Materials Literature
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We have measured the pressure dependence of the order−disorder transition temperature ( T ODT ) in two styrene−isoprene diblock copolymers containing 24 and 48 wt % styrene ( M w = 20 500 and 16 500 g mol -1, respectively). Small-angle X-ray scattering measurements indicate that T ODT rises linearly with increasing hy…
The strengthening of the interface between polystyrene (PS) and poly(methyl methacrylate) (PMMA) using a random copolymer P(S f - r -MMA 1 - f ), where f is the fraction of styrene in the copolymer, was investigated. The maximal fracture toughness, measured by crack propagation, was found when f = 0.68. Neutron reflec…
Plasma polymers of acrylic (propenoic) acid and propanoic acid were prepared from inductively coupled, radio-frequency-induced plasmas excited in vapors of the starting materials. The plasma polymers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRAS), and s…
In this paper, a macro-scale, phenomenological constitutive model for shape memory alloys is used in conjunction with energy balance equations to study the evolution of temperature and deformation profiles seen in SMA wires under specific thermal and mechanical boundary conditions. The general, fully coupled thermo-me…
Trivalent polyhedra with six square and (x– 4) hexagonal faces are candidates for fully alternating (BN)x‘inorganic fullerene’ cages. Systematic density-functional tight-binding calculations for 4 ⩽x⩽ 30 show that the most stable isomer of this type will have isolated squares, whenever mathematically possible. This ru…
In the absence of crystals of suitable quality, the crystal structures of five [MX2(bipy)](M = Ni or Cu; X = Cl or Br; bipy = 4,4′-bipyridyl) phases were determined, ab initio, from powder diffraction data. The nickel compounds contain symmetrically bridging halides and trans-D4h octahedrally co-ordinated metal atoms;…
The region of the (Na1/2Bi1/2)1−xPbxTiO3 phase diagram from 0≤x≤0.2 was established through analysis of structure and thermal anomalies associated with changes in temperature and composition. The rhombohedral-tetragonal morphotropic phase boundary (MPB) was investigated considering the dependence of the rhombohedral l…
A novel family of silica-based mesoporous molecular sieve M41S was synthesized by one of the Mobil research groups. Surfactant molecules were mixed with a silica solution, resulting in a regular array of uniform mesopores, 2−10 nm in diameter, capable of acting as a potential catalyst. The final long-range ordering of…
Magnetic and electrochemical interactions between two redox-active, paramagnetic {Mo(Tp*)(NO)Cl} fragments [Tp* = tris(3,5-dimethylpyrazolyl)hydroborate] attached to either end of various bis(pyridyl) bridging ligands may be related to the substitution pattern, conformation, length, and symmetry of the bridge. The sig…
Several unsymmetrically substituted TTFs bearing the S(CH2)2CN protecting group have been prepared by standard cross coupling in triethyl phosphite from the key intermediate 4,5-bis(2′-cyanoethylsulfanyl)1,3-dithiol-2-one 1 and an appropriate 1,3-dichalcogenole-2-chalcogenone, 2–8. TTFs 10, 11 and 12 of type I have be…
The stability of weakly flocculated, nonaqueous suspensions of aluminum oxide with adsorbed poly(methyl methacrylate) (PMMA) layers as a function of nonadsorbed PMMA volume fraction was studied through rheological measurements and optical microscopy. In the absence of nonadsorbed polymer, suspensions exhibited strong…
Both discharge capacity and charge–discharge cycle life of MgNi negative electrodes prepared by mechanical alloying (MA) are greatly improved by surface modification with graphite using a planetary mill.
A general theoretical framework for the study of anisotropic composition fluctuations about an ordered block copolymer phase is developed. The approach is based on the idea that, in order to study the effects of fluctuations around an ordered broken symmetry phase, the theory must be formulated as a self-consistent ex…
The three-dimensional structure of amyloid beta peptide (25-35), which has neurotoxic activity, in lithium dodecyl sulfate micelles was determined by two-dimensional 1H NMR spectroscopy with simulated annealing calculations. A total of 20 converged amyloid beta peptide structures were obtained on the basis of 110 expe…
The lattice cluster theory (LCT) is used to study the influence of monomer structure, i.e., short chain branching, on the miscibility of binary polymer blends. The systems are chosen as corresponding to united atom models of the monomer structures in the binary polyolefin blends studied by Graessley and co-workers. We…
The mechanism of polymerization of ε-caprolactone (εCL) initiated with aluminum isopropoxide (Al(O i Pr) 3 ) trimer (A 3 ) and/or tetramer (A 4 ) carried out in the presence of ethanol, 2-propanol, 1,2-ethanediol, 1,5-pentanediol (PD), and poly(ethylene glycol) as chain-transfer agents was studied. It has been establi…
Poly( l, l -lactide) microspheres were synthesized directly during the ring-opening precipitation polymerizations of l, l -lactide. The polymerizations were carried out in heptane−1,4-dioxane (4:1 v/v) mixed solvent in the presence of various poly(dodecyl acrylate)- g -poly(ε-caprolactone) copolymers (poly(DA−CL)) use…
A novel manganese(IV) monomer, [Mn(IV)(Me(3)TACN)(OMe)(3)](PF(6)), has been synthesized in methanol by the reaction of MnCl(2) with the ligand, N,N',N"-trimethyl-1,4,7-triazacyclononane (Me(3)TACN), in the presence of Na(2)O(2). The resulting product was isolated as the red/brown crystalline hexafluorophosphate salt.…
The electrochemical synthesis of linear symmetrical octaethylporphyrin−octaethylporphyrin and unsymmetrical tetraphenylporphyrin−octaethylporphyrin dimeric porphyrins with one viologen as a spacer and of their precursor porphyrin monomers is reported. The mechanism of the electrochemical substitution leading to the di…
Abstract The principal objectives and methods of surface modification of polymers are reviewed in this paper. The techniques covered include physical, chemical, mechanical and biological methods.