Theoretical methods were first screened and validated with available experimental data on conventional conjugated polymers and/or their oligomers, and then they were used to predict and design various novel intrinsic low band gap conducting polymers. We proposed a series of novel types of ladder polymers with conventional conjugated polymers, polyacetylene, polydiacetylene, and polytriacetylene serving as sidepieces, and with conjugated acetylenic blocks (-C≡C-)m serving as crosspieces. The band gap of the so-constructed acetylenic coupled ladder polymers can be reduced to as low as 0.3-0.4 eV without doping, significantly lower than the parent sidepiece polymers. In addition to the popular aromatic→quinonoid transition concept, we also proposed the aromatic-quinonoid matching concept to minimize the band gap through aromatic-quinonoid copolymers.
The recent discovery of very long carbon chain encapsulated within carbon nanotubes were investigated with first principles methods. The combined system is predicted to be metallic with a high density of states at the Fermi level. The bond length alternation of the sp-hybridized carbon chain inside the carbon nanotube can be suppressed through charge transfer and orbital hybridization with the nanotube. The geometry, energetics, and vibrational properties of the isolated finite linear carbon clusters and the infinite carbon chain (polyyne) were also studied with state of the art theoretical methods.
To accurately predict vibrational spectroscopy of extensively conjugated systems has been challenging to computational chemists due to the strong electron-phonon coupling in these systems. Currently available theoretical models failed for this problem, especially for the extremely conjugated system, polyyne. A novel linear/exponential hybrid quantum mechanical force field scaling scheme was applied successfully, yielding highly accurate frequency prediction for various isotopes of polyacetylene in addition to polyyne. The new method can also be extended to other extensively conjugated systems.
|School Location:||United States -- District of Columbia|
|Source:||DAI-B 69/12, Dissertation Abstracts International|
|Subjects:||Physical chemistry, Polymer chemistry|
|Keywords:||Conjugated polymers, Low-bandgap, Oligomers, Polymers, Vibrational|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be