Anionic polymerization of MMA and renewable methylene butyrolactones by resorbable potassium salts

Abstract

AbstractThree resorbable potassium salts of hydride (K[H]), enolate Me2CC(OiPr)OK (K[E]), and allyl K[1,3‐(SiMe3)2C3H3] (K[A]) have been investigated for controlled anionic polymerization of methyl methacrylate (MMA) and its cyclic analogs, naturally renewable methylene butyrolactones including α‐methylene‐γ‐butyrolactone (MBL) and γ‐methyl‐α‐methylene‐γ‐butyrolactone (MMBL). When used alone at ambient temperature in toluene, these salts exhibit no (K[H]) to low (K[A]) to modest (K[E]) polymerization activity. Mixing of K[H] and Al(C6F5)3 leads to the formation of an “ate” complex, K+[HAl(C6F5)3]−, which has been structurally characterized by X‐ray diffraction; this complex has a high polymerization activity producing atactic PMMA, but addition of another equiv of Al(C6F5)3 further enhances both the rate and the efficiency of the polymerization, now producing syndiotactic PMMA with a narrow molecular weight (MW) distribution of 1.04. The K[H]/2Al(C6F5)3 system also exhibits high activity for polymerization of (M)MBL. In sharp contrast, addition of Al(C6F5)3 to K[A] shuts down the polymerization at various temperatures. The most active, controlled, and syndioselective polymerization system in this series is K[E]/2Al(C6F5)3. Accordingly, the polymerization control and kinetics of this most effective system have been examined in more detail. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011