Comparison of the structure property relationships in LB films of zwitterionic TCNQ adducts

2005 ◽  
Vol 15 (14) ◽  
pp. 1437 ◽  
Author(s):  
Norman A. Bell ◽  
Christopher S. Bradley ◽  
Richard A. Broughton ◽  
Simon J. Coles ◽  
David E. Hibbs ◽  
...  
Keyword(s):  
Structure Property ◽  
Lb Films ◽  
Structure Property Relationships

Aggregation of squaraine dyes: Structure–property relationships and solvent effects

1995 ◽  
Vol 73 (10) ◽  
pp. 1605-1615 ◽  
Author(s):  
Andrew J. McKerrow ◽  
Erwin Buncel ◽  
Peter M. Kazmaier
Keyword(s):  
Solvent Effects ◽  
Absorption Maximum ◽  
Type A ◽  
Spectral Features ◽  
Type B ◽  
Structure Property ◽  
Absorption Properties ◽  
Lb Films ◽  
Squaraine Dyes ◽  
Structure Property Relationships

In characterizing the UV–visible absorption properties of a series of seven anilino class squaraine dyes in dimethyl sulfoxide (DMSO) – water mixtures, spectral features characteristic of aggregation were observed. These included hypsochromic and hypochromic shifts of the absorption maximum, relative to the nonassociated state of these dyes. Previously aggregation of this class of squaraine dyes had only been reported in studies of Langmuir–Blodgett (LB) films prepared with squaraine dyes. In the present study two distinctly different and novel solution dye aggregates, designated as type A and type B, were identified on the basis of their characteristic absorption properties. The type A aggregate was characterized by an absorption maximum that was hypsochromically and hypochromically shifted, in comparison with that of the nonassociated dyes, and had a secondary absorption occurring at approximately the same wavelength at which nonassociated squaraine dyes absorb. These spectral features are believed to be the result of a "face-to-face" alignment of molecules in the aggregate. The type B aggregate featured a broad absorption typically from 525 to 700 nm. Based on similarities between the spectral features of type B aggregates and LB films of surfactant squaraines, the alignment of molecules in the solution aggregate was believed to be such that the electron-deficient squarylium moieties interacted with the electron-rich dialkylamino phenyl moieties. Certain squaraine dyes that were investigated as part of this study were found to form both type A and type B aggregates, depending upon the composition of the DMSO–water medium. Typically, the type A aggregate formed preferentially in media of intermediate DMSO content (50–70% DMSO) and the type B aggregate in more water-rich media (<20% DMSO). In the intervening region it was possible to monitor spectroscopically a dynamic conversion from the type B aggregate to the type A aggregate. An examination of structure–property relationships indicated that dyes with less hydrophobic N-alkyl substituents formed only type A aggregates. Squaraine dyes with more hydrophobic N-alkyl substituents were found to form type B aggregates in water and type A aggregates in some DMSO–water mixtures. A model of squaraine aggregation was proposed in which the type A squaraine aggregate was "thermodynamically" preferred while the type B aggregate was "kinetically" preferred. The stability of the type B aggregate was proposed to be enhanced by increasing hydrophobicity of the N-alkyl substituents and decreased by increasing amounts of DMSO in the solvent system. Keywords: squaraine dyes, aggregation, crystallochromy, solvent effects.

Structure-property relationships of PE/PP sandwiched films

1987 ◽  
Vol 45 ◽  
pp. 454-455
Author(s):  
J. Petermann ◽  
G. Broza ◽  
U. Rieck ◽  
A. Jaballah ◽  
A. Kawaguchi
Keyword(s):  
Mechanical Tests ◽  
Polymer Materials ◽  
Ionic Crystals ◽  
Structure Property ◽  
Polymer Systems ◽  
Structure Property Relationships ◽  
Oriented Films ◽  
Materials Used ◽  
Polymer Laminates ◽  
Heated Glass

Oriented overgrowth of polymer materials onto ionic crystals is well known and recently it was demonstrated that this epitaxial crystallisation can also occur in polymer/polymer systems, under certain conditions. The morphologies and the resulting physical properties of such systems will be presented, especially the influence of epitaxial interfaces on the adhesion of polymer laminates and the mechanical properties of epitaxially crystallized sandwiched layers.Materials used were polyethylene, PE, Lupolen 6021 DX (HDPE) and 1810 D (LDPE) from BASF AG; polypropylene, PP, (PPN) provided by Höchst AG and polybutene-1, PB-1, Vestolen BT from Chemische Werke Hüls. Thin oriented films were prepared according to the method of Petermann and Gohil, by winding up two different polymer films from two separately heated glass-plates simultaneously with the help of a motor driven cylinder. One double layer was used for TEM investigations, while about 1000 sandwiched layers were taken for mechanical tests.

Approaches for TEM imaging of cavitation in toughened nylon

1989 ◽  
Vol 47 ◽  
pp. 352-353
Author(s):  
Barbara A. Wood
Keyword(s):  
Morphological Characteristics ◽  
Structure Property ◽  
Polymer Systems ◽  
Selective Staining ◽  
Structure Property Relationships ◽  
Rubber Toughened ◽  
Shear Yield ◽  
Controversial Topic ◽  
Selection Of ◽  
Diamond Knife

A controversial topic in the study of structure-property relationships of toughened polymer systems is the internal cavitation of toughener particles resulting from damage on impact or tensile deformation.Detailed observations of the influence of morphological characteristics such as particle size distribution on deformation mechanisms such as shear yield and cavitation could provide valuable guidance for selection of processing conditions, but TEM observation of damaged zones presents some experimental difficulties.Previously published TEM images of impact fractured toughened nylon show holes but contrast between matrix and toughener is lacking; other systems investigated have clearly shown cavitated impact modifier particles. In rubber toughened nylon, the physical characteristics of cavitated material differ from undamaged material to the extent that sectioning of heavily damaged regions by cryoultramicrotomy with a diamond knife results in sections of greater than optimum thickness (Figure 1). The detailed morphology is obscured despite selective staining of the rubber phase using the ruthenium trichloride route to ruthenium tetroxide.

Catalyst Halogenation Enables Rapid and Efficient Polymerizations with Visible to Near-Infrared Light

2020 ◽  
Author(s):  
Alex Stafford ◽  
Dowon Ahn ◽  
Emily Raulerson ◽  
Kun-You Chung ◽  
Kaihong Sun ◽  
...  
Keyword(s):  
Near Infrared ◽  
Transient Absorption ◽  
Reaction Times ◽  
Infrared Light ◽  
Structure Property ◽  
Light Emitting ◽  
Structure Property Relationships ◽  
Nir Light ◽  
Light Intensities ◽  
Emission Quenching

Driving rapid polymerizations with visible to near-infrared (NIR) light will enable nascent technologies in the emerging fields of bio- and composite-printing. However, current photopolymerization strategies are limited by long reaction times, high light intensities, and/or large catalyst loadings. Improving efficiency remains elusive without a comprehensive, mechanistic evaluation of photocatalysis to better understand how composition relates to polymerization metrics. With this objective in mind, a series of methine- and aza-bridged boron dipyrromethene (BODIPY) derivatives were synthesized and systematically characterized to elucidate key structure-property relationships that facilitate efficient photopolymerization driven by visible to NIR light. For both BODIPY scaffolds, halogenation was shown as a general method to increase polymerization rate, quantitatively characterized using a custom real-time infrared spectroscopy setup. Furthermore, a combination of steady-state emission quenching experiments, electronic structure calculations, and ultrafast transient absorption revealed that efficient intersystem crossing to the lowest excited triplet state upon halogenation was a key mechanistic step to achieving rapid photopolymerization reactions. Unprecedented polymerization rates were achieved with extremely low light intensities (< 1 mW/cm<sup>2</sup>) and catalyst loadings (< 50 μM), exemplified by reaction completion within 60 seconds of irradiation using green, red, and NIR light-emitting diodes.

A Review on Camptothecin Analogs with Promising Cytotoxic Profile

2019 ◽  
Vol 18 (13) ◽  
pp. 1796-1814 ◽  
Author(s):  
Sk. Abdul Amin ◽  
Nilanjan Adhikari ◽  
Tarun Jha ◽  
Shovanlal Gayen
Keyword(s):  
Cell Lines ◽  
Cancer Cell ◽  
Cancer Cell Lines ◽  
Structure Property ◽  
Cytotoxic Potential ◽  
Structure Property Relationships ◽  
Structure Activity ◽  
Camptothecin Analogs ◽  
Pharmacokinetic Properties ◽  
Quantitative Structure Activity Relationships

Camptothecin (CPT), obtained from Camptotheca acuminata (Nyssaceae), is a quinoline type of alkaloid. Apart from various traditional uses, it is mainly used as a potential cytotoxic agent acting against a variety of cancer cell lines. Though searches have been continued for last six decades, still it is a demanding task to design potent and cytotoxic CPTs. Different CPT analogs are synthesized to enhance the cytotoxic potential as well as to increase the pharmacokinetic properties of these analogs. Some of these analogs were proven to be clinically effective in different cancer cell lines. In this article, different CPT analogs have been highlighted extensively to get a detail insight about the structure-property relationships as well as different quantitative structure-activity relationships (QSARs) modeling of these analogs are also discussed. This study may be beneficial for designing newer CPT analogs in future.

Structure-property relationships in bainitic steels

1990 ◽  
Vol 21 (6) ◽  
pp. 1527-1540 ◽  
Author(s):  
D. V. Edmonds ◽  
R. C. Cochrane
Keyword(s):  
Structure Property ◽  
Structure Property Relationships ◽  
Bainitic Steels

scholarly journals Expanding Monomers as Anti-Shrinkage Additives

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 806
Author(s):  
Philipp Marx ◽  
Frank Wiesbrock
Keyword(s):  
Ring Opening ◽  
Covalent Bond ◽  
Volumetric Shrinkage ◽  
Structure Property ◽  
Atomic Packing ◽  
Materials Properties ◽  
Volumetric Expansion ◽  
Structure Property Relationships ◽  
Ring Opening Reaction ◽  
Measuring Techniques

Commonly, volumetric shrinkage occurs during polymerizations due to the shortening of the equilibrium Van der Waals distance of two molecules to the length of a (significantly shorter) covalent bond. This volumetric shrinkage can have severe influence on the materials’ properties. One strategy to overcome this volumetric shrinkage is the use of expanding monomers that show volumetric expansion during polymerization reactions. Such monomers exhibit cyclic or even oligocyclic structural motifs with a correspondingly dense atomic packing. During the ring-opening reaction of such monomers, linear structures with atomic packing of lower density are formed, which results in volumetric expansion or at least reduced volumetric shrinkage. This review provides a concise overview of expanding monomers with a focus on the elucidation of structure-property relationships. Preceded by a brief introduction of measuring techniques for the quantification of volumetric changes, the most prominent classes of expanding monomers will be presented and discussed, namely cycloalkanes and cycloalkenes, oxacycles, benzoxazines, as well as thiocyclic compounds. Spiroorthoesters, spiroorthocarbonates, cyclic carbonates, and benzoxazines are particularly highlighted.

Structure–Property Relationships in Photoluminescent Bismuth Halide Organic Hybrid Materials

2021 ◽  
Author(s):  
R. Lee Ayscue ◽  
Valérie Vallet ◽  
Jeffery A. Bertke ◽  
Florent Réal ◽  
Karah E. Knope
Keyword(s):  
Hybrid Materials ◽  
Structure Property ◽  
Organic Hybrid ◽  
Structure Property Relationships
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