pH‐Switchable Complexation between Double Hydrophilic Heteroarm Star Copolymers and a Cationic Block Polyelectrolyte

Abstract

Double hydrophilic heteroarm star copolymers of poly(methacrylic acid) (PMAA) and poly(ethylene oxide) (PEO) were synthesized via atom‐transfer radical polymerization (ATRP) using the “in‐out” method. The synthesis consisted of three steps. Namely, ATRP was applied to the preparation of a star macroinitiator with PEO arms and a cross‐linked core resulting from the polymerization of divinylbenzene (DVB) in the first step, chain extension with tert‐butyl methacrylate (tBMA) under ATRP conditions, and subsequent hydrolysis of the tert‐butyl groups afforded (PEO)n‐PDVB‐(PMAA)n heteroarm star copolymers with a cross‐linked microgel core. This novel type of double hydrophilic heteroarm star copolymer can be considered as unimolecular micelles with hybrid coronas. The star copolymers exhibited pH‐dependent solubility in water, being soluble at high pH and insoluble at low pH, due to the formation of hydrogen‐bonded complexes between the PEO and PMAA arms. A mixed solution of the heteroarm star copolymer and a PEO‐b‐PQDMA diblock copolymer, where PQDMA is poly(2‐(dimethylamino)ethyl methacrylate) fully quaternized with methyl iodide, remained stable in the whole pH range, and exhibited an intriguing pH‐switchable complexation behavior accompanied with structural rearrangement.magnified image

Polymeric Micelles Induced by Interpolymer Complexation

“…Ge et al investigated the formation of onion‐like micelles from a stimuli‐responsive double hydrophilic heteroarm star copolymer and a linear diblock copolymer in aqueous solution 73. The star copolymer was composed of a cross‐linked microgel core of PDVB segments and a mixed corona of PEO and PMAA chains.…”

Miktoarm stars of poly(ethylene oxide) and poly(dimethylaminoethyl methacrylate): manipulation of micellization by temperature and light

“…1 Anionic polymerization is the classical method for the preparation of those architectures, [2][3][4][5][6][7][8][9][10] whereas controlled radical polymerization widened the repertoire considerably. [11][12][13][14][15][16][17][18] Miktoarm stars aggregate in selective solvents. The effect of the architecture on the aggregation behavior has been investigated in previous studies.…”

“…There are also examples given for double hydrophilic species, enabling morphological changes upon exertion of stimuli. 15,17,21 Photosensitivity was also introduced into miktoarm stars, though no distinct morphological changes were reported upon illumination. 22,23 Further, chelating polymeric ligands enabled the preparation of miktoarm stars by coordination with photoactive europium or ruthenium.…”

Giant tubular and toroidal vesicles from self-assembled triblock copolymer–polyaniline complexes in water

“…In aqueous self-assembly of amphiphilic block copolymers, depending on required morphology, additives can be added that form complex with either wall 12 or corona 13 forming blocks. The additives range from small molecules to block copolymers through metal ions and homopolymers.…”