Unravelling the formation of BAB block copolymer assemblies during PISA in water

Abstract

BAB triblock copolymers prepared by PISA in water self-assemble into a transient network of bridged micelles. The slowdown of the exchange of B blocks between micelles during PISA is highlighted as well as the parameters affecting the polymerization.

Thermoresponsive dynamic BAB block copolymer networks synthesized by aqueous PISA in one-pot

“…38,46 We can therefore conclude that the changes in viscosity were not related to a change in particle morphology. The observations -together with previous results on samples containing pure PDAAm B blocks 39 -rather suggest that a percolated network of bridged flower-like micelles is formed, and that increasing the DMAc content in the B blocks decreases the lifetime of the B blocks within the micellar cores and/or decreases the number of elastically active chains, thereby decreasing the viscosity of the samples. S4).…”

“…In contrast, the reference sample without DMAc in the B blocks, 80-100-0, formed a transparent brittle gel, attributed to the formation of a frozen system. 39 Shear tests performed at 5 wt% and 30 °C on samples 180-100-20 and 180-100-33, confirmed the strong impact of the DMAc content on sample viscosity (see results in Table S4). TEM and cryo-TEM analyses (performed at 0.1 and 1 wt %, respectively) showed that the dispersions -regardless of the DMAc content -were generally constituted of sub-50 nm spherical aggregates (see Figure S6 and Table S5), in agreement with previous results.…”

“…In our previous work on BAB triblock copolymers comprising pure PDAAm B blocks, we had shown that the degree of ionization of the BA moiety strongly affects both the colloidal stability of the dispersion and the control over the polymerization. 38,39 Phase separation indeed occurred in the absence of charge in the central BA moiety because of intermicellar attraction caused by the ability of the BAB triblock copolymers to form bridges between micelles. This resulted in loss of colloidal stability (and occasionally loss of control over molar mass).…”

“…In a subsequent study, we demonstrated that nanometric aggregates of bridged flower-like micelles were formed in stirred polymerization conditions. 39 The latter resulted from the formation of a frozen network of bridged micelles, which was irreversibly broken into tiny pieces through the mechanical stirring.…”

Polymerizations by RAFT: Developments of the Technique and Its Application in the Synthesis of Tailored (Co)polymers

“…Low temperature photo‐RAFT‐PISA polymerization of poly( N ‐acryloylpyrrolidin)‐ b ‐polystyrene (PAPy‐ b ‐PS), yields monodisperse nanospheres with tunable size exhibiting thermosensitive character (hydrodynamic diameter linearly increasing with the temperature between 10 and 70 °C). [ 104 ] Other PISA prepared thermoresponsive nanoparticles have been synthesized via and BAB triblock copolymer of poly( N,N ‐dimethylacrylamide)‐ b ‐poly(diacetone acrylamide), [ 105 ] or nanogels based on poly(oligo(ethylene glycol) methyl ether acrylate)‐ b ‐poly( N ‐acryloyl glycinamide) in aqueous media. [ 106 ] Binary mixtures of PEO and poly(glycerol monomethacrylate) (PGMA) macro‐CTAs were used to prepare diblock copolymers by polymerizing thermoresponsive poly(hydroxypropyl methacrylate) (HPMA).…”