Novel polymer composites based on a mixture of preformed nanosilica‐filled poly(methyl methacrylate) particles and a diepoxy/diamine thermoset system

In this work, a new material based on an epoxy thermoset modified with a thermoplastic filled with silica nanoparticles was investigated. When thermoplastic particles are filled with nanoparticles with unique properties such as high efficiency for absorbing ultraviolet light, electric or magnetic shielding, high electrical conductivity, and high dielectric constants, more than an enhancement of the mechanical properties is expected to be achieved for modified epoxy‐based thermosets. Particles of poly(methyl methacrylate) (PMMA) filled with silica nanoparticles were used to modify a thermoset based on a full reaction between diglycidyl ether of bisphenol A and 3‐(aminomethyl)benzylamine. When the preformed thermoplastic particles were mixed with the reactive constituents of the epoxy system under certain curing conditions in which total miscibility was avoided, uniform particle dispersions could be obtained. The relationships between the composition, morphology (nanoscale and microscale), glass‐transition temperature, mechanical properties, and fracture toughness were considered. Four main results were obtained for consideration of the potential of silica‐filled PMMA as an important modifier of brittle epoxy thermoset systems: (1) a good dispersion of the silica nanoparticles in the PMMA domains, (2) a good dispersion of the silica‐filled PMMA microparticles in the epoxy matrix, (3) the possibility of partial dissolution of the PMMA‐rich domains into the epoxy system, and (4) a slight increase in properties such as the hardness, indentation modulus, and fracture toughness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Organic base‐catalyzed sol–gel route to prepare PMMA–silica hybrid materials

A series of sol–gel‐derived organic–inorganic hybrid materials that comprise organic poly(methyl methacrylate) (PMMA) and inorganic silica (SiO₂) was successfully prepared using aniline as an organic base catalyst to catalyze the sol–gel reactions of tetraethylorthosilicate (TEOS). Aniline was adopted not only as a catalyst but also as a dispersing agent during the preparation of the hybrid materials. The as‐prepared hybrid materials were then characterized using transmission electron microscopy, SEM/energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy. The characteristic temperatures (including T_d and T_g) of the hybrid materials slightly exceeded those of neat PMMA, as revealed from thermogravimetric analysis and differential scanning calorimetry evaluations. Studies of the protection against corrosion demonstrated that the hybrid coatings all improved the protection performance on cold‐rolled steel coupons relative to that of neat PMMA coatings, according to measurements of electrochemical corrosion parameters. Additionally, incorporating silica particles into the polymer may effectively reduce the gas permeability of the polymer membrane. Reducing the size of silica particles (at the same silica feeding) further improved the gas barrier property. Optical clarity studies indicated that introducing silica particles into the PMMA matrix may slightly reduce the optical clarity of the films/membranes, as determined by UV‐visible transmission spectroscopy. The contact angle of H₂O of the hybrid films increased with the amount of aniline. Copyright © 2006 Society of Chemical Industry Society of Chemical Industry     

Preparation and characterization of hybrid organic–inorganic epoxide‐based films and coatings prepared by the sol–gel process

Hybrid organic–inorganic coatings and free‐standing films were prepared and characterized. The hybrids were prepared from [3‐(glycidyloxy)propyl]trimethoxysilane, diethoxy[3‐(glycidyloxy)propyl]methylsilane, poly(oxypropylene)s of different molecular weights end‐capped with primary amino groups (Jeffamines D230, D400, and T403), and colloidal silica particles with hydrochloric acid as a catalyst for the sol–gel process and water/propan‐2‐ol mixtures as solvents. The structure evolution during the network formation was followed by NMR spectroscopy and small‐angle X‐ray scattering; the surface morphology was tested by atomic force microscopy. The influence of the reaction conditions (the organosilicon precursor, oligomeric amine, ratio of functional groups, and method of preparation) on the network buildup and product properties was studied and examined. The mechanical testing, based on stress–strain experiments, in combination with dynamic mechanical thermal analysis served as an effective instrument for the optimization of the reaction conditions for the preparation of products with desired properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 937–950, 2004     

Synthesis of well‐defined poly(methyl methacrylate) nanoparticles by reverse atom transfer radical polymerization in a microemulsion

Well‐defined poly(methyl methacrylate) (PMMA) with an α‐isobutyronitrile group and an ω‐bromine atom as the end groups was synthesized by the microemulsion polymerization of methyl methacrylate (MMA) at 70°C with a 2,2′‐azobisisobutyronitrile/CuBr₂/2,2′‐bipyridine system. The conversion of the polymerization reached 81.9%. The viscosity‐average molecular weight of PMMA was high (380,000), and the polydispersity index was 1.58. The polymerization of MMA exhibited some controlled radical polymerization characteristics. The mechanism of controlled polymerization was studied. The presence of hydrogen and bromine atoms as end groups of the obtained PMMA was determined by ¹H‐NMR spectroscopy. The shape and size of the final polymer particles were analyzed by scanning probe microscopy, and the diameters of the obtained particles were usually in the range of 60–100 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3670–3676, 2006     

Fine polystyrene latexes with reactive poly(ethylene oxide) –poly(propylene oxide)–poly(ethylene oxide) triblock macrosurfactants in modified miniemulsion polymerization

Polystyrene latexes were produced via a newly accessible miniemulsion polymerization where reactive poly(ethylene oxide)–poly(propylene oxide) –poly(ethylene oxide) triblock macrosurfactants were used to impart the interfacial activity during the emulsification and the reactivity in the polymerization. Through atomic force microscopy studies, it was found that the polystyrene latexes produced were extremely small to about 50 nm in a proper experimental condition, and covered richly with poly(ethylene oxide) groups. The polystyrene latexes were expected to have great applicability in the production of structured latex films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 328–332, 2002     

Preparation of titanium dioxide/polyacrylate nanocomposites by sol–gel process in reverse micelles and in situ photopolymerization

UV‐curable, transparent acrylic resin/titania organic–inorganic hybrid films were prepared by controlled hydrolysis of titanium tetrabutoxide in Span‐85/Tween 80 reverse micelles and the subsequent in situ photopolymerization of the acrylic monomers. UV–vis spectra and atomic force microscopy (AFM) indicated the presence of a nanoscale hybrid composition. The onset of absorption (λ_onset) of titania in the hybrids appeared between 363.4 and 383.5 nm, which exhibited blue shifts relative to that of bulk anatase (λ_onset = 385 nm). The titania content increased rapidly at higher temperature and higher TTB content, whereas it increased slowly with longer post‐thermal treatment times. The refractive index and UV shielding properties of the organic polymer were obviously improved with increasing titania content. AFM images showed the inorganic domains (mean size 25.3–28.8 nm) were uniformly dispersed in the polymeric networks. The roughness parameters of the hybrid material were: toughness, 1.5–2.3 nm; root mean square roughness, 4.5–4.6 nm; and peak and valley distance, 9.7–19.4 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5105–5112, 2006     

Synthesis and characterization of temperature‐responsive poly(vinyl alcohol)‐based copolymers

A poly(vinyl alcohol) (PVA)/sodium acrylate (AANa) copolymer was synthesized to improve the water solubility of PVA at the ambient temperature. Furthermore, a series of temperature‐responsive acetalyzed poly(vinyl alcohol) (APVA)‐co‐AANa samples of various chain lengths, degrees of acetalysis (DAs), and comonomer contents were prepared via an acid‐catalysis process. Fourier transform infrared and ¹H‐NMR techniques were used to analyze the compositions of the copolymers. The measurement of the turbidity change for APVA‐co‐AANa aqueous solutions at different temperatures revealed that the lower critical solution temperature (LCST) of the copolymers could be tailored through the control of the molecular weight of the starting PVA‐co‐AANa, DA, and comonomer ratios. Lower LCSTs were observed for APVA‐co‐AANa with a longer chain length, a higher DA, and fewer acrylic acid segments. In addition, the LCSTs of the APVA‐co‐AANa aqueous solutions appeared to be salt‐sensitive. The LCSTs decreased as the concentration of NaCl increased. Moreover, atomic force microscopy images of APVA‐co‐AANa around the LCST also proved the temperature sensitivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphology of poly(styrene‐block‐dimethylsiloxane) copolymer films

The morphologies of poly(styrene‐block‐di‐methylsiloxane) (PS‐b‐PDMS) copolymer thin films were analyzed via atomic force microscopy and transition electron microscopy (TEM). The asymmetric copolymer thin films spin‐cast from toluene onto mica presented meshlike structures, which were different from the spherical structures from TEM measurements. The annealing temperature affected the surface morphology of the PS‐b‐PDMS copolymer thin films; the polydimethylsiloxane (PDMS) phases at the surface were increased when the annealing temperature was higher than the PDMS glass‐transition temperature. The morphologies of the PS‐b‐PDMS copolymer thin films were different from solvent to solvent; for thin films spin‐cast from toluene, the polystyrene (PS) phase appeared as pits in the PDMS matrix, whereas the thin films spin‐cast from cyclohexane solutions exhibited an islandlike structure and small, separated PS phases as protrusions over the macroscopically flat surface. The microphase structure of the PS‐b‐PDMS copolymer thin films was also strongly influenced by the different substrates; for an asymmetric block copolymer thin film, the PDMS and PS phases on a silicon substrate presented a lamellar structure parallel to the surface at intervals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1010–1018, 2007     

Phase structural analyses of polyethylene extrusion coatings on high‐density papers. I. Monoclinic crystallinity

In the present work the morphology of high‐density polyethylene (HDPE) extrusion coating layer on high‐density paper (HDP) has been investigated. An uneven layer with a high content of crystallinity against the paper surface was discovered. The methods applied were solid‐state ¹³C NMR Spectroscopy and Atomic Force Microscopy. The highly crystalline layer was found to be mainly monoclinic crystallinity. The formation of the monoclinic crystallites was probably initiated by orientation of the polyethylene molecules by drawing, adhesion to the fibrous paper surface, and pressure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 218–225, 2004     

Thermal and optical properties of PMMA–titania hybrid materials prepared by sol‐gel approach with HEMA as coupling agent

A series of sol‐gel derived organic–inorganic hybrid materials consisting of organic poly(methyl methacrylate) (PMMA) and inorganic titania (TiO₂) were successfully synthesized by using 2‐hydroxyethyl methacrylate (HEMA) as coupling agent. In this work, HEMA is first copolymerized with methyl methacrylate monomer at specific feeding ratios by using benzoyl peroxide (BPO) as initiator. Subsequently, the as‐prepared copolymer (i.e., sol‐gel precursor) is then cohydrolyzed with various contents of titanium butoxide to afford chemical bondings to the forming titania networks to give a series of hybrid materials. Transparent organic–inorganic hybrid materials with different contents of titania are always achieved. Effects of the material composition on the thermal stability, optical properties, and morphology of neat copolymer and a series of hybrid materials, in the form of both coating and free‐standing film, are also studied by differential scanning calorimetry, thermogravimetric analysis, UV–Vis transmission spectra, refractometer, and atomic force microscopy, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 400–405, 2004     

Optimization of polyethylene/binder/polyamide extrusion blow‐molded films. III. Slippability improvement with fatty acid amides

The slippability of packaging films has to be controlled to facilitate confectionary operations and guarantee an easy opening for filling. In the case of single‐layer polyethylene (PE) films, the addition of slip agents made of fatty acid amides such as erucamide or oleamide usually allows the tailoring of the coefficient of friction (COF) in the film to match industrial targets, which depend on the final application. The coupling of Fourier transform infrared spectroscopy and atomic force microscopy analysis showed that this method has a limited efficiency and may even be detrimental in the case of multilayer PE + ethylene vinyl acetate (EVA)/maleic anhydride grafted polyethylene (PEgMAH) + EVA/polyamide films. The reason is that the migration of the slip additives toward the outermost surface of the PE layer, which leads to a reduction in the COF, are strongly affected by both the existence of the adjacent layers and the presence of EVA in the PE and PEgMAH layers. Nevertheless, a proper knowledge of the effect of this perturbation allows one to reach a slippability level that is required for some confectionary operations and/or for an easy opening for filling without the degradation of the heat sealability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Formation and structure of polyacrylamide–silica nanocomposites by sol–gel process

The formation of nanocomposites by the sol–gel reaction of tetraethoxysilane (TEOS) in polyacrylamide (PAAm) is studied. The nanocomposites are prepared in aqueous solution. Fourier transform IR spectroscopy shows that substantial hydrogen bonding occurs in the nanocomposites. The fracture surfaces of the nanocomposites are observed by atomic force microscopy (AFM) as a function of the TEOS content. The AFM images reveal that the PAAm–silica nanocomposite exhibits particle–matrix morphology. It is also found that aggregate formation is more dominant than the particle growth with the TEOS contents. The solution of composite precursor is also applied to spin coating. Furthermore, during the calcination there is an observable change in the silica networks, and then a microinterconnected structure is generated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1817–1823, 2002     

Bone cell viability on collagen immobilized poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) membrane: Effect of surface chemistry

The effect of surface chemistry on proliferation and morphology of bone cells cultured on surface modified poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) (PHBV) and untreated PHBV was evaluated. The surface of cast PHBV film was physically and chemically immobilized with collagen. For preparing chemically immobilized collagen surface, PHBV film was ozone treated followed by grafting of PMAA chains and the immobilization of collagen. The surface roughness and hydrophilicity of PHBV film were determined by atomic force microscopy (AFM) and contact angle measurements, respectively. It was found that the duration of ozone exposure and monomer concentration used for grafting PMMA chains influenced the amount of collagen immobilized. The cell proliferation on PHBV surfaces with chemically and physically immobilized collagen was compared with untreated PHBV using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay. The bone cell activity on chemically and physically immobilized collagen PHBV films was found to be 246 and 107% for UMR‐106 and 68 and 9% for MC3T3 cell lines, respectively. Although the results are very preliminary, the chemically grafted collagen on PHBV surface provided a favorable matrix for cell proliferation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2445–2453, 2004     

Organic–inorganic composite materials from acrylonitrile–butadiene–styrene copolymers (ABS) and silica through an in situ sol‐gel process

Nonbonded and chemically bonded organic–inorganic composite materials, ABS/SiO₂ and ABS Si(OCH₃)₃/SiO₂, were prepared by the sol‐gel processing of tetraethoxysilane (TEOS) in the presence of ABS and trimethoxysilyl functionalized ABS, ABS Si(OCH₃)₃, under the catalization of NH₄F. The ABS Si(OCH₃)₃ was obtained by oxidizing the cyano group in ABS with hydrogen peroxide, then subsequently underwent ring‐opening reaction with 3‐glycidoxypropyltrimethoxysilane (GPTS). The ABS Si(OCH₃)₃/TEOS sol‐gel liquid solution system, in which the ABS chains formed the covalent bonds with silica network and helped fix the polymer chains in the silica network, had a shorter gelation time than that of the ABS/TEOS system, which linked ABS chains to the silica network only by hydrogen bonding the cyano groups in ABS to the silanol groups. The morphology and properties of composite were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), tensile tests, and thermogravimetry. It was found that the composite prepared from ABS Si(OCH₃)₃ had higher tensile strength, glass transition point (T_g), thermal stability, and more homogeneous morphology because of the existence of the covalent bond between ABS chains and silica network that increased the compatibility between the organic and inorganic phases. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 275–283, 2000     

Characterization of lignocellulosic–poly(lactic acid) reinforced composites

The effects of adding poly(lactic acid) (PLA) to the physical strength of paper test sheets prepared from three unbleached loblolly pine kraft pulps with different amounts of lignin and an aspen bleached chemothermomechanical pulp were studied. The physical strength studies demonstrated that relatively low levels of PLA addition (0.5–4.0%) could dramatically improve the tensile and burst strength properties as a function of the amount of PLA added. Hot pressing the test sheets was shown to be an important treatment for enhancing the strength properties. An analysis of untreated and PLA‐treated hot‐pressed test sheets by atomic force microscopy indicated that the addition of PLA markedly altered the surface properties of the sheets. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1346–1349, 2006     

Synthesis and characterization of poly(methyl acrylate‐co‐itaconic anhydride)/TiO2 hybrid materials via sol–gel process

In the presence of 3‐aminopropyltriethoxysilane (APTES), the transparent and yellowish poly(methyl acrylate‐co‐itaconic anhydride)/TiO₂ [P(MA‐co‐Itn)/TiO₂] hybrid materials were prepared from the copolymer of methyl acrylate and itaconic anhydride [P(MA‐co‐Itn)] and tetrabutyl titanate (TBT) via a sol–gel process. At first, the triethoxysilane groups were incorporated into the copolymer P(MA‐co‐Itn) as pendant side chains by the aminolytic reaction between the itaconic anhydride units of the copolymer and the amino group of 3‐aminopropyltriethoxysilane (APTES), and then the covalent bonds between the organic and inorganic phases were introduced by the hydrolysis and polycondensation of the triethoxysilane groups on the copolymer with TBT. FTIR analysis proved the existence of the covalent bonds. The influences of APTES on glass transition and morphology of the hybrid materials was studied by differential scanning calorimetry, scanning electron microscope, and atomic force microscope. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1763–1768, 2000     

Synthesis and thermal properties of poly(methyl methacrylate)‐poly(L‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer

Poly(methyl methacrylate)‐poly(L ‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer was prepared using atom transfer radical polymerization (ATRP). The structure and properties of the copolymer were analyzed using infrared spectroscopy, gel permeation chromatography, nuclear magnetic resonance (¹H‐NMR, ¹³C‐NMR), thermogravimetry, and differential scanning calorimetry. The kinetic plot for the ATRP of methyl methacrylate using poly(L ‐lactic acid) (PLLA) as the initiator shows that the reaction time increases linearly with ln[M]₀/[M]. The results indicate that it is possible to achieve grafted chains with well‐defined molecular weights, and block copolymers with narrowed molecular weight distributions. The thermal stability of PLLA is improved by copolymerization. A new wash‐extraction method for removing copper from the ATRP has also exhibits satisfactory results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of plasticizers in poly(vinyl alcohol)‐based hybrid solid polymer electrolytes

Hybrid solid polymer electrolyte films consisting of poly(vinyl alcohol) (PVA), poly(methyl methacrylate) (PMMA), LiBF₄, and ethylene carbonate/propylene carbonate (EC/PC) were prepared with a solvent‐casting technique. The complexation was investigated with Fourier transform infrared and X‐ray diffraction. The ionic conductivities of the electrolyte films were determined with an alternating‐current impedance technique for various temperatures in the range of 302–373 K. The maximum conductivity value, 1.2886 × 10^?3 S/cm, was observed for a PVA–PMMA–LiBF₄–EC complex. Thermogravimetry/differential thermal analysis was performed to ascertain the thermal stability of the electrolyte with the maximum conductivity value. For an examination of the cyclic and reversible performance of the film, a cyclic voltammetry study was carried out. The surface morphology of the EC‐and PC‐based electrolytes was examined with scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2794–2800, 2003     

Preparation of silica‐filled poly(2‐hydroxymethyl methacrylate) nanocomposites cured by photoirradiation during the sol–gel process

The sol–gel process was used to prepare a photosensitive inorganic–organic composite, silica/poly(2‐hydroxymethyl methacrylate). Its nanoscale morphology was observed with field emission scanning electron microscopy at high magnifications (e.g., 160,000×). The size of the particles in the nanocomposite synthesized under various preparation conditions fell in the range of 20–50 nm. The effects of the pH, reactant composition, and solvent content in the reaction mixture on the thermal and mechanical properties of the nanocomposite were studied with thermogravimetric analysis, dynamic mechanical analysis, and thermomechanical analysis. The thermal stability of the synthesized nanocomposite could generally be improved by an increase in the molar ratio of the inorganic component, a reduction in the reaction pH, or an increase in the solvent content. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1927–1935, 2004     

Nanostructured polymer blends based on polystyrene‐b‐polybutadiene‐b‐poly(methyl methacrylate) triblock copolymers modified with polystyrene and/or poly(methyl methacrylate) homopolymers

Morphologies of polymer blends based on polystyrene‐b‐ polybutadiene‐b ‐poly(methyl methacrylate) (SBM) triblock copolymer were predicted, adopting the phase diagram proposed by Stadler and co‐workers for neat SBM block copolymer, and were experimentally proved using atomic force microscopy. All investigated polymer blends based on SBM triblock copolymer modified with polystyrene (PS) and/or poly(methyl methacrylate) (PMMA) homopolymers showed the expected nanostructures. For polymer blends of symmetric SBM‐1 triblock copolymer with PS homopolymer, the cylinders in cylinders core?shell morphology and the perforated lamellae morphology were obtained. Moreover, modifying the same SBM‐1 triblock copolymer with both PS and PMMA homopolymers the cylinders at cylinders morphology was reached. The predictions for morphologies of blends based on asymmetric SBM‐2 triblock copolymer were also confirmed experimentally, visualizing a spheres over spheres structure. This work presents an easy way of using PS and/or PMMA homopolymers for preparing nanostructured polymer blends based on SBM triblock copolymers with desired morphologies, similar to those of neat SBM block copolymers. © 2017 Society of Chemical Industry