Effect of calcium malonate on the formation of β crystalline form in isotactic poly(propylene)

Calcium malonate (Camt) is used to induce the β crystalline form in isotactic polypropylene (iPP) for the first time. The relative content of the β crystalline form (K value) increases markedly with the addition of Camt and attains the maximum value of 73.48% at 0.40% Camt. The amounts of bright and colorful β spherulites increase and the spherulitic sizes decrease with the increase in Camt contents. The tensile strength and the Izod notched impact strength of the nucleated iPP samples increase with the addition of Camt; in particular, the latter almost doubles at 0.40% Camt compared to that of the blank iPP sample. The β nucleation mechanism of Camt is analyzed by the dimensional lattice match criterion. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermal analytical and infrared spectroscopic investigations on polymorphic organic compounds-III

Six polymorphic compounds, having between two and five modifications, are described. Enantiotropic modifications were found for three of them: 9-fluorenylmethanol (2 modifications), polyester red A (3 modifications) and polyester red B (3 modifications). There were no indications of enantiotropy in the other three: diphenylcarbamoyl chloride (4 modifications), 4-hydroxyphenylacetic acid (5 modifications) and 2-hydroxy-1-naphthalenecarbaldehyde (5 modifications).     

鲫鲤杂交F1及其亲本RAPD标记

用RAPD技术对红鲫(♀)×野鲤(♂)及其F1个体进行了研究．15个引物在鲤鱼中扩增出86条带(33条具多态性),红鲫75条带(24条呈多态性),两者共享25条(16条呈多态性)．F     

Effect of Metallic Salts of Pimelic Acid and Crystallization Temperatures on the Formation of β Crystalline Form in Isotactic Poly(propylene)

The effect of crystallization temperatures (100–140°C) on the formation of β crystalline form in isotactic polypropylene nucleated by pimelic acid and sodium, magnesium, zinc, calcium, barium and aluminium salts of pimelic acid has been investigated. It is found that β crystalline form can be produced from polypropylene melt, isothermally crystallized at 120 or 130°C. Aluminium pimelate is a α nucleator which suppresses the production of β crystalline form in polypropylene. Pimelic acid and magnesium pimelate are weak β nucleators. Sodium pimelate is a moderate β nucleator. Zinc pimelate, calcium pimelate and barium pimelate are good β nucleators for polypropylene with calcium pimelate being the best.     

Polymorphism of 4-Fluorophenylpyruvic Acid Studied by X-Ray Crystallography and Vibrational Spectroscopy

Two polymorphic forms (I and II) of 4-fluorophenylpyruvic acid (F-PPA) were obtained by crystallization from different solvents, showing a melting point at 163.2 and 171.0 °C. Crystal structures of polymorphs I and II were determined by X-ray crystallography. IR and Raman spectra of the two polymorphs were measured and the spectral characteristics were compared with those of phenylpyruvic acid. the two polymorphs show similar molecular and crystal structures to each other, except for the molecular geometries of the enol and the carboxylic acid moieties. Distinct IR spectral differences which result from the crystal field splitting were observed between the two polymorphs.     

Optical Absorption Spectra of Gd2BaCoO5 and Y2BaCoO5

The marked differences found in the optical spectra of the brown coloured G₂BaCoO₅ and the green coloured Y₂BaCoO₅ oxides, have been explained taking into account the different crystal structures that they present. While Gd₂BaCoO₅ shows orthorhombic symmetry, space group lmmm, with the cobalt located at distorted octahedral coordination (CoO₆), the Y₂BaCoO₅ crystallizes with orthorhombic symmetry, space group Pnma, in which the cobalt is surrounded by five oxygen atoms, forming distorted square pyramids (CoO₅) which belong to the C_4v group symmetry.     

Role of non-lamellar-forming lipid in promotion of liposomal fusion

Membrane fusion is an important process in a wide range of cellular and sub-cellular activities. It is evident that during the intermediate stages of fusion some transitory non-bilayer configurations must appear within the lipid moiety. Using fluorescence techniques, we have studied here the process of aggregation and fusion of liposomes made of lipids, namely 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). When mixed together, the complete fusion between these two liposomes took around 44 h as both DPPC and DMPC favour lamellar configuration. When the mixture was incubated at 42°C the fusion process was completed after 23 h. But, when 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) was added in the liposomal matrix the time for fusion was reduced to 21 h for mixture without incubation and 17 h when the mixture was incubated. This indicates that DPPE having a tendency to assume non-lamellar conformation, promoted destabilisation of the lamellar conformation within the liposome which facilitated the fusion between two apposing bilayers.     

Crystallization of poly(butylene adipate) in the presence of nucleating agents

The effect of nucleating agents on the polymorphic crystallization behavior of poly(butylene adipate) (PBA) was studied with four kinds of commercially available nucleating agents, such as talc and boron nitride. The crystal structures of the α and β forms were studied with wide‐angle X‐ray diffraction. The β‐to‐α‐crystal transformation of PBA in the absence and presence of the nucleating agents in isothermal crystallization and nonisothermal crystallization processes was studied with differential scanning calorimetry and polarized optical microscopy. In both isothermal and nonisothermal crystallization, the introduction of nucleating agents selectively initiated the nucleation of the α‐form crystal, which was relatively slow in the absence of nucleating agents. The nucleating activity of the four kinds of nucleating agents in the crystallization of the PBA α‐form crystal was determined by the study of the nonisothermal crystallization, spherulite morphology, and isothermal kinetics. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2340–2351, 2005     

Thermal and X‐ray analysis of polymorphic crystals,melting, and crystalline transformation in poly(butylene adipate)

Polymorphic crystals and complex multiple melting behavior in an aliphatic biodegradable polyester, poly(butylene adipate) (PBA), were thoroughly examined by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). Further clarification on mechanisms of multiple melting peaks related to polymorphic crystal forms in PBA was attempted. More stable α‐form crystal is normally favored for crystallization from melt at higher temperatures (31–35 °C), or upon slow cooling from the melt; while the β‐form is the favored species for crystallization at low temperatures (25–28 °C). We further proved that PBA crystallization could also result in all α‐form even at low temperatures (25–28 °C) if it crystallized with the presence of prior α‐form nuclei. PBA packed with both crystal forms could display as many as four melting peaks (P1 ? P4, in ascending temperature order). However, PBA initially containing only the α‐crystal exhibited dual melting peaks of P1 and P3, which are attributed to dual lamellar distributions of the α‐crystal. By contrast, PBA initially containing only the β‐crystal could also exhibit dual melting peaks (P2 and P4) upon scanning. While P2 is clearly associated with melting of the initial β‐crystal, the fourth melting peak (P4), appearing rather broad, was determined to be associated with superimposed thermal events of crystal transformation from β‐ to α‐crystal and final re‐melting of the new re‐organized α‐crystal. Crystal transformation from one to the other or vice versa, lamellae thickening, annealing at molten state, and influence on crystal polymorphism in PBA were analyzed. Relationships and mechanisms of dual peaks for isolate α‐ or β‐crystals in PBA are discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1662–1672, 2005