Redox Responsive Behavior of Thiol/Disulfide-Functionalized Star Polymers Synthesized via Atom Transfer Radical Polymerization
A poly(n-butyl acrylate)-based star polymer, polyEGDA-(polyBA)(n), was synthesized by atom transfer radical polymerization using a modified core-first method. Further polymerization of a disulfide (SS) cross-linking :went bis(2-methacryloyloxyethyl) disulfide from the arm end produced a SS cross-linked star polymer. The disulfide functionality could be cleaved via reducing reactions, generating individual stars containing SH groups at the chain ends. The transformation between SS cross-linked star and SH-star was reversible via repetitive reduction and oxidation. Dynamic fiat scattering measurements showed that the average diameter of the cleaved star polymer was around 20 nm. The dynamic mechanical properties of these star copolymers were characterized through examination of the temperature dependencies or their shear moduli. The results showed that SS-functionalized star polymers respond to reduction-oxidation conditions, indicating that the disulfide bonds do cleave and re-form. These stimuli responsive star polymers have potential utility as intelligent polymeric materials such as self-healing materials.