Loop-stabilized BAB triblock copolymer morphologies by PISA in water

Abstract

Assemblies of BAB triblock copolymers are prepared by PISA via aqueous RAFT dispersion polymerization. The importance of charges in the middle of the hydrophilic stabilizer loops is highlighted.

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

“…We observed in our former PISA study on PDAAm-b-PDMAc-b-PDAAm particles, 13 that changing the initial concentration of macroRAFT agent, the ionization degree of the central benzoic acid function on the R group of the macroRAFT agent or the length of its terminal alkyl chains (C4 or C12) on its Z groups (see Scheme 2) could result in the loss of colloidal stability during PISA, and was in some cases accompanied by a loss of control over the polymerization. In contrast, suspensions that remained colloidally stable always resulted in controlled polymerizations.…”

“…The synthesis of the macroRAFT agents (C12-TTC-PDMAc)2-BA and (C4-TTC-PDMAc)2-BA (named respectively in this study C12-macroRAFT agent and C4-macroRAFT agent) were described in a former study 13 and detailed in the SI (Scheme S1, Table S1, Figure S1). The macroRAFT agent extensions with DAAm (Scheme 2) conducted with stirring were performed according to a formerly developed protocol 13 at 70°C, in a 2 mL round bottom flask using an oliveshaped stirring bar (5×10 mm) and a stirring speed of 500 rpm as detailed in the SI (Table S2, Figure S2). The macroRAFT agent extensions with DAAm conducted without stirring during the polymerization as well as the kinetic study performed in D2O in NMR tubes are described in details in the SI, section 2.…”

“…In order to investigate in more details what happens at the nano-scale during the synthesis of BAB triblock copolymers by PISA and understand the role of stirring, we used LS to characterize the self-assembly in aqueous medium of the BAB triblock copolymers for different degrees of polymerization of the B blocks (corresponding to different monomer conversions during the PISA process). In our previous study 13 we had shown that the pH of the solution, i.e. the ionization degree (α) of the central benzoic acid group had an impact on the assembly.…”

“…[9][10][11][12] In more detail, depending on the macroRAFT agent used, spherical particles, complex aggregates or higher order morphologies (and their aggregates) were observed. 9,11 Recently, our group reported the first successful synthesis of BAB copolymers by PISA in pure water 13 : symmetrical bifunctional poly(N,N-dimethylacrylamide) (PDMAc) macroRAFT agents with a central benzoic acid group and two outer alkyl chains as Zgroups were used in the aqueous dispersion polymerization of diacetone acrylamide (DAAm) (see structure in Scheme S1). The study notably highlighted the crucial role of the central benzoic acid group in the stabilization of the nano-objects and also revealed an impact of the length of the alkyl chains ends.…”

Rapid production of block copolymer nano-objects via continuous-flow ultrafast RAFT dispersion polymerisation

“…Aqueous PISA of poly(dimethyl acrylamide)-b-poly(diacetone acrylamide) (PDMAm-b-PDAAm) is one of the most widely reported and predictable systems, allowing easy access to the full range of morphologies. [48][49][50][51][52][53][54][55][56] Conveniently, this is an allacrylamide system, meaning the monomers have high k p values and thus are ideally suited to ultrafast RAFT polymerisation. 18 Herein, we evaluate whether ultrafast RAFT polymerisation of diacetone acrylamide (DAAm) in the presence of a PDMAm x macromolecular chain transfer agent can be conducted in a flow reactor.…”