Porous bioresorbable radiopaque embolic microspheres for drug delivery

Embolic spherical microparticles, comprising:

• a copolymer material having at least one radiopaque iodine-containing component and at least one rubbery component;
• wherein the rubbery component comprises oligomers or macromers of PEG (polyethylene glycol), PCL (polycaprolactone), PTMO poly(tetramethylene oxide), PTMC poly(trimethylene carbonate) or combinations thereof, and the rubbery component has a Tg below about 37° C.;
• wherein the radiopaque iodine-containing component comprises iodinated phenyl-containing monomers, oligomers, or macromers,
• wherein the at least one radiopaque iodine-containing component and the at least one rubbery component are connected by two or more different types of chemical bonds comprising fast degrading and slow degrading chemical bonds with different affinities to hydrolysis such that the different chemical bonds have different rates of in vivo hydrolytic degradation, and one type of chemical bonds is oxalate bond, and
• wherein the microparticles have internal and/or external porosity formed by the decomposition of fast degrading oxalate bonds.