Morphology and degradation of biodegradable poly(L-lactide-co-β-malic acid)

Poly(L -lactide-co-β-malic acid) was obtained after the hydrogenolysis of the copolymer of L -lactide (L-LA) and β-benzyl malate (MA). ¹H-NMR demonstrated that the composition of the copolymer was identical to the feeding dose. Thermal property study revealed the morphology of the copolymer could be changed from semi-crystalline to amorphous with increasing hydrophilic β-malic acid content. The copolymers with 8 and 13 mol% β-malic acid content possessed enough mechanical property for fabricating cell scaffold. Degradation result demonstrated that most of the hydrophilic β-malic acid units broke down from the copolymer within 1 week and the ester bond between L -lactide and β-malic acid hydrolyzed prior to the inner ester bond of poly(L -lactide) (PLLA). Copyright © 2003 John Wiley & Sons, Ltd.     

Investigation of the rigid amorphous fraction in Nylon-6

A three-phase model, comprising crystalline, mobile amorphous, and rigid amorphous fractions (χ _c, χ _MA, χ _RA, respectively) has been applied in the study of semicrystalline Nylon-6. The samples studied were Nylon-6 alpha phase prepared by subsequent annealing of a parent sample slowly cooled from the melt. The treated samples were annealed at 110°C, then briefly heated to 136°C, then re-annealed at 110°C. Temperature-modulated differential scanning calorimetry (TMDSC) measurements allow the devitrification of the rigid amorphous fraction to be examined. We observe a lower endotherm, termed the ‘annealing’ peak in the non-reversing heat flow after annealing at 110°C. By brief heating above this lower endotherm and immediately quenching in LN₂-cooled glass beads, the glass transition temperature and χ _RA decrease substantially, χ _MA increases, and the annealing peak disappears. The annealing peak corresponds to the point at which partial de-vitrification of the rigid amorphous fraction (RAF) occurs. Re-annealing at 110°C causes the glass transition and χ _RA to increase, and χ _MA to decrease. None of these treatments affected the measured degree of crystallinity, but it cannot be excluded that crystal reorganization or recrystallization may also occur at the annealing peak, contributing to the de-vitrification of the rigid amorphous fraction. Using a combined approach of thermal analysis with wide and small angle X-ray scattering, we analyze the location of the rigid amorphous and mobile amorphous fractions within the context of the Heterogeneous and Homogeneous Stack Models. Results show the homogeneous stack model is the correct one for Nylon-6. The cooperativity length (ξ_A) increases with a decrease of rigid amorphous fraction, or, increase of the mobile amorphous fraction. Devitrification of some of the RAF leads to the broadening of the glass transition region and shift of T _g.     

Perfluoro-1,3,5-tris(p-oligophenyl)benzenes: Amorphous Electron-Transport Materials with High-Glass-Transition Temperature and High Electron Mobility

Perfluoro-1,3,5-tris(p-quaterphenyl)benzene (PF-13Y) and perfluoro-1,3,5-tris(p-quinquephenyl)benzene (PF-16Y) have been synthesized and characterized. They showed higher glass transition temperatures compared with perfluoro-1,3,5-tris(p-terphenyl)benzene (PF-10Y). Organic light-emitting diodes were fabricated using these materials as the electron-transport layers. PF-13Y and -16Y are better electron transporters than PF-10Y. The electron mobilities of PF-10Y and Alq₃ were measured by the time-of-flight technique. PF-10Y showed higher electron mobilities (10⁻⁴ cm²/V s) and weaker electric field dependence compared with Alq₃.     

Synthesis of polyanionic glycopolymers for the facile assembly of glycosyl arrays

Polyanionic glycopolymers were synthesized aiming at establishing a simple process for assembling glycosyl arrays. The synthetic glycopolymers carry the key carbohydrate epitopes of α-d-galactobioside (Gb₂), β-lactoside, and α-d-mannopyranoside, each of which serves as a ligand of bacterial toxins and adhesion proteins. The Gb₂ epitope, prepared from penta-O-acetyl-d-galactopyranose, was coupled with poly(ethylene-alt-maleic anhydride) in a polymer reaction to afford a Gb₂-embedded glycopolymer having also carboxylate (COO⁻) polyanions at the side chain. The polyanionic glycopolymer was then applied to a preparation of sugar-coated gold electrodes, which involves an alternating layer-by-layer adsorption based on electrostatic interactions. The presence of the Gb₂-coat on the surface was evidenced by Fourier transform infrared reflection absorption spectroscopy. The Gb₂-coated glyco-chip was stable in 10 mM HEPES buffer containing 150 mM NaCl aq. Other glycopolymers carrying the β-lactoside and α-d-mannopyranoside epitopes were applied to the same assembling process. The derived glycosyl arrays will be useful for detecting Shiga toxins, other pathogenic toxins and viruses when applied as glyco-chips for surface plasmon resonance or quartz crystal microbalance technique.     

Applications of Thermal Analysis and Coupled Techniques in Pharmaceutical Industry

Thermal analysis methods are well-established techniques in research laboratories of pharmaceutical industry. The robustness and sensitivity of instrumentation, the introduction of automation and of reliable software according to the industrial needs widened considerably the areas of applications in the last decade. Calibration of instruments and validation of results follow the state of the art of cGMP as for other analytical techniques. Thermal analysis techniques are especially useful for the study of the behavior of the poly-phasic systems drug substances and excipients and find a unique place for new delivery systems. Since change of temperature and moisture occur by processing and storage, changes of the solid state may have a considerable effect on activity, toxicity and stability of compounds. Current requirements of the International Conference of Harmonisation for the characterization and the quantitation of polymorphism in new entities re-enforce the position of thermal analysis techniques. This challenging task needs the use of complementary methods. Combined techniques and microcalorimetry demonstrate their advantages. This article reviews the current use of thermal analysis and combined techniques in research and development and in production. The advantage of commercially coupled techniques to thermogravimetry is emphasized with some examples. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and thermal transformations of polyphosphosiloxane based on trimethyl phosphate and (3-aminopropyl)triethoxysilane

A method for the synthesis of polyphosphosiloxane by the thermal condensation of an equimolar mixture of trimethyl phosphate and (3-aminopropyl)triethoxysilane at 200 °C was developed. The reaction affords ethanol and polyphosphosiloxane-{Si(OEt)[(CH₂)₃NR¹R²]-O-P(O)(OMe)-O}_n-(R¹ = H, Me; R² = Me), whose composition and structure were confirmed by ¹H, ¹³C, and ³¹P NMR spectroscopy, IR spectroscopy, and elemental analysis. The scheme of polymerization involving the intermediate formation of methyl-and dimethylphosphoric acids and their condensation with ethoxysilanes was proposed. The calcination of the obtained polyphosphosiloxane in vacuo at 350 °C results in the elimination of the amino groups and alkoxide substituents, and a spatially cross-linked polymer is formed as an amorphous powder. Its further thermolysis at 600 and 1000 °C gives crystalline phosphosilicates Si₅O(PO₄)₆ or SiP₂O₇. Their amorphous and crystalline samples were characterized by IR spectroscopy, X-ray diffraction analysis, and solid-state ¹³C and ³¹P spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2138–2148, November, 2007.     

Observation of defect clustering in Gd-doped calcium fluoride

Abstract

Solid solutions Ca_1-xGd_xF_2+x for 3 × 10^?7≤ x ≤10^?1 have been studied by electron paramagnetic resonance (EPR) and ionic thermal currents (ITC). The EPR experiments show the presence of two single-ion sites a cubic and a tetragonal Gd³⁺ center which co-exist with comparable abundances for intermediate impurity concentrations. The cubic center predominates at very low and high concentrations. Seven different relaxation processes have been identified from the ITC spectra and the variation of their intensity vs. x was measured. The absolute concentrations of the cubic and nn Gd³⁺ dipoles were calculated. The scavenging of interstitial fluorines by the neutral clusters explains both the abundance of cubic sites at high concentration and the variety of orientable clusters detected by ITC.     

Improved Electrochemical Cycling Durability in a Nickel Oxide Double‐Layered Film

For the first time, a crystalline–amorphous double‐layered NiO_x film has been prepared by reactive radio frequency magnetron sputtering. This film has exhibited improved electrochemical cycling durability, whereas other electrochromic parameters have been maintained at the required level, namely, a short coloration/bleaching time (0.8 s/1.1 s) and an enhanced transmittance modulation range (62.2 %) at λ =550 nm. Additionally, the double‐layered film has shown better reversibility than that of amorphous and crystalline single‐layered films.     

Amorphous High-Entropy Hydroxides of Tunable Wide Solar Absorption for Solar Water Evaporation

The high-entropy materials have raised much attention in recent years due to their extraordinary performances in mechanical, catalysis, energy storage fields. Herein, a new type of high-entropy hydroxides (e.g., NiFeCoMnAl(OH)_x) that are amorphous and capable of broad solar absorption is reported. A facile one-pot co-precipitation method is employed to synthesize these amorphous high-entropy hydroxides (a-HEHOs) under ambient conditions. The a-HEHOs thus obtained display widely tunable bandgap (e.g., from 2.6 to 1.1 eV) due to their high-entropy and amorphous characteristics, enabling efficient light absorbance and photothermal conversion in the solar regime. Further solar water evaporation measurements show that the a-HEHOs delivered a considerable energy conversion efficiency of 55%, comparable to black titanium oxides that are synthesized using more complex and expensive methods.     

Formation of a crosslinked POSS network by an unusual hydrosilylation: Thermo‐oxidative stabilization of the α‐cristobalite phase in its amorphous regions

A semicrystalline inorganic–organic hybrid crosslinked network containing polyhedral oligomeric silsesquioxane (POSS) cores was constructed by the unusual hydrosilylation of the terminal vinyl groups of an internal acetylene‐containing silane linker by a POSS monomer. Products from the thermal treatments of this network in either argon or air at 250, 550, and 1000 °C, respectively, were characterized by Fourier transform infrared, Solid‐state ¹³C and ²⁹Si magic angle spinning NMR, X‐ray diffraction and XPS analyses. The highly symmetrically functionalized POSS silica clusters, in the fluorite silica phase, in the network were found to remain unchanged on thermal treatment possibly due to the shielding of the silica core by the functionalities and a cancellation of thermal stresses on the silica core. Stabilization of the metastable α‐cristobalite phase, which is typically formed on cooling by a β‐ to α‐transition of the β‐cristobalite phase formed above 1400 °C, was observed in the amorphous regions in the network sample treated only to 1000 °C in air. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012