Polymer capsules from amphiphilic graft copolymers comprising reactive, hydrophobic polyolefin backbones, and hydrophilic poly(ethylene glycol) (PEG) grafts are produced by self-assembly of the polymers at the oil-water interface, and crosslinking the assembly with bis-cyclooctene PEG derivatives in conjunction with ring-open metathesis polymerization catalysts. The use of the graft copolymer architecture in capsule synthesis provides significant opportunities to tune both the surface properties, in terms of recognition, and the membrane properties, in terms of mechanical strength, encapsulation, and release.