Reversible Interpolyelectrolyte Shell Cross-Linked Micelles from pH/Salt-Responsive Diblock Copolymers Synthesized via RAFT in Aqueous Solution

Abstract

Herein we report the synthesis and characterization of a series of pH reversible shell cross-linked micelles. A series of novel pH/salt-responsive block copolymers of poly(sodium 2-acrylamido-2-methyl-1-propanesulfonate-block-N-acryloyl-l-alanine) (P(AMPS-b-AAL)) were synthesized utilizing aqueous reversible addition−fragmentation chain transfer (RAFT) polymerization. Micellization of P(AMPS-b-AAL) is induced by rendering the PAAL block hydrophobic through protonation of the carboxylic acid (pH 1−3). The pH at which micelle formation occurs and the hydrodynamic diameters of the resultant micelles are dictated by block copolymer composition and electrolyte concentration. The anionic PAMPS micelle shells were subsequently cross-linked with a RAFT synthesized cationic homopolymer of either poly(N-[3-(dimethylamino)propyl]acrylamide) (PDMAPA, pK a = 8.5) or poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA, pK a = 7.3). Upon deprotonation of the PAAL block, these cross-linked micelles swell but remain stable and intact. Significantly, the reversibility of the cross-linking was determined to be tunable by utilizing the different cationic homopolymers for cross-linking. This was demonstrated by increasing the pH above the pK a of the cationic homopolymer cross-linker, resulting in deprotonation of the cationic cross-linker and dissociation of the cross-linked micelles.

Living Radical Polymerization by the RAFT Process – A Third Update

“…15. [203,587] 357 [357] 358 [582] 356 [239] 353 [222] 352 [222] 354 [236] 355 [427] 359 [170] 360 [533] 368 [292] 366 [486] 367 [423] 369 [58] 370 [383] 371 [245,246] 372 [464] AMPS Ϫ ϩ ϩ Ϫ ϩ ϩ Ϫ 363 [245,246] 361 [328] 362 [328] 364 [289] 365 [383] Ϫ Fig. 8.…”

Multifunctional covalently stabilized vesicles acting simultaneously as the template of gold nanoparticle cluster and the nanocarrier of guest molecules

“…Update, a vast amount of covalent stabilized micelles [28][29][30][31][32][33][34][35][36][37][38] and vesicles [39][40][41][42][43][44][45][46] has been prepared on the basis of the self-assembly of amphiphilic linear polymers. However, the study on the stabilization of the aggregates derived from the branched polymers is scarce [47,48].…”

RAFT polymerization mediated bioconjugation strategies

“…40,41 It is also possible to create various polymer architectures such as block and graft copolymers, stars, and nanostructures using RAFT polymerization. 42,43,[44][45][46][47][48][49][50][51] RAFT polymerization offers a highly versatile platform for controlled synthesis and molecular engineering of polymer bioconjugates. [13][14][15][16]25 The strength of the RAFT approach for generation of polymer bioconjugates lies in its ability to control the polymerization of a wide range of monomers in varying solvents including water, at moderate temperatures, using only chain transfer agents and common free radical initiators (without the need for any additional polymerization component such as metal catalysts and sacrificial initiators).…”