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Tuning the properties of hydrogen-bonded block copolymer worm gels prepared via polymerization-induced self-assembly

DOI: 10.1039/D1SC03156B DOI Help

Authors: Eleanor Raphael (University of Sheffield) , Matthew J. Derry (University of Sheffield) , Michael Hippler (University of Sheffield) , Steven P. Armes (University of Sheffield)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemical Science

State: Published (Approved)
Published: August 2021
Diamond Proposal Number(s): 21776

Open Access Open Access

Abstract: Polymerization-induced self-assembly (PISA) is exploited to design hydrogen-bonded poly(stearyl methacrylate)-poly(benzyl methacrylate) [PSMA-PBzMA] worm gels in n-dodecane. Using a carboxylic acid-based RAFT agent facilitates hydrogen bonding between neighboring worms to produce much stronger physical gels than those prepared using the analogous methyl ester-based RAFT agent. Moreover, tuning the proportion of these two types of end-groups on the PSMA chains enables the storage modulus (G’) of the 20% w/w worm gel to be tuned from ~4.5 kPa up to ~114 kPa. This is achieved via two complementary routes: (i) an in situ approach using binary mixtures of acid- and ester-capped PSMA stabilizer chains during PISA or (ii) a post-polymerization processing strategy using a thermally-induced worm-to-sphere transition to mix acid- and ester-functionalized spheres at 110 °C that fuse to form worms on cooling to 20°C. SAXS and rheology studies of these hydrogen-bonded worm gels provide detailed insights into their inter-worm interactions and physical behavior, respectively. In the case of the carboxylic acid-functionalized worms, SAXS provides direct evidence for additional inter-worm interactions, while rheological studies confirm both a significant reduction in critical gelation concentration (from approximately 10% w/w to 2-3% w/w) and a substantial increase in critical gelation temperature (from 41 °C to 92 °C). It is remarkable that a rather subtle change in the chemical structure results in such improvements in gel strength, gelation efficiency and gel cohesion.

Subject Areas: Materials, Chemistry

Instruments: I22-Small angle scattering & Diffraction

Added On: 11/08/2021 09:36


Discipline Tags:

Soft condensed matter physics Chemistry Materials Science Organic Chemistry Polymer Science

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)