Structural Tailoring Of Layer-by-Layer Assembled Films Of Polymeric Complexes

The Layer-by-layer (LbL) assembly technique is a versatile and convenient method to construct film materials via alternate deposition of building blocks driving by various kinds of molecular weak interactions. The fine structural tailoring of LbL assembled films is the foundation of fabricating functional film materials. It has been proved that building blocks possessing versatile structures facilitate the fabrication of LBL assembled films with well-tailored structures which can be further used for the fabrication of functional film materials. Polymeric complexes represent a large variety of supramolecular assemblies held together by multiple weak interactions between polymers or polymers and other species. Recently, polymeric complexes have been proved to be a kind of promising building blocks for the rapid fabrication of functional film materials benefited from their large dimension, diverse and controllable structures in solution. However, the structural tailoring of LBL assembled films using polymeric complexes as building blocks is much more complicated than that of the films fabricated from uncomplexed building blocks owing to the more complicated composition and structures of polymeric complexes, which makes the research on structural tailoring of films fabricated from polymeric complexes to be of great importance for fully exploiting the advantages of LBL assembly of polymeric complexes. In this dissertation, the structural tailoring of LBL assembled films fabricated from polymeric complexes by post-treatment or spin-assembly method was systematically investigated. Mainly including the following two parts:â… . Complexes formed by weak polyelectrolytes poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) based on electrostatic interactions were first layer-by-layer assembled with negatively charged poly(sodium 4-styrenesulfonate) (PSS). The as-prepared PAA-PAH/PSS films were then post-treated by immersing them into acid solutions with different pH to induce the structure transformation. It is proved that PAA-PAH/PSS films fabricated from PAA-PAH complexes with larger dimension experienced structural transformation on a larger scale which led to macroporous film structures. Meanwhile, lowering pH of the post-treatment solutions or elongating incubation time for the post-treatment favors the structural transformation of PAA-PAH/PSS films on a larger scale.â…¡. Complexes formed by Poly(vinylpyrrolidione) (PVPON) and poly(acrylic acid) (PAA) based on Hydrogen-bonding interactions were used as building blocks for fabrication of LBL assembled films with Poly(methacrylic acid) (PMAA) by spin LbL assembly technique. The structural tailoring of PVPON-PAA/PMAA films by changing the complex ratios of PVPON-PAA complexes and the spin rate was studied. It has been proved that the structure of the complexes in solution together with the spin rate determined the structures of the PVPON-PAA/PMAA films. The smaller dimensions of complexes and higher spin rate led to the thinner and smoother film structure while the larger dimensions of complexes and lower spin rate were in favor of the relatively thick films with rough and bumpy structures.