Conformational Analysis of Oligomeric Models of Siloxane, Silazane and Siloxazane Ladder Polymers

Abstract

AbstractOligomeric models of linear ladder silanes, siloxanes and siloxazanes with seven repeat units consisting of four-, six-, or eight-membered rings were designed and their conformations in chloroform were explored. The Low Mode–Monte Carlo conformational method was used to explore oligomeric flexibility on the OPLS-2005/GBSA(CHCl3) potential energy surface to obtain a set of low energy structures for each oligomer. These structures were then optimized using B3LYP/6-31G*/SCRF-PBF(CHCl3) calculations. The results indicate complex conformational dynamics with mostly non-planar, curved structures. Electron delocalization from the lone pair of electrons on N or O into empty 3d orbitals on Si was not observed.