Poly(butadiene)-b-poly(ethylene oxide) (PBut2.5-b-PEO1.3) giant polymersomes were prepared using an emulsion-centrifugation method. The impact of a fast decrease of the osmotic pressure inside the lumen of giant PBut-b-PEO vesicles was studied by confocal microscopy. This osmotic imbalance was created by performing the photo-induced polymerization of acrylamide inside these giant polymersomes, mimicking cell-like confinement. Experimental conditions (irradiation time, relative concentration of monomer and photo-initiator) were optimized to induce the fastest and highest osmotic pressure difference in bulk solution. When confined inside polymersomes with low permeability membrane made of PBut-b-PEO copolymers, this hyper-osmotic shock induced a fast disruption of the membrane and polymersome burst. These findings, complementary to hypo-osmotic shock approaches previously reported, are demonstrating the versatility and relevance of controlling and modulating osmotic pressure imbalance in self-assembled artificial cell systems and protocells.