Self-assembly Of Micro Or Nanoparticles And Visible Controlled Hydrogel Shape Transformation

As we all know, the research of self-assembly area is the most interesting point in rentyears. Self-assembly is a type of process in which a disordered system of pre-existingcomponents forms an organized structure or pattern as a consequence of specific, localinteractions among the components themselves, without external direction. When theconstitutive components are molecules, the process is termed molecular self-assembly.Self-assembly process can be classified as either static or dynamic process. In staticself-assembly, the ordered state forms as a system approaches equilibrium, reducing its freeenergy. However in dynamic self-assembly, patterns of pre-existing components organized byspecific local interactions are not commonly described as "self-assembled" by scientists in theassociated disciplines. These structures are better described as "self-organized". This thesisdescribed the development of new strategies for the preparation of micro-structured organicinorganic hybrid materials and control shape transformation in macroscopic size. In particular,this thesis focused on: i) based on nanoparticle self-assembly at the surface of oil and waterphase method, synthesis of hybrid particles and capsules, ii) the self-assembly of inorganicNano-rods in microfluidic chip, and iii) hydrogel sheet self-assembly in macroscopic size.Firstly, this thesis presented the synthesis of hybrid particles and capsules by thecombination of Pickering emulsion and solvent evaporation method. For the first work, wefirstly demonstrated that “to be particles” or “to be capsules” was depended by different kindsof nanoparticles. And we also proposed the machansem of the formation progress. When theSiO2and Halloysite Nanotubes as particular emulsifier, the final structure is PLGAmicroparticles; while if chitason and Fe2O3as particular emulsifier, the final structure isPLGA microcapsules. In our opinion, this reason is due to different nanoparticles. In themicroparticle system, nano SiO2and Halloysite Nanotubes are rigid particles, and the zetapotential of them is a little higher. There are a small inferforce between them. So in theprocess of the solvent evaporation, the nano particle can easily move to the inferface of the oiland water and finally covered the surface of the PLGA microparticles. In the microcapsulesystem, the emulsifiers are colloidal nano particles and memagnetic nanoparticles. This kindof nanoparticles has a low Zeta potential and a strong inferforce between. So in the process ofthe solvent evaporation, the colloidal particles are difficult to move. According to theprinciple of minimum energy, the lower the energy is; the more stable the system is. Tominimize the interface energy between water and PLGA-CH2Cl2solution, these PLGA chainswill spontaneously precipitate at the watereoil interface from the PLGA-CH2Cl2emulsion droplet to combine with chitosan nanoparticles. At the end of the evaporation of CH2Cl2, thePLGA-CH2Cl2emulsion droplet would change to be a shrink microcapsule. In order todescribe the kinetics of drug release and the discernment of the releasemechanisms, we usethe Higuchi law, Weibull equation, First-order kinetic equation and the Hixcon–Crowell to fitthe curve of IBU release from the bare PLGA microparticle at different pH value. The releasecurve can be nicely fitted by the Weibull equationand the release follows Fickian diffusion.Secondly, we first demonstrated a new pH responsive Pickering emulsion stabilized bylignin colloidal particles. In this work, the alkaline lignin was extracted from furfural residues.Based on this kind of pH responsive Pickering emulsion, lignin-coated polystyrene (PS)microparticles are prepared using Pickering emulsion polymerization with free surfactants.Pure PS microparticles are also obtained after removal of lignin. In conventional emulsionpolymerization, chemical surfactants or emulsifiers are necessary, which could lead to thecontamination of the resultant product and the pollution of the environment. Herein, wepropose a cheap and recyclable route for industrial emulsion polymerization. This method isexpectedto be a potential and valuable candidate in waste utilization and green chemistry.Thirdly, we brought forward a new route for preparation of giant vesicles byhydrodynamically driven self-assembly method in microfluidic chip. In this work, we havedeveloped a hydrodynamically controlled self-assembly method for amphiphilic(Nanoparticles, NPs) in MFs. This strategy enables both the dimension and the morphology ofNPs self-assemblies to be controlled. The key to manipulating this self-assembly is to balancethe competition of the mixing of solvents and the assembly kinetics of (Au-Nano rods,AuNRs). By varying the flow rate of water and THF phases, AuNRs can assemble into avariety of nanostructures, including micelles, giant vesicles and disk-like micelles. Inparticular, giant vesicles were continuously generated without the use of templates throughthe self-assembly of amphiphilic NPs. This ability to use flow to control the organization ofNPs into complex structures paves a new route to fabricating materials and devices throughNP self-assembly. We have further demonstrated the NIR-triggered burst release ofencapsulated compounds from the giant vesicles. These smart vesicles may find applicationsin noninvasive on-command drug delivery or chemical reactions. This work will also have animpact in the areas of composites, optical resonators, sensing, catalysis, and electronics andphotonics.Finally, we reported the fabrication of multi-responsive rolling up and helicalprogrammable-folding structures by photolithography method at the first time. We can wellcontrol the “right side” by adjust stimuli condition. Poly (N-isopropyl acrylamide) is a well-known temperature-responsive polymer that can change its hydrophilicity and swelling.The properties of PNIPAM allow the design of dynamic systems. We used a photolithographicmethod to combine multiple, small-scale structural components with different compositions ina planar PNIPAM hydrogel sheet. The main idea is to use a binary hydrogel planar film, inwhich one component is physical hydroge (PG, PNIPAm cross-linked by Laponite) and theother component is chemical hydrogel (CG, PNIPAm cross-linked by MBAA). This binaryhydrogel film has rectangular planar sheet with several slender strips. All of the PG and CGPNIPAm hydrogel slender strips have a clear responsive to temperature, ionic strength andsolvent. And there is a significant volume variation between the PG and CG componentsunder the same stimuli. Due to the different modulus of the PG and CG, asymmetricswelling/shrinking will induce a strong internal stress. As a result, the binary hydrogel planarfilm not only uniformly expands/shrinks but also folds and unfolds into3D and2D shapes,respectively. And we also characterized and studied this self-folding process and proposed atheoretical model to illustrate the mechanism of this binary hydrogel self-folding. In order todemonstrate the application, the rolling up tube was applied for control release air bubble.And, this binary hydrogel possesses a good biocompatible property. This foundational workoffers an applicable environment for the bio-tissues or bio-engineer.