Absorbable, essentially non-absorbable, and non-absorbable crystalline, amphiphilic, block/graft copolymeric compositions exhibit an inherent viscosity of at least 0.5 dL/g, a heat of fusion of at least 10 J/g and undergo swelling in the biological environment due to a water up-take of at least 10 percent of original dry mass. These compositions are designed for use in swellable surgical sutures, coatings of medical devices, and carriers for the delivery of bioactive agents.