The lower the Ts temperature, the higher the crystallization of both blocks and, in particular, the PEG block, as judged by the latent enthalpies of crystallization reported in alcohols while PhNCS-co-OX is not, we hypothesized that the polymer could be applied in solution self-assembly, which is particularly interesting due to the semi-crystalline but slowly crystallising nature of the PhNCS-co-OX block. This is an unexplored field for sulfurated ROCOP and ROP polymers (except polyethylenesulfide) as the synthesis of the required amphiphiles can be challenging. First, self-assembly in water was investigated via aqueous precipitation. For this purpose, the block polymer was dissolved in 1,4dioxane and then added dropwise to an aqueous solution under vigorous stirring. Self-assembly is immediately apparent from the formation of a cloudy but homogeneous solution due to the Tyndall effect. Dynamic light scattering (DLS) shows nano-objects with an average size of 126 nm and a dispersity of 0.27. The solution remains stable and the DLS trace remains unchanged over multiple weeks highlighting the stability the aggregates. Cryo transmission electron microscopy (Cryo-TEM) reveals the formation of spherical aggregates. Statistical evalulation of 100 nano objects reveals an average core-diameter of 29.6 ± 0.2 nm (Figure ). Other than these we observe some elongated aggregates with an approximate length of 100-200 nm and a thickness of 10-30 nm although there are too few for a statistical evaluation (ESI Figure S 42). Furthermore a 5-10 nm thick corona presumably corresponding to the water-soluble PEG periphery surrounding a hydrophobic PhNCS-co-OX core can be observed. Assuming a stretched conformation of the PhNCS-co-OX core implies a single repeat unit extends across approximately 0.8 nm based on simple trigonometric considerations and hence 37 repeat units extend across a maximum of 30 nm (Figure S 47). Therefore, the formation of micellar aggregates appears likely as the core diameter of the object observed fall within this range. The elongated aggregates comprise multiples spherical aggregates merging rather than regular cylindrical structures, and this suggest that the cores are amorphous in nature rather than semi-crystalline. We infer that this is due to the slow crystallisation kinetics of PhNCSco-OX as observed in our DSC studies. We hypothesized that moving to a weaker nonsolvent for the PhNCS-co-OX block in the self-assembly procedure and introducing an additional annealing step might provide sufficient time for corecrystallisation as the insoluble central block is precipitated less abruptly. This procedure is efficiently used in crystallization-induced selfassembly (CDSA) of crystalline-coil diblock copolymers, yielding defined core-crystalline micelles in selective solvents for the corona forming blocks. Hence, we repeated the self-assembly procedure outlined above with ethanol in place of water as the nonsolvent for the crystallizable PhNCS-co-OX block followed by heating the resulting dispersion at 80°C for 1 day. Formation of a turbid solution due to the Tyndall effect that exhibits no sedimentation of the precipitate over the course of weeks again suggest self-assembly of the block copolymer.