Conjugated polymers have been the subject of extensive research, particularly for their application in the field of organic electronics. Attributes such as their semiconducting nature, solution processability, degree of flexibility, and infinite tunability have led to their successful implementation as light-harvesting or light-emitting materials.

In the first chapter, we introduce and describe several key concepts within the area of organic electronics. These concepts include the understanding of how conjugated polymers function and their relevance within the field. We explore the various applications with detailed device characteristics. Additionally, we examine various strategies for modifying monomers to adapt and control the molecular bandgap of the polymers to suit specific applications. Furthermore, we consider the influence of conjugation length and aggregation on the electronic properties and device performance. Lastly, we discuss different synthetic procedures employed to achieve high molecular weight conjugated polymers.

The second chapter begins with the introduction of different techniques to lower the formation of aggregates in conjugated polymers. It describes both non-covalent and covalent encapsulations that have been previously employed, offering examples of their efficacy in reducing nonradiative decay processes. Past research on molecularly encapsulated conjugated polymers has extensively focused on molecular backbones such as diketopyrrolopyrrole (DPP), naphthalene diimide (NDI) and perylene diimide (PDI). In the context of this work, the research is centered around narrow bandgap encapsulated conjugated polymers based on benzodithiophene (BDT). Consequently, this chapter delves into BDT-based conjugated copolymers and their naked (unencapsulated) counterparts. This study highlights that molecular encapsulation serves to suppress intermolecular interactions, resulting in polymers exhibiting a lower degree of energetic disorder and increased spacing between polymer chains. However, it is noteworthy that the photoluminescence quantum yield (PLQY) in the solid state is unexpectedly lower (1%) compared to previous studies. Nevertheless, when assessing the performance of devices in comparison to the record breaker PM6:Y6 system, our materials demonstrate remarkably high efficiencies. These outcomes prompt a deeper investigation into the reasons underlying the reduced emissivity with encapsulation, and whether this phenomenon is linked to the BDT core or the acceptor comonomer component.

The third chapter focuses on increasing the order within the polymer backbone by having a higher density of encapsulation throughout the entire polymer chain. To achieve this objective, this chapter explores the synthesis of BDT-based encapsulated conjugated homopolymers, and their reference counterparts. The control of interpolymer distance is achieved through various ways including: the nature of the solubilising chain, the nature of the encapsulating chain, and the length of the encapsulated chain. Through ultraviolet-visible (UV-Vis) and photoluminescence (PL) measurements, our studies reveal that encapsulation mitigates aggregation to a certain extent. Nevertheless, even with increasing the distance between polymer chains, the emission remains suppressed. Notably, as excimer formation can be discarded due to the reduced cross-communication, our findings point towards nonradiative loss being attributed to an intramolecular process. Through thorough transient absorption (TA) measurements, we identify this loss as being linked to polaron pair formation. Collectively, these results lead us to the conclusion that BDT-based polymers might not be as suitable for solar cell applications as was previously believed, with the root cause lying in intricate intramolecular processes that prove challenging to control effectively.

The final chapter (chapter IV) explores a distinct property offered by molecular encapsulation. It firstly describes chirality within conjugated polymers, providing examples of materials holding higher dissymmetry factors of absorption and emission, albeit at the cost of the conjugation length of these polymers. Therefore, the research focus was shifted towards the synthesis of main-chain planar chiral conjugated polymers, aiming to achieve a high degree of chiroptical properties. Specifically, the study centeres on [n]paracyclophane-based ([n]PC) conjugated polymers, designed to investigate various effects. These include altering the cyclophane chiral centre by changing the ansa unit, modifying the polymer morphology by changing the side chains, and varying the choice of comonomers used for polymerisation to encompass a broader spectal range. It was demonstrated that the chiral response can be predominantly influenced either by the size of the encapsulating chain, resulting in more twisted conjugated polymers, or by the morphology of the sample, with higher responses observed for less crystalline materials. Furthermore, the synthesis of the paracyclophane comonomers is enantioselective, rendering it more suitable for industrial applications and thus next-generation circularly polarised organic light-emitting diodes (CP-OLEDs) materials.