Figure shows the potentiometric titration of [PEG27-b-PDha6]4 dissolved in 0.1 M NaOH (c = 0.2 mg mL-1) which was afterwards titrated with 0.1 M HCl. For the corresponding ζ-potential measurements the titration was paused at desired pH values and samples were taken before the titration was continued. Figure shows the mean values of a triple determination for each of these corresponding samples. Starting around pH 12.5 the first titration steps until pH 11 correspond mainly to the neutralization of excess NaOH. Afterwards, from pH 11 to pH 7 the stepwise protonation of the -NH2 groups of the PDha segment can be observed, being in accordance with earlier work on PDha homopolymers where a pKB of 9.2 for the -NH2 groups was determined. Within this pH range the star-shaped block copolymer shows a negative net charge, which we further support with the negative ζ-potential measurements (Figure ). However, in literature typical pKA values of compariable -COOH groups of alanine are reported around a pKA of 2.35, fitting to our measurements. Due to that at pH values of 6 and below the protonation of the -COO -groups of the PDha block should increase, leading to charge neutrality at the isoelectric point and afterwards a positive net charge due to protonation of the -COOH groups and the presence of positively charged -NH3 + moieties. The potentiometric titration shows clearly a second equivalence point around pH = 3-4 corresponding to the pKa of the carboxylic acid groups, while the ζ-potential measurements detect the isoelectric point between pH 2 and 4 and an overall positive charge below pH= 2. With that both, the potentiometric titration and the corresponding ζ-potential measurements describe the same trend for the charge inversion of the PDha block. The differences can be tentatively explained due to the influence of the PEG core which might influence the overall charge of the star-shaped block copolymers. At higher concentrations of 20 mg/mL, lower pH values then pH= 7 lead to aggregation observable by turbidity and finally precipitation of the star-shaped block copolymer at pH values lower than 4. In case of lower concentrations (0.2 mg/mL), no precipitation was observed.