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Molecular Modeling and Synthesis of Substituted Poly(p-Phenylene)s.

Hill, Saylina. (2004) Molecular Modeling and Synthesis of Substituted Poly(p-Phenylene)s. Doctoral thesis, University of Surrey (United Kingdom)..

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In this investigation computational molecular mechanics is used to optimise the energies and geometries of p-terphenyl and p-quaterphenyl and their analogues crosslinked with adipic dihydrazide (ADH). The Dreiding 2.21 force field is used and proves to be a good overall force field when applied to very simple molecules. The p-terphenyl systems studied in this chapter generally show good optimisation except for systems where heavy atoms like bromine and iodine are present. Systems containing ADH are successfully optimised although the presence of several methyl groups in their structures causes the optimisation to take longer than 'rigid' p-terphenyl systems. The high degree of conjugation present in poly(p-phenylene) systems is not well modelled by molecular mechanics. Semi-empirical molecular orbital calculations using MOP AC version 6.0, for models that are generated in chapter 3 show improved optimisation of geometries, particularly where heavy atoms (e.g. bromine) are present. Band gap calculations performed using Koopmans' theorem and employing a scaling factor of 0.32, yield good energies for the band gaps. The latter proves that the band gap energies have a strong influence by the nature of the substituent. Hence the systems possessing substituents are predicted to be poorer conductors. The synthesis of oligomer of p-phenylene via a Suzuki coupling method is reported. The oligomer is characterised using a variety of spectroscopic techniques and elemental analysis. The effect of substitution is examined by incorporating carboxylic acid groups to produce a potential site for cross-linking. The poly(p-phenylene) is examined and an approximately linear response is obtained for voltage vs. current, yielding a d.c. conductivity value of 2 x 10e-8 Scm-2. The latter compare favourably with the published data.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Hill, Saylina.
Date : 2004
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 2004.
Depositing User : EPrints Services
Date Deposited : 30 Apr 2019 08:08
Last Modified : 20 Aug 2019 15:32

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