scholarly journals Direct C-H arylation as a tool for synthesis of conjugated polymers : from 1D linear polymers to 2D/3D porous networks

2018 ◽  
Author(s):  
Hassan Bohra
Keyword(s):  
Conjugated Polymers ◽  
Linear Polymers ◽  
Porous Networks

Photocatalytic Hydrogen Evolution from Water Using Heterocyclic Conjugated Microporous Polymers: Porous or Non-Porous?

2018 ◽  
Author(s):  
Reiner Sebastian Sprick ◽  
Yang Bai ◽  
Catherine M. Aitchison ◽  
Duncan J. Woods ◽  
Andrew I. Cooper
Keyword(s):  
Hydrogen Evolution ◽  
External Quantum Efficiency ◽  
Structural Analog ◽  
Linear Polymers ◽  
Porous Network ◽  
Photocatalytic Hydrogen Evolution ◽  
Microporous Polymers ◽  
Porous Networks ◽  
Hole Scavenger ◽  
Conjugated Microporous Polymers

<p>Three series of conjugated microporous polymers (CMPs) were studied as photocatalysts for producing hydrogen from water using a sacrificial hole-scavenger. In all cases, dibenzo[<i>b</i>,<i>d</i>]thiophene sulfone polymers outperformed their fluorene analogs. A porous network, S-CMP3, showed the highest hydrogen evolution rate of 6076 µmol h<sup>-1</sup> g<sup>-1</sup> (λ > 295 nm) and 3106 µmol h<sup>-1</sup> g<sup>-1</sup> (λ > 420 nm), with an external quantum efficiency of 13.2% at 420 nm. S-CMP3 outperforms its linear structural analog, P35, while in other cases, non-porous linear polymers are superior to equivalent porous networks. This suggests that microporosity can be beneficial for sacrificial photocatalytic hydrogen evolution, but not for all monomer combinations.</p>

Photocatalytic Hydrogen Evolution from Water Using Heterocyclic Conjugated Microporous Polymers: Porous or Non-Porous?

2018 ◽  
Author(s):  
Reiner Sebastian Sprick ◽  
Yang Bai ◽  
Catherine M. Aitchison ◽  
Duncan J. Woods ◽  
Andrew I. Cooper
Keyword(s):  
Hydrogen Evolution ◽  
External Quantum Efficiency ◽  
Structural Analog ◽  
Linear Polymers ◽  
Porous Network ◽  
Photocatalytic Hydrogen Evolution ◽  
Microporous Polymers ◽  
Porous Networks ◽  
Hole Scavenger ◽  
Conjugated Microporous Polymers

<p>Three series of conjugated microporous polymers (CMPs) were studied as photocatalysts for producing hydrogen from water using a sacrificial hole-scavenger. In all cases, dibenzo[<i>b</i>,<i>d</i>]thiophene sulfone polymers outperformed their fluorene analogs. A porous network, S-CMP3, showed the highest hydrogen evolution rate of 6076 µmol h<sup>-1</sup> g<sup>-1</sup> (λ > 295 nm) and 3106 µmol h<sup>-1</sup> g<sup>-1</sup> (λ > 420 nm), with an external quantum efficiency of 13.2% at 420 nm. S-CMP3 outperforms its linear structural analog, P35, while in other cases, non-porous linear polymers are superior to equivalent porous networks. This suggests that microporosity can be beneficial for sacrificial photocatalytic hydrogen evolution, but not for all monomer combinations.</p>

Electronic structure studies of conducting polymers by electron energy-loss spectroscopy

1996 ◽  
Vol 54 ◽  
pp. 160-161
Author(s):  
J. Fink
Keyword(s):  
Electronic Structure ◽  
Conducting Polymers ◽  
Conjugated Polymers ◽  
Electron Acceptors ◽  
Electron Donors ◽  
Light Emitting ◽  
One Dimensional ◽  
New Class ◽  
Electrical Conductivities ◽  
Electron Energy Loss

Conducting polymers comprises a new class of materials achieving electrical conductivities which rival those of the best metals. The parent compounds (conjugated polymers) are quasi-one-dimensional semiconductors. These polymers can be doped by electron acceptors or electron donors. The prototype of these materials is polyacetylene (PA). There are various other conjugated polymers such as polyparaphenylene, polyphenylenevinylene, polypoyrrole or polythiophene. The doped systems, i.e. the conducting polymers, have intersting potential technological applications such as replacement of conventional metals in electronic shielding and antistatic equipment, rechargable batteries, and flexible light emitting diodes.Although these systems have been investigated almost 20 years, the electronic structure of the doped metallic systems is not clear and even the reason for the gap in undoped semiconducting systems is under discussion.

On the surface tension of directed linear polymers

1989 ◽  
Vol 50 (6) ◽  
pp. 599-608 ◽  
Author(s):  
V.B. Priezzhev ◽  
S.A. Terletsky
Keyword(s):  
Surface Tension ◽  
Linear Polymers

Arrangement Of Monomeric Units In Fibrin

1979 ◽  
Author(s):  
Jan Hermans
Keyword(s):  
Fiber Axis ◽  
High Symmetry ◽  
Linear Polymers ◽  
Fiber Volume ◽  
High Fiber ◽  
Rotation Axes ◽  
Small Set ◽  
Helical Turn ◽  
The One ◽  
Kinetics Of

Measurements of light scattering have given much information about formation and properties of fibrin. These studies have determined mass-length ratio of linear polymers (protofibrils) and of fibers, kinetics of polymerization and of lateral association and volume-mass ratio of thick fibers. This ratio is 5 to 1. On the one hand, this high value suggests that the fiber contains channels that allow the diffusion of enzymes such as Factor XHIa and plasmin; on the other hand, the high value appears paradoxical for a stiff fiber made up of elongated units (fibrin monomers) arranged in parallel. Such a high fiber volume is a property of only a small set out of many high-symmetry models of fibrin, which may be constructed from overlapping three-domain monomers which are arranged into strands, are aligned nearly parallel to the fiber axis and make adequate longitudinal and lateral contacts. These models contain helical protofibrils related to each other by rotation axes parallel to the fiber axis. The protofibrils may contain 2, 3 or 4 monomers per helical turn and there are four possible symmetries. A large specific volume is achieved if the ends of each monomer are slightly displaced from the protofibril axis, either by a shift or by a tilt of the monomer. The fiber containing tilted monomers is more highly interconnected; the two ends of a tilted monomer form lateral contacts with different adjacent protofibrils, whereas the two ends of a non-tilted monomer contact the same adjacent protofibril(s).

Oriented Luminescent Nanostructures From Single Molecules Of Conjugated Polymers

2003 ◽  
Vol 771 ◽  
Author(s):  
Adosh Mehta ◽  
Pradeep Kumar ◽  
Jie Zheng ◽  
Robert M. Dickson ◽  
Bobby Sumpter ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Polarization Anisotropy ◽  
Emission Pattern ◽  
Spectral Signatures ◽  
Dipole Emission ◽  
Ink Jet ◽  
Molecular Scale ◽  
Jet Printing ◽  
Photochemical Stability ◽  
Printing Techniques

AbstractDipole emission pattern imaging experiments on single chains of common conjugated polymers (solubilized poly phenylene vinylenes) isolated by ink-jet printing techniques have revealed surprising uniformity in transition moment orientation perpendicular to the support substrate. In addition to uniform orientation, these species show a number of striking differences in photochemical stability, polarization anisotropy,[1] and spectral signatures[2] with respect to similar (well-studied) molecules dispersed in dilute thin-films. Combined with molecular mechanics simulation, these results point to a structural picture of a folded macromolecule as a highly ordered cylindrical nanostructure whose long-axis (approximately collinear with the conjugation axis) is oriented, by an electrostatic interaction, perpendicular to the coverglass substrate. These results suggest a number of important applications in nanoscale photonics and molecular-scale optoelectronics.

Toward highly photoluminescent and bipolar charge-transporting conjugated polymers

2000 ◽  
Vol 154 (1) ◽  
pp. 245-252 ◽  
Author(s):  
Zhonghua Peng ◽  
Yongchun Pan ◽  
Bubin Xu ◽  
Jianheng Zhang
Keyword(s):  
Conjugated Polymers ◽  
Bipolar Charge

Mapping the “Extra Solvent Power, ESP” of Ionic Liquids for Monomers, Polymers and Globular Nanoparticles

2017 ◽  
Author(s):  
Jose A. Pomposo
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Linear Polymers ◽  
Green Solvents ◽  
Ionic Polymers ◽  
First Time ◽  
Solvent Power

Understanding the miscibility behavior of ionic liquid (IL) / monomer, IL / polymer and IL / nanoparticle mixtures is critical for the use of ILs as green solvents in polymerization processes, and to rationalize recent observations concerning the superior solubility of some proteins in ILs when compared to standard solvents. In this work, the most relevant results obtained in terms of a three-component Flory-Huggins theory concerning the “Extra Solvent Power, ESP” of ILs when compared to traditional non-ionic solvents for monomeric solutes (case I), linear polymers (case II) and globular nanoparticles (case III) are presented. Moreover, useful ESP maps are drawn for the first time for IL mixtures corresponding to case I, II and III. Finally, a potential pathway to improve the miscibility of non-ionic polymers in ILs is also proposed.

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