Binding Mode Simulations and Predictions of Quaternary Ammonium Salts-Containing Silsesquioxane Nanoparticles for Possible Semi-Solid Electrolyte Application

Chan, Derek Kwan Hoe (2021) Binding Mode Simulations and Predictions of Quaternary Ammonium Salts-Containing Silsesquioxane Nanoparticles for Possible Semi-Solid Electrolyte Application. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

ion battery (LIB) electrolytes can cause environmental problems, are highly fragile, and possess relatively low lifespan. Environmentally friendly hybrid polyhedral oligomeric silsesquioxane (POSS) material could be used to replace LIB to overcome the disadvantages. DMAEA(N+)-SQ[FSI-] and DMAEA(N+)-SQ[TFSI-], two novel hybrid POSS materials have been synthesized with condensation followed by quaternization and anion exchange method, and measured for their ionic conductivities (IC). DMAEA(N+)-SQ[FSI-] was confirmed by FTIR and NMR spectra and its IC was found to be greater (6.2 x 10-6 S/cm) than DMAEA(N+)-SQ[TFSI-] (3.2 x 10-6 S/cm). Research work often requires tedious experimental work as far as tests for different parameters are involved. Computational chemistry is a new approach which helps to shorten the time required for experimental work and reduce the use of valuable chemicals. Computational chemistry is capable of predicting new structures, mechanisms, and even reaction systems. In this research study, computational chemistry software Gaussian09W with molecular mechanics and semi-empirical methods was used extensively to predict the binding modes of the DMAEA+ with its respective ions: FSI- and TFSI- in DMAEA-FSI and DMAEA-TFSI complexes. The binding modes were able to predict that DMAEA(N+)-SQ[FSI-] has a lower IC because it has an interaction energy (manually docked: -65.4 kcal/mol; auto docked: -62.3 kcal/mol) more positive than DMAEA(N+)-SQ[FSI-] (manually docked: -73.5 kcal/mol; auto docked: -63.7 kcal/mol) indicating weaker binding and hence better IC in DMAEA(N+)-SQ[FSI-] which agrees with the IC results obtained from experimental work. HOMO/LUMO energy levels and energy were investigated where the HOMO-LUMO energy gap between DMAEA+ and FSI- (0.169 au) is greater than energy gap between DMAEA+ and TFSI-, indicating that DMAEA+ and FSI- bind less well with each other resulting in higher IC of DMAEA-FSI where the results support the experimental finding that DMAEA(N+)-SQ[FSI-] is the better ionic conductor.