Hollow polymer nanocapsules are produced by the polymerization within hydrophobic interior of lipid bilayers that act as temporary self-assembled scaffolds. Pore-forming templates are codissolved with monomers in the bilayers to create pores with controlled size and chemical environment. Polymerization was monitored with UV spectroscopy and dynamic light scattering. High-resolution magic angle spinning NMR characterization provided detailed structural information about nanocapsules. Spherical shape was confirmed by electron microscopy. Medium-sized molecules can be entrapped within porous nanocapsules. No release of encapsulated molecules was observed within 240 days.