scholarly journals Stress-induced colouration and crosslinking of polymeric materials by mechanochemical formation of triphenylimidazolyl radicals

2016 ◽  
Vol 52 (55) ◽  
pp. 8608-8611 ◽  
Author(s):  
F. Verstraeten ◽  
R. Göstl ◽  
R. P. Sijbesma
Keyword(s):  
Polymeric Materials ◽  
Radical Reactions ◽  
Damage Repair ◽  
Polymer Architectures ◽  
Stress Sensing ◽  
Secondary Radical

Subjecting hexaarylbiimidazole in polymer architectures to stress generates coloured triphenylimidazolyl radicals that initiate secondary radical reactions unifying stress-sensing and damage-repair.

scholarly journals Mechanochemically Gated Photoswitching: Expanding the Scope of Polymer Mechanochromism

Synlett ◽  
2019 ◽  
Vol 30 (15) ◽  
pp. 1725-1732 ◽  
Author(s):  
Ross W. Barber ◽  
Molly E. McFadden ◽  
Xiaoran Hu ◽  
Maxwell J. Robb
Keyword(s):  
Mechanical Activation ◽  
Uv Light ◽  
Cycloaddition Reaction ◽  
Polymeric Materials ◽  
Diels Alder ◽  
Information Storage ◽  
Chemical Transformations ◽  
History Of ◽  
Polymer Mechanochemistry ◽  
Stress Sensing

Mechanophores are molecules that undergo productive, covalent chemical transformations in response to mechanical force. Over the last decade, a variety of mechanochromic mechanophores have been developed that enable the direct visualization of stress in polymers and polymeric materials through changes in color and chemiluminescence. The recent introduction of mechanochemically gated photoswitching extends the repertoire of polymer mechanochromism by decoupling the mechanical activation from the visible response, enabling the mechanical history of polymers to be recorded and read on-demand using light. Here, we discuss advances in mechanochromic mechanophores and present our design of a cyclopentadiene–maleimide Diels–Alder adduct that undergoes a force-induced retro-[4+2] cycloaddition reaction to reveal a latent diarylethene photoswitch. Following mechanical activation, UV light converts the colorless diarylethene molecule into the colored isomer via a 6π-electrocyclic ring-closing reaction. Mechanically gated photoswitching expands on the fruitful developments in mechanochromic polymers and provides a promising platform for further innovation in materials applications including stress sensing, patterning, and information storage.1 Introduction to Polymer Mechanochemistry2 Mechanochromic Reactions for Stress Sensing3 Regiochemical Effects on Mechanophore Activation4 Mechanochemically Gated Photoswitching5 Conclusions

scholarly journals Polymer Architectures for Optical and Photonic Applications

2021 ◽  
Author(s):  
Ana-Maria Albu ◽  
Vlad Marian Târpă
Keyword(s):  
High Performance ◽  
Organic Materials ◽  
Functional Materials ◽  
Polymeric Materials ◽  
Optical Nonlinearity ◽  
Fundamental Relationship ◽  
Polymer Architectures ◽  
Materials Used ◽  
Molecule Interactions ◽  
Relationship Of

The last decade of the last century is marked by a revolution in the synthesis of materials for optical and photonic applications, against the background of the growing need for new high-performance materials to increase the efficiency, reliability and speed of response linked to environmental aspects. The diversity of requirements and the optimization of the responses has led to a major dispute over the structure and composition of these materials: Inorganic or Organic, Natural or Synthetic, Hybrid or Pure, which has stimulated interest in the development of various architectures. Special attention shall be paid to establishing a fundamental relationship to correlate the non-linear optical response and chemical structure, especially for the category of organic materials- particularly polymers- distinguished by structural/compositional versatility and suitable for processing by simple technique which allows serial production. In fact, optical nonlinearity (NLO) is not an exotic phenomenon. Indeed, all materials are optically nonlinear if light is sufficiently intense. The synthesis of functional photonic organic materials is a major challenge of contemporary community of material scientists to imagine new functional materials based of” collective” phenomena by virtue of the “engineered” molecule- molecule interactions and spatial relationships. In this context, this paper aims to highlight the most important features concerning the structural - compositional relationship of polymeric materials used in optoelectronic and photonic applications.

scholarly journals Cycloparaphenylene-Norbornene Monomers Afford Access to Carbon Nanohoop-Based Polymers

2019 ◽  
Author(s):  
Ruth Maust ◽  
Penghao Li ◽  
Lev N. Zakharov ◽  
Ramesh Jasti
Keyword(s):  
Small Molecule ◽  
Ring Opening ◽  
Polymeric Materials ◽  
Building Blocks ◽  
Functional Polymers ◽  
Size Dependent ◽  
Molecular Building Blocks ◽  
Polymer Architectures ◽  
Different Diameters ◽  
Critical Challenge

Although impressive strides have been made toward achieving precise polymer architectures, the pursuit of monomers with diverse structures and functions remains a critical challenge for polymer design. Herein we disclose the first polymers constructed from cycloparaphenylenes (CPPs), a family of strained, pi-rich macrocycles. Poly-CPPs were prepared via ring-opening metathesis polymerization (ROMP) of benzonorbornene-embedded CPPs. The distinctive size-dependent properties of CPPs, including fluorescence and host-guest chemistry, are preserved in poly-CPPs, offering a means to capitalize on these properties in polymeric materials. Moreover, copolymerizing CPPs of two different diameters results in polymers with emergent photophysical and supramolecular properties not achievable with small molecule CPP units. This work sets the stage for CPP derivatives to serve as molecular building blocks for the next generation of functional polymers.

scholarly journals Cycloparaphenylene-Norbornene Monomers Afford Access to Carbon Nanohoop-Based Polymers

2019 ◽  
Author(s):  
Ruth Maust ◽  
Penghao Li ◽  
Lev N. Zakharov ◽  
Ramesh Jasti
Keyword(s):  
Small Molecule ◽  
Ring Opening ◽  
Polymeric Materials ◽  
Building Blocks ◽  
Functional Polymers ◽  
Size Dependent ◽  
Molecular Building Blocks ◽  
Polymer Architectures ◽  
Different Diameters ◽  
Critical Challenge

Although impressive strides have been made toward achieving precise polymer architectures, the pursuit of monomers with diverse structures and functions remains a critical challenge for polymer design. Herein we disclose the first polymers constructed from cycloparaphenylenes (CPPs), a family of strained, pi-rich macrocycles. Poly-CPPs were prepared via ring-opening metathesis polymerization (ROMP) of benzonorbornene-embedded CPPs. The distinctive size-dependent properties of CPPs, including fluorescence and host-guest chemistry, are preserved in poly-CPPs, offering a means to capitalize on these properties in polymeric materials. Moreover, copolymerizing CPPs of two different diameters results in polymers with emergent photophysical and supramolecular properties not achievable with small molecule CPP units. This work sets the stage for CPP derivatives to serve as molecular building blocks for the next generation of functional polymers.

The Resolution and Contrast in Biological Sections Determined by Inelastic and Elastic Scattering

1973 ◽  
Vol 31 ◽  
pp. 224-225
Author(s):  
D. L. Misell
Keyword(s):  
Electron Microscopy ◽  
Adverse Effect ◽  
Elastic Scattering ◽  
Inelastic Scattering ◽  
Amorphous Carbon ◽  
Polymeric Materials ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Quantitative Estimates ◽  
Elastic Ratio

In the electron microscopy of biological sections the adverse effect of chromatic aberration on image resolution is well known. In this paper calculations are presented for the inelastic and elastic image intensities using a wave-optical formulation. Quantitative estimates of the deterioration in image resolution as a result of chromatic aberration are presented as an alternative to geometric calculations. The predominance of inelastic scattering in the unstained biological and polymeric materials is shown by the inelastic to elastic ratio, I/E, within an objective aperture of 0.005 rad for amorphous carbon of a thickness, t=50nm, typical of biological sections; E=200keV, I/E=16.

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