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Shear-induced alignment of block copolymer worms in mineral oil

DOI: 10.1039/D1SM01011E DOI Help

Authors: Matthew Derry (University of Sheffield) , Oleksandr Mykhaylyk (University of Sheffield) , Steven P. Armes (University of Sheffield)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Soft Matter , VOL 283

State: Published (Approved)
Published: September 2021
Diamond Proposal Number(s): 10237

Open Access Open Access

Abstract: Poly(stearyl methacrylate)–poly(benzyl methacrylate) [PSMA–PBzMA] diblock copolymer worms were synthesized directly in mineral oil via reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization at 90 °C. Free-standing gels were obtained from this polymerization-induced self-assembly (PISA) formulation when targeting PSMA13–PBzMA65 dispersions at 5% w/w to 20% w/w copolymer concentration. Gel permeation chromatography (GPC) studies indicated that almost identical copolymer chains were obtained in all cases, while transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies confirmed that highly anisotropic worms were formed with mean cross-sectional diameters of 11.9–13.1 nm. These worms undergo a thermoreversible worm-to-sphere transition on heating up to 150 °C. Rheological studies were conducted to characterize the shear rate- and concentration-dependent behaviour caused by this change in copolymer morphology, where the initial shear-thinning worm gels form spheres (i.e. a Newtonian fluid) on heating up to 150 °C. Complementary shear-induced polarized light imaging (SIPLI) experiments confirmed the formation of aligned linear worms under applied shear between 80 °C and 110 °C, with high-viscosity dispersions of branched worms being obtained at 20–60 °C and low-viscosity spheres being produced at 150 °C. This study informs the use of such block copolymer worms as rheology modifiers for non-polar oils, which is of potential interest for the automotive industry.

Subject Areas: Materials, Chemistry

Instruments: I22-Small angle scattering & Diffraction

Added On: 22/09/2021 13:30


Discipline Tags:

Soft condensed matter physics Chemistry Materials Science Organic Chemistry Polymer Science

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)