Effects of polyethyleneimine-functionalized MCM-41 on flame retardancy and thermal stability of polyvinyl alcohol

Hyperbranched polyethylenimine（PEI）-functionalized mesoporous silica（MCM@PEI） was synthesized and used to produce poly（vinyl alcohol）（PVA） nanocomposites.The modified nanofiller was characterized with infrared spectroscopy,thermogravimetric analysis,X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and N₂ adsorption.When compared with pure mesoporous silica（MCM）,the MCM@PEI nanoparticles exhibited better dispersion in the PVA matrix.The effects of MCM@PEI on the thermal and flame properties of PVA nanocomposites were also studied.Improvement in the thermal properties was confirmed by enhanced thermal stability and char yield.Incorporation of MCM@PEI in PVA led to a significant drop in the heat release rate and the total heat release.     

Magnetic and Heat Resistant Poly(imide-ether) Nanocomposites Derived from Methyl Rich 9H-xanthene: Synthesis and Characterization

In this study a new series of magnetic and heat resistant nanocomposites were prepared based on a highly soluble poly(imideether)(PIE) reinforced with two different types of magnetic nanoparticles via a solution intercalation technique. New PIE with good solubility and desired molar mass containing bulky xanthene rings and amide groups in the side chains was synthesized via thermal cyclization of the poly(amic acid) precursor, obtained from the reaction of a new diamine derived from 9 H-xanthene and 4,4′-oxydiphthalic dianhydride(ODPA). Improved solubility was attributed to the presence of xanthene group and flexible ether linkage in the polyimide backbones that reduce the chain-chain interaction and enhance solubility by penetrating solvent molecules into the polyimide chains. Fe3 O4 nanoparticles(MNPs) which synthesized from chemical co-precipitation route were coated with silica(Si O2), sequentially with(3-aminopropyl)triethoxysilane and poly-melamine-terephthaldehyde(MNPs-PMT), and then separately dispersed in the poly(amic acid) solutions and thermally imidized to form PIE/Fe3 O4 and PIE/MNPs-PMT nanocomposites. The nanostructures and properties of the resultant materials were investigated using FTIR spectroscopy, X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), vibrating sample magnetometer(VSM), thermal gravimetric analysis(TGA) and differential scanning calorimetry(DSC). The properties of the nanocomposites were strongly related to the dispersion and interaction between the nanoparticles and PIE matrix. The thermogravimetric analysis(TGA) results showed that the addition of MNPs-PMT nanoparticles resulted in a substantial increase in the thermal stability of the corresponding PIEN. The temperature at 10% weight loss(T10) was increased from 416 °C to 428 °C for PIEN containing 3 wt% MNPs-PMT as compared to neat PIE, as well the char yield enhanced. Furthermore, the MNPs-PMT nanoparticles had better dispersion in the polymer matrix due to the strong intermolecular hydrogen bond interactions between the NH and C=N groups of surface-modified nanoparticles and the PIE matrix than the uncoated Fe3 O4 nanoparticles, and exhibited a better intercalated morphology and improved thermal properties. Also, the PIEN nanocomposites under applied magnetic field exhibited the hysteretic loops of the superparamagnetic nature.     

Introduction of antimony triiodide (SbI3) as a new and efficient catalyst for synthesis of polyfunctionalized piperidines

Research on Chemical Intermediates - In the present work, an efficient and convenient one-pot multi-component reaction is reported for the synthesis of highly diversified piperidines by tandem...     

New clay-reinforced polyamide nanocomposite based on 4-phenylenediacrylic acid: Synthesis and properties

New type of aromatic polyamide/montmorillonite nanocomposites were produced using solution intercalation technique in N-methyl-2-pyrrolidone. High-molecular-weight amide chains were synthesized from 4,4′-diaminodiphenyl ether and 4-phenylenediacrylic acid in N-methyl-2-pyrrolidone. The resulting nanocomposite films containing 5–20 wt.% of organoclay (Cloisite® 20A) were characterized for FT-IR, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), optical transparency and water absorption measurements. The distribution of organoclay and nanostructure of the composites were investigated by (XRD) and SEM analyses. Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared to pristine polyamide. The percentage optical transparency and water absorption of these hybrids was found to be much reduced upon the addition of modified layered silicate indicating decreased permeability.     

An investigation on the structural characteristics and reinforcement of melt processed polyamide 66/multiwalled carbon nanotube composites

Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of nanocomposite properties at higher nanotube contents. Surface modification of nanotube provided better polymer‐nanotube interaction; however, it increased the mechanical properties marginally. Copyright © 2014 John Wiley & Sons, Ltd.     

One-pot synthesis of N-alkyl purine and pyrimidine derivatives from alcohols using TsIm: a rapid entry into carboacyclic nucleoside synthesis

A convenient and efficient one-pot N-alkylation of nucleobases from alcohols using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, treatment of alcohols with a mixture of purine or pyrimidine nucleobase, TsIm, K₂CO₃, and triethylamine in refluxing DMF regioselectively furnishes the corresponding N-alkyl nucleobases in good yields. This methodology is highly efficient for various structurally diverse primary alcohols.     

Synthesis of 2-amino-3-cyano 4-<Emphasis Type="Italic">H</Emphasis>-chromenes containing quinoline in water: computational study on substituent effects

An efficient, high yielding and environmentally benign strategy to the synthesis of new 2-amino-3-cyano-4-H-chromene derivatives, via one-pot three-component reaction involving malononitrile, various α- or β-naphthol and appropriate aromatic aldehydes including 2-chloroquinoline-3-carbaldehydes in the presence of morpholine in water, was achieved. During the development of the synthesis five new chromene derivatives were fruitfully synthesized. It was found that employing this approach, aromatic aldehydes bearing electron-withdrawing groups give higher yields of the corresponding products in shorter reaction times. This observation was in agreement with topological analysis of calculated electron density functions using density functional theory and quantum theory of atoms in molecules approaches.     

Synthesis and characterization of new thermally stable poly(amide-imide)s based on bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide and aromatic diamines

N,N′-bis-(4-carboxyphenyl)bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide was prepared by reaction of bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetra carboxylic dianhydride with p-aminobenzoic acid in a mixture of acetic acid and pyridine (3: 2). Polycondensation of N,N′-bis-(4-carboxyphenyl)bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide with six different aromatic diamines produced a series of new poly(amide-imide)s (PAIs) in high yields with inherent viscosities between 0.49–0.95 dl/g. All PAIs were characterized by means of elemental analysis, viscosity measurement, solubility test, FTIR spectroscopy and ¹H-NMR spectroscopy. Dynamic TGA of PAIs shows 10% weight loss temperatures from 410 to 435°C under nitrogen.     

Minimal Number of Generators and Minimum Order of a Non-Abelian Group Whose Elements Commute with Their Endomorphic Images

A group in which every element commutes with its endomorphic images is called an “E-group″. If p is a prime number, a p-group G which is an E-group is called a “pE-group″. Every abelian group is obviously an E-group. We prove that every 2-generator E-group is abelian and that all 3-generator E-groups are nilpotent of class at most 2. It is also proved that every infinite 3-generator E-group is abelian. We conjecture that every finite 3-generator E-group should be abelian. Moreover, we show that the minimum order of a non-abelian pE-group is p ⁸ for any odd prime number p and this order is 2⁷ for p = 2. Some of these results are proved for a class wider than the class of E-groups.     

New optically active poly（amide-imide）s derived from N, N′-（4,4-diphthaloyl）-bis-L-leucine and hydantoin derivatives： Synthesis and properties

Six new optically active poly(amide-imide)s(5a-f) were synthesized through the direct polycondensation reaction of N,N'-(4,4'- diphthaloyl)-bis-L-leucine(3) with six hydantoin derivatives(4a-f).Triphenyl phosphite(TPP)/pyridine in the presence of calcium chloride(CaCl_2) and N-methyl-2-pyrrolidone(NMP) were successfully applied for direct polycondensation.The polycondensation reactions produce a series of new poly(amide-imide)s(5a-f) in high yields,and inherent viscosity between 0.42 and 0.55 dL/g.The re...