Fig. 4: Negative staining of polymersomes with protrusions formed among the membrane with copper sulfate (CuSO4).

TEM image of polymersomes with 15 mM (a) and 60 mM (b) added during shape changing and stained with CuSO4, coordination of Cu2+ with amides from PNIPAm chains make it visible (black dots). c EDX element maps of polymersomes with multiple protrusions, O, Cu, N, C were detected.