Synthesis of poly(vinyl laurate)-b -poly(vinyl stearate) diblock copolymers by cobalt-mediated radical polymerization in solution

Abstract

Poly(vinyl laurate) (PVL) and poly(vinyl stearate) (PVS) were synthesized by means of cobalt-mediated radical polymerization (CMRP). Cobalt(II) diacetylacetonate (Co(acac)2) was demonstrated to control the radical polymerization of these monomers in solution. Molecular weights up to 15,000 g·mol−1 were obtained with reasonably low polydispersity indices (PDI < 1.3). The efficiency of the redox initiator [lauroyle peroxide (LPO)/citric acid (CA)] was found to be low (around 10%) as already reported for vinyl acetate. The solvent and temperature were found to have a very weak influence on the initiator efficiency. It appeared that CA played no role in the initiation process that only involved a redox reaction between LPO and Co(acac)2. PVL-b-PVS diblock copolymers could be synthesized using two strategies: (1) Sequential addition, that is, addition of the second monomer (VS) at high conversion of the first one (VL). (2) Macroinitiator technique, that is, isolation of a PVL macroinitiator then polymerization of VS from this cobalt functionalized macroinitiator. Both techniques allowed the synthesis of diblock copolymers with molar masses around 25,000 g·mol−1 and PDI lower than 1.4. The resulting materials were characterized by DSC, revealing that both blocks exhibit side-chain crystallinity and phase segregate in the bulk. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012