Controlled Synthesis of π-Conjugated Materials Beyond 1D

Dr. Nagarjuna Gavvalapalli, Georgetown University

Host: Dr. Lyle Isaacs

Abstract: Extension of π-conjugation beyond 1-dimension results in materials with novel optical, electronic, and optoelectronic properties. However, strong π-π intermolecular interactions hamper solution phase synthesis of 2D-π-conjugated materials (e.g. graphene), induce aggregation of dispersed graphene sheets, and make it challenging to control the growth morphology (1D, 2D or 3D) of π-conjugated microcrystals. A common theme in the Gavvalapalli group is controlled synthesis of higher dimensional π-conjugated materials using novel building blocks. My talk is divided into two parts.
Part-1 focuses on developing π-face masked aryl monomers to generate soluble 1D- and 2D-π-
conjugated materials without pendant solubilizing chains. We used aryl repeat units containing cycloalkyl
straps to synthesize high molecular weight soluble 1D- and 2D-π-conjugated strapped materials without
pendant solubilizing chains. Cycloalkyl straps mask the polymer π-face and therefore reduce interchain π-π interactions. The unique advantages rendered by the cycloalkyl straps enabled diverse materials
including soluble conjugated microporous polymers and 1-D polymers with spatially controlled binding
sites.
Part-2 focuses on developing novel aryl amphiphiles and using them as morphology directors to
control π-conjugated microcrystal growth along the π-stacking direction to realize novel growth
morphologies. We have shown that the aryl amphiphiles’ aryl hydrophobe geometry and size play a key
role in determining the π-stacking facet growth rate and morphology and result in hitherto unknown
microcrystal morphologies with high π-stacking facet surface area. The rod shaped perylene microcrystals showed unprecedented exciton-polariton waveguiding along the edge-to-edge packing direction of the perylene molecules.

Organic/Inorganic Seminar