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A multifunctional hybrid curing component (GSD) for epichlorohydrin-modified novolac resin (ENR) was synthesized via grafting poly(amidoamine) (PAMAM)-modified silica nanoparticles (SD) on graphene oxide (GO) using a ring opening reaction. SD and GSD, as two different curing components, were also used in different contents as reinforcing fillers of ENR matrix. Fourier-transform infrared spectroscopy and thermal gravimetric analysis (TGA) results proved amine-decoration of silica nanoparticles and also successful preparation of GSD. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy results were utilized to investigate structure of the SD and GSD multifunctional curing components and also the resulted composites. XRD pattern of GSD shows two peaks at 10.1 and 21.8° which belong to characteristic peaks of GO and silica nanoparticles, respectively, with weak intensities due to grafting of SD on the GO surface. Thermal investigation of the prepared composites by TGA showed that curing ENR with higher contents of GSD was resulted in higher thermal properties. The ENR composite cured with 5 wt% of GSD presented the highest char residue of 20.5% among the other hybrid composites. [ABSTRACT FROM AUTHOR]

Polyurethane/crystalline nanocellulose (PU/CNC) nanocomposites were fabricated through in-situ polymerization by using polydimethylsiloxane (PDMS), methylene diphenyl diisocyanate (MDI), and 1,4-butanediol (BDO) as polyol, aromatic diisocyanate, and chain extender, respectively. CNC content affected the microstructure and thermophysical properties of the nanocomposites. Incorporation of CNCs into PU affected the interactions between soft and hard segments. Although CNCs had slight effect on thermal degradation of nanocomposites, they significantly affected thermophysical properties. For example, CNCs decreased the crystallization of hard segment and glass transition temperatures of hard and soft segments were shifted to higher temperatures. PU showed a relatively high toxicity against human fibroblast cells because of presence of aromatic segments in its structure. Although cytocompatibility was improved by addition of CNCs, PU/CNC nanocomposites showed relatively cytotoxic behavior at higher concentrations. [ABSTRACT FROM AUTHOR]

Optical chemosensors and ionochromic cellulosic papers based on oxazolidine chromophores were developed for selective photosensing of metal ions and information encryption as security tags, respectively. The oxazolidine molecules have been displayed highly intense fluorescent emission and coloration characteristics that are usable in sensing and anticounterfeiting applications. Obtained results indicated that oxazolidine molecules can be used for selective detection of pb2+ (0.01 M), and photosensing of Fe3+, Co2+ and Ag+ metal ion solutions by colorimetric and fluorometric mechanisms with higher intensity and sensitivity. Also, oxazolidine derivatives were coated on cellulosic papers via layer-by-layer method to prepare ionochromic papers. Prepared ionochromic papers were used for printing and handwriting of optical security tags by using of metal ion solutions as a new class of anticounterfeiting inks with dual-mode fluorometric and colorimetric securities. The ionochromic cellulosic papers can be used for photodetection of metal ions in a fast and facile manner that presence of metal ions is detectable by naked eyes. Also, key-lock anticounterfeiting technology based on ionochromic papers and metal ion solution as ink is the most significant strategy for encryption of information to optical tags with higher security. [ABSTRACT FROM AUTHOR]

The poly(amidoamine) (PAMAM) dendrimer-grafted silica nanoparticles were utilized as a curing and composite agent for epoxy-terminated polyurethane (PU). For this purpose, surface-hydroxylated silica nanoparticles (SiH) were modified with (3-aminopropyl)triethoxysilane to obtain the core for PAMAM dendrimer synthesized via consecutive addition of methyl acrylate and ethylenediamine. Effect of different chain extenders, pyromellitic dianhydride (PMDA) and 1,4-butanediol (BD), on thermal characteristics of the composites was also studied in detail. Successful incorporation of PMDA and BD chain extenders and also epoxy groups to the PU backbone was confirmed by proton nuclear magnetic resonance analysis. Chemical modification of silica nanoparticles via PAMAM dendrimer in each of the generation steps was studied using Fourier-transform infrared spectroscopy and also their thermal degradation characteristics. The thermogravimetric analysis results proved that increasing content of the PAMAM-modified silica nanoparticles in combination with incorporation of PMDA as the chain extender resulted in higher thermal stabilities of the PU composites. The cured epoxy-modified PU with PMDA chain extender showed higher char residue compared with the cured epoxy-modified PU with BD chain extender (7.1 against 0.8%). X-ray diffraction analysis confirmed amorphous nature of silica and the PU composites. Scanning and transmission electron microscopies were also used for morphological investigation of the pure and PAMAM-modified silica in addition to the PU composite. [ABSTRACT FROM AUTHOR]

Good resistance to the solvent and excellent adhesion to many substrates are the significant features of polysulfide polymers. They are known to have extensive applications as sealants, adhesives and coatings. In this research, a series of polysulfide polymers of linear organic monomer (ethylene dichloride) and sodium-based aqueous monomers are synthesized using interfacial polymerization and zinc oxide (ZnO) is used as a curing agent. The curing process of the synthesized polymers is studied using a rheometer at 160 °C. The cured and uncured samples are characterized by Fourier-transform infrared, Raman, XRD, DSC, Shore A and tensile tests. XRD results showed that cured samples possessed complete amorphous behavior whereas in the non-cured samples the structure shifts to the amorphous phase by increasing the sulfur content. The study of mechanical properties showed that with increasing sulfur content, the elastic modulus and elongation at break were increased. Furthermore, the glass transition temperature and crosslinking density were increased with increasing sulfur content whereas hardness was decreased. Besides, Thermogravimetric analysis results showed that in the cured samples the thermal stability was increased with increasing sulfur content. Also, all samples were resistant to benzine, gasoline, white spirit, engine oil and brake-fluid. [ABSTRACT FROM AUTHOR]

Among molecular structures, colloidal molecules have attracted the attention of the scientific community because of their distinct geometry (topology, size on a nanometer scale). In this field, dendrimers are an example of colloidal polymeric molecules which have a specific size and are identified and regulated by repeating units as generations. The dendrimers are very similar to the colloidal particles in geometric form and size, which is more evident in the higher generations of the colloidal dendrimers. On the other hand, the unique structural features of these macromolecules resemble them as macromolecular colloids. These properties including the high degree of freedom, the controllable molecular size and weight, the need for no initiator, the presence of end groups, the high drug transfer capacity, etc., have made dendrimers applicable to a variety of fields such as medicine, biomedical, pharmaceutical, catalyst, and so on. [ABSTRACT FROM AUTHOR]

Novel magnetic halloysite‐based molecularly imprinted polymer (MMIP) is fabricated for sunset yellow dye removal from water solution. Field emission scanning electron microscopy, vibrating sample magnetometer, Zeta potential test, thermogravimetric, and nitrogen gas adsorption analysis were all employed for characterizations of the obtained magnetic halloysite and the final adsorbent. Transmission electron microscope images proved the synthesis of polymeric shell onto the magnetic nanotubes with the thickness of 10 nm. The adsorption kinetics were assessed by pseudo‐first order, pseudo‐second order, and intraparticle diffusion models and the results revealed that the obtained MMIP adsorption procedure would be controlled by chemical adsorption due to the high correlation coefficient (R2 ≥ 0.99) achieved for pseudo‐second order model. The effect of dye initial concentration was observed on the pseudo‐second order rate constant and the final equilibrium capacity of the MMIP. The adsorption isotherm at different temperatures (30 and 60°C) was assessed by two popular models, Langmuir and Freundlich. The resulting data were well fitted by Langmuir isotherm model, suggesting that the monolayer adsorption of sunset yellow onto the MMIP would occur. The exothermic behavior of the adsorption was justified by determining the effect of temperature on the Langmuir isotherm constant. The fabricated MMIP represented high adsorption capacity and imprinting factor of 46.43 μmol/g and 1.33, respectively. Moreover, the high selective recognition ability toward sunset yellow was observed for MMIP in the dyes mixture solution. [ABSTRACT FROM AUTHOR]

In this work, a series of polysulfide polymers were synthesized using organic monomer (ethylene dichloride) and sodium-based aqueous monomers via interfacial polymerization. The structural characteristics of aqueous monomers and synthesized polysulfide polymers were identified by Fourier transform infrared (FT-IR), Raman, and ultraviolet–visible-near infrared (UV–VIS-NIR) spectroscopies. The Optimum temperature of polymerization was obtained at 75°C. Benzyltriethylammonium chloride (BTEACl) and tetrabutylammonium bromide (TBAB) were used as phase transfer catalysts (PTC) where BTEACl showed better performance regarding the polymerization yield. Moreover, adding ethanol to polymerization media increased the polymerization yield significantly. The results showed that along with increasing sulfur in the structure of polymers, solubility and flexibility were increased whereas it decreased the hardness, melting point (Tm) and glass transition temperature (Tg) of obtained polymers. [ABSTRACT FROM AUTHOR]

Response surface methodology (RSM) with central composite design was used to optimize and analyze the molar ratio of catalyst components for polymerization of 1,3-butadiene (Bd) using Ziegler–Natta catalyst. In this research work, the catalyst component includes neodymium versatate (NdV3) as catalyst, triethylaluminum as cocatalyst or activator and ethylaluminum sesquichloride as chloride donor. The symbols [Nd], [Al], [Cl] and [Bd] were used for catalyst, cocatalyst, donor and monomer concentration, respectively. The interaction between three important and critical variables was studied and modeled. For this purpose, independent variables are [Bd]/[Nd], [Al]/[Nd] and [Cl]/[Nd] molar ratios at three levels to optimize the dependent or response ones which are monomer conversion, molecular weight and cis content of resulting polymer. Quadratic models were achieved and developed to correlate the catalyst components' molar ratio with dependent variables. The optimum conditions predicted via RSM were in good agreement with experimental data obtained from the experimental runs. The statistical analysis of the results showed that [Cl]/[Nd] molar ratio had a significant effect on monomer conversion and cis content. Furthermore, the catalyst components' molar ratio to reach the desirable response parameters is forecasted and experimentally verified. The optimum catalyst components' molar ratio derived via RSM is as follows: [Bd]/[Nd] = 5363.0, [Al]/[Nd] = 27.2 and [Cl]/[Nd] = 2.2. [ABSTRACT FROM AUTHOR]

A series of hydrogel nanocomposites was fabricated by in situ polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) in presence of different amounts of (amine- and alkyl-modified) nanocrystalline cellulose (NCC). Modification and nanocomposites properties were proved by different analysis methods such as Fourier-transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), and field emission scanning electron microscopy (FE-SEM). The new hydrogel nanocomposites were applied for removing methyl orange (MO) used as anionic dye and presented in process water at different pH values. The effects of the fabrication process such as modification and content of NCC, contact time, and pH value on swelling ratio (SR), and equilibrium adsorption kinetics were studied. Results showed that the swelling ratio of PDMAEMA-based nanocomposites varied with the different types of nanoparticles showing the significant effect of the modification process. The MO adsorption into the hydrogel nanocomposites was affected by intermolecular and electrostatic interactions between functional groups of hydrogel and dye. The adsorption capacity decreased at high pH value, and it was significantly affected type of nanoparticles introduced into the hydrogel network. The addition of unmodified NCC did not affect adsorption kinetics significantly. Finally, adsorption kinetics was investigated by pseudo-first-order, pseudo-second-order and intraparticle diffusion models where pseudo-first-order model showed the best correlation with experimental results. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid composites have received much attention of scientists in the recent years due to the notable improvement of thermal properties without using of organic or inorganic nanoparticles. Hence, we have developed a facile strategy to prepare a 3D hybrid network based on silane materials and novolac resin via sol–gel process. At first step, novolac resin was prepared by general procedure with appropriate thermal properties and then modified with (3-chloropropyl)triethoxysilane (CPTES) to form MNR. In second step, to cure MNR and prepare hybrid composite structures, general amine-cured system and sol–gel process were applied to prepare MNH and MNSG samples, respectively. XRD analysis was used to support the formation of silane networks in hybrid samples. Investigation of thermal properties by DSC and TGA showed that cured samples had much higher thermal stability and char yield with respect to novolac and modified resin (MNR) originated from formation of 3D Si–O–Si network. Presented method limited some disadvantages of using nanoparticles such as aggregation and poor distribution. Such hybrid composites with high thermal stability have potential applications in advanced fields such industrial molds, coatings, adhesives and composites. [ABSTRACT FROM AUTHOR]