Stimulus-Responsive Self-Assembly: Reversible, Redox-Controlled Micellization of Polyferrocenylsilane Diblock Copolymers

Abstract

In depth studies of the use of electron transfer reactions as a means to control the self-assembly of diblock copolymers with an electroactive metalloblock are reported. Specifically, the redox-triggered self-assembly of a series of polystyrene-block-polyferrocenylsilane (PS-b-PFS) diblock copolymers in dichloromethane solution is described. In the case of the amorphous polystyrene(n)-b-poly(ferrocenylphenylmethylsilane)(m) diblock copolymers (PS(n)-b-PFMPS(m): n = 548, m = 73; n = 71, m = 165; where n and m are the number-averaged degrees of polymerization), spherical micelles with an oxidized PFS core and a PS corona were formed upon oxidation of more than 50% of the ferrocenyl units by [N(C(6)H(4)Br-4)(3)][SbX(6)] (X = Cl, F). Analogous block copolymers containing a poly(ferrocenylethylmethylsilane) (PFEMS) metalloblock, which has a lower glass transition temperature, behaved similarly. However, in contrast, on replacement of the amorphous metallopolymer blocks by semicrystalline poly(ferrocenyldimethylsilane) (PFDMS) segments, a change in the observed morphology was detected with the formation of ribbon-like micelles upon oxidation of PS(535)-b-PFDMS(103) above the same threshold value. Again the coronas consisted of fully solvated PS and the core consisted of partially to fully oxidized PFS associated with the counteranions. When oxidation was performed with [N(C(6)H(4)Br-4)(3)][SbF(6)], reduction of the cores of the spherical or ribbon-like micelles with [Co(η-C(5)Me(5))(2)] enabled full recovery of the neutral chains and no significant chain scission was detected.

Disassembly of redox responsive poly(ferrocenylsilane) multilayers: The effect of blocking layers, supporting electrolyte and polyion molar mass

“…Poly(ferrocenylsilane) (PFS) is a unique organometallic polymer, exhibiting alternating ferrocene and silane units within the main chain [11][12][13]. Since reversible redox processes affect the ferrocene group within its backbone, PFS is undergoing dramatic and reversible changes in physicochemical properties upon oxidation.…”

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].…”

Electric field manipulated nanopatterns in thin films of metalorganic 3-miktoarm star terpolymers

“…The electric field would further enhance the polarity difference between polar PFEMS and non-polar PS, increasing chloroform solubility in PFEMS. 37,38 The change in solvent solubility of the PFS block through oxidation of the ferrocene moieties of PS-b-PFS copolymers has furthermore been reported by Eloi et al 39 (ii) Cylinder forming PS-b-PFEMS Diblock Copolymer Blends. To confirm the assumption that the applied voltage leads to an oxidation of the ferrocenyl groups and hence an increase in PFEMS volume fraction thin films of a cylinder forming block copolymer blend were analyzed at various electric field strengths.…”