Polymethacrylic acid/Na-montmorillonite/SiO<Subscript>2</Subscript> nanoparticle composites structures and thermal properties

In this article, polymethacrylic acid/Na-montmorillonite/SiO₂ nanoparticle (PMAA/Na-MMT/SiO₂) composites were prepared via in situ polymerization. Fourier transform infrared spectroscopy (FTIR) indicated that the polymerization of SiO₂ nanoparticle and MAA have been taken place. X-ray diffraction (XRD) results suggest that Na-MMT layers are exfoliated during the polymerization process. As evidenced by the transmission electron microscopy (TEM), the Na-MMT layers and SiO₂ nanoparticles exhibit good dispersion in the polymer matrix. It was found that the PMAA/Na-MMT/SiO₂ composite exhibit considerably enhanced thermal properties compared with the PMAA/Na-MMT.     

An explanation of silicate exfoliation in polyacrylonitrile/silicate nanocomposites prepared by in situ polymerization using an initiator adsorbed on silicate

Sodium montmorillonite (Na-MMT) absorbed a radical initiator, potassium persulfate (KPS), by way of hydrogen bonding between hydroxyl groups in the Na-MMT lattice and the sulfonic anions of KPS. FT-IR absorbance bands of hydroxyl groups in the Na-MMT lattice and the sulfonic anions of KPS shifted to lower wavenumber regions, compared with the free silicate and the initiator. The amounts of initiator adsorbed on the silicate were determined by using thermogravimetric analysis. The initiator adsorbed on silicate (IAS) commenced the polymerization of acrylonitrile (AN), delaminating silicate layers in polyacrylonitrile (PAN)/silicate nanocomposites. Molecular weights of PANs extracted from the nanocomposites decreased as the amount of initiator in IAS increased. Heterogeneous nucleation, polymerization in the basal spacing of the silicate layers, was analyzed by high performance liquid chromatograph. Storage moduli, E′, of the nanocomposites were enhanced with the molecular weights of PAN matrixes. Glass temperatures, T_g, of the nanocomposites were dependent on the molecular weights of the PAN matrixes and the contents of the 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) charged.     

Preparation and evaluation of polyaniline and polypyrrole modified water‐dispersible conducting nanocomposites of polyacrylonitrile with silica

Water‐dispersible conducting nanocomposites were prepared by precipitating polyaniline (PANI)/polypyrrole (PPY) in an aqueous suspension of polyacrylonitrile–SiO₂ (PAN–SiO₂) via K₂CrO₄–NaAsO₂ redox polymerization. Incorporation of PANI and PPY in the composites was confirmed by the FTIR spectrum. Scanning electron microscopic analyses for the PANI–(PAN–SiO₂) and PPY–(PAN–SiO₂) composites indicated formation of lumpy aggregates with irregular sizes. TEM analyses revealed formation of spherical particles with size ranging between 80 and 150 nm for PANI–(PAN–SiO₂) nanocomposite and 75–150 nm for PPY‐(PAN‐SiO₂) nanocomposites, respectively. Thermal stabilities of the PANI–(PAN–SiO₂) and PPY–(PAN–SiO₂) nanocomposites were higher than those of the individual base polymers. Conductivity values of PANI–(PAN–SiO₂) nanocomposite (10^?3 S cm^?1) and PPY–(PAN–SiO₂) nanocomposite (10^?4 S cm^?1) were remarkably improved relative to that for PAN homopolymer (>10^?11 S cm^?1). Both of these composites produced a permanently stable aqueous suspension when the polymerization was conducted in presence of nanodimensional SiO₂ as a particulate dispersant. Copyright © 2004 Society of Chemical Industry     

Preparation and crystallization of poly(ethylene terephthalate)/SiO2 nanocomposites by in‐situ polymerization

Poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO₂ nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO₂ nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO₂ nanoparticles exhibited strong nucleating effects. It was found that SiO₂ nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006     

Synthesis and characterization of PMMA/SiO2 nanocomposites by in situ suspension polymerization

Poly(methyl methacrylate) (PMMA)/SiO₂ nanocomposites were prepared by in situ suspension polymerization. Two types of modified methods were used to modify nano‐SiO₂: one was modification by γ‐methacyloxypropyl trimethoxy silane (KH570) and lauryl alcohol (12COH) while the other was grafting PMMA onto the surface of KH570 treated SiO₂. Transmission electron microscopy (TEM) and Fourier transformed infrared (FTIR) were used to characterize the structures of the nanocomposites. The influence of synthetic conditions, for instance, surface modification, initial SiO₂ contents and reaction temperature, on the microsphere's size and molecular weight of the extracted PMMA were studied by gel permeation chromatograph (GPC) and optical microscopy (OM) in details. Thermal property of the nanocomposites was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that the presence and content of SiO₂ have a vital effect on the shape and size of the nanocomposite microspheres, as well as molecular weight of the extracted PMMA. Grafting polymer to the surface of SiO₂ is an effective way for the purpose of effective in situ suspension polymerization. Compared to pure PMMA, the thermal properties of the nanocomposites were improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and rheological behaviors of PA6/SiO2 nanocompiste

The polyamide 6 (PA6)/SiO₂ nanocomposites were prepared by in situ polymerization and the rheological behaviors were investigated. The morphology of resultant materials was characterized by scanning electron microscopy (SEM) and the rheological behaviors were characterized by capillary rheometer. The results showed that the SiO₂ particle size was around 50 nm and the particles dispersed evenly in PA6 matrix. The nanocomposites were pesudoplastic fluids and the apparent viscosities of nanocomposites increased initially and then decreased with the increase in nano-SiO₂ content at the same temperature. The non-Newtonian indexes of nanocomposites were smaller than those of pure PA6. With the increase in nano-SiO₂ content the apparent viscous activation energies of nanocomposites increased initially and then decreased. The rheological behaviors revealed that there were strong interactions between PA6 macromolecule chains and nano-SiO₂ particles.     

Preparation and characterization of thermoplastic vulcanizate/silica nanocomposites

This article describes the preparation, characterization, and properties of thermoplastic vulcanizate (TPV)/silica nanocomposites. The nanocomposites were prepared by the melt blending of TPV and maleic anhydride grafted polypropylene (mPP) into organically modified SiO₂ (m‐SiO₂), treated with n‐hexadecyl trimethylammonium bromide as a grafting agent for TPV during the melt mixing. The thermal stability and storage modulus of the 1 wt % m‐SiO₂ containing TPV/mPP/m‐SiO₂ nanocomposite were higher than those of pristine TPV. The most important observation was obtained from dynamic mechanical analysis, which revealed that the glass‐transition temperature of the polypropylene phase of the nanocomposites increased (in comparison with that of virgin TPV), whereas the ethylene–propylene–diene monomer phase remained almost the same. The adhesion strength between the TPV/mPP/m‐SiO₂ nanocomposites and steel also increased with increasing m‐SiO₂ content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2058–2063, 2005     

Characterization and non-isothermal crystallization behavior of biodegradable poly(ethylene sebacate)/SiO2 nanocomposites

Poly(ethylene sebacate) (PESeb) and PESeb/silica nanocomposites (PESeb/SiO₂) were prepared by in situ polymerization from the direct esterification of ethylene glycol with sebacic acid in the presence of proper amounts of silica nanoparticles. The non-isothermal crystallization behavior of PESeb/SiO₂ nanocomposites has been studied using different theoretical equations such as Avrami, Ozawa and combined Avrami and Ozawa equations. It is found that the addition of nanoparticles of SiO₂ influenced the mechanism of nucleation and the growth of PESeb crystallites. Also, the nanocomposites show a higher Avrami value than the neat PESeb, implying a more complex crystallization configuration. Moreover, the combined Avrami and Ozawa equation can successfully describe the crystallization model under the non-isothermal crystallization. The crystallization activation energies, E _a, calculated from “Kissinger’s equation” have shown that the synthesized PESeb/SiO₂ nanocomposites have lower energy than the neat PESeb, reflecting the much lower energy barrier for the rapid heterogeneous nucleation.     

Preparation and characterization of poly(2‐chloroaniline)/SiO2 nanocomposite via oxidative polymerization: Comparative UV–vis studies into different solvents of poly(2‐chloroaniline) and poly(2‐chloroaniline)/SiO2

Poly(2‐chloroaniline)/silica (P2ClAn)/SiO₂ nanocomposites have been chemically prepared by oxidative polymerization of 2‐chloroaniline in acidic medium containing SiO₂. The prepared composites were characterized by FTIR, UV–vis, TGA, XRD, SEM, ESEM, conductivity, and magnetic susceptibility. The incorporation of P2ClAn in composites was endorsed by FTIR studies. The effect of the solution concentration of P2ClAn and P2ClAn/SiO₂ prepared in protonated, deprotonated, and reprotonated structures on the UV–vis spectra was investigated into three different solvents (DMF, NMP, and H₂SO₄). In all forms, the oxidation state of P2ClAn and P2ClAn/SiO₂ composite increased with increasing concentration of the testing solution into H₂SO₄. Thermogravimetric study exhibited that the composite has a higher thermal stability than P2ClAn. XRD measurement of the composite revealed that the crystal structure of incorporated SiO₂ undergone a distortion and converted into amorphous. Thus, the XRD pattern of P2ClAn was predominant. SEM analysis results revealed interesting morphological features for the composites converted to different forms and confirmed the formation of monodispersed composite particles. ESEM image of P2ClAn/SiO₂ has particle diameter of less than 1 μm. The conductivity of P2ClAn and P2ClAn/SiO₂ was measured by four‐probe technique. Magnetic susceptibility measurements revealed that the composite has a paramagnetic properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:935–943, 2006     

Towards transparent PMMA/SiO2 nanocomposites with promising scratch‐resistance by manipulation of SiO2 aggregation followed by in situ polymerization

Poly(methyl methacrylate) grafted silica (SiO₂‐g‐PMMA) was synthesized via in situ suspension polymerization. To achieve better uniform dispersion, hexadecyltrimethylammonium bromide (CTAB) was introduced into xylene to manipulate SiO₂ aggregation. SiO₂‐g‐PMMA or SiO₂ was incorporated into PMMA matrix by in situ polymerization to prepare PMMA‐based nanocomposites. The effect of CTAB amount, in the range 0–35 wt %, on the modification was evaluated by DLS, TGA, and FTIR. Furthermore, morphology, optical, mechanical, and thermal properties of PMMA nanocomposites was characterized by SEM, UV–vis, DMA, and TGA. Owing to surface functionalization, SiO₂‐g‐PMMA exhibited far more excellent compatibility and dispersion in matrix compared with SiO₂. Surface hardness and thermal properties of nanocomposites were enhanced significantly under the premise in high transparency. It is expected that transparent nanocomposites with promising scratch‐resistance could have wide applications, such as airplane shielding window and daily furniture. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44612.     

Synthesis of CoNi/SiO2 core-shell nanoparticles decorated reduced graphene oxide nanosheets for enhanced electromagnetic wave absorption properties

In this research, the nanocomposites, CoNi/SiO₂ core-shell nanoparticles decorated reduced graphene oxide (RGO) nanosheets, are successfully synthesized via liquid-phase reduction reactions combined with a sol-gel route. The structures, morphologies, chemical composition and magnetic properties of CoNi nanoparticles, CoNi/SiO₂ core-shell nanoparticles and RGO/CoNi/SiO₂ nanocomposites have been investigated in exhaustive detail. The electromagnetic (EM) parameters of RGO/CoNi/SiO₂ nanocomposites are measured using a vector network analyzer. The results reveal that the RGO/CoNi/SiO₂ nanocomposites display enhanced EM wave absorption properties with the maximum reflection loss (R_L) of ??46.3?dB at 6.2?GHz with a matching thickness of 4.2?mm. Additionally, the absorption bandwidth corresponding to the R_L less than ??10?dB is up to 14.3?GHz (3.7–18.0?GHz) with a matching thickness range of 2.0–5.0?mm. To comprehensively consider the absorption bandwidth and the maximum R_L, the integrational method which defines ΔS as the integration area of R_L (R_L < ??10?dB) and R_E as EM wave absorption efficiency is adopted to reveal that the RGO/CoNi/SiO₂ nanocomposites exhibit the excellent absorption properties with the matching thickness of only 2.0?mm. Accordingly, the as-prepared RGO/CoNi/SiO₂ nanocomposites could be applied as promising EM wave absorption materials.     

Facile preparation of superhydrophobic polyester surfaces with fluoropolymer/SiO2 nanocomposites based on vinyl nanosilica hydrosols

A facile method to prepare superhydrophobic fluoropolymer/SiO₂ nanocomposites coating on polyester (PET) fabrics was presented. The vinyl nanosilica (V? SiO₂) hydrosols were prepared via one‐step water‐based sol‐gel reaction with vinyl trimethoxy silane as the precursors in the presence of the base catalyst and composite surfactant. Based on the V? SiO₂ hydrosol, a fluorinated acrylic polymer/silica (FAP/SiO₂) nanocomposite was prepared by emulsion polymerization. The FAP/SiO₂ nanocomposites were coated onto the polyester fabrics by one‐step process to achieve superhydrophobic surfaces. The results showed that silica nanoparticles were successfully incorporated into the FAP/SiO₂ nanocomposites, and a specific surface topography and a low surface free energy were simultaneously introduced onto PET fibers. The prepared PET fabric showed excellent superhydrophobicity with a water contact angle of 151.5° for a 5 μL water droplet and a water shedding angle of 12° for a 15 μL. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40340.     

Electrospun hydrophilic fumed silica/polyacrylonitrile nanofiber-based composite electrolyte membranes

Hydrophilic fumed silica (SiO₂)/polyacrylonitrile (PAN) composite electrolyte membranes were prepared by electrospinning composite solutions of SiO₂ and PAN in N,N-dimethylformamide (DMF). Among electrospinning solutions with various SiO₂ contents, the 12 wt% SiO₂ in PAN solution has highest zeta potential (−40.82 mV), and exhibits the best dispersibility of SiO₂ particles. The resultant 12 wt% SiO₂/PAN nanofiber membrane has the smallest average fiber diameter, highest porosity, and largest specific surface area. In addition, this membrane has a three-dimensional network structure, which is fully interconnected with combined mesopores and macropores because of a good SiO₂ dispersion. Composite electrolyte membranes were prepared by soaking these porous nanofiber membranes in 1 M lithium hexafluorophosphate (LiPF₆) in ethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1 vol%). It is found that 12 wt% SiO₂/PAN electrolyte membrane has the highest conductivity (1.1 × 10⁻² S cm⁻¹) due to the large liquid electrolyte uptake (about 490%). In addition, the electrochemical performance of composite electrolyte membranes is also improved after the introduction of SiO₂. For initial cycle, 12 wt% SiO₂/PAN composite electrolyte membrane delivers the discharge capacity of 139 mAh g⁻¹ as 98% of theoretical value, and still retains a high value of 127 mAh g⁻¹ as 89% at 150th cycle, which is significantly higher that of pure PAN nanofiber-based electrolyte membranes.     

Superfine structure,physical properties,and dyeability of alkaline hydrolyzed soly(ethylene terephthalate)/silica nanocomposite fibers prepared by in situ polymerization

In this study, poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were synthesized by in situ polymerization and melt‐spun to fibers. The superfine structure, physical properties, and dyeability of alkaline hydrolyzed PET/SiO₂ nanocomposite fibers were studied. According to the TEM, SiO₂ nanoparticles were well dispersed in the PET matrix at a size level of 10–20 nm. PET/SiO₂ nanocomposite fibers were treated with aqueous solution of sodium hydroxide and cetyltrimethyl ammonium bromide at 100°C for different time. The differences in the alkaline hydrolysis mechanism between pure PET and PET/SiO₂ nanocomposite fibers were preliminarily investigated, which were evaluated in terms of the weight loss, tensile strength, specific surface area, as well as disperse dye uptake. PET/SiO₂ nanocomposite fibers showed a greater degree of weight loss as compared with that of pure PET fibers. More and tougher superfine structures, such as cracks, craters, and cavities, were introduced, which would facilitate the certain application like deep dyeing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3691–3697, 2006     

微滴乳液聚合制备PDMS/SiO2纳米复合材料

采用超声分散的方法,以少量八甲基环四硅氧烷(D₄)对硅溶胶粒子进行表面接枝改性。然后在改性硅溶胶存在下,以十二烷基苯磺酸(DBSA)为乳化剂兼催化剂进行D₄的微滴乳液聚合,得到聚硅氧烷(PDMS)/二氧化硅(SiO₂)纳米复合乳液。采用FTIR、TGA、纳米粒度仪、TEM和拉力机分别对样品进行了表征。结果表明:采用超声分散的方法,能够有效地实现硅溶胶粒子的表面改性。通过微滴乳液聚合得到的复合乳胶粒是聚合物包覆二氧化硅粒子的核壳结构形态。SiO₂的引入提高了有机硅复合膜力学性能,增强了热稳定性。     

Preparation and Characterization of PAN/SiO2 Hybrid Fibers

Summary  Two kinds of hybrid PAN/SiO₂ sols were prepared via either sols blend or in-situ polymerization, respectively, and their spinnability was investigated. Hydrolysis time (t₁) and spinnable time (t₂) of both hybrid sols increased with PAN content. The hybrid fibers were characterized with FTIR, DSC, SEM and TG. As evidenced from the FT-IR spectra and DSC measurements, different chemical structures of hybrid fibers were different with CN groups hydrolyzed in the hybrid fibers via in-situ polymerization. SEM measurements showed the interior structures of the hybrid fibers via in-situ polymerization were more homogeneous. TG measurements suggest both of the hybrid fibers show better resistance to heat than pure PAN.     

A novel approach to prepare PBT nanocomposites with elastomer‐modified SiO2 particles

Poly(butylenes terephthalate) (PBT)/SiO₂ nanocomposites with uniform dispersion, strong interfacial adhesion, and improved mechanical properties have been prepared by a novel approach. Ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) elastomer chains were first chemically grafted onto the surface of SiO₂ nanoparticles. Fourier transform infrared spectra result shows that elastomer‐modified SiO₂ nanoparticles exhibit absorption at 2963–2862 cm⁻¹ of the stretching modes of C H, which suggests the reaction between the hydroxyl groups of SiO₂ surface and epoxy groups of E‐MA‐GMA. And the binding energy of Si2p and O1s of the elastomer‐modified SiO₂ shifts to lower binding energy, which further confirms the formation of Si O C bonds. This surface treatment allows SiO₂ nanoparticles homogeneously dispersing in PBT matrix. The morphology with loose aggregates contains networked SiO₂ particles with an interparticle distance ranging from 0 to 30 nm. As a result, the storage modulus and the tensile properties of PBT/E‐MA‐GMA‐SiO₂ nanocomposites are higher than those of pure PBT and PBT with untreated SiO₂. The incorporation of E‐MA‐GMA‐modified SiO₂ particles increases the tensile strength and modulus to 58.4MPa and 2661MPa respectively, which is 8% and 16% higher than those of pure PBT. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

In‐situ synthesis of poly(ethylene terephthalate)/clay nanocomposites using TiO2/SiO2 sol‐intercalated montmorillonite as polycondensation catalyst

A novel organic montmorillonite, which could act as both polycondensation catalyst of poly(ethylene terephthalate) (PET) and filler of PET/clay nanocomposites, was prepared. Original montmorillonite was first treated with different amounts of poly(vinylpyrrolidone) (PVP), and then intercalated by TiO₂/SiO₂ sol to gain polycondensation catalytic activity. The acquired clay possessed excellent thermal stability and would not degrade during the polycondensation step. PET/clay nanocomposites were prepared via in‐situ polymerization using the organo‐clay as polycondensation catalysts. The morphologies of the nanocomposites were characterized by X‐ray diffraction and transmission electron microscope. The results indicated that the amount of PVP and TiO₂/SiO₂ sol strongly affected the dispersion state of the clay, and finally, partially exfoliated PET/clay nanocomposites were obtained. The nanocomposites had better properties than pure PET due to the incorporation of the delaminated clay layers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Electromagnetic wave absorbing performance of multiphase (SiC/HfC/C)/SiO2 nanocomposites with an unique microstructure

Dielectric properties and electromagnetic (EM) wave absorbing performance of monolithic (SiC/HfC/C)/SiO₂ nanocomposites (denoted as SHCOs) have been investigated in the X-band (8.2–12.4 GHz). The multiphase SHCOs are composed of insulating SiO₂ and SiC/HfC/C nanocomposite fillers (SHC), which fillers composed of semiconducting β-SiC, conductive HfC-Carbon core-shell nanoparticles, and interconnected carbon nanoribbons. Dielectric response indicates that the increased SHC content results in an enhanced imaginary part of the permittivity and dielectric loss, leading to an improved EM absorbing performance. The unique microstructure with an EM wave-transparent SiO₂ matrix is favorable for impedance matching and effective EM wave propagation. The enhanced interface polarization and conduction loss are considered as the key mechanisms for EM wave attenuation. The minimum reflection loss of the SHCOs achieves – 60.7 dB containing 20 vol% of SHC (at 9.98 GHz) with the sample thickness of 3.33 mm, and the effective absorbing bandwidth (EAB) covers ca. 72 % of the X-band. The monolithic (SiC/HfC/C)/SiO₂ nanocomposites with outstanding EM wave absorbing performance are promising candidates for EM application at high temperatures.     

In situ synthesis and properties of PMR PI/SiO2 nanocomposites

Phenylethynyl-terminated polymerization of monomer reactant thermosetting polyimide (PI) was synthesized, and the PI/SiO₂ nanocomposite films were prepared via in situ polymerization of monomer with the nano-SiO₂ particles. Analysis indicated that the surfaces of the nano-SiO₂ slightly react to the PI, and nano-SiO₂ was homogeneously dispersed in the PI at low filling content while agglomerate was a presence of high filling content. Thermogravimetric analysis showed that the decomposition temperatures of the PI/SiO₂ nanocomposites were increasing as the increasing of filler contents when the nano-SiO₂ content was below 9 wt %, but it showed a decreased tendency when it was above 9 wt %. Tribological studies showed that the nano-SiO₂ contributed to the significant decreasing of the friction coefficient and wear rates of the PI at dry sliding condition of low filler content, and the PI/SiO₂ nanocomposites could be promising material used as tribomaterial in dry sliding condition against GCr15 steel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012