This study reports on the synthesis and characterization of a novel four-arm reagent and its use in the synthesis of core degradable star polymers and block copolymers using the reversible addition fragmentation chain transfer (RAFT) polymerization process. The star RAFT polymers prepared from methyl methacrylate (MMA), styrene (ST) and N,N-dimethylacrylamide (DMA) were characterized by size exclusion chromatography (SEC). The PMMA star polymer was further polymerized with poly(ethylene glycol) methyl ether methacrylate (POEGMA(8-9)) to produce a star block copolymer. The core degradability of the star polymers (PMMA(40))(4), (PMMA(80))(4), (PS40)(4), (PS80)(4) and star block copolymer P[MMA(46)-b-(POEGMA(8-9))(46)](4) under reductive conditions to cleave the disulfide linkages was demonstrated. The results demonstrated the complete degradation of the star polymer to produce linear polymer and confirmed the near equal degree of polymerization in each of the arms. The star polymer (PDMA(80))(4) degraded slowly under acidic and enzymatic conditions demonstrating that the ester linkage can also be degraded.