Multi-Stimuli-Responsive Polymer Materials: Particles, Films, and Bulk Gels

Abstract

Stimuli-responsive polymers have received tremendous attention from scientists and engineers for several decades due to the wide applications of these smart materials in biotechnology and nanotechnology. Driven by the complex functions of living systems, multi-stimuli-responsive polymer materials have been designed and developed in recent years. Compared with conventional single- or dual-stimuli-based polymer materials, multi-stimuli-responsive polymer materials would be more intriguing since more functions and finer modulations can be achieved through more parameters. This critical review highlights the recent advances in this area and focuses on three types of multi-stimuli-responsive polymer materials, namely, multi-stimuli-responsive particles (micelles, micro/nanogels, vesicles, and hybrid particles), multi-stimuli-responsive films (polymer brushes, layer-by-layer polymer films, and porous membranes), and multi-stimuli-responsive bulk gels (hydrogels, organogels, and metallogels) from recent publications. Various stimuli, such as light, temperature, pH, reduction/oxidation, enzymes, ions, glucose, ultrasound, magnetic fields, mechanical stress, solvent, voltage, and electrochemistry, have been combined to switch the functions of polymers. The polymer design, preparation, and function of multi-stimuli-responsive particles, films, and bulk gels are comprehensively discussed here.

Hyaluronic acid hydrogel nanoscaffolds: production and assessment of the physicochemical properties

“…Bulk gels or the traditional HA hydrogels exhibit macroscopic network, which contains indiscriminate interconnected HA chains [28]. This structure is missing the functional diversity of the endogenous ECM [29].…”

Bio-responsive smart polymers and biomedical applications

“…The multi-stimuli responsive films are commonly prepared via the layer-by-layer (LBL) assembling or by using polymer brushes. LBL assembling involves alternatively depositing different polymers on a substrate, and the deposited polymers can be assembled into the LBL coating via various interactions such as electrostatic interactions, host-guest interactions, hydrogen bonding and coordination bonding [70]. For the polymer brush strategy, the initiator is anchored to the substrate and the polymer brushes with different functions are then formed via the surface-initiated living polymerization [71].…”

Light-responsive azo-containing organogels

“…This effect was exploited for the preparation of model adhesives that were shown to display de-bonding-on-demand capability. 20a, 27 We envision that the approach can be used to equip a wide range of materials with desirable, light-responsive properties.…”