Functionalized Polyesters with Tunable Degradability Prepared by Controlled Ring-Opening (Co)polymerization of Lactones

Abstract

Various well-defined diblock copolymers with poly(α-methylene−β-butyrolactone) (PMβBL) segment were prepared by salen–aluminum complexes or aminoalkoxybis(phenolate)yttrium amido complex mediated living ring-opening polymerization of racemic α-methylene-β-butyrolactone (rac-MβBL) and different lactones via one-pot, two-step method. These diblock copolymers all consist of semicrystalline and amorphous segments, possessing both a melting point and a glass transition temperature. With the use of simple salenAlMe with bulky (tert-butyldimethylsilyl) groups on the phenolate ortho position as catalyst in conjunction with equivalent benzyl alcohol, MβBL and β-butyrolactone (BL) have nearly identical reactivity in their copolymerization, affording the copolymers P(MβBL-ran-BL) with random distributions of the two monomers. Notably, these copolymers exhibited tunable degradability in the presence of Lewis base, dependent on the MβBL unit content in the random copolymers. Moreover, the vinylidene groups in P(MβBL-ran-BL) copolymers could be further functionalized through radical-initiated cross-linking reactions and thiol–ene click chemistry, producing functionalized and cross-linking polymers with enhanced thermal property. These strategies will provide enormous possibilities to synthesize diverse well-defined block and random copolymers with designable segments or functional groups.