Materials Literature
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An investigation about the possibilities of atactic polypropylene in order to be chemically modified either in solution or in molten state processes, and further predictions about the reaction conditions' influence in the process, have been carried out. For those purposes the Box–Wilson experimental design method has…
The reactions between polymeric diphenyl methane diisocyanate (polymeric MDI) and conventional polyols to produce foamed polyurethane products are well documented and published. Current polyurethane foams are predominantly produced from these reactions whereby the polyol components are usually obtained from petrochemi…
The critical temperature of thin Fe layers on Ir(100) is measured through Mößbauer spectroscopy as a function of the layer thickness. From a phenomenological finite-size scaling analysis, we find an effective shift exponent lambda = 3.15 +/- 0.15, which is twice as large as the value expected from the conventional fin…
Novel solvent systems for cellulose are reviewed in terms of their potential for supporting chemical modification reactions that lead to highly engineered derivatives. Systems capable of sustaining homogeneous phase conditions include (1) dissolution with non-derivatizing solvents; (2) dissolution with partial derivat…
The hypothetical polyethylene melt at room temperature is of interest for the purposes of developing the atomic level modeling of gas solubilities in rubbery polymers. In the present study, the gas solubilities in completely amorphous polyethylene are predicted by extrapolating alkane behavior to the long chain limit…
The crystal structure of poly( l -hydroxyproline) (PHypro) with trans planar conformation of the peptide group is reexamined. The electron diffraction pattern obtained from solution-grown triangular single crystals confirms the unit-cell geometry determined by Sasisekharan ( Acta Crystallogr . 1959, 12, 903) (trigonal…
Wood and dietary fiber products all belong to a class of biomolecular composites that are rich in cellulose and lignin. The interaction between cellulose and lignin determines such properties as mechanical strength (wood); creep, durability and aging; cellulose purity (pulp); and digestibility (nutrients). The underst…
We studied the effect of monomer immobilization (quenching) on the orientation of the lamellae in symmetric diblock copolymer thin films with neutrally wetting surfaces. A small fraction of the monomers immediately next to the solid substrate is presumed to be quenched. Our calculations demonstrate that quenching favo…
Recent studies on the solution properties of cellulose derivatives disclosed that two classes have to be distinguished, i.e. the fully and partially substituted chains. Molecularly dispersed solutions are obtained when all OH groups are substituted, while in the other case free OH groups can undergo hydrogen-bonding r…
The irreducible representations of all of the 80 diperiodic groups, being the symmetries of the systems translationally periodical in two directions, are calculated. To this end, each of these groups is factorized as the product of a generalized translational group and an axial point group. The results are presented i…
A new synthesis concept in cellulose chemistry is described. Cellulose dissolved in the solvent system N,N -dimethylacetamide/LiCl as well as organo-soluble cellulose derivatives of different hydrolytic stability (dissolved in dimethyl sulfoxide) were converted into cellulose ethers of unusual substituent patterns aft…
Both “condensation” and “hydrosilylation” reactions have been successfully applied for the synthesis of silicon-based interpenetrating polymer networks (IPNs) consisting of a stable Si−O and Si−C linkage. We adopted a ladder silsesquioxane oligomer (LDS 1; commercial name, Glass Resin GR100) and a polycarbosilane (PCS…
Electrochemical oxidation of the tetrathiafulvalene (TTF) type organic donor bis(ethylenediseleno)tetrathiafulvalene (BEST) in the presence of the Keggin polyoxometalate [PMo(12)O(40)](3)(-) affords the radical salt formulated as (BEST)(3)H[PMo(12)O(40)] (crystal data: triclinic, space group P&onemacr; with a = 13.056…
The photochemical and photophysical behavior of (dodecafluorosubphthalocyanaoto)boron(III) chloride was examined in room-temperature solutions. The lowest energy absorption maximum of the complex is 570 nm, and the luminescence mirrors the absorption with a maximum at 586 nm (Stokes shift = 480 cm -1 ). The emission i…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTPractical Synthesis of Starburst PAMAM α-Thiosialodendrimers for Probing Multivalent Carbohydrate−Lectin Binding PropertiesDiana Zanini and René RoyView Author Information Department of Chemistry, University of Ottawa, Ottawa, ON, Canada K1N 6N5 Cite this: J. Org. Chem. 1998, 6…
Polymer complexes of a basic polymer, poly( N- methyl-4-piperidinyl methacrylate) (PMPMA), with a weak acidic polymer poly( p -vinylphenol) (PVPh), and strong acidic polymers such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), poly(styrenesulfonic acid) (PSSA), and poly(vinylphosphonic acid) (PVPA), have…
Obstacles to the heterogeneous esterification of cellulose with long-chain alkanoic acids were overcome (a) by reacting cellulose in homogeneous phase solution (in DMAc/LiCl) in the presence of dicyclohexyldicarbodiimide (DCC) and 4-pyrrolidinopyridine (PP) or tosyl chloride; or (b) by reaching cellulose heterogeneous…
Dihydridocarbonyltris(triphenylphosphine)ruthenium catalyzed copolymerization of acetophenone and 1,4-bis((trimethylsilyl)ethynyl)benzene yields a linear copolymer copoly[2-acetyl-1,3- phenylene/α,α‘-bis((trimethylsilyl)methylene)-1,4-xylenylene]. This reaction involves regioselective catalytic addition of the ortho C…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTLinear and Hyperbranched m-Polyaniline: Synthesis of Polymers for the Study of Magnetism in Organic SystemsNikolaos Spetseris, Rachel E. Ward, and Tara Y. MeyerView Author Information Department of Chemistry, University of Pittsburg…
Novel solvent systems for cellulose are reviewed in terms of their potential for supporting chemical modification reactions that lead to highly engineered derivatives. Systems capable of sustaining homogeneous phase conditions include (1) dissolution with non-derivatizing solvents; (2) dissolution with partial derivat…