The CG model of P(NDI2OD-T2) was parameterised to reproduce the structural properties of an AA system. The methods used to parametrise and simulate the AA model are described in Section 2.1, while those for the CG model are given in Sections 2.2 and 2.3. The behaviour of the parameterised CG model of P(NDI2OD-T2) in simulations under conditions corresponding to varying solvent qualities is described in Section 3. The types of aggregates formed under different solvent conditions are examined in Section 3.1 and are related to the aggregate structure to the strength of intermolecular interactions and the persistence of aggregates composed of partially overlapping chains in Section 3.2. Finally, the kinetics of the competing effects of singlechain folding and multi-chain aggregation, and how these may vary with concentration, molecular weight, and chain flexibility, are considered in Section 3.3.