Preparation of hybrid composite microspheres containing nanosilicon via microsuspension polymerization

Hybrid composite microspheres with nano‐Si as the core and poly(styrene‐co‐acrylonitrile) as a shell are successfully prepared by a two‐step polymerization technique, which includes dispersion polymerization of styrene and 3‐methacryloxypropyl trimethoxysilane in ethanol for surface modification of nano‐Si followed by microsuspension polymerization of styrene and acrylonitrile in an aqueous phase for encapsulating nano‐Si into an SAN copolymer matrix. The structure and surface properties of modified nano‐Si are investigated by Fourier transform infrared spectroscopy (FTIR) and contact angle. The hybrid composite microspheres are systematically characterized by energy dispersive spectroscopy, thermogravimetric analysis, and transmission electron microscopy (TEM). According to the FTIR spectra and the contact angle experiments, it was determined that a hydrophobic polymer layer was formed on the surface of nano‐Si. TEM showed that nano‐Si was homogeneously dispersed in SAN particles when the loading capacity of nano‐Si in the hybrid composite microspheres was less than 20 wt %. Moreover, scanning electron microscopy and X‐ray photoelectron spectroscopy revealed that there were large amounts of nano‐Si absorbed on the surface of the hybrid composite microspheres, and the mean particle size became much larger when the loading amounts of nano‐Si reached 25 wt %. From this, it can be inferred that nano‐Si overflows from the inner core to the outside surface in the emulsification process and acts as an inorganic dispersant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43101.     

Polymer microspheres with surface chains prepared by dispersion copolymerization using poly(oxyethylene) macromonomer

Polymer microspheres were prepared by dispersion copolymerization of styrene with poly(oxyethylene) (peo) macromonomer. A dispersion terpolymerization of styrene, PEO macromonomer and acrylic acid was also conducted to prepare polymer microspheres with both surface carboxyl groups and PEO polymer chains. The microspheres thus obtained were characterized with TEM, IR, and X‐ray photoelectron spectroscopy analyses. Palladium nanoparticles were then formed on the surface of these copolymer microspheres forming polymer/metal nanocomposites which were then studied by TEM and X‐ray diffraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2732–2736, 2002     

Surface modification of temperature‐responsive polymer particles by an electrically conducting polyaniline shell layer

In this research an attempt was made to prepare biocompatible electrically conductive composite polymer particles in view of their wide applications in biotechnology. Temperature‐sensitive polymer particles have applications as drug carriers, bioseparators, bioreactor cell activators and diagnostic reagents. So a combination of diverse properties in a single polymer composite is expected to increase its application potential. Here temperature‐responsive poly(N‐isopropyl acrylamide‐methyl methacrylate‐N,N′‐methylene‐bis‐acrylamide) (P(NIPAM‐MMA‐MBAAm)) core particles were prepared by emulsion copolymerization without using any stabilizer. In a second step seeded chemical oxidative polymerization of different amounts of aniline was carried out in the presence of submicron‐sized core particles to obtain P(NIPAM‐MMA‐MBAAm)/polyaniline composite particles. For a comparative study, reference polyaniline particles were prepared by chemical oxidative polymerization. Fourier transform IR spectroscopy, UV?visible spectroscopy, thermal and X‐ray diffraction analyses showed that composite particles prepared with higher aniline content (0.8 g) per unit mass (g) of core particles had high surface coverage compared with lower aniline content (0.1 g). © 2013 Society of Chemical Industry     

Small‐angle X‐ray scattering analysis of nanophase titanium dioxide,poly[N‐(4‐sulfophenyl)aniline], and their composite

Small‐angle X‐ray scattering and spectroscopic (infrared and ultraviolet–visible) techniques were used to investigate the interactions between titanium dioxide (TiO₂) and the semiconductor polymer poly[N‐(4‐sulfophenyl)aniline] (PSA) in a poly[N‐(4‐sulfophenyl)aniline]/TiO₂ composite (TPSA). The radius of gyration of the cross section, the radius and length of the rodlike particle, the persistence length, the surface fractal dimension, and the PSA layer thickness on TiO₂ in aqueous solutions and in powder form were calculated. The results indicated that the aggregation of TiO₂ particles on drying was reduced by the formation of the composite with the semiconductor polymer. Only the particle length of the TPSA particle (which had a rodlike shape) increased on drying, probably because of increasing void sizes and the formation of aggregation. The persistence length of the TPSA particles decreased with respect to its individual components. The PSA layer thickness on TiO₂ was about 3.6 nm and decreased (to 2.6 nm) on dehydration because of the expulsions of water molecules from the TiO₂/PSA composite. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 3183–3187, 2003     

Structural changes of polylactic‐acid (PLA) microspheres under hydrolytic degradation

Low molecular‐weight polylactic acid (PLA) was obtained by direct polycondensation of a mixture of 95% l and 5% d ‐lactic acid isomers, without catalyst, at 195°C. This polymer was used for the synthesis of microspheres by emulsion–solvent evaporation method. Gel Permeation Chromatography (GPC), X‐ray Scattering (XRD), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) techniques were applied to follow morphological and structural changes of particles along in vitro degradation at 37°C. The original microspheres were amorphous but could crystallize partially upon heating. Samples stored in a humid environment exhibited an increase in the crystallization capability upon heating. Initial smooth‐surface microspheres were transformed to porous particles at the time of degradation at pH = 7 (37°C). The shape of mass loss vs. time curve supports the presence of a heterogeneous bulk degradation process. After hydrolytic degradation the residual particles showed a molecular weight decrease and a crystallinity increase. After 90 days the crystallinity attained a value of 53%. The X‐ray diffraction spectrum indicated the formation of a crystalline oligomeric structure. Crystallization of low molecular weight species will not enable the desired PLA absorption in drug delivery systems. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1223–1230, 1999     

Fabrication of anisotropic janus composite particles based on natural renewable urushiol

Urushiol praseodymium‐polystyrene (UPr‐PS) Janus composite particles were synthesized by emulsion swelling assisted protruding from UPr/PS core‐shell composite microspheres. The effects of sulfonated time and the outer electronic configuration of metal on the shell of urushiol metal/PS composite microspheres, together with the effects of monomer type, monomer dosage and swelling time on the swelling behaviour, were studied. The morphology, chemical composition and thermal performance of UPr/PS core‐shell composite microspheres and UPr‐PS Janus composite particles were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X‐ray analyzer (EDX), Thermogravimetric analysis (TG) and infrared spectrometer (IR). Results showed that the morphology could be controlled by the metal kind, the sulfonated time, the monomer type, the monomer dosage and the swelling time. Attributing to the novel anisotropic structure, the UPr‐PS Janus composite particles will be expected to be applied in oriented catalyst. POLYM. ENG. SCI., 59:411–417, 2019. © 2018 Society of Plastics Engineers     

Preparation of heat resisting poly(methyl methacrylate)/graphite composite microspheres used as ultra‐lightweight proppants

Ultra‐lightweight heat resisting poly(methyl methacrylate) (PMMA)/graphite microspheres were successfully prepared via in situ suspension polymerization. The Fourier transform infrared and X‐ray powder diffraction results confirmed the successful preparation of the composite microspheres. Field emission scanning electron microscope analysis illustrated that the graphite particles were dispersed in microspheres and the PMMA/graphite composite microspheres had good sphericity and roundness. Furthermore, density analysis indicated that the apparent density of composites microspheres was about 1.055–1.135g/cm³ which was suitable for the transmission with water carrying. The results from thermodynamic test revealed that the thermal stability of the composite was significantly improved with increasing graphite content, which could be used as ultra‐lightweight proppant in deep underground. In addition, the crushing rate decreased to 0.5% with graphite ratio of 3.0% at the pressure of 69 MPa. Therefore, PMMA/Graphite composite microspheres exhibit a promising application in petroleum or gas exploitation as water carrying fracturing proppants. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41924.     

Study of the orientation and the degree of exfoliation of nanoparticles in poly(ethylene‐vinyl acetate) nanocomposites

Nanocomposites formed from organically modified montmorillonite and poly(ethylene‐co‐vinyl acetate) were studied by X‐ray diffraction techniques. Wide‐ and small‐angle X‐ray scattering intensities (SAXS and WAXS) were recorded by transmission mode on test bars cut from compression‐molded plaques tilted by different angles with respect to the plane of the plaque. The height of the Bragg peaks characteristic of intercalated particles reduced to the baseline at tilt angles greater than 30°. Guinier analysis of the SAXS characteristic of particle scattering showed a radius of gyration of 0.69 nm and the scattering intensity was slightly dependent on the tilt angle. Recording of WAXS in the usual (i.e., in reflective) mode enhanced the effect of the structural features of the surface area and showed much higher degree of intercalation and particle size of the scattering particles than that in transmission mode. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3026–3031, 2003     

Synthesis and characterization of nanocomposites of silicon dioxide and polyurethane and epoxy resin interpenetrating network

Nanocomposites with varying concentrations of nanosized silicon dioxide particles were prepared by adding nanosilica to interpenetrating polymer networks (IPN)s of polyurethane and epoxy resin (PU/EP). The PU/EP IPNs and nanocomposites were studied by dynamic mechanical analysis, scanning electronic microscopy, wide‐angle X‐ray diffraction and small‐angle X‐ray scattering. The result showed that adding nanosize silicon dioxide can improve the properties of compatibility, damping and phase structure of IPN matrices. Copyright © 2003 Society of Chemical Industry     

Hydroxyapatite as a filler for biosynthetic PHB homopolymer and P(HB–HV) copolymers

This paper deals with some of the fundamental problems encountered when using a semicrystalline polymer as the matrix phase for a particulate‐filled composite. As our model system we adopted poly‐(R)‐3‐hydroxybutyrate, PHB, and two copolymers of (R)‐3‐hydroxybutyrate and (R)‐3‐hydroxyvalerate, P(HB–HV), for the matrix phase, and the mineral calcium hydroxyapatite as a particulate filler. The structure and properties of compression‐moulded films of various compositions were investigated by polarized light microscopy, wide‐angle X‐ray scattering and mechanical testing. It was found that the degree of crystallinity of the matrix was lower in filled samples, and that the spherulitic crystallization of the matrix appeared to cause the filler particles to form agglomerates, which would not be as effective a reinforcement as finely dispersed primary filler particles. The tensile strength, strain‐to‐break and tensile modulus of samples of different compositions were analysed using well‐known theories for composite behaviour. Copyright © 2003 Society of Chemical Industry     

Preparation and characterization of ceria nanoparticles supported on poly(4‐vinyl pyridine‐co‐divinyl benzene)

Formation of ceria nanoparticles in 2% divinyl benzene (dvb) crosslinked 4‐vinyl pyridine (4vp) polymer [poly(4vp‐co‐dvb)] microspheres was investigated. The polymer was prepared by free radical suspension polymerization method. Poly(4vp‐co‐dvb)/ceria nanocomposites were prepared by reacting CeCl₃·7H₂O and NaOH in the presence of poly(4vp‐co‐dvb) at room temperature in aqueous media. The mole ratio of the metal to polymer was varied from 2.5 to 10% with an increment of 2.5. The polymer and nanocomposities were characterized by various spectrochemical methods. The coordination of nitrogen atoms of the polymer with Ce(IV) of ceria (CeO₂) has been confirmed from X‐ray photoelectron spectroscopy (XPS). The method has yielded ceria nanoparticles in an average size of 15 nm according to transmission electron microscopy. Differential scanning calorimetry, thermogravimetric analysis, X‐ray diffractometry and XPS analysis with respect to mole percentage of ceria in the composite are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3439–3445, 2006     

A simple method to generate spontaneous chemisorption of metallic particles mediated by carboxylate groups from silylated oligomeric poly(amide‐imide)s

The present work describes oligomeric poly(amide‐imide)s (PAIs) containing several l ‐amino acidic residues and two silicon atoms in their repeat unit, whose carboxylate terminal group was chemisorbed onto metallic particles (Cu, Ag or Au) previously deposited in controlled conditions via physical vapor deposition. Thus, for each prepared polymer–metallic hybrid, the surface morphology, particle size distribution, and percentage of organic material, silicon and metal were studied using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. The results show that the hybrids are formed probably via electrostatic interaction between the carboxylate anions of the PAIs and nanoparticle cations. This bridging ligand was visualized using Raman spectroscopy and corroborated with X‐ray diffraction. Optical studies and resistivity measurements (conductivity) of each hybrid were developed using UV‐visible and the four‐point probe method, respectively. X‐ray photoelectron spectroscopy was used to study the oxidation states of the metallic particles at surface level. Thus, a simple and spontaneous protocol is proposed for the preparation of metallic particles stabilized in situ by an oligomer, a procedure that takes place from seconds to a few minutes. Finally, particle diameters were measured using atomic force microscopy in order to study possible agglomeration of the metallic particles with time. © 2017 Society of Chemical Industry     

Preparation of inner asymmetric composite microspheres

Novel inner asymmetric composite microspheres were prepared by encapsulating surface‐modified magnetic particles via mini‐emulsion polymerization. Most of the surface‐modified magnetic particles encapsulated into the polymer matrix aggregate in one side of each microsphere, while only a few particles randomly disperse in the remaining part. The magnetic content of these novel asymmetric composite microspheres is 46.7% and the saturation magnetization is 23.8 emu g^?1. Copyright © 2012 Society of Chemical Industry     

On the structural and optical properties of gold–polyaniline nanocomposite synthesized via a novel route

Gold nanoparticle embedded polyaniline (PANI) was synthesized by in situ oxidative polymerization of monomer aniline. X‐ray diffraction and Fourier transform IR techniques were used to establish the structure of the gold–PANI composite. UV–visible absorption studies have shown that, along with the normal absorption peak of polyaniline, the composite has an absorption peak characterized by surface plasmon resonance. The presence of surface plasmon resonance is a signature of the nano size of the gold particles embedded in the PANI. Energy‐dispersive X‐ray spectroscopy (EDS) has revealed the elemental composition of the composite sample quantitatively. Raman spectroscopy studies have strengthened the presence of plasmon resonance. Single‐beam Z‐scan results confirm the third‐order optical nonlinearity associated with the nanocomposite. The present investigations show that gold nanoparticle embedded PANI composite can be of potential application in the fields of both linear and nonlinear optics. Copyright © 2012 Society of Chemical Industry     

Enhanced dielectric properties of poly(vinylidene fluoride)–surface functionalized BiFeO3 composites using sodium dodecyl sulfate as a modulating agent for device applications

In this work, we prepared a series of poly(vinylidene fluoride) (PVDF)–surface functionalized BiFeO₃ (h‐BFO)–Sodium dodecyl sulfate (SDS) composite films by solvent casting method to investigate the effect of SDS in the composites. The X‐ray diffraction confirmed that the structure of h‐BFO significantly changed in the PVDF‐(h‐BFO)‐SDS composite in comparison with the rhombohedral structure of pure BiFeO₃. The microscopic study illustrated that the composite with a higher percentage of SDS content facilitated the dispersion as well as proper distribution of ceramic particles in the polymer matrix. The presence of different functionalities of respective polymer and the modified fillers was confirmed by FTIR Spectrophotometer. The dielectric and electrical study done by Impedance Analyzer revealed that the SDS treated surface functionalized composites showed relatively higher dielectric properties than that of two phase composites and pure polymer. Finally, the ferroelectric properties of the composite films done by P‐E loop tracer revealed that the SDS‐treated composites showed an enhanced remanent polarization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45040.     

Vertically aligned carbon nanotube‐based composite: Elaboration and monitoring of the nanotubes alignment

We present the different elaboration steps of a composite formed of carbon nanotubes (CNT) carpet embedded in an epoxy polymer. Detailed characterization at each step of the elaboration process is performed. The good alignment of CNT in as‐grown carpets is kept all along the elaboration process of the composite, as it is measured at both macro and microscopic scales by X‐ray scattering. We also ensured by X‐ray fluorescence measurements that the iron‐based catalyst particles used for the synthesis were removed from the carpet after a high temperature post‐annealing treatment. These measurements give valuable information for further applications involving unidirectional nanotube composites and membranes, where CNT alignment is a key parameter. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39730.     

Processing and properties of nano‐ and macro‐hydroxyapatite/poly(ethylene‐co‐acrylic acid) composites

Hydroxyapatite (HAp)/poly(ethylene‐co‐acrylic acid) composites have been synthesized by a solution‐based method, using nanosized (n‐HAp) and coarse hydroxyapatite (c‐HAp) particles, respectively. X‐ray diffraction study has indicated the development of compressive and tensile stresses in composites because of the thermal expansion mismatch between the particles and polymer matrix. Fourier transform infrared absorption spectra and thermal analysis have showed the presence of strong interfacial bonding between the particles and polymer. The surface roughness and the homogeneous dispersion of HAp particles in the polymer matrix have been observed by scanning electron microscopy. A comparison in mechanical properties between composites prepared with n‐HAp and c‐HAp particles, respectively, has been studied. Nanosized particles contribute excellent improvement of mechanical properties of the composites rather than the coarse particles. The uniform dispersion of HAp particles, followed by the improvement in mechanical properties of the composite, provides a means of preparing HAp/polymer composites for low load‐bearing implant applications. POLYM. COMPOS., 27:633–641, 2006. © 2006 Society of Plastics Engineers     

α‐Amylase immobilized by Fe3O4/poly(styrene‐co‐maleic anhydride) magnetic composite microspheres: Preparation and characterization

Fe₃O₄/poly(styrene‐co‐maleic anhydride) core–shell composite microspheres, suitable for binding enzymes, were prepared using magnetite particles as seeds by copolymerization of styrene and maleic anhydride. The magnetite particles were encapsulated by polyethylene glycol, which improved the affinity between the magnetite particles and the monomers, thus showing that the size of the microspheres, the amount of the surface anhydrides, and the magnetite content in the composite are highly dependent on magnetite particles, comonomer ratio, and dispersion medium used in the polymerization. The composite microspheres, having 0.08–0.8 μm diameter and containing 100–800 μg magnetite/g microspheres and 0–18 mmol surface‐anhydride groups/g microsphere, were obtained. Free α‐amylase was immobilized on the microspheres containing reactive surface‐anhydride groups by covalent binding. The effects of immobilization on the properties of the immobilized α‐amylase [magnetic immobilized enzyme (MIE)] were studied. The activity of MIE and protein binding capacity reached 113,800 U and 544.3 mg/g dry microspheres, respectively. The activity recovery was 47.2%. The MIE had higher optimum temperature and pH compared with those of free α‐amylase and showed excellent thermal, storage, pH, and operational stability. Furthermore, it can be easily separated in a magnetic field and reused repeatedly. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 328–335, 2005     

Study on the polymerization of ϵ‐caprolactam in the interlamellar spaces of [TEACOOH]–montmorillonite intercalations complex and its characterization

The polymerization of ?‐caprolactam between the interlamellar spaces of the [TEACOOH]–montmorillonite intercalations complex was attempted using Na–montmorillonite and 10‐carboxy‐n‐decyltriethylammonium bromide to achieve [TEACOOH]–polycaprolactam–montmorillonite, in which montmorillonite (inorganic polymer) is chemically bonded with the polycaprolactam (organic polymer). The results of X‐ray and IR analysis for the samples obtained after polymerization showed that the polymerization reaction has been successfully accomplished. For the purpose of studying the polymeric reaction product more precisely, we have isolated the polymerized product from the silicate layers and analyzed it with X‐ray diffractometer and IR spectrometer. Comparison of the results of X‐ray and IR analysis between the isolated polymer and the polymer that was synthesized by the reaction of ?‐caprolactam only with the organic cation without montmorillonite showed that both obtained polymers are the same compounds. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1904–1910, 2003     

Preparation and electrorheological characterization of suspensions of poly(urethane acrylate)/clay nanocomposite particles

Micron‐sized poly(urethane acrylate) (PUA)/clay nanocomposite particles were synthesized by suspension polymerization. UA containing a poly(ethylene oxide) group in the main chain was first inserted into the silicate layers of montmorillonite clay through mixing the UA with the clay. Then, ethylene glycol dimethacrylate and an oil‐soluble initiator were added into this UA/clay mixture, followed by the emulsification of the monomer mixture in an aqueous solution of polymeric stabilizer. Suspension polymerization was carried out at 60°C for 12 h to obtain the PUA/clay composite particles. The incorporation of clay into the polymer phase was verified by FTIR spectroscopy, and the intercalation structure of the clay composite was confirmed by X‐ray diffraction analysis. Other characterizations including thermal analysis, morphological observation, and dielectric analysis were also performed. After suspensions of bare PUA and PUA/clay nanocomposite particles in silicone oil were prepared, their electrorheological properties were measured under various electric fields and compared. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 458–464, 2003