Previously, we found that the reversible cooling-induced thermogelation of pMeOx-b-pPheOzi-b-pMeOx is accompanied by a transition from spherical to worm-like micelles. To investigate whether the thermogelation of the new variants of the pPheOzi-based system is also linked to the formation of worm-like aggregates, we performed negative stain transmission electron microscopy (TEM) imaging of precooled aqueous polymer solutions (Fig. , Sup. Fig. ). The obtained images confirm that worm-like aggregates are also formed for all the studied architectures (P_D, P_G and P_S), and when replacing the hydrophilic pMeOx blocks by PEG (P_PEG). Interestingly, while P_D and P_S seem to form rather thin worm-structures, P_G and P_PEG-based worm-aggregates appear somewhat thicker and partially also double layered. Further, a notable difference between the samples is the coexistence of spherical aggregates. While spherical aggregates of varying sizes are present in P_S images, this is not the case -or at least very much less the casefor the other polymer samples. In addition, partial blurring of the P_S worm network is apparent. We interpret this as signs of starting disintegration of the worm-like aggregates, possibly as a result of the sample preparation. Rather instable worm-aggregates could explain the poor rheological properties of P_S and may also result in the rearrangement to spherical aggregates during TEM sample preparation. Thus, at this point it remains unclear whether the occurrence of spherical aggregates in the TEM images of P_S is an artefact of the sample preparation or indicates the coexistence of both spherical micelles and worm-like aggregates when equilibrated in the cold. The confirmation of worm-like aggregates for all pPheOzi-variants indicates that the cooling-induced thermogelation based on a sphere-to-worm transition in polymer self-assembly is not restricted to the triblock pMeOx-b-pPheOzi-b-pMeOx. Recently, Greenall and Derry used self-consistent field theory to study temperature-dependent transitions in polymer self-assembly. They suggest that a high compatibility between polymer blocks leads to a transition of less curved (worm-like micelles) to more curved suprastructures (spherical micelles) upon increasing the incompatibility of the solvophobic block (here: pPheOzi) and the solvent (here: water). A high compatibility between pMeOx and pPheOzi can be assumed as differential scanning calorimetry (DSC) analysis indicates absence of microphase separation of the blocks in the bulk (Sup. Fig. ) and in previous work a nonclassical interaction between the blocks in the cold was suggested based on results from in-depth NMR analysis and MD simulations. POx and POzi generally show improved aqueous solubility in the cold, ergo a decreased solubility upon heating. Consequently, the transition from worm-like to spherical micelles could be connected with an increasing incompatibility of pPheOzi and water. However, this interpretation is at odds with results from previous NMR data, showing increasing mobility of the pPheOzi moieties upon heating. Following the suggestions by Greenall and Derry, the presence of worm-like aggregates for the PEG/pPheOzi thermogels suggests that PEG and pPheOzi similarly exhibit high compatibility allowing for pronounced polymer-polymer interactions. However, unravelling the underlying mechanism leading to the worm-formation of P_PEG is outside the scope of this study and remains to be investigated.