Redox-Responsive Dynamic-Covalent Assemblies: Stars and Miktoarm Stars

Abstract

Dynamic-covalent macromolecular stars were prepared by cross-linking block copolymers containing reactive maleic anhydride units with a disulfide-containing diamine.Here we report the synthesis of disulfide-cross-linked star polymers obtained by the arm-first process. Well-defined block copolymers containing a reactive poly(styrene-alt-maleic anhydride) (P(S-alt-MAn)) segment and an inert polystyrene or poly(N-isopropylacrylamide) segment were obtained by reversible addition−fragmentation chain transfer (RAFT) polymerization. Facile ring-opening of the pendant anhydride groups in the block copolymers by a disulfide-linked diamine cross-linker led to core-cross-linked stars with redox-responsive cores. The reductive cleavage of the disulfide linkages in the cross-linked cores resulted in star dissociation into linear arms with pendant thiol groups. Oxidation of the pendant thiol units of the resulting unimers in the presence of air led to reassembly or self-healing of the stars without the need for an externally added oxidizing agent.

Star Polymers

“…231 In addition, star polymers composed of POSS or β-CD cores and polycation arms were designed by Xu and co-workers with myriad functional groups, allowing for effective gene therapeutics. 192,212,461−463 Star polymers that are able to respond to stimuli such as pH, 464−470 redox potential, 30,223,237,471 light, 472−476 temperature, 477−480 and enzymatic changes 120,481 have been prepared for targeted drug and gene delivery applications. For gene delivery, Liu and co-workers synthesized a cationic star polymer with a cleavable cross-linked core consisting of poly(N,Nbis(acryloyl) cystamine) (PBAC) and multiple PDMAEMA arms by ATRP.…”

Protected thiol strategies in macromolecular design

“…It is also possible to build in redox-cleavable sites in the polymer backbone through disulfidecontaining monomers or cross-linkers [86,[116][117][118][119][120]. In contrast to pendant disulfide bonds, the cleavage of disulfide bonds incorporated in the polymer backbone results in the (partial or total) degradation of the polymer (network).…”

“…Moreover, the gels swelled in acidic environment, which also offers potential for releasing compounds in acidic (inflamed) tissue. Besides hydrogels and nanogels [79][80][81][82], redox-responsive disulfide containing polymers were for example also used for the synthesis of hollow microspheres [83], star polymers [84][85][86] and micelles [87,88].…”

Porous Carbons – Hyperbranched Polymers – Polymer Solvation

“…The gas transport properties of hb-PI blend membranes of 4,4 0 -(hexafluoroisopropylidene) diphthalic anhydride/1,3,5-tris(4-aminophenoxy)benzene (6FDA/TAPOB) and 4,4 0 (hexafluoroisopropylidene) diphthalic anhydride/ 3,3 0 -dihydroxybenzidine (6FDA/HAB) blends and their silica hybrid membranes were investigated by Suzuki et al [289]. The formation of a hb-PI blend silica hybrid membrane is presented in Scheme 34 in a simplified manner.…”