Probing the use of small‐angle light scattering for characterizing structure of titanium dioxide/low‐density polyethylene nanocomposites

Small‐angle light scattering (SALS) measurements were used to study the structure of titanium dioxide (TiO₂)/low‐density polyethylene (LDPE) nanocomposites. The results showed that the scattering from LDPE crystalline structures and the scattering from TiO₂ nanoparticles can be resolved and separated. It is shown that the independent effects of crystallization conditions and the presence of nanoparticle aggregates on the spherulitic structure of the LDPE matrix can be determined by analyzing the scattering patterns using the methods proposed. From the SALS results, we conclude that the nanoparticle surface chemistry affects both nucleation of spherulites and their structure particularly under rapid cooling conditions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1084–1095, 2006     

Recent trends and open issues in reverse engineering

This paper discusses recent trends in the field of reverse engineering, particularly those highlighted at the Second Working Conference on Reverse Engineering, held in July 1995. The trends observed include increased orientation toward tasks, grounding in complex real-world applications, guidance from empirical study, analysis of non-code sources, and increased formalization. The paper also summarizes open research issues and provides pointers to future events and sources of information in this area.     

Closo → nido cage degradation of 1-(substituted-phenyl)-1,2-dicarbadodecaborane(12)s in wet DMSO under neutral conditions

1-(2-Nitrophenyl)-1,2-dicarba-closo-dodecaborane(12) shows C-H?O intramolecular hydrogen bonding in chloroform. The reaction of isomeric 1-(nitrophenyl)-1,2-dicarba-closo-dodecaborane(12)s and of 1-(4-fluorophenyl)-1,2-dicarba-closo-dodecaborane(12) with wet DMSO causes the removal of 3-B or 6-B, leading cleanly to nido-carboranes. The rank order of rates of these deboronations is consistent with developing negative charge in the rate-determining step.     

Synthesis and structure of fluorotricyanomethane

Fluorotricyanomethane is prepared from potassium tricyanomethanide and perchlorylfluoride. The crystal structure of this compound (orthorhombic, space group P2₁2₁2₁, with a=6.270, b=6.734, c=11.776 Å) has been determined by X-ray analysis. The results are discussed in relation to those of (NC)₃C? X (X=? CH₃, ? Cl, ? Br or ? CN).     

Dirhodium(II)-catalyzed carbonyl ylide generation. Stereoelectronic control in dioxolane formation

The combination of ethyl diazoacetate with aryl aldehydes in the presence of copper(I) or rhodium(II) catalysts results in the formation of 1,3-dioxolane products in moderate to good yields. These reactions occur through a pathway that involves ylide intermediates. Catalyst-dependent diastereocontrol is observed and suggests that metal-associated ylides are involved in the product-determining step. The influence of aryl aldehyde substituents has been determined. Current address. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 961–965, May, 1998.     

The hydrolysis mechanism of bis(2,4-di-tert-butyl)pentaerythritol diphosphite (Alkanox P24): An atmospheric pressure photoionisation mass spectrometric study

Alkanox P24 is a commercial phosphite antioxidant, well known in the literature for its excellent processing stability. As in the case of many processing phosphites, however, Alkanox P24 might undergo hydrolysis when exposed to small amounts of water. A number of products proposed recently in the hydrolytic pathway of the phosphite [Ortuoste N, Allen NS, Papanastasiou M, McMahon A, Edge M, Johnson B, et al. Polym Degrad Stab; 2006;91:195-211] are investigated in this study by atmospheric pressure ionisation-mass spectrometry (API-MS). The applicability of atmospheric pressure photoionisation (APPI) and atmospheric pressure chemical ionisation (APCI) ion sources is tested and the ion formation characteristics of Alkanox P24 are compared in both sources. In positive ion mode, ionisation of the parent phosphite occurred by protonation. In negative ion mode no pseudo-molecular ion peak was detected and the deprotonated species were more dominant in APPI. This source was employed further for the investigation of the hydrolysis products, since it exhibited lower limits of detection. High performance liquid chromatography (HPLC) with single ion monitoring (SIM) detection was used for the separation of the species formed. Hydrolysis of the phosphite proceeded via the scission of the two P-O_phenol bonds exclusively to give 2,4-di-tert-butyl phenol quantitatively as a final product.     

Polymorphic forms of cilostazol

Two unique conformational polymorphic forms of the compound 6‐[4‐(1‐cyclo­hexyl‐1H‐tetrazol‐5‐yl)­butoxy]‐3,4‐di­hydro­quinolin‐2(1H)‐one (cilostazol), C₂₀H₂₇N₅O₂, have been discovered and characterized using single‐crystal X‐ray structural analysis. A third polymorph also exists, but acceptable crystals could not be obtained. Features of both reported polymorphic structures include a chair conformation of the cyclo­hexyl ring and puckering in the quinolinone ring. The major feature distinguishing the two polymorphic forms is a rotational twisting of the butoxy chain between the tetrazole and quinolinone rings. This difference in conformation influences the intermolecular forces, and hence the packing of the two mol­ecules during crystallization.