Polymer science is rapidly advancing towards the precise construction of synthetic macromolecules of formidable complexity. The impressive advances in control over polymer composition, topology and uniformity, enabled by the living polymerisation revolution, now permit the introduction of compartmentalisation within macromolecules. Despite the straightforward and versatile synthetic approaches to produce block copolymer, nanostructures built-up from these linear building-blocks rarely reaches dimensions beyond the 5–50 nm range and can be sensitive to their environment. The development of robust controlled polymerisation techniques has enabled the synthesis of covalently-bond polymer architectures that can be used as nano-scale building-blocks. One of these architectures are molecular polymer brushes (also known as bottlebrush polymers or cylindrical polymer brushes). Molecular polymer brushes (MPBs) are unique materials that possess astonishing properties arising from their densely grafted and extended chain structure. The field of MPBs, especially as compartmentalised entities, is rapidly growing. Recent efforts have focussed on achieving MPBs with programmed complexity and the introduction of orthogonal chemical functionality. Compartmentalised brushes can elevate their functionality beyond that of their linear constituent parts, thus offering immense potential in self-assembly and template chemistry. The aim of this thesis is to demonstrate how the compartmentalisation in MPBs can be used for the construction of complex, yet precise, polymer nano- and microstructures with the scope to develop advanced functional materials.