Scanning electron microscopy of the polymer solutions were frozen with liquid nitrogen in the gel state and lyophilized afterwards. The dried powder was mounted on aluminium sample holders with conductive carbon tape and sputtered with a 4 nm layer of platinum in a sputter coater (Leica Microsystems ACE 400, Wetzlar, Germany). The morphology of the samples was subsequently analyzed using a Crossbeam 340 field emission scanning electron microscope (Carl Zeiss Microscopy, Oberkochen, Germany) by setting the acceleration voltage (ETH) to 2 kV and detection of secondary electron (SE) with an Everhart-Thornley detector. To visualize the native hydrogel structure, we also investigated a cryogenic sample preparation procedure.