Synthesis and Characterization of Asymmetric A₁BA₂ Supramolecular Triblock Copolymers via Noncovalent Interactions: A Solution and Solid-State Study

Abstract

We present the design, synthesis, and characterization of triple hydrogen-bond-forming precursors and their supramolecular triblock copolymers. Thymine end-functionalized polystyrene-b-polyisoprene (PS-b-PI-Thy) and diaminotriazine end-functionalized polystyrene (PS-DAT) were successfully synthesized via anionic polymerization followed by suitable organic reactions and then solution-mixed to form supramolecular triblocks via hydrogen-bonding interactions. Three different types of asymmetric A1-b-B-sb-A2 supramolecular triblock copolymers were prepared by varying the molecular weight of the A1-b-B diblock copolymers and A2 homopolymers. Proton nuclear magnetic resonance spectroscopy was used for the detailed structural characterization of the polymers in solution, and gel permeation chromatography was used to determine the molecular weight and polydispersity index of all homopolymers and block copolymers. Additionally, transmission electron microscopy and small-angle X-ray scattering measurements were employed to assess the solid-state morphological structures of the supramolecular triple hydrogen-bond triblocks, the diblocks, and single hydrogen-bond mixtures of diblocks with homopolymers.

Quo Vadis Carbanionic Polymerization?

“…Microphase separation studies of the obtained supramolecular block copolymers were also performed and compared to the corresponding covalently linked analogues. This strategy was further developed for the synthesis of asymmetric supramolecular triblock copolymers (PS- b -PI- sb -PS′) …”

“…Toward this direction, many reports were documented by employing anionic polymerization and postpolymerization reactions for synthezing noncovalent bonded block polymers (hydrogen bonding, stereocomplexation, etc. ). − Our group reported the synthesis of supramolecular block copolymers (PS-DAT- sb -PI-Thy) via anionic polymerization and hydrogen bonding. Well-defined thymine end-functionalized PI (PI-Thy) and diaminotriazine (DAT) end-functionalized PS were synthesized by employing the EO end-capping method of the corresponding carbanionic living chains followed by suitable transformation reactions.…”

“…This strategy was further developed for the synthesis of asymmetric supramolecular triblock copolymers (PS-b-PI-sb-PS′). 210 Recently, significant attention and many contributions were reported on the synthesis of amphiphilic diblock copolymer nanoparticles via polymerization-induced self-assembly (PISA). 213,214 This strategy offers many advantages over traditional self-assembly procedures, which typically involve postpolymerization techniques that are performed in dilute solution (<1% w/w).…”