Formation Efficiency of ABA Blockcopolymers via Enhanced Spin Capturing Polymerization (ESCP): Locating the Alkoxyamine Function

Enhanced spin capturing polymerization (ESCP) constitutes a versatile method for controlling the molecular weights during free radical macromolecular growth. The methodology employs nitrones as controlling agents, which are incorporated as alkoxyamines into the macromolecules in a midchain position (Ri−NO−Rj). It is demonstrated—via both simulations and experiments—that if the radical initiator and the nitrone are judiciously chosen, midchain functionalizations of over 90% can be achieved. Macromolecules with a nitroxide position in the midchain position can be employed in subsequent nitroxide mediated polymerizations to prepare ABA-type block copolymers. It is demonstrated that high yields of midchain macroalkoxyamine are generated as long as the employed nitrone displays low primary radical addition (governed by the addition rate coefficient kad) in combination with a relatively rapid chain growth initiation rate (characterized by the primary radical initiation rate coefficient, ki). The absolute value ...