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Controlled synthesis of advanced supramolecular structures based on conjugated polymers.
This work focuses on making copolymer structures more available for conjugated polymers. The discovery of the first controlled chain-growth mechanism for these materials a decade ago, enabled a whole new array ofpossibilities. This discovery therefore initiated intensive research, resulting already in great progress in the field. Several different conjugated polymers can be synthesized with good control over the molar mass and endgroups and also several copolymer structures, which combine different monomer systems in one polymer chain, have been reported. This further led to an extensive characterization of many of these materials, resulting in a thorough knowledge of many of their properties. However, thescope of materials that can be produced in a controlled way is still rather narrow compared to the variety of conjugated monomer systems that have been used in non-controlled synthesis of conjugated polymers. A lot of work still needs to be performed to bring the research field forward.This manuscript aims to contribute to this goal. </></>
In research towards conjugated polymers that does not implement a controlled synthesis, the polymer properties can be tuned to some extent by combining the right parameters (e.g. combining the appropriate monomer types in donor-acceptor copolymers). The research performed in this dissertation tries to combine this concept of polymer tuning with the benefits of a controlled synthesis. This is addressed in several different aspects. The first part focuses on the benchmark polymer of the research field, i.e. poly(3-alkylthiophene). A random copolymerization of the two 3‑alkylthiophene isomers is established by comparing the polymer composition to a predicted value, enabling the unambiguous investigation of the effect of the regioregularity on these polymers. Also, well-defined poly(3-octylthiophene)-b-poly(3-butylthiophene) is synthesized in order to clearly visualize the microphase separation behavior that is present in this block copolymer. This insight allows for a better interpretation of microphase separation properties in general. After the first part, this dissertation moves away from the benchmark polymer towards new monomer systems to implement in (co)polymer materials. More in particular, monomersystems with a reduced bandgap compared to poly(3‑alkylthiophene)are considered. The reduced bandgap is obtained by a planarization of the monomers by locking two thiophene units in one plane, as is the case for cyclopenta[2,1-b;3,4-b]dithiophene and thieno[3,2-b]thiophene. Alson-type materials are investigated, since they have proven to be particularly challenging, as only a couple of reports on these monomer types are available. In the scope of this work, </></>cyclopenta[2,1-b;3,4-b]dithiophene with electron-withdrawing substituents and thieno[3,4-b]pyrazine are selected.</>
The investigation of these new monomer systems did not always result in the controlled polymerization of these systems. In fact, the success of the available monomer formation methods and polymerization mechanisms shows to be very system dependent, leading to varying results for the different monomer systems. The underlying causes of the observed polymerization behavior were further investigated, from which important implications could be deduced that should be considered for further research.</></></>
In research towards conjugated polymers that does not implement a controlled synthesis, the polymer properties can be tuned to some extent by combining the right parameters (e.g. combining the appropriate monomer types in donor-acceptor copolymers). The research performed in this dissertation tries to combine this concept of polymer tuning with the benefits of a controlled synthesis. This is addressed in several different aspects. The first part focuses on the benchmark polymer of the research field, i.e. poly(3-alkylthiophene). A random copolymerization of the two 3‑alkylthiophene isomers is established by comparing the polymer composition to a predicted value, enabling the unambiguous investigation of the effect of the regioregularity on these polymers. Also, well-defined poly(3-octylthiophene)-b-poly(3-butylthiophene) is synthesized in order to clearly visualize the microphase separation behavior that is present in this block copolymer. This insight allows for a better interpretation of microphase separation properties in general. After the first part, this dissertation moves away from the benchmark polymer towards new monomer systems to implement in (co)polymer materials. More in particular, monomersystems with a reduced bandgap compared to poly(3‑alkylthiophene)are considered. The reduced bandgap is obtained by a planarization of the monomers by locking two thiophene units in one plane, as is the case for cyclopenta[2,1-b;3,4-b]dithiophene and thieno[3,2-b]thiophene. Alson-type materials are investigated, since they have proven to be particularly challenging, as only a couple of reports on these monomer types are available. In the scope of this work, </></>cyclopenta[2,1-b;3,4-b]dithiophene with electron-withdrawing substituents and thieno[3,4-b]pyrazine are selected.</>
The investigation of these new monomer systems did not always result in the controlled polymerization of these systems. In fact, the success of the available monomer formation methods and polymerization mechanisms shows to be very system dependent, leading to varying results for the different monomer systems. The underlying causes of the observed polymerization behavior were further investigated, from which important implications could be deduced that should be considered for further research.</></></>
Date:1 Jan 2011 → 31 Dec 2014
Keywords:Conjugated (block co)polymers, Controlled polymerization
Disciplines:Inorganic chemistry, Organic chemistry, Macromolecular and materials chemistry, Theoretical and computational chemistry, Other chemical sciences
Project type:PhD project