Figure 8.

(a) Dependence of geometric mean particle radius, R, on the mass fraction of acid groups in the PU particles, M_frac,B, calculated from the volume fraction of dissolved chains for PUD composed of PTMO with M_n = 650 g mol^–1 (blue crosses), 1000 g mol^–1 (green crosses), and 2000 g mol^–1 (red crosses). Error bars indicate the multiplicative standard deviation. The dotted curves show fits of the PSC model³⁴ adapted for wt % acid group content (eqs 2–7). (b) The fraction of the particle surface covered by hydrophilic B units (SA_frac) required for stable spherical particles of PU in dispersion with respect to PTMO M_n in the soft segment of PU. A dashed straight line is given for guidance.