CO2-based block copolymers are gaining significant
momentum
as high-value-added and functional materials. However, current synthetic
achievements mainly rely on well-designed organometallic catalysts
and only give access to linear polymeric products. Herein, we report
the organocatalytic three-component polymerization of propylene oxide
(PO), phthalic anhydride (PA), and CO2 mediated by commercial
Lewis pairs composed of triethyl borane (Et3B) and organic
bases, wherein the chemoselectivity over the reaction and Lewis basicity
of the cocatalysts exhibit a negative correlation. Notably, the interplay
of Et3B and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) bridges
and discriminates the ring-opening copolymerization (ROCOP) of PO/PA
and ROCOP of PO/CO2 without interferences, thus affording
poly(propylene phthalate)-b-poly(propylene carbonate)
(PPE-b-PPC) with linear and hyperbranched topologies
by using benzyl alcohol and 1,3,4-benzene tricarboxylic anhydride
as the chain transfer agent, respectively. Notably, the formation
of undesirable cyclic byproducts was completely circumvented by rationally
modulating the Et3B/CTA ratio. Moreover, the effect of
topology on the viscosity, glass transition temperature, and thermal
stability of PPE-b-PPC has been exploited.