Synthesis of TiO(2)-PMMA nanocomposite: using methacrylic acid as a coupling agent

Enhanced actuated strain of titanium dioxide/nitrile-butadiene rubber composite by the biomimetic method

An excellent dielectric elastomer was fabricated by incorporating titanium dioxide nano-particles into nitrile-butadiene rubber by a simple dopamine biomimetic method.

Thermal, mechanical and optical transport properties of nanocomposite materials based on triethoxysilane-terminated polyimide and TiO2 nanoparticles

Novel polyimide/TiO₂ nanocomposites with good mechanical, optical and thermal properties were prepared by the incorporation of TiO₂ nanoparticles into silane terminated polyimide.

Investigation of the antibacterial effects of silver-modified TiO2 and ZnO plasmonic photocatalysts embedded in polymer thin films

Nanosilver-modified TiO2 and ZnO photocatalysts were studied against methicillin-resistant Staphylococcus aureus on the surface and against naturally occurring airborne microorganisms. The photocatalysts/polymer nanohybrid films were prepared by spray coating technique on the surface of glass plates and on the inner surface of the reactive light source. The photoreactive surfaces were activated with visible light emitting LED light at λ = 405 nm. The optical properties of the prepared photocatalyst/polymer nanohybrid films were characterized by diffuse reflectance measurements. The photocatalytic properties were verified with the degradation of ethanol by gas chromatography measurements. The destruction of the bacterial cell wall component was examined with transmission electron microscope. The antibacterial effect of the photocatalyst/polymer nanohybrid films was tested with different methods and with the associated standard ISO 27447:2009. With the photoreactive coatings, an extensive disinfectant film was developed and successfully prepared. The cell wall component of S. aureus was degraded after 1 h of illumination. The antibacterial effect of the nanohybrid films has been proven by measuring the decrease of the number of methicillin-resistant S. aureus on the surface and in the air as the function of illumination time. The photocatalyst/polymer nanohybrid films could inactivate 99.9 % of the investigated bacteria on different thin films after 2 h of illumination with visible light source. The reactive light source with the inner-coated photocatalyst could kill 96 % of naturally occurring airborne microorganisms after 48 h of visible light illumination in indoor air sample. The TEM results and the microbiological measurements were completed with toxicity tests carried out with Vibrio fischeri bioluminescence bacterium.

Resin composites reinforced by nanoscaled fibers or tubes for dental regeneration

It has been stated clearly that nanofillers could make an enhancement on the mechanical performances of dental composites. In order to address current shortage of traditional dental composites, fillers in forms of nanofibers or nanotubes are broadly regarded as ideal candidates to greatly increase mechanical performances of dental composites with low content of fillers. In this review, the efforts using nanofibers and nanotubes to reinforce mechanical performances of dental composites, including polymeric nanofibers, metallic nanofibers or nanotubes, and inorganic nanofibers or nanotubes, as well as their researches related, are demonstrated in sequence. The first purpose of current paper was to confirm the enhancement of nanofibers or nanotubes' reinforcement on the mechanical performances of dental restorative composite. The second purpose was to make a general description about the reinforcement mechanism of nanofibers and nanotubes, especially, the impact of formation of interphase boundary interaction and nanofibers themselves on the advanced mechanical behaviors of the dental composites. By means of the formation of interface interaction and poststretching nanofibers, reinforced effect of dental composites by sorts of nanofibers/nanotubes has been successfully obtained.

Laser-induced disaggregation of TiO₂ nanofillers for uniform nanocomposites

Exploiting the intrinsic photosensitivity of TiO₂ nanoparticles, we demonstrated how ultraviolet (UV) pulsed laser irradiation of acrylate polymer nanocomposite solutions can separate the initial clusters of these colloidal semiconductor nanorods into clearly distinct units. From the irradiated solutions, optically clear nanocomposite films are obtained which exhibit enhanced optical properties with respect to the nanocomposites obtained without previous UV treatment.

Synthesis and characterization of novel TiO2-poly(propylene fumarate) nanocomposites for bone cementation

A novel composite material made from poly(propylene fumarate) (PPF) and titania nanofibers has been synthesized for potential use as an orthopaedic biomaterial with TiO₂ nanofibers chemically linked to the PPF matrix as a reinforcing phase to enhance its mechanical properties.

Manufacture and microstructure characterization of optically active poly(esterimide)/TiO2 bionanocomposites derived from natural amino acid–based diacid

Bio-based nanocomposites were successfully synthesized by incorporation of bioactive titanium dioxide (TiO2) nanoparticles in biodegradable poly(esterimide) (PEI) matrix via ultrasonic irradiation. The optically active PEI was prepared by direct polycondensation of amino acid–based diacid (4) with 4,4′-thiobis(2-tert-butyl-5-methylphenol) (5) in the presence of tosyl chloride, pyridine, and N,N-dimethylformamide. The obtained bionanocomposites (BNCs) were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and thermogravimetric analysis. FE-SEM and TEM images of the nanocomposites revealed homogeneity and uniformity in the distribution of TiO2 nanoparticles in PEI matrix.

Nano-TiO2/polyurethane composites for antibacterial and self-cleaning coatings

Grafting from polymerization was used to synthesize nano-titania/polyurethane (nTiO(2)/polyurethane) composite coatings, where nTiO(2) was chemically attached to the backbone of the polyurethane polymer matrix with a bifunctional monomer, 2,2-bis(hydroxymethyl) propionic acid (DMPA). This bifunctional monomer can coordinate to nTiO(2) through an available -COOH group, with two available hydroxyl groups that can react with diisocyanate terminated pre-polyurethane through step-growth polymerization. The coordination reaction was monitored by FTIR and TGA, with the coordination reaction found to follow first order kinetics. After step-growth polymerization, the polyurethane nanocomposites were found to be stable on standing with excellent distribution of Ti in the polymer matrix without any significant agglomeration compared to simple physical mixtures of nTiO(2) in the polyurethane coatings. The functionalized nTiO(2)-polyurethane composite coatings showed excellent antibacterial activity against gram-negative bacteria Escherichia coli; 99% of E. coli were killed within less than one hour under solar irradiation. Self-cleaning was also demonstrated using stearic acid as a model for 'dirt'.

Synthesis and biological evaluation of PMMA/MMT nanocomposite as denture base material

Inorganic-polymer nanocomposites are of significant interest for emerging materials due to their improved properties and unique combination of properties. Poly (methylmethacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by in situ suspension polymerization with dodecylamine used as MMT-modifier. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the structures of the nanocomposites. Cytotoxicity test, hemolysis test, acute systemic toxicity test, oral mucous membrane irritation test, guinea-pig maximization test and mouse bone-marrow micronucleus test were used to evaluate the biocompatibility of PMMA/MMT nanocomposites. The results indicated that an exfoliated nanocomposite was achieved, and the resulting nanocomposites exhibited excellent biocompatibility as denture base material and had potential application in dental materials.

Biological and mechanical properties of novel composites based on supramolecular polycaprolactone and functionalized hydroxyapatite

Supramolecular polymers based on quadruple hydrogen-bonding ureido-pyrimidinone (UPy) moieties hold promise as dynamic/stimuli-responsive materials in applications such as tissue engineering. Here, a new class of materials is introduced: supramolecular polymer composites. We show that despite the highly ordered structure and tacticity-dependent nature of hydrogen-bonded supramolecular polymers, the bioactivity of these polymers can be tuned through composite preparation with bioceramics. These novel supramolecular composites combine the superior processability of supramolecular polymers with the excellent bioactivity and mechanical characteristics of bioceramics. In particular, the bioactive composites prepared from supramolecular polycaprolactone and UPy-grafted hydroxyapatite (HApUPy) are described that can be easily formed into microporous biomaterials. The compression moduli increased about 40 and 90% upon composite preparation with HAp and HApUPy, respectively, as an indication to improved mechanical properties. These new materials show excellent potential as microporous composite scaffolds for the adhesion and proliferation of rat mesenchymal stem cells (rMSCs) as a first step toward bone regeneration studies; rMSCs proliferate about 2 and 2.7 times faster on the conventional composite with HAp and the supramolecular composite with (HApUPy) than on the neat PCL1250(UPy)(2).

Synthesis and characterization of poly(methyl methacrylate)-based experimental bone cements reinforced with TiO2-SrO nanotubes

In an attempt to overcome existing limitations of experimental bone cements we here demonstrate a simple approach to synthesizing strontium-modified titania nanotubes (n-SrO-TiO(2) tubes) and functionalize them using the bifunctional monomer methacrylic acid. Then, using 'grafting from' polymerization with methyl methacrylate, experimental bone cements were produced with excellent mechanical properties, radiopacity and biocompatibility. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy mapping and backscattered SEM micrographs revealed a uniform distribution of SrO throughout the titanium matrix, with retention of the nanotubular morphology. Nanocomposites were then reinforced with 1, 2, 4 and 6 wt.% of the functionalized metal oxide nanotubes. Under the mixing and dispersion regime employed in this study, 2 wt.% appeared optimal, exhibiting a more uniform dispersion and stronger adhesion of the nanotubes in the poly(methyl methacrylate) matrix, as shown by TEM and SEM. Moreover, this optimum loading provided a significant increase in the fracture toughness (K(IC)) (20%) and flexural strength (40%) in comparison with the control matrix (unfilled) at P<0.05. Examination of the fracture surfaces by SEM showed that toughening was provided by the nanotubes interlocking with the acrylic matrix and crack bridging during fracture. On modifying the n-TiO(2) tubes with strontium oxide the nanocomposites exhibited a similar radiopacity to a commercial bone cement (CMW 1), while exhibiting a significant enhancement of osteoblast cell proliferation (242%) in vitro compared with the control at P<0.05.

Weak polyion multilayer-assisted in situ synthesis as a route toward a plasmonic Ag/TiO2 photocatalyst

Nanocrystalline Ag/TiO(2) composite thin films were synthesized using a two-step synthesis methodology: the in situ precipitation of Ag nanoparticles followed by an in situ sol-gel reaction of titanium iso-propoxide in a weak polyion multilayer (PEM) template formed by the layer-by-layer (LbL) self-assembly of poly(acrylic acid) (PAA) and polyallylamine (PAH). Because the PEM template is assembled from weak polyions, it contains nonionized carboxylic groups that are able to react with the inorganics, resulting in the formation of a homogeneous Ag(x)/TiO(2)-PEM precursor film, where the content of Ag is controlled by repeating the Ag loading cycle. The subsequent annealing of the precursor yields nanostructured Ag(x)/TiO(2) films with thicknesses controlled by the PEM template on the nanometer scale. Transmission electron, field-emission scanning electron, and atomic force microscopy methods were employed to evaluate the morphology and growth characteristics of the metallic and semiconductor nanocrystallites in the Ag(x)/TiO(2) composite thin films. The as-formed Ag(x)/TiO(2) composite thin films exhibited UV-visible photoactivity monitored by the decomposition of methylene blue (MB). In the near-UV range, the expected photocatalytic behavior of TiO(2) is greatly enhanced because it is assisted by the near-field amplitudes of the localized surface plasmon resonance (LSPR) of the Ag nanoparticles in the Ag(x)/TiO(2) films.

Imogolite Reinforced Nanocomposites: Multifaceted Green Materials

This paper presents an overview on recent developments of imogolite reinforced nanocomposites, including fundamental structure, synthesis/purification of imogolite, physicochemical properties of nanocomposites and potential applications in industry. The naturally derived nanotubular material of imogolite represents a distinctive class of nanofiller for industrially significant polymer. The incompatibility between the surface properties of inorganic nanofiller and organic matrix has prompted the need to surface modify the imogolite. Early problems in increasing the binding properties of surface modifier to imogolite have been overcome by using a phosphonic acid group. Different approaches have been used to gain better control over the dispersal of nanofiller and to further improve the physicochemical properties of nanocomposites. Among these, polymer grafting, in situ synthesis of imogolite in polymer matrix, and spin-assembly are some of the promising methods that will be described herein. This imogolite reinforced nanocomposite of enhanced optical and mechanical properties, and with unique biological and electronic properties, is expected to become an important category of hybrid material that shows potential for industrial applications.

Physical and mechanical properties of PMMA bone cement reinforced with nano-sized titania fibers

X-ray contrast medium (BaSO(4) or ZrO(2)) used in commercially available PMMA bone cements imparts a detrimental effect on mechanical properties, particularly on flexural strength and fracture toughness. These lower properties facilitate the chance of implant loosening resulting from cement mantle failure. The present study was performed to examine the mechanical properties of a commercially available cement (CMW1) by introducing novel nanostructured titania fibers (n-TiO(2) fibers) into the cement matrix, with the fibers acting as a reinforcing phase. The hydrophilic nature of the n-TiO(2) fibers was modified by using a bifunctional monomer, methacrylic acid. The n-TiO(2) fiber content of the cement was varied from 0 to 2 wt%. Along with the mechanical properties (fracture toughness (K (IC)), flexural strength (FS), and flexural modulus (FM)) of the reinforced cements the following properties were investigated: complex viscosity-versus-time, maximum polymerization temperature (T (max)), dough time (t (dough)), setting time (t (set)), radiopacity, and in vitro biocompatibility. On the basis of the determined mechanical properties, the optimized composition was found at 1 wt% n-TiO(2) fibers, which provided a significant increase in K (IC) (63%), FS (20%), and FM (22%), while retaining the handling properties and in vitro biocompatibility compared to that exhibited by the control cement (CMW1). Moreover, compared to the control cement, there was no significant change in the radiopacity of any of the reinforced cements at p = 0.05. This study demonstrated a novel pathway to augment the mechanical properties of PMMA-based cement by providing an enhanced interfacial interaction and strong adhesion between the functionalized n-TiO( 2) fibers and PMMA matrix, which enhanced the effective load transfer within the cement.

Composites of plasma surface functionalized barium titanate nanoparticles covalently attached to epoxide matrices: synthesis and evaluation

Inorganic/organic nanocomposites consisting of surface functionalized barium titanate (BTO) nanoparticles covalently bonded to epoxy polymeric matrices are described. A plasma-enhanced CVD process was employed to functionalize the particle surfaces with reactive amine groups. Subsequently, these modified particles were reacted with an epoxide monomer to synthesize the final nanocomposites, containing particle loadings ranging from 1 to 5 weight percent. Control samples, containing unmodified BTO, were also synthesized under identical reaction conditions and particle loading. The resultant nanocomposites were characterized spectroscopically and microscopically, and their physical and thermal properties were evaluated. The results obtained reveal a more uniform distribution of the surface modified BTO in the composites relative to that observed with the unmodified particles. Additionally, the physical and thermal properties of the nanocomposites containing the plasma modified particles were determined to be significantly improved over that of the pure polymer or the composites containing the unmodified particles, for each level of loading employed in this study. In light of these improved properties, it appears that the surface modifications employed significantly improve the interfacial interactions between the inorganic particles and the organic matrices in these nanocomposites.

Influence of the way of synthesis of poly(methyl methacrylate) in the presence of surface modified TiO2 nanoparticles on the properties of obtained nanocomposites

Incorporation of inorganic nanoparticles can significantly affect the properties of the polymer matrix. The properties of polymer nanocomposites depend on the type of incorporated nanoparticles, their size and shape, their concentration, and interactions with the polymer matrix. Homogeneity of polymer nanocomposites is influenced very much by the preparation method. In this study, TiO2 nanoparticles surface modified with 6-palmitate ascorbic acid (6-PAA) were incapsulated in poly(methyl methacrylate) (PMMA) by in situ radical polymerization of methyl methacrylate initiated by 2,2'-azobisisobutyronitrile (AIBN). The surface modification of the TiO2 nanoparticles was achieved by the formation of a charge transfer complex between TiO2 nanoparticles and 6-palmitate ascorbic acid. The radical polymerization of MMA in the presence of TiO2-PAA nanoparticles was conducted in solution (PMMA/TiO2-PAA-R), in bulk (PMMA/TiO2-PAA-M) or in suspension (PMMA/TiO2-PAA-S). The main purpose of this study was to investigate the influence of the preparation method on the molar masses and thermal properties of PMMA/TiO2-PAA nanocomposite. It was obtained that molar masses of PMMA extracted from the composites had smaller values compared to molar masses of pure PMMA synthesized in the same manner, which indicated that TiO2-PAA nanoparticles affected the reaction of termination. Thermal properties were investigated by DSC and TGA. The values of glass transition temperature, Tg, were influenced by the way the radical polymerization was conducted, even in the case of the pure PMMA. The Tg of composite samples was always smaller than the value of the corresponding PMMA sample and the smallest value was obtained for PMMA/TiO2-PAA-M since they contained the largest amount of low molar mass residue. The TGA results showed that thermal and thermooxidative stability of polymer composites obtained in solution and in suspension was better than for the pure PMMA obtained in the same way.

Reinforcement of resin based cement with titania nanotubes

OBJECTIVE

One of the limitations of resin cements and flowable dental composites is their poor mechanical properties such as low flexural strength and fracture resistance under body conditions. The present study was performed to enhance the mechanical properties of commercial acrylic cement (CMW1) by introducing novel nanostructured titania tubes (n-TiO(2) tubes) into the cement matrix, with the tubes acting as a reinforcing phase. The long term objective is to add these fillers as reinforcement to dental resin cements and flowable composites in combination with existing fillers.

METHODS

The surface of the n-TiO(2) tubes was modified using a bi-functional monomer, methacrylic acid. The n-TiO(2) tube content of the cement was varied from 0 to 2 wt.%. The following cement properties were investigated: maximum polymerization temperature (T(max)), dough time (t(dough)), setting time (t(set)), complex viscosity-versus-time, radiopacity, fracture toughness (K(IC)), flexural strength (FS), flexural modulus (FM) and in vitro biocompatibility.

RESULTS

Based on the determined mechanical properties, the optimized composition was found at 1 wt.% n-TiO(2) tubes, which provided a significant increase in K(IC) (73%), FS (42%) and FM (56%). However the rheology, radiopacity and biocompatibility were not different from the control (CMW1).

SIGNIFICANCE

Enhanced interaction and strong adhesion between the functionalized n-TiO(2) tubes and polymer matrix allows external mechanical stress to be more effectively transferred through the filler-matrix interface. This novel filler in conjunction with the existing ones can be used to reinforce orthopedic and dental cements as well as flowable dental composites without altering the rheology, radiopacity and biocompatibility.

A comparison of several nanoscale photocatalysts in the degradation of a common pollutant using LEDs and conventional UV light

A comparative study on the photocatalytic activities of four different catalysts, P-25 TiO(2), TiO(2) nanofibers, tin-doped TiO(2) nanofibers under UV light irradiation at 350 nm, and coumarin (C-343) coated TiO(2) nanofibers at 436 nm light emitting diodes (LED) is reported. Catalysts performance has been compared based on their reflectance spectrum and activity. A common water contaminant 4-chlorophenol was used as a substrate to compare the activity of the different catalysts under both direct and dye sensitized conditions. Results indicated that amongst the four different catalysts the activity of P-25 was the highest. However the activity of C-343 coated TiO(2) nanofibers in the LED (436 nm) based reactor was competitive. Identification of reaction intermediates implied that the reaction pathways under UV (band gap) and visible (dye sensitized) irradiation were different. Nonetheless, ring opening took place in all reactions with both maleic and dihydroxymaleic have been identified as intermediates. The study indicates that ordered arrays of TiO(2) irradiated by panels of arrays of low cost high intensity LEDs might be used for the design of reactors. The near monochromaticity, long life, and operation under direct currents are advantages of using LEDs.