Preparation, Assembly And Complexation Of Poly(Allylamine Hydrochloride)-Dextran Microgel

In the past decades, the synthesis, assembly and complexation of polymeric microgels have attracted much attention because of the potential applications of polymeric microgels in areas such as separation, biomimetics, coatings for controlled release, and so forth. In this dissertation, a novel PAH-D microgel was prepared by chemically cross-linking poly(allylamine hydrochloride) and dextran. The advantage of the present method to the synthesis of PAH-D microgels is :i) the synthesis was conducted in aqueous solution and no poison chemicals were used; ii) the synthesis was conducted at mild condition with a simple process for purification and a high yield of ~93.6%; iii) the PAH-D microgels contain abundance of amine groups for loading of functional materials. The as-prepared PAH-D microgels can undergo large swelling-deswelling transitions in response to changes in pH and ionic strength of the aqueous solution. The dry PAH-D microgels have an average size of ~258.6 nm, as revealed by scanning electron microscopy (SEM) measurement.In chapter 3, multilayer films containing PAH-D microgels were fabricated by layer-by-layer deposition of PAH-D and poly(styrene sulfonate) (PSS). The successful fabrication of PAH-D/PSS multilayer films was verified by quartz crystal microbalance measurements and cross-sectional scanning electron microscopy. The as-prepared PAH-D/PSS multilayer films can reversibly load and release negatively charged dyes such as methyl orange (MO) and fluorescein sodium and mercaptoacetic acid stabilized CdTe nanoparticles. The loading capacity of the film for MO can be as large as ~3.0μg/cm2 per bilayer, which corresponds to a MO density of 0.75 g/cm3 in the film. The high loading capacity of the PAH-D/PSS films originates from the cross-linked film structure with sufficient binding groups of protonated amine groups, as well as their high swelling capability by solvent. The loaded material can be released slowly when immersing the films in 0.9% normal saline. The microgel films of PAH-D/PSS are expected to be widely useful as matrixes for loading functional guest materials and even for controlled release.In chapter 4, multilayer films of PAH-D/Haluronic acid (HA) films were deposited on surgical sutures for sustainable release of ibuprofen. For layer-by-layer (LbL) assembled multilayer films, the modification of the substrate with charged groups is critically important but sometimes difficult, especially for hydrophobic and plastic substrates. We found that the PAH-D/PSS multilayer films could deposit directly on either hydrophilic or hydrophobic substrates such as quartz, polytetrafluoroethylene, polystyrene, poly(ethylene terephthalate), and polypropylene. By exploring the capability of PAH-D to deposit directly on hydrophilic and hydrophobic surfaces, we deposited PAH-D/HA multilayer films directly on the fibroin surgical sutures for loading and release of Ibuprofen. The fibroin surgical suture, with a diameter of ~0.3 mm, has a hydrophobic surface. SEM image and dye-adsorption experiments confirmed the successful deposition of PAH-D/HA multilayer films on the outer surface of fibroin surgical suture. The negatively charged Ibuprofen can be incorporated into the PAH-D/HA films based on electrostatic interaction as the driving force. Ibuprofen could be slowly released from the PAH-D/HA covered fibroin surgical sutures when the suture were immersed in 0.9% normal saline.In chapter 5, PAH-D microgels encapsulated with magnetic Fe3O4 and luminescent CdTe nanoparticles were successfully fabricated. The superparamagnetic Fe3O4 nanoparticles were firstly incorporated into PAH-D microgels by in situ synthesis of Fe3O4 nanoparticles in the presence of PAH-D microgels. CdTe nanocrystals with different emissions were then covalently attached to Fe3O4-funcionalized PAH-D microgels through the coupling reaction of amine groups of PAH-D and carboxyl groups of CdTe nanocrystals. The successful fabrication of PAH-D microgels functionalized with Fe3O4 and CdTe nanoparticles (Fe3O4&CdTe@PAH-D) was verified by the luminescence of the microgels and their simultaneous manipulation by an external magnetic field. Fe3O4&CdTe@ PAH-D microgels have the capability to load model drug of methyl orange and release it in a sustainable way because of free amine groups in the corresponding PAH-D microgels. The magnetic and luminescent PAH-D microgels with loading capacity are expected to be widely useful as carriers for magnetic separation and drug delivery followed by luminescent detection.