A New Associative Diblock Copolymer of Poly(ethylene glycol) and Dense 1,2,3‐Triazole Blocks: Self‐Association Behavior and Thermoresponsiveness in Water

Abstract

In this work, new diblock copolymers of poly(ethylene glycol) (PEG) and dense 1,2,3‐triazole blocks (EGm‐b‐APn and EGm‐b‐ABn, where m and n denote the degrees of polymerization), are synthesized by copper(I)‐catalyzed azide–alkyne cycloaddition polymerization of 3‐azido‐1‐propyne (AP) and 3‐azido‐1‐butyne (AB), respectively, in the presence of PEG possessing a propargyl group. Their self‐association behavior and thermoresponsive property in water are investigated. The characterization data indicate that EG45‐b‐AP6 and EG45‐b‐AP14 form dominantly spherical micelles, EG18‐b‐AP4 and EG18‐b‐AP10 form vesicles, and EG18‐b‐AB7 forms rodlike micelles. Aqueous solutions of EG18‐b‐AP10, EG45‐b‐AP14, and EG18‐b‐AB7 undergo lower critical solution temperature (LCST)‐type phase separation. The thermoresponsive association behavior can be controlled by adjusting the ratio of block lengths and by attaching methyl substituents.

Synthesis of Dense 1,2,3-Triazole Polymers Soluble in Common Organic Solvents

“…Because of the poor solubility, it was not possible to obtain high-molecular-weight polymers from the AP derivatives by CuAAC polymerization. However, it was possible to obtain dense 1,2,3-triazole oligomers or polymers soluble in common solvents by quaternization of the AP oligomer with methyl iodide [ 34 ] or by connecting to poly(ethylene glycol) (PEG) blocks, i.e., the formation of block copolymers [ 35 , 36 ]. The block copolymers of PEG and dense 1,2,3-triazole blocks form aggregates in water, e.g., spherical micelles and vesicles, depending on the ratio of block lengths, and undergo phase separation at higher temperatures because of cooperative dehydration of the PEG block [ 36 ].…”

“…However, it was possible to obtain dense 1,2,3-triazole oligomers or polymers soluble in common solvents by quaternization of the AP oligomer with methyl iodide [ 34 ] or by connecting to poly(ethylene glycol) (PEG) blocks, i.e., the formation of block copolymers [ 35 , 36 ]. The block copolymers of PEG and dense 1,2,3-triazole blocks form aggregates in water, e.g., spherical micelles and vesicles, depending on the ratio of block lengths, and undergo phase separation at higher temperatures because of cooperative dehydration of the PEG block [ 36 ]. In this study, we have synthesized an AP derivative possessing t -butyl ester, i.e., t -butyl 4-azido-5-hexynoate (tBuAH), which may improve the solubility of its polymer, and conducted CuAAC and HC polymerizations of tBuAH to obtain high-molecular-weight polymers soluble in common organic solvents.…”

Synthesis of a New Polyanion Possessing Dense 1,2,3-Triazole Backbone

“…CuAAC has been also utilized for synthesis of polymers possessing 1,2,3-triazole units [ 23 , 24 , 25 , 26 ]. We have been working on synthesis of polymers with the backbone composed of dense 1,2,3-triazole units by CuAAC polymerization of 3-azido-1-propyne (AP) and its derivatives [ 27 , 28 , 29 , 30 , 31 ]. Unfortunately, AP polymer was insoluble in all the solvents examined presumably because of strong dipole–dipole interaction of dense 1,2,3-triazole units.…”

Self-Healing Thermoplastic Elastomers Formed from Triblock Copolymers with Dense 1,2,3-Triazole Blocks

“…Since AP oligomers are insoluble in many solvents, we synthesized diblock copolymers possessing a dense 1,2,3-triazole block and a soluble poly(ethylene glycol) (PEG) as a new associative polymer. 66,67 The diblock copolymer dissolved in polar organic solvents, e.g., N,Ndimethylformamide (DMF) and dimethyl sulfoxide (DMSO), 66 while forming aggregates, i.e., spherical micelles or vesicles, in aqueous solution depending on the block lengths. 67 It is known that BAB-type triblock copolymers, which possess two associative blocks at both ends, form a wider variety of aggregates compared to AB diblock copolymers because of the formation of loops and bridges.…”

“…66,67 The diblock copolymer dissolved in polar organic solvents, e.g., N,Ndimethylformamide (DMF) and dimethyl sulfoxide (DMSO), 66 while forming aggregates, i.e., spherical micelles or vesicles, in aqueous solution depending on the block lengths. 67 It is known that BAB-type triblock copolymers, which possess two associative blocks at both ends, form a wider variety of aggregates compared to AB diblock copolymers because of the formation of loops and bridges. 68−74 In this study, we synthesized BAB-type triblock copolymers consisting of dense 1,2,3-triazole outer blocks and a PEG middle block (poly(3-azido-1-propyne)-block-poly(ethylene glycol)-blockpoly(3-azido-1-propyne)) (APn-b-EGm-b-APn, Scheme 1) using CuAAC polymerization and explored their structural, thermal, viscoelastic, and mechanical properties.…”