Thermoreversible Hydroferrogels with Tunable Mechanical Properties Utilizing Block Copolymer Mesophases As Template

Abstract

Thermoreversible hydroferrogels (FGs) have been prepared via gelation of aqueous maghemite ferrofluids (FFs) using the triblock copolymer Pluronic P123 as gelator. In the investigated concentration range of 28-42 wt % P123, long-term stable homogeneous FGs can be prepared from FFs with a maximum maghemite content of 14 wt %. For higher FF concentrations up to 29 wt %, however, homogeneous FGs were formed only for gelator contents up to ca. 33 wt %. A combination of rheology and μ-DSC was applied as an alternative method to construct the P123 phase diagram, without the need for visual methods or scattering techniques. Using this procedure, we could show that maghemite nanoparticles can be effectively templated by the cubic and hexagonal P123 mesophases in a concentration range of 33-38 wt % P123 and FF concentrations up to 14 wt %, respectively. Most importantly, the phase behavior and the corresponding phase-transition temperatures of P123 were not significantly altered. As a result, the FGs show a reversible temperature-triggered transition from a cubic hard gel to a hexagonal gel, which is linked with a softening of the gel. Furthermore, this concept can be applied to template cobalt ferrite nanoparticle effectively, too. Magnetization experiments revealed that the superparamagnetic behavior of the maghemite nanoparticles, which show a Néel type relaxation, is not altered in the corresponding FGs. In contrast, FGs based on blocked cobalt ferrite nanoparticles show a hysteretic behavior, which indicates a strong mechanical coupling between the P123 mesophase and the magnetic nanoparticles.

Hardening transition in a one-dimensional model for ferrogels

“…This coupling is rather weak if the particles are small enough so that their magnetic moments can easily flip with respect to the particle axes, or if the particles themselves are only loosely incorporated into the polymer matrix and can easily rotate with respect to their environment. [27][28][29] On the contrary, this magneto-mechanical coupling is strong, e.g., for bigger ferro-particles that are covalently bound to the polymer network. [30][31][32][33] Despite the importance of ferrogels in both applications and from a fundamental point of view as tunable soft matter, a complete theoretical description of their properties is missing.…”

Magnetic iron oxide nanoparticles (MIONs) cross‐linked natural polymer‐based hybrid gel beads: Controlled nano anti‐TB drug delivery application

“…Supporting, mCS‐PEG‐40 exhibited utmost nano RIF releasing efficiency (65.67 ± 0.76%) under the magnetic field. Therefore, the nano‐drug releasing properties of mCS‐PEG gel beads can also be used in the hydrogel based dual responsive (pH and the magnetic field) nano drug delivery applications …”

Synthesis and Characterization of pH- and Temperature-sensitive Hydrogels of Poly (Styrene-alt-Maleic Anhydride)-co-Pluronic for Drug Release

“…However, the low mechanical strength, fast dissolution, and rapid drug release under physiological conditions, primarily caused by immediate dilution of polymer concentration with the body fluid below a critical gelation concentration, has limited its biomedical applications. [18][19][20][21] Krekhova et al, [22] however, prepared thermoreversible hydroferrogels (FGs) by gelation of aqueous maghemite ferrofluids (FFs) using copolymer P123 as gelator.…”