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Synthesis and aqueous solution properties of shape-shifting stimulus-responsive diblock copolymer nano-objects

DOI: 10.1021/acs.chemmater.1c02096 DOI Help

Authors: Oliver J. Deane (University of Sheffield) , James Jennings (University of Sheffield) , Thomas J. Neal (University of Sheffield) , Osama M. Musa (Ashland Specialty Ingredients) , Alan Fernyhough (Ashland Specialty Ingredients) , Steven P. Armes (University of Sheffield)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Chemistry Of Materials , VOL 1

State: Published (Approved)
Published: September 2021
Diamond Proposal Number(s): 27967

Open Access Open Access

Abstract: We report the synthesis of poly(N-(2-acryloyloxyethyl)pyrrolidone)-poly(4-hydroxybutyl acrylate) (PNAEP85-PHBAx) diblock copolymer nano-objects via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 4-hydroxybutyl acrylate (HBA) at 30 °C using an efficient two-step one-pot protocol. Given the relatively low glass transition temperature of the PHBA block, these nano-objects required covalent stabilization prior to transmission electron microscopy (TEM) studies. This was achieved by core crosslinking using glutaraldehyde. TEM analysis of the glutaraldehyde-fixed nano-objects combined with small-angle X-ray scattering (SAXS) studies of linear nano-objects confirmed that pure spheres, worms or vesicles could be obtained at 20 °C in an acidic aqueous solution by simply varying the mean degree of polymerization (x) of the PHBA block. Aqueous electrophoresis, dynamic light scattering and TEM studies indicated that raising the dispersion pH above the pKa of the terminal carboxylic acid group located on each PNAEP chain induced a vesicle-to-sphere transition. 1H NMR studies of linear PNAEP85-PHBAx nano-objects indicated a concomitant increase in the degree of partial hydration of PHBA chains on switching from pH 2-3 to pH 7-8, which is interpreted in terms of a surface plasticization mechanism. Rheological and SAXS studies confirmed that the critical temperature corresponding to the maximum worm gel viscosity could be tuned from 2 to 50 °C by adjusting the PHBA DP. Such tunability is expected to be useful for potential biomedical applications of these worm gels.

Journal Keywords: Vesicles; RAFT polymerization; Copolymers; Colloids; Transmission electron microscopy

Subject Areas: Materials, Chemistry

Instruments: I22-Small angle scattering & Diffraction

Added On: 30/09/2021 21:47


Discipline Tags:

Soft condensed matter physics Chemistry Materials Science Chemical Engineering Engineering & Technology Organic Chemistry Polymer Science

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)