Crystallization of post-consumer polypropylene in the presence of β-nucleating agent

Journal of Thermal Analysis and Calorimetry - In this paper, the heat transfer characteristics of the nanofluid through a parallel plate soft nanochannel are investigated under the fully developed...     

Effect of a Nematic Liquid Crystalline Polymer as Highly Active β-Nucleator on Crystallization Structure and Morphology of Isotactic Polypropylene

The effects of nematic liquid crystalline polymer as a new β-nucleator (LCP-N) on crystallization structure and morphology of isotactic polypropylene (iPP) were investigated using wide-angle X-ray diffraction and polarized optical microscopy. The experimental results showed that LCP-N could lead to substantial changes in the crystallization structure and morphology of iPP. The nucleating activity of LCP-N mainly depended on its content, mesogenic molecules, and thermal history of processing. A high content of β-form (K _β) was obtained by the combined effect of the optimum LCP-N content and crystallization temperature. The maximum K _β reached 84% when the LCP-N content and crystallization temperature and time were 0.4 wt.%, 125°C, and 1 h, respectively. In addition, the birefringence of β spherulite was stronger than that of α spherulite; this difference is related to their particular way of growing and lamellar morphology. Due to its particular sheaf-like growth, the β spherulite was brighter and more colorful.     

Synthesis of a New Liquid Crystalline Polymer as a Highly Active β-Nucleator and Its Effect on Melting and Crystallization Behaviors of Isotactic Polypropylene

A new nematic liquid crystalline polymer as a highly active β-nucleator (LCP-N) of isotactic polypropylene (iPP) was synthesized and characterized. The effect of LCP-N on thermal behavior of the iPP was investigated with differential scanning calorimetry. LCP-N showed a melting transition at 85.0°C and a nematic to isotropic phase transition at 278.0°C. The incorporation of LCP-N could lead to substantial changes in the thermal behavior of the iPP. The nucleating activity of LCP-N mainly depended on its content, mesogenic molecular structure, and thermal history of processing. A high content of β-form could be obtained by the combined effect of the optimum LCP-N concentration and crystallization temperature and time. The Φ_β reached 77% when the LCP-N content, crystallization temperature, and crystallization time were 0.4 wt.%, 125°C, and 1 h, respectively.     

Stereoselective synthesis of a β-D-phosphatidylgalactose

The stereoselective synthesis of a -D-phosphatidylgalactose has been achieved by the interaction of a benzyl phosphatidate with D-galactose tert-butyl orthoacetate or trichloroacetimidate.M. V. Lomonosov Institute of Fine Chemical Technology, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 16–19, January–February, 1991.     

Synthesis of a New β-Mercaptoalcohol

Mercaptoalcohols are a rare class of natural products. Some optically active mercaptoalcohols have been used as catalysts in asymmetric reduction of prochiral Ketone1,2. In this letter, we report the synthesis of a new optically active (-mercaptoalcohols, (R)-1,1-diphenyl-2-mercapto-3-methyl-1-butanol 7, from L- valine.Our first attempt is showed in Scheme 1. According to literature's method L-valine was converted to (S)-2-Hydroxy-3-methylbutanoic acid 21,2. 2 was treated with MeOH/SOCl2…     

Synthesis of a 1,3,4,5-tetrahydrobenzindole β-ketoester

Pd(OAc)₂-catalyzed decomposition of ethyl 2-diazo-4-(4-indolyl)-3-oxobutanoate leads to a tricyclic tetrahydrobenzindole compound formed by a formal C-H insertion reaction. This tricyclic indole rearranges to a novel and thermodynamically more stable naphthalene derivative. Treatment of N-tosyl-protected ethyl 2-diazo-4-(4-indolyl)-3-oxobutanoate with a base induces facile pyrazole formation.     

Swern oxidation of a hindered β-hydroxyester

The highly hindered β-hydroxyester 3 fails to oxidize under the usual Swern reaction conditions, whereas closely related compounds react successfully. Swern oxidation of 3 occurs if the work-up conditions are modified or if diazabicycloundecane (DBU) rather than triethylamine (TEA) is used as the base in the reation. A mechanistic rationale is proposed in which the kinetic acidity of a dimethylsulfoxonium salt derived from 3 is postulated to be suppressed by intramolecular complexation.     

Crystallization and melting behaviors of polypropylene admixed by graphene and β-phase nucleating agent

In this work, the crystallization and melting behaviors of different polypropylene (PP) materials containing a certain amount of graphene, β-phase nucleating agent (β-NA), and their mixture, respectively, were comparatively investigated. The results showed that graphene exhibited the typical sheet structure in the PP matrix, and the presence of β-NA did not change the dispersion of graphene apparently. Both graphene and β-NA exhibited great nucleating effect for the crystallization of PP. However, the nucleation efficiency of β-NA was much larger than that of graphene. With the simultaneous presence of graphene and β-NA, the crystallization ability of PP matrix was greatly improved, which indicated that there was a synergistic effect between graphene and β-NA in accelerating crystallization of PP matrix. Furthermore, it was proved that the synergistic effect was greatly dependent upon the crystallization conditions. The higher the isothermal crystallization temperature or the bigger the cooling rate, the more apparent the synergistic effect was.     

Amine-promoted β-elimination of a β-aryloxy aldehyde for fluorogenic chemodosimeters

We previously reported a fluorescent chemodosimeter for ozone. The β-elimination step after the ozonolysis of the chemodosimeter was too slow to be practical for real-time monitoring of ozone. We examined primary, secondary, and tertiary amines at various pHs. It was found that pyrrolidine in pH 9 buffer could accelerate the elimination to generate a fluorescence signal. The elimination step is now sufficiently rapid to monitor ozone exposure in real time. We also discovered that azetidine was distinctly effective for the same elimination reaction in a pH 6 buffer.     

Microemulsion‐Facilitated Crystallization of Carbamazepine

The crystallization patterns of carbamazepine precipitated from a confined microemulsion reservoir were studied by DSC, TGA, Powder XRD, single crystal XRD, SEM, and optical microscopy. The results suggest that interfacial fast nucleation and slow growth from O/W microemulsion leads to a selective, large, and better‐ordered single crystals of dihydrate form with primitive monoclinic unit cell with parameters a=10.16 Å, b=28.70 Å, c=4.93 Å, β=103.33°, cell volume of 1400.7 ų, and space group P21/c. The crystal structure, as well as the habit, are strongly influenced by the heat dissipation and prefered molecular orientation at the interface.     

A concise synthesis of a β-lactamase inhibitor

MK-7655 (1) is a β-lactamase inhibitor in clinical trials as a combination therapy for the treatment of bacterial infection resistant to β-lactam antibiotics. Its unusual structural challenges have inspired a rapid synthesis featuring an iridium-catalyzed N-H insertion and a series of late stage transformations designed around the reactivity of the labile bicyclo[3.2.1]urea at the core of the target.     

Crystallization and Preliminary Crystallographic Analysis of β-Trichosanthin, an Isoform of Trichosanthin from the Root Tuber of Trichosanthe kirilowii

β-Trichosanthin, a type 1 ribosome-inactivating protein (RIP) isolated from the root tuber of Trichosanthe kirilowii Maxim, is an isoform of trichosanthin. Here we report its crystal- lization in two crystal forms using the hanging-drop vapor-diffusion method. The form A and form B crystals belong to the orthorhombic space group P212121 and monoclinic space group P21, respectively. X-ray data have been collected to 1.6 and 1.2 (A) resolution for form A and form B crystals, respectively, using a synchrotron source.     

Molecular recognition of a self-assembled monolayer of a polydithiocarbamate derivative of β-cyclodextrin on silver

The synthesis and molecular recognition properties of a new sulfur containing β-cyclodextrin (β-CD) derivative chemisorbed on a silver surface are described. Hepta-6-amino-6-deoxy-β-CD was allowed to react with CS₂ in the presence of ammonia to give a mixture of partially substituted dithiocarbamate derivatives with an average degree of substitution of 4.5. A modified silver electrode with this derivative is capable of discriminating between the three positional isomers of nitrobenzoate ion and nitrophenol, as determined by cyclic voltammetry. Only the meta- and para-isomers give a signal corresponding to the reduction of the nitro group. This is attributed to the different orientations of the nitro group with respect to the silver surface after inclusion in the CD cavity. Experiments in the presence of cyclohexanol showed a decrease in signal intensity of the meta- and para-isomers which is associated with the competitive complexation of this guest, suggesting that the electroactive probe is complexed to the cavity.     

Evidence for Non-Innocence of a β-Diketonate Ligand

β-Diketonates, such as acetylacetonate, are amongst the most common bidentate ligands towards elements across the entire periodic table and are considered wholly redox-inactive in their complexes. Herein we show that complexation of 1,1,1,5,5,5-hexafluoroacetylacetonate (hfac⁻) to Cr^II spontaneously affords Cr^III and a reduced β-diketonate radical ligand scaffold, as evidenced by crystallographic analysis, magnetic measurements, optical spectroscopy, reactivity studies, and DFT calculations. The possibility of harnessing β-diketonates as electron reservoirs opens up possibilities for new metal–ligand concerted reactivity in the ubiquitous β-diketonate coordination chemistry.     

Computational design of a self-assembling β-peptide oligomer

The first computationally designed self-assembling oligomer consisting of exclusively β-amino acids (βAAs) is presented. The packing of a β-3(14) helix into coiled-coils of varying stoichiometries as a function of amino acid sequence is examined. β-Peptides with hVal repeating every third residue in the sequence appeared to have a strong propensity to pack into hexameric bundles. The designed sequence was synthesized and characterized with CD spectroscopy, NMR, and analytical ultracentrifugation, suggesting that the peptide adopts a well-folded hexameric structure.     

Unusual Formation of a β-linked Disaccharide in a Nis Glycosylation

Abstract

The N-halosuccinimide glycosylation is a highly selective reaction that leads to trans-configured 1-alkoxy-2-halo-glycosides (halo = bromo, iodo).²³ As an exception to the generally observed exclusive formation of α-linked glycosides in such reactions,² we obtained a 3 / 1 mixture of α- and β-disaccharide 6 and 7, when we treated the silylated glycal 4 with NIS (N-iodosuccinimide) and the glycoside 5.⁴ The similarly protected arabino glycal 9, on the other hand, gave exclusively the expected α-linked saccharide 11, when treated with NIS and the alcohol component 10.⁵ Silylated glycals 4 and 9 were obtained from L-digitoxal 1 ⁶ and L-rhamnal 8 ⁷ by treatment with tert-butyldiphenylchlorosilane⁸ and tert-butyldimethylchlorosilane,⁹ respectively. In both cases the 3-O-silylated derivatives formed in high yields. Only in case of the ribo-configuration minor amounts of a 4-O-silylated product 3 were identified.     

Crystallization and Preliminary Crystallographic Analysis of β- Trichosanthin, an Isoform of Trichosanthin from the Root Tuber of Trichosanthe kirilowii

β-Trichosanthin,a type 1 ribosome-inactivating protein (RIP) isolated from the root tuber of Trichosanthe kirilowii Maxim,is an isoform of trichosanthin. Here we report its crystal-lization in two crystal forms using the hanging-drop vapor-diffusion method. The form A and form B crystals belong to the orthorhombic space group P212121 and monoclinic space group P21,respectively. X-ray data have been collected to 1.6 and 1.2 resolution for form A and form B crystals,respectively,using a synchrotron source.