Book Description

"Conjugated polymers have emerged over the last decades as an intriguing class of electronic materials with potential applications ranging from polymer-based light emitting diodes, sensors, transistors, photovoltaics and many other areas. Despite the development of many useful variants of conjugated polymers, a challenge that remains in this area is their synthesis. All except the most simple conjugated polymers are constructed by a multistep synthesis, where a complex monomer is first assembled prior to polymerization. This not only creates waste with each step, but also makes it challenging to modify polymer structures, as each monomer must be independently prepared. The objective of the research described in this thesis is to develop a new approach to prepare conjugated polymers via multicomponent polymerization reactions. These have provided tunable methods to assemble pyrrole-based conjugated polymers in one pot reactions from combinations of available substrates, such as diimines, diacid chlorides, alkynes and/or alkynes. In addition, these reactions provide access to new classes of conjugated polymers: poly(Münchnones) and poly(phospha-Münchnones). In Chapter 2, we describe the palladium-catalyzed coupling of diimines, diacid chlorides, carbon monoxide and alkynes. This reaction provides access to families of conjugated poly(pyrroles) in one pot reactions, and with independent control of all the substituents and conjugated units. Moreover, a new class of conjugated polymer, a poly(1,3-dipole), can be isolated. The latter exhibits low electronic band-gaps, and can serve as an intermediate in the synthesis of a range of conjugated poly(heterocycles) via 1,3-dipolar cycloadditions. Chapter 3 describes an alternative, phosphonite-mediated multicomponent synthesis of poly(pyrroles). In analogy to the results in Chapter 2, this transformation also uses diimines and diacid chloride monomers, which are in this case coupled by the addition of (catechyl)PPh rather than palladium catalyzed carbonylation. This generates another class of poly(1,3-dipole) that can react with a variety of alkynes or alkenes to form poly(pyrroles). This approach offers several advantages over the one presented in Chapter 2: the polymers exhibit higher molecular weights, it tolerates a broader scope of monomers, and it does not rely on transition metal catalysis. Notably, to the best of our knowledge, this represents the first metal-free multicomponent synthesis of conjugated polymers. In Chapter 4, a new type of donor-acceptor conjugated polymer containing 1,3-dipole units is described: a poly(phospha-Münchnone). These can be isolated from the multicomponent polymerization of diimines, diacid chlorides and (catechyl)PPh presented in Chapter 3. UV-Vis spectroscopy shows that these polymers are low band-gap materials. Moreover, their properties can be easily tuned by choice of the diimine or diacid chloride monomers. In Chapter 5, we studied the use of renewable starting materials in the phosphonite-mediated multicomponent polymerization presented in Chapter 3. The lignin degradation product bis-vanillin is readily incorporated into this platform to generate cross-conjugated polymers, including poly(1,3-dipoles) and poly(pyrroles). Changing the diacid chloride or the alkyne / alkene coupling partner allowed access to a range of polymers with tunable optical properties. 2,5-furandicarboxylic acid (FDCA), a monomer derived from cellulose oxidation, can also be employed as a precursor to the diacid chloride monomer. The latter provides the first example of a conjugated polymer obtained from both components of lignocellulosic biomass." --