Triphilic pentablock copolymers with perfluoroalkyl segment in central position

Abstract

Adding perfluoroalkyl (PF) segments to amphiphilic copolymers yields triphilic copolymers with new application profiles. Usually, PF segments are attached as terminal blocks via Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC). The purpose of the current study is to design new triphilic architectures with a PF segment in central position. The PF segment bearing bifunctional atom transfer radical polymerization (ATRP) initiator is employed for the fabrication of triphilic poly(propylene oxide)-b-poly(glycerol monomethacrylate)b-PF-b-poly(glycerol monomethacrylate)-b-poly(propylene oxide) PPO-b-PGMA-b-PF-b-PGMA-b-PPO pentablock copolymers by a combined ATRP and CuAAC reaction approach. Differential scanning calorimetry indicates the PF-initiator to undergo a solid-solid phase transition at 63 C before the final crystal melting at 95 C. This is further corroborated by polarized optical microscopy and X-ray diffraction studies. The PF-initiator could successfully polymerize solketal methacrylate (SMA) under typical ATRP conditions producing well-defined Br-PSMA-b-PF-b-PSMA-Br triblock copolymers that are then converted into PPO-b-PSMA-b-PF-b-PSMA-b-PPO pentablock copolymer via CuAAC reaction. Subsequently, acid hydrolysis of the PSMA blocks afforded water soluble well-defined triphilic pentablock copolymers PPO-b-PGMA-b-PF-b-PGMA-b-PPO with fluorophilic central segment, hydrophilic middle blocks, and lipophilic outer blocks. The triphilic block copolymers could self-assemble, depending upon the preparatory protocol, into spherical and filament-like phase-separated nanostructures as revealed by transmission electron microscopy.

Effect of Block Sequence on the Solution Self-Assembly of Symmetric ABCBA Pentablock Polymers in a Selective Solvent

“…Amphiphilic ABCBA pentablock polymers have attracted considerable attention for applications as pH- and/or temperature-responsive drug carriers − and hydrogels. − In the field of molecular medicine, for example, pentablock polymer aggregates have been used for the intracellular delivery of doxorubicin for cancer chemotherapy; they have been also used to deliver both drugs and unimolecular pluronics to reverse multidrug resistance in cancer cells . In addition, stimuli responsive pentablock copolymers have also been used as rheology modifiers in cosmetics and coatings as well as injectable hydrogels in pharmaceutical formulations .…”