To better understand the effect of the single-chain folding kinetics on multi-chain aggregation properties, we examined the behavior of the same P(NDI2OD-T2) polymer with the artificially flexible backbone. Single chains of this flexible polymer exclusively collapsed into more compact structures within the 10 µs singlechain simulations, with relaxation times on the order of 1 µs, rather than remaining extended (Figs. and). At the same concentration as the regular-flexibility 20mers (6 g/L), the flexible 20mers did not meet the metric discussed above for the calculation of τ c (single-chain concentration fallen to 25% of the original concentration) within the simulation time of 3 µs. The average aggregate size also remained below 2 chains over this entire period. Given the value of τ s of ≈ 1 µs for these chains, the critical concentration c † must be > 6 g/L. For the concentrations simulated, single-chain collapse therefore dominates multi-chain aggregation for the flexible chains, in stark contrast to the stiffer regular-flexibility chains.