Materials Literature
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A series of side-chain liquid crystal polymers, the poly[ω-(4′-methoxybiphenyl-4-yloxy)alkyl methacrylate]s, have been synthesized in which the spacer length is varied from 3 to 12 methylene units. This is the first example of a poly(methacrylate)-based side-chain liquid crystal polymer series for which as many as 10…
Ring‐opening polymerization (ROP) of cyclic monomers is most suitable for the preparation of sequential copolymers of the type (AAB) n , the sequence being determined by the structure of the monomer. The thermodynamics and mechanisms of ROP are reviewed, including radical, cationic, anionic, and metathetical ROP, with…
Abstract Hydrolytic degradation of intrinsically amorphous poly( DL ‐lactic acid) was re‐examined in pH 7.4 isoosmolar phosphate buffer at 37°C. Size‐exclusion chromatogarphy, X‐ray scattering and differential scanning calorimetry were used to monitor molecular weight and morphology changes up to the ultimate degradat…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe use of NMR to study sodium dodecyl sulfate-gelatin interactionsDavid D. Miller, William Lenhart, Brian J. Antalek, Antony J. Williams, and J. Michael HewittCite this: Langmuir 1994, 10, 1, 68–71Publication Date (Print):January 1, 1994Publication History Published online1…
A review of papers on “seignettomagnetic” oxides is given. Data on crystal structure, physical properties and phase transitions of different groups of these oxides, especially of the perovskite type, have been described. Perspectives of synthesis and search for new seignettomagnetics of various crystal types, includin…
The effects of such constituents as the crosslinked part, non-crosslinked LDPE part, antioxidant, and residual byproducts on the formation of space charge in XLPE have been investigated. It has been found that homocharge is developed in the pure crosslinked part of XLPE. The non-crosslinked LDPE part encourages the fo…
The influence of postdeposition annealing on sputtered indium tin oxide (ITO) film characteristics were investigated. The annealing experiments were carried out in air or vacuum atmosphere. Both air and vacuum annealing decreased the resistivity up to heat treatment of 200° C. Over 300° C treatment, air annealing incr…
In 1959, about 1400 compounds forming liquid crystalline phases were known; by 1992, this number had increased to about 50 000. In portable devices like wristwatches, pocket caculators, measuring inst
The simplest mathematical model based on a new approach to the moving contact-line problem is examined, and is shown to adequately reflect the main features of wetting phenomena revealed by experiments. A simple algebraic equation describing the dependence of the dynamic contact angle on the contact-line speed and oth…
It is shown that the relevant spectral features which arise in the infrared spectrum of poly(3-methylthiophene) upon chemical doping or photoexcitation (i.e., in the electrically conducting form) can be properly explained by means of the effective conjugation coordinate (ECC) formalism. This theoretical dynamical mode…
A variety of monosulfonated phthalocyanine, benzonaphthoporphyrazine and porphyrin derivatives have been prepared as single positional isomers in moderate to high yield using modified Meerwein reaction conditions. These amphiphilic dyes have a potential application as photosensitizers in the photodynamic therapy of ca…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of DNA binding to electrically conducting polypyrrole filmsDaniel S. Minehan, Kenneth A. Marx, and Sukant K. TripathyCite this: Macromolecules 1994, 27, 3, 777–783Publication Date (Print):January 1, 1994Publication History Published online1 May 2002Published inissue…
Discover what constitutes a composite material, how a composite is made, when a composite is best for a given application, how a composite material or structure responds to a thermal or mechanical load, and how to design a polymer composite that meets a set of property requirements. A general reference book for practi…
Existing matrix models for transformers reproduce specified short-circuit tests, portraying leakage flux in air, but do not explicitly model the core. Therefore, a precise relation between core flux and air flux is not clearly established. Core representation is defined simply on the basis of a specified excitation cu…
Zirconium alloys are susceptible to a stable cracking process called delayed hydride cracking (DHC). DHC has two stages: (a) crack initiation that requires a minimum crack driving force (the threshold stress intensity factor, KIH) and (b) stable crack growth that is weakly dependent onKl,. The value of KIH is an impor…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymerization of (Z)-1,3-pentadiene with CpTiCl3/MAO. Effect of temperature on polymer structure and mechanistic implicationsGiovanni Ricci, Salvatore Italia, and Lido PorriCite this: Macromolecules 1994, 27, 3, 868–869Publication Date (Print):January 1, 1994Publication His…
Festschrift remark-It was an honor to be invited to honor Allan Hoffman on the occasion of his 60th birthday. It seems like yesterday that Allan and I shared an office in old Building 12 on the M.I.T. campus. At that time Allan had lost a bout with a snow covered mountain while on skis, and consequently moved about aw…
β-Bromoporphyrins undergo Suzuki cross-coupling reactions with aryl boronic acids to give β-arylporpyrins in high yields and X-ray analysis shows that H2TPP(Ph)42a(TPP = tetraphenylporphyrin) is centrosymmetric and possesses a hydrogen-bonded inner core.
ABA block copolymers of polyethylene glycol and poly-DL-lactic acid were prepared by ring-opening polymerization of DL-dilactide with alpha,omega-dihydroxy polyethylene glycol, Mn 1000 or 2000. The morphology of the resulting copolymers, with PEG:PLA ratios(mol/mol) of 1:2, 1:3 and 1:4, was characterized by DSC and ES…
A new kind of PbS nanoparticles/polymer composite is synthesized whose microstructure observed under TEM proves that the nanoparticles are well dispersed and even in size; electron diffraction results identify the PbS nanoparticles to be of the cubic rock salt structure, and the particle size can be varied from 4 to 1…