In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professors Richard M. Laine and Theodore Goodson III of the Macromolecular Science and Engineering Program at the University of Michigan are exploring the synthesis and properties of three-dimensional, structurally precise cages based on silicon and oxygen. These cages offer unique optical properties, and the team is studying methods to functionalize them asymmetrically. The results of this project could be used to develop new materials for applications ranging from components for organic light-emitting diodes, organic solar cells, and hybrid laser materials to novel semiconducting thin films. Professors Laine and Goodson are providing an educational environment targeting the training of under-represented minorities as well as outreach activities for K-12 students
Structurally precise silsequioxanes (SQs) of the types [(RSiO1.5)8], [(RSiO1.5)10] and [(RSiO1.5)12] are being investigated to prepare asymmetric molecules. On linking SQ cages via conjugated organic tethers, these systems also exhibit three-dimensional excited state conjugation through the cages as witnessed by delocalization leading to emission red-shifts normally associated with extended conjugation. Furthermore, these same macromolecules exhibit large and unexpected two-photon absorption (TPA) cross-sections that are associated with both three-dimensional delocalization and charge transfer from peripheral organic functionality to the cage cores. Professors Laine and Goodson are mapping the effects of asymmetry and RR'SiO introduction on the photophysics and chemical properties of new families of SQ macromonomers. Two approaches being studied include "sequential assembly" wherein two RR'SiO groups are added as simply units in "double decker" formulations that will be followed by functionalization, as well as the fluoride anion catalyzed incorporation of preformed RR'SiO and R'SiO1.5 units to existing SQs. Collaborations with both groups at the University of Michigan and abroad are being used to assess the utility of these compounds for various photonic applications including lasing and photo-magnetism applications and to map their photophysical and electronic properties as individual compounds and after assembly. Annually, both groups are hosting and training 4-8 undergraduates and 2-4 high school summer student researchers from local high schools including under-represented minorities, with approximately half of these being women scholars.
