The difference in particle size, crystallinity, but also the used synthesis conditions do influence the transition temperature T1/2 and the hysteresis width of the samples, two further relevant spin crossover properties which need to be discussed to evaluate the application potential of the nanocomposites. Both parameters change upon thermal treatment, but the progression of those changes strongly depends on the particle size and composition (see Figures , Table ). Again, for the as-synthesized samples the hysteresis width and transition temperature are very similar. Upon annealing, for all samples a similar shift of the transition temperature to higher temperatures is observed (Figure ), independent of particle size, complex loading and bipy excess. In contrast to this, a significant impact of those three parameters on the change in hysteresis width upon thermal treatment is observed (Figure ). Please note the almost identical thermal hysteresis width for all as-synthesized samples. For the larger particles of samples 5c-e, both the hysteresis width and the completeness of the SCO significantly improved already after the first heating cycle. Indeed, the thermal hysteresis loop is wider than for the corresponding bulk material (27 K in the composite nanoparticles vs. 18 K for the bulk). In contrast to this, for the smallest particles (samples 1e, 2e) the HS fraction did not change significantly for the first two annealing cycles and the hysteresis is slowly increasing with each cycle. In the settle mode, the final hysteresis widths of the samples 1-5e are smaller compared to the sweep mode and furthermore they all are in the same order of magnitude (see Table and Figure ). This indicates that the pronounced differences observed in the sweep mode during the annealing are kinetic effects imposed by the polymer matrix, which are more pronounced for the smaller particles and lower complex loading. For the smaller particles the PS matrix is more rigid due to the higher overall PS fraction leading to a more pronounced influence on the SCO properties. Interestingly, for the largest particles 5c and 5d, where a higher bipy excess was used during the synthesis, significantly wider thermal hysteresis loops are observed also in the settle mode (Figure ). Thus both parameters, the used dBCP and the synthesis conditions can be used to fine-tune the SCO properties of the nanocomposite.