Small‐Angle X‐Ray Scattering Studies of Block Copolymer Nano‐Objects: Formation of Ordered Phases in Concentrated Solution During Polymerization‐Induced Self‐Assembly

• Published in: Angewandte Chemie International Edition Vol. 60; no. 23; pp. 12955 - 12963
• Main Authors: Rymaruk, Matthew J., O'Brien, Cate T., György, Csilla, Darmau, Bastien, Jennings, James, Mykhaylyk, Oleksandr O., Armes, Steven P.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-06-2021; John Wiley and Sons Inc
• Edition: International ed. in English
• Subjects: Assembly; Block copolymers; Dilution; Dodecane; lyotropic phases; NMR; Nuclear magnetic resonance; Phases; Polybutadiene; Polymerization; polymerization-induced self-assembly; RAFT dispersion polymerization; SAXS; Scattering; block copolymers; polymerization-induced self-assembly; RAFT dispersion polymerization; SAXS; lyotropic phases
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202101851

We report that polymerization‐induced self‐assembly (PISA) can be used to prepare lyotropic phases comprising diblock copolymer nano‐objects in non‐polar media. RAFT dispersion polymerization of benzyl methacrylate (BzMA) at 90 °C using a trithiocarbonate‐capped hydrogenated polybutadiene (PhBD) steric stabilizer block in n‐dodecane produces either spheres or worms that exhibit long‐range order at 40 % w/w solids. NMR studies enable calculation of instantaneous copolymer compositions for each phase during the BzMA polymerization. As the PBzMA chains grow longer when targeting PhBD80–PBzMA40, time‐resolved small‐angle X‐ray scattering reveals intermediate body‐centered cubic (BCC) and hexagonally close‐packed (HCP) sphere phases prior to formation of a final hexagonal cylinder phase (HEX). The HEX phase is lost on serial dilution and the aligned cylinders eventually form disordered flexible worms. The HEX phase undergoes an order–disorder transition on heating to 150 °C and a pure HCP phase forms on cooling to 20 °C.
Polymerization‐induced self‐assembly (PISA) can produce lyotropic phases of block copolymer nano‐objects. Time‐resolved SAXS studies confirm that reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate in n‐dodecane initially produces spheres exhibiting long‐range order that subsequently evolve to form hexagonally packed worms. Serial dilution leads to disordered worms.