Abstract
A simple and versatile low-shear approach for assembling hydrogels containing aligned rod-like particles (RLPs) that are birefringent and exhibit pH-triggered anisotropic swelling is developed. Anisotropic composite hydrogels are prepared by applying low shear (0.1 s–1) to mixtures of pH-responsive nanogels (NGs) and RLPs. The NGs, which contained high methacrylic acid contents, acted as both shear transfer vehicles and macro-cross-linkers for anisotropic gel formation. Three model RLP systems are investigated: (i) soft triblock copolymer worms, (ii) stiff self-assembled β-sheet peptide fibers, and (iii) ultrahigh modulus nanocrystalline cellulose fibers. RLP alignment was confirmed using polarized light imaging, atomic force microscopy, and small-angle X-ray scattering as well as modulus and anisotropic swelling experiments. Unexpectedly, the composite gel containing the soft copolymer worms showed the most pronounced anisotropy swelling. The copolymer worms enabled higher RLP loadings than was possible ...
Highlights
A major challenge for hydrogel research is the design of hydrogels with controlled morphology over a range of length scales
The NGs and copolymer worms were synthesized by emulsion polymerization and RAFT solution polymerization, respectively (Scheme S1)
This paper reports a new low-shear approach for the preparation of anisotropic gel composites
Summary
A major challenge for hydrogel research is the design of hydrogels with controlled morphology over a range of length scales. A preliminary investigation was conducted of the ability of binary NG/worm dispersions to form isotropic covalent gels and to determine the compositional limits of DX NGx/W1−x systems (see Supporting Discussion and Figure S5).
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