Preparation Of Layer-by-Layer Assembled Films Of Polyaspartic Acid

Layer-by-layer (LBL) assembly provides a way to prepare a multilayer film on a substrate via alternative deposition, whereas intermolecular interactions are involved, and it has attracted extensive attention since its conception. The assembly process takes place on the surface of a substrate from beginning to end, forming assembled films. Subsequently the assembled films are functionalized accordingly to fulfill different practical requirements. And the finally prepared assembled films are of various structures and functions. Based on the present research, it could be concluded that the choice of primitives with complex structures is a prerequisite for the preparation of assembled films with various structures. A single polymer only owns a small dimension and simple structure. On the contrary a polymer composite owns many advantages. A polymer composite essentially is a kind of supra-molecular aggregate which could be formed among polymers or between polymers and small molecules via weak intermolecular interactions. The polymer composite is of larger dimension, thereby being able to prepare a multilayer as thick as micrometers. In addition the polymer composite is of more structures by chemical modification, so the finally obtained multilayer will be of more structures therefore. Finally the polymer composite is of more functions generally, which makes it possible for the preparation of functionalized films. In this paper, we use polyaspartic acid and chitosan to prepare polyaspartic assembled film layers via the traditional immersion method. These two molecules are both biocompatible polymers. The detailed process is as follows.1. Based on reprecipitation method and N, N-dimethylformamide (DMF) being the good solvent of the PSI, PSI dilute solution was prepared. Subsequently by dropping a poor solvent of PSI to water, PSI organic nanoparticles were obtained. Meanwhile four factors that influence PSI organic nanoparticles were analyzed, which experimentally provides basis for the further preparation of PSI nanoparticles with core-shell structures.2. PASP & CHI complexes were prepared based on the weak poly electrolyte poly aspartic acid (PASP) and chitosan (CHI) via electrostatic interactions. By changing the content of complexs, negatively charged PASP & CHI (-) and positively charged CHI & PASP (+) polymer composites were fabricated. Then the film forming process is monitored by UV-visible spectrophotometer, and the effect of different contents on the multilayer film is analyzed finally.