Well-Defined Functional Linear Aliphatic Diblock Copolyethers: A Versatile Linear Aliphatic Polyether Platform for Selective Functionalizations and Various Nanostructures

Abstract

Low-temperature anionic ring-opening homopolymerizations and copolymerizations of two glycidol derivatives (allyl glycidyl ether (AGE) and ethoxyethyl glycidyl ether (EEGE)) are studied using a metal-free catalyst system, 3-phenyl-1-propanol (PPA) (an initiator) and 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris-(dimethylamino)phosphoranylidenamino]-2?5,4?5-catenadi(phosphazene) (t-Bu-P4) (a promoter) in order to obtain well-defined functional linear polyethers and diblock copolymers. With the aid of the catalyst system, AGE is found to successfully undergo anionic ring-opening polymerization (ROP) even at room temperature (low reaction temperature) without any side reactions, producing well-defined linear AGE-homopolymer in a unimodal narrow molecular weight distribution. Under the same conditions, EEGE also undergoes polymerization, producing a linear EEGE-homopolymer in a unimodal narrow molecular-weight distribution. In this case, however, a side reaction (i.e., chain-transfer reaction) is found to occur at low levels during the early stages of polymerization. The chemical properties of the monomers in the context of the homopolymerization reactions are considered in the design of a protocol used to synthesize well-defined linear diblock copolyethers with a variety of compositions. The approach, anionic polymerization via the sequential step feed of AGE and EEGE as the first and second monomers, is found to be free from side reactions at room temperature. Each block of the obtained linear diblock copolymers undergoes selective deprotection to permit further chemical modification for selective functionalization. In addition, thermal properties and structures of the polymers and their post-modification products are examined. Overall, this study demonstrates that a low-temperature metal-free anionic ROP using the PPA/t-Bu-P4 catalyst system is suitable for the production of well-defined linear AGE-homopolymers and their diblock copolymers with the EEGE monomer, which are versatile and selectively functionalizable linear aliphatic polyether platforms for a variety of post-modifications, nanostructures, and their applications.