Selective oxidation of olefins and aromatic alcohols with tert‐butylhydroperoxide catalyzed by polymer‐anchored transition‐metal complexes

Three polymer‐anchored metal complexes (Co, Cu, and Pd) were synthesized and characterized. The catalytic performance of these complexes was tested for the oxidation of olefins and aromatic alcohols. These complexes showed excellent catalytic activity and high selectivity. These complexes selectively gave epoxides and aldehydes from olefins and alcohols, respectively. Individually, the effect of various solvents, oxidants, substrate oxidant molar ratios, temperatures, and catalyst amounts for the oxidation of cyclohexene and benzyl alcohol were studied. Under optimized reaction conditions, 96, 81, and 71% conversions of cyclohexene and 86, 79, and 73% conversions of benzyl alcohol were obtained with Co(II), Cu(II), and Pd(II) catalysts, respectively. The catalytic results reveal that these complexes could be recycled more than five times without much loss in activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Recovery of pyridine from water by pervaporation using filled and crosslinked EPDM membranes

Organoselective membrane was prepared from ethylene propylene diene monomer (EPDM) rubber. Crosslinked EPDM rubber was filled with 2, 4 and 6 wt% N330 carbon black filler to produce three different filled membranes designated as EPDMCV2, EPDMCV4 and EPDMCV6, respectively. These filled rubber membranes were used for pervaporative recovery of low concentration of pyridine from water. These filled membranes were characterized by crosslink density, SEM, XRD and mechanical properties. Sorption thermodynamics were discussed. Partial permeability, intrinsic membrane selectivity and diffusion coefficients of solvents were also determined. The filled membranes showed much higher pyridine selectivity than most of the membranes reported for similar system.     

A Thermoplastic Polyurethane /Nanosilica Composite via Melt Mixing Process and its Properties

Silicon - This investigation reports the preparation and properties of thermoplastic polyurethane/silica nanocomposite prepared via melt mixing process. In this case, nanosilica at different...     

Spectroscopic investigation confirms retaining the pristine nature of single-walled carbon nanotubes on dissolution in aniline

Carbon nanotubes in all forms are very much insoluble in both organic and inorganic solvents due to its high agglomeration and entangled morphology. General methods for dissolution of single-walled carbon nanotubes (SWNTs) are mostly associated with complexation or polymerization or addition of macromolecules which change the physical or chemical properties of SWNTs and the pristine nature of SWNTs is lost. Dissolution of SWNTs in a solvent like aniline is practiced here which is a very simple reaction method. Here aniline is capable to form a SWNT-aniline charge transfer complex without attachment of macromolecules or polymer which is also soluble in other organic solvents. Solvation of SWNTs by this method is also capable of maintaining the similarity between the structure of SWNTs before and after the dissolution, which means that the pristine nature of SWNTs is preserved. Formation of charge transfer complex in this reaction has been proven by UV-Vis/NIR absorption and photoluminescence spectroscopy. Raman spectroscopy and electron microscopy (FESEM and TEM) are the evidences for protection of the pristine nature of SWNTs even after high-temperature complexation reaction with aniline and also after solubilization in organic solvents.     

Waste natural gum as a multifunctional additive in rubber

Bahera gum, extracted from the bark of Terminalia bellerica, is a waste material. The present study involves the use of this natural gum as a multifunctional additive in natural rubber (NR) and brominated isobutylene‐co‐paramethyl styrene (BIMS). Fourier transform infrared (FTIR) analysis was employed to study the functional groups present in the gum. It was found that fatty acids/esters in the gum act as accelerator activator and can replace stearic acid in rubber formulations. Polyphenols in the gum act as antioxidant and the action is comparable with the commercial antioxidant 2,2,4‐trimethyl‐1,2‐dihydroquinoline (TQ) in natural rubber. The gum improves the tack strength of the rubbers (21% at 2.5 phr loading for NR and 54% at 10 phr loading for BIMS). The gum imparts plasticization effect which is reflected in the reduction in k and enhancement in n values, the exponents in the power law equation, with increasing gum concentration. The activation energy of flow is also reduced with the addition of the gum. Moreover, it decreases the elastic memory of the system which causes reduction in die swell. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4897–4907, 2006     

Pseudohalogens in atom transfer radical polymerization of methyl methacrylate

In recent advances in controlled radical polymerization, atom transfer radical polymerization (ATRP) has achieved increasing interest. This investigation reports the ATRP of methyl methacrylate (MMA) using pseudohalogens as initiator as well as an anion for copper catalyst. The results were compared with the conventional halide system. Different pseudohalides were used as the initiator for the ATRP of MMA in combination with CuX (X = pseudohalide or halide) as the catalyst. Pseudohalide initiator in combination with Cu(halide) catalyst leads to inefficient ATRP due to slow initiation. Pseudohalide initiator in combination with Cu(pseudohalide) catalyst leads to uncontrolled or no polymerization. The polymers were characterized by using GPC, IR, MALDI‐TOF‐MS, and TGA analysis. IR and MALDI analysis showed that the resultant polymer had pseudohalide as the end group. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3857–3864, 2007     

Influence of electron beam radiation on mechanical and thermal properties of styrene‐butadiene‐styrene block copolymer

Electron beam crosslinking of elastomers is a special type of crosslinking technique that has gained importance over conventional chemical crosslinking method, because the former process is fast, pollution free, and simple. The technique involves the impingement of high‐energy electrons generated from electron accelerators and the subsequent production of free radicals on target elastomers. These radicals result in crosslinking of elastomers via radical–radical coupling. In the process, some chain scission may also take place. In this work, a high‐vinyl (～ 50%) styrene‐butadiene‐styrene (S‐B‐S) block copolymer was used as the base polymer. An attempt was made to see the effect of electron beam radiation on the mechanical and thermal properties of the block copolymer. Radiation doses were varied from 25 to 300 kGy. Mechanical properties like tensile strength, elongation at break, modulus at different elongations, hardness, tear strength, crosslink density, and crosslink to chain scission of the irradiated samples were studied and compared with those of unirradiated ones. In this S‐B‐S block copolymer, a relatively low‐radiation dose was found effective in improving the level of mechanical properties. Differential scanning calorimeter and dynamic mechanical analyzer were used to study the thermal characteristics of the irradiated polymer. Influence of a stabilizer at different concentrations on the properties of S‐B‐S at varied radiation doses were also focused on. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrochemical synthesis of nanostructured polyaniline: Heat treatment and synergistic effect of simultaneous dual doping

Different nanostructured polyaniline (PAni) has been synthesized via facile template‐free electrochemical synthesis approach in aqueous medium. Instead of conventionally used aniline, aniline sulphate was used in electrochemical polymerization. The synthesis process involves simultaneous doping with combination of inorganic and organic acid, i.e., sulfuric acid (H₂SO₄) and p‐toluenesulfonic acid (PTSA) at different ratios keeping total dopant concentration constant. Synergistic increase in conductivity is observed and the best conductivity is achieved at 3:1 ratio of [H₂SO₄]:[PTSA]. Different nanostructures of PAni are revealed through morphological analysis consisting of nanosphere, nanorod, and clustered particles among which finer nanorods show the best electrical conductivity. Upon controlled heat treatment followed by further cooling, resistivity increases, but after one day it decreases again and in the optimized dual doped PAni, it approaches approximately the same value of initial resistance. Lattice strain and benzenoid to quinonoid ratio increases with heat treatment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A highly efficient polymer‐anchored palladium(II) complex catalyst for hydrogenation,Heck cross‐coupling and cyanation reactions

BACKGROUND: Precise architectures of steric and electronic properties of palladium species play a crucial role in designing highly functionalized catalyst systems responsible for target organic transformations. Pd catalysts supported on polymer materials have been employed extensively as catalysts not only for hydrogenation but also for coupling reactions in the production of fine chemicals. RESULTS: A new polymer‐anchored Pd(II) complex has been synthesized and characterized. The catalyst shows high catalytic activity in the hydrogenation of styrene oxide, Heck cross‐coupling and cyanation reactions of aryl halides. The effect of various reaction parameters were investigated to optimize reaction conditions. The catalytic system shows good activity in the hydrogenation of styrene oxide (conversion 98%) with a selectivity to 2‐phenylethanol (93%) which is higher than its homogeneous analogues. The catalyst also exhibits excellent catalytic activity for the Heck cross‐coupling and cyanation reactions of various substituted and non‐substituted aryl halides. CONCLUSIONS: Results demonstrate that the catalyst is robust and stable and can be recovered quantitatively by simple filtration and reused several times without loss of activity. Copyright © 2010 Society of Chemical Industry