Novel Ferrocenyl-Terminated Linear–Dendritic Amphiphilic Block Copolymers: Synthesis, Redox-Controlled Reversible Self-Assembly, and Oxidation-Controlled Release

Abstract

Novel linear-dendritic amphiphilic block copolymers with hydrophilic poly(ethylene glycol) (PEG) block and hydrophobic Percec-type dendrons containing ferrocenyl terminals were synthesized by the esterification reaction of poly(ethylene glycol) methyl ether with ferrocenyl-terminated alkyl-substituted benzoic acid dendrons. On the basis of the results that the critical aggregation concentration (CACox) of the oxidation state polymer is much higher than CACred of the corresponding reduction state, these polymers can reversibly self-assemble into various aggregates, such as spherical, wormlike micelles, and vesicles, and also disassemble into irregular fragments in aqueous solution by redox reaction when changing the polymer concentrations. Copolymer PEG45-b-Fc3 (3) with 3,4,5-tris(11-ferrocenylundecyloxy) benzoic acid (2) can self-assemble into nanoscale wormlike micelles when the polymer concentration in aqueous solution is above its CACox. These wormlike micelles can be transformed into nanosized vesicles by Fe2(SO4)3 and regained by vitamin C. Interestingly, copolymer PEG45-b-Fc2 (5) with 3,5-bis(11-ferrocenylundecyloxy) benzoic acid (4) can reversibly self-assemble into spherical micelles with two different sizes by redox reaction above the CACox, indicating that the terminal hydrophobic tail number of dendrons plays a key role in determining the self-assembled structures. Furthermore, rhodamine 6G (R6G)-loaded polymer aggregates have been successfully used for the oxidation-controlled release of loaded molecules, and the release rate can be mediated by the concentrations of oxidant and copolymers. The results provide an effective approach to the reversible self-assembly of linear-dendritic amphiphilic block copolymers and also promise the potential of these novel redox-responsive amphiphilic block copolymers in drug delivery systems, catalyst supports, and other research fields.

Synthesis of amphiphilic block copolymers containing ferrocene–boronic acid and their micellization, redox-responsive properties and glucose sensing

“…Ferrocene-containing block copolymers self-assemble and may induce change in polarity of ferrocene-bearing blocks due to reversible redox reactions. Thereby, these block copolymers form micelles with redoxtriggered activity, which are particularly useful for potential applications of redox-regulated release of encapsulants [9][10][11][12].…”

Voltage-responsive reversible self-assembly and controlled drug release of ferrocene-containing polymeric superamphiphiles

“…10 As previously reported, water-soluble doublehydrophilic block copolymers with ionic and nonionic hydrophilic segments and oppositely charged surfactants could form a polymeric superamphiphile after simple mixing in aqueous solution drived by electrostatic interactions. 30,31 This clearly shows that ferrocenyl amphiphiles have a great potential for stimuli-responsive controllable self-assembly systems. 24 ).…”

“…33 The block copolymers PEG 113 -b-PAA 30 were synthesized by atom transfer radical polymerization (ATRP) 34,35 and were detailed in the supporting Information ( Figure S1 and S2, Table S1, ESI †). 33 The block copolymers PEG 113 -b-PAA 30 were synthesized by atom transfer radical polymerization (ATRP) 34,35 and were detailed in the supporting Information ( Figure S1 and S2, Table S1, ESI †).…”

“…The block copolymer PEG 113 -b-PAA 30 was dissolved in 0.10 M NaCl aqueous solution at pH=10 in which the molar concentration of carboxylate group is 4.2 mM. FTMA was dissolved in 0.10 M NaCl aqueous solution with a concentration of 4.2 mM.…”

“…In this work, we describe a new voltage-responsive block polymeric superamphiphile made of the cationic ferrocenyl surfactant ((11-ferrocenylundecyl) trimethyl ammonium bromide, FTMA) and oppositely charged double-hydrophilic block copolymer poly-(ethylene glycol)-b-poly(acrylic acid) (PEG 113 -b-PAA 30 ) drived by electrostatic and hydrophobic interactions, as shown in Scheme 1. Firstly, we report that this kind of polymeric superamphiphile could form voltage-responsive micelles that undergo reversible selfassembly and disassembly controlled by the electrochemical redox in terms of the critical micelle concentration (cmc) difference between oxidation and reduction state FTMA.…”