Switchable Polymerization Organocatalysis: From Monomer Mixtures to Block Copolymers

Abstract

One‐pot production of sequence‐controlled block copolymer from mixed monomers is a crucial but rarely reached goal. Using a switchable Lewis‐pair organocatalyst, we have accomplished sequence‐selective polymerization from a mixture of O‐carboxyanhydride (OCA) and epoxide. Polymerization of the OCA monomer occurs first and exclusively because of its exceedingly high polymerizability. When OCA is fully consumed, alternating copolymerization of epoxide and CO2 liberated in OCA polymerization is triggered from the termini of the first block. The two polymerizations thus occur in tandem, both in chemoselective fashion, so that a sequence‐controlled block polymer with up to 99 % CO2 conversion is furnished in this one‐pot protocol. Calculations and experimental results demonstrate a chemoselective and cooperative mechanism, where the high polymerizability of the OCA monomers guarantees exquisite sequence selectivity and the cooperative decarboxylation partly arose from the stabilization effect by triethylborane, which facilitates the smooth transformation of the chain end from carbonate to alkoxide.

Triblock Copolymers from CO2, Propylene Oxide, and p-Tosyl Isocyanate of Higher Toughness than Polyethylenes

“…Indeed, PTPU exhibits a glass transition temperature of 107 °C, a value comparable to that of PCHC, but its chemical nature should be more favorable to phase separation with low T g polycarbonates (PPPC) than PCHC. The utilization of switchable polymerization catalysts has gained popularity in recent years as such catalysts allow the synthesis of sequence-selective copolymers from a mixture of monomers. − The TEB/onium salt system is supposed to be capable of switching from PO/CO 2 copolymerization to PO/TSI copolymerization or PO homopolymerization. Herein, the synthesis of high-molar-mass PTPU- b -PPPC- b -PTPU (U-PC-U) ABA triblock copolymers is reported using TEB/onium salt as a switchable system from PO/CO 2 copolymerization to PO/TSI copolymerization (Scheme ).…”

A one-pot approach towards polycarbonate-b-polyester block copolymers via chemoselective polymerization catalyzed by a one-component phosphonium borane Lewis pair

“…S1 †). 24,[30][31][32][33][34][35][36][37][38][39][40][41][42] Although borane-based Lewis pairs offer a promising alternative for the generation of low carbon polymers, the success of the ROP of lactone or lactide is rare, especially an extra hydrogen-bonding additive needs to be introduced. 25,43 We previously reported a one-component phosphonium bisborane Lewis pair, PBB-Br, enabling living/ controlled polymerization of PO.…”

One-Pot Synthesis of Hyperbranched Polymers via Visible Light Regulated Switchable Catalysis

“…12,13 In 2015, Williams et al pioneered a switchable catalytic system involving ring-opening copolymerization (ROCOP) of epoxide/cyclic anhydride and ring-opening polymerization (ROP) of cyclic ester, which enables the straightforward synthesis of polyester-b-polyesters with little tapering from mixtures of monomers. [14][15][16] With the development of a myriad of organometallic [17][18][19][20] and oganic [21][22][23][24] catalysts and the ongoing expansion of monomer scope, [25][26][27] this self-switchable polymerization technique has evolved into the most popular and powerful platform to construct oxygenated block copolymers directly from mixtures of monomers. Notably, the sequences, compositions, and molecular weights of the resulting oxygenated block copolymers can be easily and precisely modulated, thus allowing for the on-demand development of advanced polymeric materials in applications such as thermoplastic elastomers (TPEs), pressure-sensitive adhesives (PSAs), and toughened plastics.…”