Pristine Matrix Research Articles

From Fossil to Bio-Based AESO–TiO2 Microcomposite for Engineering Applications

Environmental issues and the reduction of fossil fuel resources will lead to the partial or total substitution of petroleum-based materials with natural, raw, renewable ones. One expanding domain is the obtaining of engineering materials from vegetable oils for sustainable, eco-friendly polymers for different applications. Herein, the authors propose a simplified and green synthesis pathway for a thermally curable, acrylated and epoxidized soybean oil matrix formulation containing only epoxidized soybean oil, acrylic acid, a reactive diluent (5%) and just 0.15 mL of catalyst. The small amount of reactive diluent significantly reduced the initial system viscosity while eliminating the need for adding solvent, hardener, activator, etc. Both the thermally cured composite with a 2% TiO2 microparticle filler and its pristine matrix were comparably characterized in terms of structural, thermal, morphological, dielectric and wettability by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry, scanning electron microscopy, broadband dielectric spectrometry and contact angle measurements. The 2% filler in the composite generated superior thermal stability via lower mass loss (48.89% vs. 57.14%) and higher degradation temperatures (395 °C vs. 387 °C), increased the glass transition temperature from −20 °C to −10 °C, rendered the microcomposite hydrophobic by increasing the contact angle from 88° to 96° and enhanced dielectric properties compared to the pristine matrix. All investigations recommend the microcomposite for protective coatings, capacitors, sensors and electronic circuits. This study brings new contributions to green chemistry and sustainable materials.

Multiferroic properties in poly(vinylidene-fluoride)-based magnetostrictive/piezoelectric laminate composites

Multiferroic materials (MFM) have drawn considerable attention for developing smart multifunctional devices. Herein, poly(vinylidene-fluoride)-based (PVDF) MFM composite films of Ba0.85Ca0.15Zr0.1Ti0.9O3-PVDF/CoFe2O4-PVDF/Ba0.85Ca0.15Zr0.1Ti0.9O3-PVDF with sandwich-laminated structure are developed and investigated for its dielectric, magnetic, ferroelectric and magnetodielectric (MD) properties. An improved polar β–phase is formed with the particles of CoFe2O4 and Ba0.85Ca0.15Zr0.1Ti0.9O3 embedded in PVDF matrix. Both magnetic (M–H) and ferroelectric polarization (P–E) hysteresis loops indicate the multiferroic nature at room temperature, i.e., the coexistence of ferroelectric and ferromagnetic ordering in composite films. An enhanced ferroelectricity is obtained for the maximum polarization (Pmax∼1.57 μC/cm2 at 750 kV/cm) and the higher dielectric constant (εr∼16.84) as well as a lower dielectric loss tanδ < 0.04, compared to the pristine PVDF matrix (Pmax∼0.88 μC/cm2, εr∼10.26). A recyclable energy density of Wrec∼0.84 J/cm3 at 750 kV/cm is observed, together with a high efficiency (η∼87.82 %). The ferromagnetic behavior is confirmed by the M-H hysteresis loop, which exhibits significant magnetic properties, i.e., saturation magnetization (MS∼0.58 emu/g) and coercivity (HC∼1.72 kOe). Additionally, a robust magnetodielectric effect with a large negative coefficient (∼8.23 %) is achieved at a low magnetic field H∼3 kOe. The laminate composite film exhibits room temperature multiferroic with a large MD response, making it a promising candidate for utilization in intelligent multifunctional devices.

Scalable all polymer dielectrics with self-assembled nanoscale multiboundary exhibiting superior high temperature capacitive performance

Polymers are key dielectric materials for energy storage capacitors in advanced electronics and electric power systems due to their high breakdown strengths, low loss, great reliability, lightweight, and low cost. However, their electric and dielectric performance deteriorates at elevated temperatures, making them unable to meet the rising demand for harsh-environment electronics such as electric vehicles, renewable energy, and electrified transportation. Here, we present an all-polymer nanostructured dielectric material that achieves a discharged energy density of 7.1 J/cm³ with a charge-discharge efficiency of 90% at 150°C, outperforming the existing dielectric polymers and representing more than a twofold improvement in discharged energy density compared with polyetherimide. The self-assembled nano-scale multiboundaries effectively impede the charge injection and excitation, leading to more than one order of magnitude lower leakage current density than the pristine polymer matrix PEI at high electric fields and elevated temperature. In addition, the film processing is simple, straightforward, and low cost, thus this all-polymer nanostructured dielectric material strategy is suitable for the mass production of dielectric polymer films for high-temperature capacitive energy storage.

Alloy scattering to optimize carrier and phonon transport properties in PbBi2S4 thermoelectric

Ternary PbBi2S4 compound with crustal S-rich element and low lattice thermal conductivity is considered as a potential thermoelectric candidate. However, its inferior thermoelectric properties are rooted in the low electrical transport performance. Generally, enhancing electrical transport performance (power factor, PF) primarily entails optimizing the interdependent relationship between carrier mobility μ (linked to electrical conductivity σ) and effective mass m* (related to Seebeck coefficient S). In this work, we introduce the strategy of alloy scattering to independently enhance S without weakening μ and simultaneously reduce thermal conductivity, leading to a synergetic optimization of electron and phonon in PbBi2S4 thermoelectric. Heavy Sn alloying in PbBi2S4 presents uniform and orderly distribution on Pb sites as unclosed by the atomic-scale crystal structure observation. These massive Sn atom serves as scattering centers and turns the electron scattering mechanism to be dominated by alloy scattering, thus resulting in a ∼ 33% increment of S in Pb0.6Sn0.4Bi2S4. Meanwhile, Sn alloying aggravates phonon scattering further lowering lattice thermal conductivity and reaching an extremely low value of 0.34 W·m–1·K–1 at 773 K. Finally, a maximum zT of 0.68 at 773 K is obtained in Pb0.6Sn0.4Bi2S4, which is ∼ 45% higher than the pristine matrix. This study proves that the strategy of alloy scattering is effective in improving overall electrical transport properties as well as reducing lattice thermal conductivity, which paves a new way to develop high-performance thermoelectric materials.

Relevance of the Iron Distribution in Natural Smectite Clays for the Thermal Stability of PMMA-Clay Nanocomposites.

Polymer-clay nanocomposites have greater thermal stability compared to the pristine polymer matrix. This can be attributed to the physical barrier provided by the inclusion of 2D clay nanoparticles (especially of the smectite group), together with radical trapping related to the distribution of specific 3d atoms in the inorganic phase. To elucidate the relevance of the Fe3+ distribution in this synergic effect, the iron atoms present in octahedral sheets of natural nontronite clay (Non, 5.6 wt % Fe) or in maghemite (M) nanoparticles (γ-Fe2O3) were incorporated in a poly(methyl methacrylate) (PMMA) matrix. Na-laponite (Lap) clay was used to evaluate the contribution of the diffusion barrier effect to the increased thermal stability of a PMMA-Lap nanocomposite, as evidenced by the upshift of the thermogravimetric (TGA) curve compared to that for PMMA. The contribution of radical trapping to the thermal stability of the PMMA-Non nanocomposite was evidenced by a significant shift of the Fe K-edge rising edge position by -4.5 eV after iron reduction by heating in N2, while similar treatment of pristine nontronite did not lead to a significant rising edge shift in the X-ray absorption spectra (XAS). This downshift demonstrated the reduction of Fe3+ to Fe0, induced by the sequestration of radicals formed by PMMA depolymerization. Raman spectroscopy analysis evidenced the formation of graphitic char deposits above 400 °C, further improving the thermal stability of PMMA-Non by providing an additional physical barrier to mass transport. A fourth contribution of well-dispersed iron was the abstraction of carbon from the char by the iron carburization reaction, which hindered CO2 formation by oxidative coking. In contrast, no relevant contribution of graphitic layer deposition was observed for the PMMA-M-Lap nanocomposite, where its improved thermal stability was only due to the combined contributions of the gas diffusion barrier effect and radical trapping by iron atoms. The maghemite effectively captured the radicals confined by the clay sheets, resulting in significant stabilization of the nanocomposite, with a shift of the mass loss of the PMMA-M-Lap nanocomposite compared to PMMA-Lap.

Comparative study of oil palm and nettle fibers reinforced chemically functionalized high‐density polyethylene composites

AbstractThe demand of natural fiber reinforced composites has grown enormously in polymer industries owing to their renewability and sustainability and maintaining their performance and properties. In this investigation, two natural fibers have been considered as a reinforcer to develop chemically functionalized high‐density polyethylene (CF‐HDPE)‐based composites. The total holocellulose content of ~85% and ~65% for nettle fiber (NTF) and oil palm empty fruit bunch fiber (OPF) make them significant for this study. OPF/CF‐HDPE and NTF/CF‐HDPE composites have been developed and characterized to measure their desirable properties. The structural confirmation suggests reinforcement/matrix adhesion through ester and hydrogen bonds between them. NTF/CF‐HDPE and OPF/CF‐HDPE are thermally stable upto 240°C and 250°C, respectively. A significant increment of ~40% and ~64% in tensile strength were observed in addition of OPF and NTF reinforcer in pristine matrix. A similar observation has been shown in flexural strength with improvement of ~58% and ~83% with OPF and NTF as reinforcer. Among all these composite compositions, the 30/70 NTF/CF‐HDPE composite demonstrated the highest tensile and flexural properties values due to higher holocellulose of NTF. This study demonstrates the potential of OPF and NTF reinforcer to develop natural fiber reinforced polymer composites, which helps respective industries to manufactured tailored made products with desirable properties.Highlights OPF/CF‐HDPE and NTF/CF‐HDPE composites are sustainable and low cost. The composite compositions have been developed by extrusion and injection molding. The composite's mechanical (tensile and flexural) properties have been demonstrated. SEM and FTIR characterized the composites for the fiber/matrix adhesion. The composite's thermal stability has been affected by fibers and matrix.

Synergistic effect of gold nanoparticles decorated functionalized carbon nanotubes nanohybrids on the thermal, dielectric, and sensing properties of polyaniline ternary nanocomposites

AbstractThe synthesis of gold nanoparticles reinforced functionalized single‐walled/multi‐walled carbon nanotubes nanohybrid based polyaniline nanocomposites were carried out using in situ polymerization. The chemical interaction and nanostructured morphology of the synthesized nanocomposites are studied using ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, x‐ray diffraction analysis, x‐ray photoelectron spectroscopy, and field emission scanning electron microscopy. Thermal stability of synthesized PANI/Au@f‐SWNTs is boosted by a magnitude of 30°C as compared with the pristine PANI matrix, which is attributed to a strong barrier effect because of the development of tortuous path that resulted from a uniform distribution of Au@f‐CNTs throughout the PANI matrix. For PANI/Au@f‐SWNTs, the AC conductivity and dielectric permittivity are improved by a value of 83.58 S/cm and 1.35 × 10−5 as well as the dielectric loss is reduced by a factor of 0.11 in comparison with the pure PANI matrix at an applied frequency of 106 Hz. PANI/Au@f‐SWNTs and PANI/Au@f‐MWNTs ternary nanocomposites exhibited excellent selectivity toward the hazardous Cr(VI) heavy metal ions in an aqueous medium with a limit of detection of 0.74 and 0.89 μM with a binding constant of 1.028 × 105 and 3.46 × 104 M−1, respectively, that can be selective and sensitive for the detection of Cr(VI) metal ions in water at trace level.

Factors Affecting Silica/Cellulose Nanocomposite Prepared via the Sol-Gel Technique: A Review.

Cellulose/silica nanocomposites, synthesised through the sol-gel technique, have garnered significant attention for their unique properties and diverse applications. The distinctive characteristics of these nanocomposites are influenced by a range of factors, including the cellulose-to-silica ratio, precursor concentration, pH, catalysts, solvent selection, temperature, processing techniques, and agitation. These variables play a pivotal role in determining the nanocomposites' structure, morphology, and mechanical properties, facilitating tailoring for specific applications. Studies by Raabe et al. and Barud et al. demonstrated well-deposited silica nanoparticles within the interstitial spaces of cellulosic fibres, achieved through TEOS precursor hydrolysis and the subsequent condensation of hydroxyl groups on the cellulose fibre surface. The introduction of TEOS established a robust affinity between the inorganic filler and the polymer matrix, emphasising the substantial impact of TEOS concentration on the size and morphology of silica nanoparticles in the final composites. The successful functionalisation of cellulose fibres with the TEOS precursor via the sol-gel method was reported, resulting in reduced water uptake and enhanced mechanical strength due to the strong chemical interaction between silica and cellulose. In research conducted by Feng et al., the silica/cellulose composite exhibited reduced weight loss compared to the pristine cellulose matrix, with the integration of silica leading to an elevated temperature of composite degradation. Additionally, Ahmad et al. investigated the effects of silica addition to cellulose acetate (CA) and polyethylene glycol membranes, noting an increase in Young's modulus, tensile strength, and elongation at break with silica incorporation. However, concentrations exceeding 4% (w/v) resulted in significant phase separations, leading to a decline in mechanical properties.

Preparation of Three Component PVDF‐Bi4V2O11‐SDS Composites with Enhanced Dielectric and Electrical Properties

AbstractIn this work, poly(vinylidene fluoride) (PVDF)‐bismuth vanadate (Bi4V2O11; BVO)‐sodium dodecyl sulfate (SDS) composite films are fabricated by the solution casting method. The frequency dependence of the dielectric and electric performances of the resultant PVDF‐BVO‐SDS composites on various weight percentages of SDS contents is investigated. The results demonstrate that the three‐component PVDF‐BVO‐SDS composites have a superior dielectric constant (96) and suppressed dielectric loss (&lt;1) at 102 Hz for 20 wt% of SDS contents. The surface morphology of the PVDF‐BVO‐SDS composites shows that SDS is successfully reinforced on the PVDF‐BVO matrix with better homogeneity. The ac conductivity of the PVDF‐BVO‐SDS composites is also improved, which is helpful for the enhancement of the dielectric constant and relatively low loss in the composites. Moreover, the PVDF‐BVO‐SDS composite also exhibits a larger value of the dielectric constant (96) than the pristine PVDF matrix, which is 15 times higher than that of the pristine one. These significantly enhanced dielectric and electrical characteristics of PVDF‐BVO‐SDS composites will fulfill the practical criteria for their use in high dielectric‐constant capacitors and energy storage devices.

The influence of interface products on the mechanical and electrical properties of graphene aluminum composites

Graphene has been identified as an efficient filler to increase the strength and conductivity of aluminum but the reaction between aluminum and graphene at elevated temperature is inevitable. In this research, diverse interfacial products between aluminum and graphene were generated by modulating the sintering temperature, and their influences on the mechanical and electrical characteristics of graphene-aluminum composites were examined. Copper encapsulation on graphene has been utilized to isolate graphene from contacting aluminum directly as well as to doping graphene for conduction purposes. The synthesis of copper-coated graphene-reinforced aluminum composites involved several steps, including electrochemical exfoliation, electroless chemical deposition, mechanical ball milling, and high-pressure sintering. The results demonstrate that the formation of a solid solution between copper nanoparticles and aluminum promotes strong interfacial bonding with graphene, leading to a 22.76 % improvement in the conductivity of the composite compared to the pristine aluminum matrix. Additionally, by minimizing the formation of aluminum carbide, the addition of graphene results in a tensile strength of 404 MPa for the composite material, representing a significant 88.8 % increase over the aluminum matrix.

Exploring Anisotropic Mechanical Characteristics in 3D-Printed Polymer Biocomposites Filled with Waste Vegetal Fibers

The fiber-filled polymer composite is one of the best materials which provides a symmetrical superior strength and stiffness to structures. With the strengthening of people’s environmental protection and resource reuse consciousness, the development of renewable materials, especially natural fiber-filled polymer composites, is receiving great attention. This study investigated the mechanical properties of polymer composites incorporating waste materials from the food processing industry and agricultural sources. Waste vegetal fiber-filled polymer biocomposites (WVFFPBs) with varying fiber types and 3D printing orientations were systematically fabricated. Subsequently, the tensile tests were executed to comprehensively assess the anisotropic mechanical behaviors of the WVFFPBs. The results demonstrated that WVFFPBs performed excellent anisotropic mechanical properties compared to pristine matrix samples as print orientation changed. As the printing angle increased from 0° to 90°, the tensile mechanical properties of the WVFFPBs displayed a decreasing trend. Moreover, the print orientation–anisotropic mechanical behavior relationship of 3D-printed WVFFPBs was revealed through the analysis of the material manufacturing characteristics and damage features.

Degradation processes of brominated flame retardants dispersed in high impact polystyrene under UV-visible radiation.

In order to protect human health and the environment, several regulations have been introduced in recent years to reduce or even eliminate the use of some brominated flame retardants (BFRs) due to their toxicity, persistence and bioaccumulation. Dispersions of these BFRs in polymers are widely used for various applications. In this report, four different brominated molecules, decabromodiphenyl ether (DBDE), hexabromocyclododecane (HBCDD), decabromodiphenyl ethane (DBDPE) and tris(tribromophenoxy)triazine (TTBPT), were dispersed in the solid matrix of an industrial polymer, high impact polystyrene (HIPS). The possibility of degradation of these BFRs within HIPS under UV-visible irradiation in ambient air was investigated. The degradation kinetics of DBDE and HBCDD were followed by Fourier transform infrared spectroscopy (FTIR) and high-resolution two-step laser mass spectrometry (L2MS). The thermal properties of the pristine and irradiated polymer matrix were monitored by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), which showed that these properties were globally preserved. Volatile photoproducts from the degradation of DBDE, DBDPE and TTBPT were identified by headspace gas chromatography/mass spectrometry analysis. Under the chosen experimental conditions, BFRs underwent rapid degradation after a few seconds of irradiation, with conversions exceeding 50% for HIPS/DBDE and HIPS/HBCDD systems.

All-scale approach to evaluate the elasticity and strength of carbon-allotrope reinforced polyimide

This computational study conducts a comprehensive all-scale analysis to predict the mechanical behavior (elasticity and strength) of polyimide matrices (Kapton®) reinforced with carbon nanostructures, spanning nanoscale, microscale, mesoscale, and macroscale. Representative volume elements at each scale undergo tensile and shear loadings to extract mechanical properties. Homogenization techniques are applied to transition between scales, considering these properties. Two nanostructures (graphene and γ-graphyne) are explored as reinforcements, evaluating the influence of volume fraction and orientation on composite mechanical properties. Results are validated through comparison with theoretical, computational, and experimental studies. Composite materials exhibited significant improvements in stiffness (up to 44% at a volume fraction of 0.5%) and tensile strength (up to 25% at a volume fraction of 0.5%) compared to the pristine polymeric matrix.

‘Spider-like’ POSS in NIPU webs: enhanced thermal stability and unique swelling behavior

PEO-based non-isocyanate polyhydroxyurethane (NIPU, PHU) networks physically modified with octa(3-hydroxy-3-methylbutyldimethylsiloxy)POSS (8OHPOSS) were synthesized via one-pot one-step approach. POSS was introduced into the polymer matrix in the amount of 1–10 wt%. Polar hydroxyls on the vertex groups of POSS allowed for uniform dispersion even up to high loadings (10 wt%). Composites exhibit enhanced thermal stability in comparison to the pristine matrix. FTIR analysis confirmed that POSS strengthens the hydrogen bonding in the material. Upon POSS introduction, plasticization was observed with a peculiar trend change at POSS loadings over 5 wt%. Glass transition temperature of highly crystalline 8OHPOSS was measured and reported to be at around 3 °C. NIPUs at hand exhibit high water absorption (around 200 wt%) typical for hydrogels. Swelling studies show that 8OHPOSS enhances PHUs hydrogels absorption capacity in phosphate-buffered saline (PBS). Higher absorption capacity in PBS solution in comparison to distilled water is an uncommon phenomenon in hydrogels.

The molecular dynamics description of Polycaprolactone coating effect on mechanical behavior of Polycaprolactone/BG-AK bio-nanocomposites

In current computational research, the effect of Polycaprolactone (PCL) coating on the mechanical properties (MP) of biomimetic calcium phosphate (BCP)/Baghdadite (BG)-AK nanocomposite (NC) is investigated by using molecular dynamics simulation (MDS). Our study models BCP/BG-AK-PCL samples by Universal Force Field (UFF) and DREIDING potential functions. The outcomes of MDS on the MP of atomic samples are presented by computing physical factors like temperature (Temp), potential energy (PE), Young's modulus (YM), and ultimate strength (US). Physically, MD outputs indicate the physical stability of the BCP/BG-AK-PCL sample after 5 ns. Also, by inserting the PCL coat into the pristine matrix, the YM of this structure reaches 0.39 MPa, and the US increases to 20.28 MPa. These numerical results show the important effect of PCL coats on the MP of pristine BCP/BG-AK NC, which can be used for clinical applications.

Fabrication of mixed matrix polyphenylsulfone‐polysulfone blend membranes incorporated with Nickel/Hydrazine@silica core‐shell nanoparticles using VIPS‐NIPS method for efficient dye rejection

AbstractThe dye‐water treatment using nanofiltration membranes is still an important issue. In this work, we have reported the fabrication of silica nanoparticles using a robust approach with well‐controlled aspect ratios. Accordingly, we first fabricated hydrophilic Nickel/Hydrazine@silica core‐shell nanoparticles, in which Ni nanoparticles were coated with a shell of silica. Then, different content of the prepared nanoparticles were incorporated into polyphenylsulfone/ polysulfone membrane matrixes in order to enhance the membranes hydrophilicity. The pristine and mixed matrix membranes (MMMs) were fabricated via the vapor‐induced phase separation coupled with non‐solvent‐induced phase separation (VIPS‐NIPS) approach, where Dioxane was employed as the co‐solvent. The dye rejection performance of the prepared membranes was evaluated for aqueous solutions of a variety of dyes, including direct yellow (DY), crystal violet (CV), methyl green (MG), and methylene blue (MB). Accordingly, it was indicated that the membrane with 0.12 wt.% of nanoparticles could provide an outstanding rejection performance as high as 99.7, 99.3, 98.4 and 97 for DY, MG, CV and MB, respectively, a superb water flux (6.1 L/m2 h bar), a great long‐term durability and an excellent antifouling performance.

Noncytotoxic Dy3+ -activated glass emits cool white light for near ultraviolet-based white light-emitting diodes, visible lasers, and biomedical applications.

Using the melt quenching technique, a lithium zinc borate glass (LZB) system with trivalent dysprosium ions (Dy3+ ) was synthesized, and the luminescence and lasing properties of these materials were examined for the generation of white light. Structural investigation through X-ray diffraction revealed that the prepared glass had an amorphous nature. The optimized glass containing 0.5 Dy3+ had a direct optical band gap of 2.782 eV and an indirect optical band gap of 3.110 eV. A strong excitation band at 386 nm (6 H15/2 →4 I13/2 ) was recognized in the ultraviolet (UV) light region of its excitation spectrum. Emission bands could be seen in the photoluminescence spectrum at 659, 573, and 480 nm under the 386 nm excitation. These transitions of emission resembled electronic transitions such as (4 F9/2 →6 H11/2 ), (4 F9/2 →6 H13/2 ), and (4 F9/2 →6 H15/2 ). In a pristine glass matrix, the higher intensity ratio of yellow to blue can result in the production of white light. The optimized Dy3+ ion concentration was observed to be 0.5mol%. In addition, an analysis of lifetime decay was conducted for all synthesized glasses, and their decay trends were systematically investigated. Noticeably, we assessed the photometric parameters and found that they were close to the white light standard. Furthermore, a cytotoxicity study was carried out using lung fibroblast (WI-38) cell lines for the optimized 0.5Dy3+ -doped LZB glass and it appeared to be noncytotoxic. It is clear from the results that the noncytotoxic LZB glass doped with 0.5 Dy3+ ions could be a suggestive choice for the manufacture of white light-emitting diodes and lasers using near-UVs.

Preparation and Characterization of Light-Colored Polyimide Nanocomposite Films Derived from a Fluoro-Containing Semi-Alicyclic Polyimide Matrix and Colloidal Silica with Enhanced High-Temperature Dimensionally Stability.

Light-colored and transparent polyimide (PI) films with good high-temperature dimensional stability are highly desired for advanced optoelectronic applications. However, in practice, the simultaneous achievement of good optical and thermal properties in one PI film is usually difficult due to the inter-conflicting molecular design of the polymers. In the present work, a series of PI-SiO2 nanocomposite films (ABTFCPI) were developed based on the PI matrix derived from hydrogenated pyromellitic anhydride (HPMDA) and an aromatic diamine containing benzanilide and trifluoromethyl substituents in the structure, 2,2'-bis(trifluoromethyl)-4,4'-bis [4-(4-aminobenzamide)]biphenyl (ABTFMB). The inorganic SiO2 fillers were incorporated into the nanocomposite films in the form of colloidal nanoparticles dispersed in the good solvent of N,N-dimethylacetamide (DMAc) for the PI matrix. The derived ABTFCPI nanocomposite films showed good film-forming ability, flexible and tough nature, good optical transparency, and good thermal properties with loading amounts of SiO2 up to 30 wt% in the system. The ABTFCPI-30 film with a SiO2 content of 30 wt% in the film showed an optical transmittance of 79.6% at the wavelength of 400 nm (T400) with a thickness of 25 μm, yellow index (b*) of 2.15, and 5% weight loss temperatures (T5%) of 491 °C, which are all comparable to those the pristine ABTFCPI-0 matrix without filler (T400 = 81.8%; b* = 1.77; T5% = 492 °C). Meanwhile, the ABTFCPI-30 film exhibited obviously enhanced high-temperature dimensional stability with linear coefficients of thermal expansion (CTE) of 25.4 × 10-6/K in the temperature range of 50 to 250 °C, which is much lower than that of the AMTFCPI-0 film (CTE = 32.7 × 10-6/K).

Glassy and Rubbery Epoxy Composites with Mesoporous Silica

The reinforcing efficiency of SBA-15-type mesoporous silica, when used as additive in epoxy polymers, was evaluated in this study. The effects of silica loading and its physicochemical characteristics on the thermal, mechanical, and viscoelastic properties of glassy and rubbery epoxy mesocomposites were examined using SBA-15 mesoporous silicas with varying porosities (surface area, pore size, and volume), particle sizes, morphologies, and organo-functionalization. Three types of SBA-15 were used: SBA-15 (10) with 10 nm pore diameters and long particles, SBA-15 (5) with 5 nm pore diameters and short particles, and SBA-15 (sc) with 10 nm pore diameters and short particles (“sc” for short channel). SBA-15 (10) was modified with propyl-, epoxy-, and amino-groups to study the effect of functionalization. The glassy or rubbery epoxy polymers and mesocomposites were produced by the crosslinking of a diglycidyl ether of bisphenol A (DEGBA) epoxy resin with isophorone diamine (IPD) or Jeffaminje D-2000, respectively. Mesoporous silica was uniformly dispersed inside the polymer matrices; however, the opacity levels between the rubbery and glassy samples were different, with completely transparent rubbery composites being prepared with as high as a 9 wt. % addition of SBA-15. The mechanical and thermal performance properties of the mesocomposites were dependent on both the type of the curing agent, which affected the cross-linking density of the pristine polymer matrix, and the characteristics of the mesoporous silica variants, being, in general, improved by the addition of up to 6 wt. % silica for the glassy polymers and up to 9 wt. % for the rubbery polymers.

Fabrication of Helix aspersa Extract Loaded Gradient Scaffold with an Integrated Architecture for Osteochondral Tissue Regeneration: Morphology, Structure, and In Vitro Bioactivity.

Regeneration of osteochondral tissue with its layered complex structure and limited self-repair capacity has come into prominence as an application area for biomaterial design. Thus, literature studies have aimed to design multilayered scaffolds using natural polymers to mimic its unique structure. In this study, fabricated scaffolds are composed of transition layers both chemically and morphologically to mimic the gradient structure of osteochondral tissue. The aim of this study is to produce gradient chitosan (CHI) scaffolds with bioactive snail (Helix aspersa) mucus (M) and slime (S) extract and investigate the structures regarding their physicochemical, mechanical, and morphological characteristics as well as in vitro cytocompatibility and bioactivity. Gradient scaffolds (CHI-M and CHI-S) were fabricated via a layer-by-layer freezing and lyophilization technique. Highly porous and continuous 3D structures were obtained and observed with SEM analysis. In addition, scaffolds were physically characterized with water uptake test, micro-CT, mechanical analysis (compression tests), and XRD analysis. In vitro bioactivity of scaffolds was investigated by co-culturing Saos-2 and SW1353 cells on each compartment of gradient scaffolds. Osteogenic activity of Saos-2 cells on extract loaded gradient scaffolds was investigated in terms of ALP secretion, osteocalcin (OC) production, and biomineralization. Chondrogenic bioactivity of SW1353 cells was investigated regarding COMP and GAG production and observed with Alcian Blue staining. Both mucus and slime incorporation in the chitosan matrix increased the osteogenic differentiation of Saos-2 and SW1353 cells in comparison to the pristine matrix. In addition, histological and immunohistological staining was performed to investigate ECM formation on gradient scaffolds. Both characterization and in vitro bioactivity results indicated that CHI-M and CHI-S scaffolds show potential for osteochondral tissue regeneration, mimicking the structure as well as enhancing physical characteristics and bioactivity.