Synthesis of degradable polyacetals via an intramolecular phosphonium bisborane Lewis pair catalyzed copolymerization of epoxides with o-phthaladehyde

An intramolecular phosphonium bisborane Lewis pair (PBB-Br) was used for the copolymerization of o-phthalaldehyde (OPA) with epoxides under mild conditions. In particular, poly(o-phthalaldehyde-alt-propylene oxide) termed as (poly(OPA-alt-PO)), having high molecular weight (M_n = 42.5 kg/mol) with Đ = 1.12 was generated at 25 °C using PBB-Br as a highly efficient catalyst. The purity of OPA, temperature and monomer/comonomer feeding ratio effects on the copolymerization were investigated. Subsequently, the degradability and thermal stability of generated polyacetals were studied. Using alcohol as chain transfer agent, random or block polyacetal-polyethers with different structures can be obtained in one-pot synthesis. The cooperation of the two boron centers plays a pivotal role in boosting the activity of copolymerization of OPA and PO.