units were associated with new crosslinks formed at the silica fillers-matrix interface. While the main interaction between the polysiloxane network and the fillers was shown to proceed mainly through hydrogen bonding in the pristine filled samples, it was suggested that the hydrogen bonds were progressively replaced with SiO4 chemical bonds. These additional chemical crosslinks induced evolutions of the shear modulus on the rubber plateau and crosslink density that were significantly more pronounced in the filled material than in the neat one.