MQ NMR spectroscopy. Static proton solid-state NMR experiments for the quantification of connectivities and isotropic fraction are based upon the existence of motion-averaged residual dipolar couplings (RDCs) among the protons, which are non-zero for network chains that are fixed at their ends. At low overlap of the network strands (the entanglement-free limit), the magnitudes of the measured RDCs reflect roughly the elastic contribution of the respective chains and their connectivities (see Scheme 1). Experiments were carried out on a Bruker mq20 MiniSpec with the specifications mentioned in the SI. The experiment provides two signal functions as a function of a double-quantum pulse sequence duration (DQ evolution time DQ): the DQ intensity build-up (IDQ) reflecting the magnitude of the RDCs and a reference intensity (Iref). The sum of these two signals, referred to as summed multiple-quantum intensity (IMQ = IDQ + Iref) corresponds to a full dipolar echo and is used to quantify and thus compensate for transverse relaxation effects (longtime signal loss). These data were evaluated similar to Lange et al. , except for some relevant procedural differences that will be explained below. Comparable data analysis was also applied on other tetra-arm star polymer systems. Typically, three types of connectivities can be distinguished differing sufficiently in their RDC as shown in Scheme 1 (SL, DL, HOCs). This 3component fit was assumed to be a proper modelling choice for our system, since the chemical and steric differences between PEG and PCL chains are small (see SI Table ) and because all elastic strands contain a PCL and a PEG block that are under the same tension. Both types of Further, the equality of the RDCs of PEG and PCL subchains was qualitatively confirmed in preliminary chemical shift resolved RDC measurements using the POST-C7 sequence . Details will be reported elsewhere. As shown exemplarily in Figure , the proposed 3-component fit well reproduces all features in both signals.