Book Description

Efficient and versatile catalytic chemistry has continuously stimulated the syntheses of novel materials. This thesis describes the syntheses of non-linear polymers and anti-aromatic conjugated molecules using catalytic arene-norbornene annulation reactions and metathesis polymerizations. Bottlebrush polymers have a very high density of side chains grafted to the backbone, leading to an extended worm-like conformation. Efficient, modular synthesis of brush polymers is the first step for thorough understanding of their solution and assembly behaviors and to enable various applications. In the first part of this thesis, we investigated the limitations of the previous methods used for brush polymer synthesis. We further developed a streamlined one-pot macromonomer synthetic strategy to synthesize well-defined brush (co)polymers via ring-opening metathesis polymerization (ROMP). In the pursuit of facile methods for the synthesis of rigid ladder structures, we have developed Catalytic Arene-Norbornene AnnuLation (CANAL) chemistry to couple aryl bromides with norbornenes (NBEs) to form rigid fused norbornyl benzocyclobutene ladder structures. In the second part of this thesis, we utilized this efficient chemistry to synthesize various polymeric materials and conjugated molecules containing rigid ladder motifs. We first demonstrated the synthesis of polyladders via ROMP of rigid CANAL ladder oligomer to provide porous polymers with high solution processability. We further developed an efficient strategy to prepare star polymers cross-linked via telechelic CANAL ladder using ROMP. The arms of these star polymers can be readily cleaved under acidic conditions to allow isolation of soluble microporous organic nanoparticles. In another manifestation of CANAL chemistry, when oxaNBEs are used in place of NBEs, the CANAL products can be aromatized to form conjugated systems with fused four-membered rings. The conjugated four-membered rings also elicit antiaromaticity arising from cyclobutadienoid (CBD). Non-benzenoid structures with antiaromaticity have been much less explored with limited understanding of their properties due to the challenging synthesis. We developed a modular and streamlined CANAL-aromatization strategy to synthesize a series of polycyclic conjugated hydrocarbons containing CBDs. We further extended this CANAL-aromatization strategy to synthesize a series of regioisomeric CBD-fused phenazines and investigated the effect of bond fusion pattern on local antiaromaticity.