Self-healing Multilayers From Polymeric Complexes Assembled Through Layer-by-layer Assembly

Polymerie complexes represent a large variety of supramolecular assemblies held together by multiple weak interaetions such as hydrogen bonds, electrosteric interaction and coordination bonds between polymers or polymers and others pecies. In this study, a series of polymeric complexes based multilayers were assembled with polyurethane via Layer-by-layer self-assembly technique, and properties of multilayer coatings were studied.(1) Intrigued by the beauty and efficiency of natural healing processes, wide-spread attention has been paid to the preparation and application of synthetic self-healing materials over the last decade. In this work, multilayers were fabricated through alternating deposition of polyurethane(PU) and poly(acrylic acid)(PAA) with/without polyethylene glycol(PEG). The self-healing process and performance was studied using optical microscopy, SEM and CV. The result shows that the introduction of PEG can largely enhanced the healability of(PU/PAA-PEGx)n film. When the number of bilayer was 20 with the concentraiton of PEG 1.0 mg/mL, the perfect healing can be achieved in water(pH 2.0).(2) In this charpter, the self-healing mechanism of(PU/PAA-PEGx)n film was further investigated. It was found that after introducing polymeric complex, the glass transition temperature(Tg) can be largely decreased. Hence, the polymer can maintain their mobility and diffuse to the damage. The relationship between the healability of the multilayers and Tgs of PAA-PEG complexes was disclosed through investigating the self-healing behaviors of as-prepared multilayers under different temperature. Meanwhile the growth situation and swelling property of(PU/PAA-PEG1.0)20 multilayer film was researched by optical ellipsometry. The exponentially grown films showed a high swelling ratio, it was heavily dependent PAA-PEG complexes and polyelectrolytes hydrophilic. And the role of PEG in PAA-PEG complexes was testified by confocal laser scanning microscope(CLSM).(3) Laponite is a synthetic hectorite made of discoid platelets with a thickness of about 1 nm, a diameter of about 25 nm, and a negative surface charge density. In this charpter, laponite was introduced into Lb L PU/PAA multilayers by forming PAA-laponite complexes. And effect of laponite on the loading and release performance of as-perpared multilayers was investigated with methylene blue as drug model. The results showed that introduction of Laponitecan complexes can significantly change the adsorption model of multilayers and improve the stability of the multilayer films.