Layer-by-Layer Assembled Polymer Hydrogel Films: Functional Loading And Healing

Layer-by-layer (LbL) assembly technique has been proven to be a versatile andconvenient way to construct functional films with precise control of film structure andcomposition. LbL assembled polymer hydrogel films with stimuli-responsive ioniccross-linked structures and free functional groups capable of loading and release of guestmaterials are widely studied as matrices for guest material delivery. On the other hand, theLbL assembled polymer hydrogel films will inevitably be damaged during daily use, leadingto a decrease of the film functions such as the mechanical properties, the protective properties,the optical properties and so forth. Self-healing of LbL assembled polymer hydrogel films canextend their service lives, reduce the costs of reproduction and maintenance, and enhance thereliability of functional films used in many applications. Based on the LbL assembled polymerhydrogel film systems, the researches in this dissertation include:(1) The development ofmatrix films for simultaneous release of anionic and cationic molecules, and the preparation ofmagnetic resonance visibility enhancing coatings on plastic surfaces.(2) The foundation of afacile exponential LbL assembly method for the rapid fabrication of intrinsic self-healing LbLassembled polymer hydrogel films, and the exploration of the water-enabled self-healingmechanism.(3) The fabrication of transparent antibacterial LbL assembled polymer hydrogelfilms capable of repairing their transmission properties based on the combine of the loading ofantibacterial agents and the water-enabled self-healing.In chapter1, introductions on the research actuality and the challenge of the functionalLbL assembled polymer hydrogel films have been provided. The LbL assembled polymerhydrogel films are widely studied as functional coatings, such as antibacterial coatings, superhydrophobic coatings, and so forth. Currently, more attentions have been paid on thefunctional loading of guest materials within the LbL assembled polymer hydrogel films.However, it still faces many challenges, such as the preparation of matrix films forsimultaneous release of anionic and cationic molecules, and the fabrication of LbL assembledpolymer hydrogel films capable of repairing themselves, etc. Therefore, the LbL assembledpolymer hydrogel films with functional loading and self-healing abilities were developed inthis dissertation.In chapter2, matrix films for simultaneous release of anionic and cationic molecules, andmagnetic resonance visibility enhancing coatings on plastic surfaces were fabricated by usingpolymer microgels as building blocks. In previous studies, chemically cross-linked PAH-Dmicrogels with abundant amine groups and substrate-independent modification capabilitywere developed. In this chapter, CO2gas was bubbled through PAH-D microgels to synthesizepolyampholyte microgels (named PAH-D-CO2). PAH-D-CO2microgels containing amine andcarbamate groups were LbL assembled with polyanion to produce polyampholyte microgelfilms. The as-prepared polyampholyte microgel films can realize the co-loading andsimultaneous release of anionic and cationic molecules. The releasing behaviors of thepolyampholyte microgel films can be tailored by capping the films with barrier layers. Besides,magnetic microgels were synthesized based on the functional amine groups in PAH-Dmicrogels. LbL assembled multilayer films of magnetic microgels and polyanion werefabricated on hydrophobic plastic surfaces to enhance the visibility of plastic interventiontools in MRI-guided therapy.In chapter3, a water-enabled self-healing method has been established by using theexponentially grown LbL assembled polymer hydrogel films as intrinsic self-healing coatings.The as-prepared self-healing coatings are mechanically stable under ambient conditions. Thecoatings become flowable in the presence of water, and polymer chains can therefore transferto the fractured areas, then the reversible supramolecular interactions accomplish the healing.The self-healing mechanism and the fundamental parameters governing the healing ability of the coatings are clarified.In chapter4, combining the loading and healing functions, self-healing for thetransmission properties of optically transparent antibacterial coatings here was simplyaccomplished by wetting the exponentially grown LbL assembled polyelectrolyte multilayersincorporated with antibacterial agents. Hydrophobic antibacterial agents were successfullyincorporated into the hydrophilic polyelectrolyte coatings via the encapsulation with surfactantmicelles. The transparent antibacterial coatings can effectively inhibit the growth ofgram-positive and gram-negative bacteria by the sustained release of antibacterial agents.Moreover, light transmittance of the damaged antibacterial coatings can be completelyrecovered by simply immersing the coatings in water or spraying water on the coatings, andthe coatings can realize the repeatable self-repairing in the same areas for both the surfaceappearances and the transmission properties of the transparent antibacterial coatings uponmultiple large abrasion events without the participation of healing agents. The transparentantibacterial coatings capable of repairing their transmission properties are expected as a kindof clean and durable protective materials applied in touch human-machine interface.