Tuning the vesicle-to-worm transition for thermoresponsive block copolymer vesicles prepared via polymerisation-induced self-assembly


We have previously reported the synthesis of thermoresponsive poly(stearyl methacrylate)-poly(benzyl methacrylate) [PSMA-PBzMA] diblock copolymer vesicles in mineral oil via polymerisation-induced self-assembly (PISA). Such vesicles undergo a vesicle-to-worm transition on heating, which provides an interesting new oil-thickening mechanism (see M. J. Derry, et al., Angew. Chem., 2017, 56, 1746–1750). In the present study, we report an unexpected reduction in dispersion viscosity when heating vesicles of approximately the same composition above a certain critical temperature. Transmission electron microscopy (TEM) studies indicate rich thermoresponsive behavior, with vesicles present at 20 °C, worms being formed at 130 °C and spheres generated at 180 °C, indicating that a worm-to-sphere transition occurs after the initial vesicle-to-worm transition. Moreover, we have also prepared a series of new thermoresponsive diblock copolymer vesicles by RAFT dispersion copolymerization of n-butyl methacrylate (BuMA) with benzyl methacrylate (BzMA) using a poly(stearyl methacrylate) precursor in mineral oil. This model system was developed to examine whether statistical copolymerization of a suitable comonomer (BuMA) could be used to tune the critical onset temperature required for the vesicle-to-worm transition. Indeed, oscillatory rheology studies confirmed that targeting membrane-forming blocks containing up to 50 mol% BuMA lowered the critical onset temperature required to induce the vesicle-to-worm transition to 109 °C, compared to 167 °C for the reference PSMA14-PBzMA125 diblock copolymer. Variable temperature small-angle X-ray scattering (SAXS) experiments confirmed a vesicle-to-worm transition, with the vesicles initially present at 20 °C being converted into worms when heated above 130 °C. Furthermore, a substantial reduction in dispersion viscosity was again observed when heating above the critical onset temperature. TEM and shear-induced polarized light imaging (SIPLI) studies indicate that linear worms are no longer present at 160 °C and 170 °C respectively, suggesting a subsequent worm-to-sphere transition. The thermal transitions studied herein proved to be irreversible on cooling on normal experimental timescales (hours).

Publication DOI: https://doi.org/10.1039/D0PY01713B
Divisions: College of Engineering & Physical Sciences
College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
College of Engineering & Physical Sciences > Aston Institute of Materials Research (AIMR)
Additional Information: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Funding: EPSRC is acknowledged for a Centre for Doctoral Training (CDT) grant that funded a PhD studentship for I. R. D. Scott Bader Ltd is thanked for partial support of this CDT PhD studentship and for permission to publish this work. S. P. A. acknowledges an EPSRC Established Career Particle Technology Fellowship grant (EP/R003009).
Uncontrolled Keywords: Bioengineering,Biochemistry,Polymers and Plastics,Organic Chemistry
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Related URLs: https://pubs.rs ... 3B#!divAbstract (Publisher URL)
http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2021-03-07
Published Online Date: 2021-02-17
Accepted Date: 2021-02-08
Authors: Dorsman, Isabella
Derry, Matthew (ORCID Profile 0000-0001-5010-6725)
Cunningham, Victoria
Brown, Steven
Williams, Clive
Armes, Steven P.



Version: Published Version

License: Creative Commons Attribution

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