Interface Assisted The Fabrication Of Silicone Gradient Materi-als, Responsive Photonic Materials And Hydrogel Particles

The applications of polymer materials are focused on their bulk chemical compositions, structures and resultant properties, but the properties of these materials at the surface and/or the interface are of importance. For example, the exsited phase interfaces may result in the damage of the polymer blend materials. So far, the problems caused by multiple phase interfaces can be solved in terms of polymer gradient materials. In addition, stimuli responsive hydrogels have been attracted in polymer science. Also interfacial issues impacts the preparations, assemblies and applications of these hydrogels. Such that, those studies related to polymers at their interfaces are of utmost importance. The objective of this thesis is to fabricate silicone gradient and responsive gel-based photonic materials as well as various hydrogel particles, based on the polymer particle-particle interaction and particle-substrate interaction. More details can be seen as follows.3-[Tris(trimethylsilyloxy)silyl] propyl methacrylate and methylmethacrylate (pTRIS-co-MMA) copolymer emulsion was prepared via the emulsifier-free technique. Proton nuclear magnetic resonance (JH NMR) and Fourier transform infrared (FTIR) spectroscopy proved that emulsifier-free silicon-containing acrylate copolymers were obtained, and silicon content reach approxmately60wt%. The gradient distribution of silicon in the latex film was characterized by X-ray photoelectron spectroscopy (XPS), and confocal Raman spectroscopy (CRS). XPS results demonstrate the enrichment of silicon at the film-air (F-A) interface in the film that was prepared using an emulsifier-free silicon-containing acrylate copolymer. Furthermore, CRS provides considerable insights into the distribution behavior of silicon in the structure of the film from the F-A interface to the film-glass (F-G) interface. CRS data not only show that silicon preferentially located at the F-A interface, but also that its distribution behavior is formed in the direction across the film thickness in the sigmoidal model. Furthermore, we synthesized a series of pTRIS-co-MMA copolymers via activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). TRIS-co-MMA copolymers films were annealed and the chemical compositions at the F-A and F-G interfaces were studied by scanning electron microscopy with X-ray energy-dispersive (SEM-EDX). The results show that enhanced the silicon content in the copolymer results more silicone enriches at the F-A interface.The effect of annealing on the self-organized morphology and component gradient distribution of films prepared from bimodal latexes blend containing1:1silicon-containing acrylate copolymer/silicon-free acrylate copolymer blend was studied using attenuated total reflectance-FTIR (ATR-FTIR) spectroscopy, SEM-EDX, and atomic force microscopy (AFM). The distribution of silicon through the whole thickness of the film as a function of annealing was investigated using CRS. AFM results show that poly(methylmethacrylate-co-butyl acrylate) latex fuses to form a continuousfilm at25℃. The wettability of the acrylate components and the heterogeneous composition of pTRIS-co-MMA result in a graded block film. ATR-FTIR and SEM-EDX measurements reveal silicon-containing components segregate at the F-A interface upon annealing. CRS further shows that the nonlinear model gradient distribution of silicon is obtained, where the content of silicon component is enhanced and it gradually varies in the bulk. When the annealing temperature increases to120and180℃, blend latexes films demonstrate varying topography and phase images, indicating phase separation is induced by annealing. Furthermore, CRS implies that the destruction of the gradient structure is attributed to the phase separation of the two blend components.We synthesized poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgels by free radical polymerization. The resultant microgels have a hydrodynamic diameter (DH)=1105±133nm in DI water at25℃. Futhermore, we fabricated pNIPAm-co-AAc microgel-based one dimensional photonic materials, so-called Fabry-Perot etalons (or simply etalons). And we present the hysteresis of the response of the pNIPAm-co-AAc microgel-based etalons to solution temperature and pH changes.We find that the optical hysteresis of the etalon can be controlled using various solution ionic strengths and/or counterions, as well as by varying the microgel’s acrylic acid concentration.PNIPAm-co-AAc microgels have been shown to exhibit visible color and unique optical spectra. While these properties have been studied on whole etalons, it is unclear if the etalon’s optical properties can be independently modulated on spatially isolated regions of the same etalon. We show that indeed the optical properties of spatially isolated regions could be changed independently in response to temperature and pH. This was shown via both visible color changes and reflectance spectroscopy. Furthermore, etalons on flexible devices can be fabricated, and the color of independent spots separately modulated.Last but not least, we show that hydrogel particles could easily be synthesized by adding drops of aqueous solution containing monomer, comonomer, crosslinker, and initiator to the surface of a polytetrafluoroethylene (PTFE or Teflon) disk immersed in2,2,4-trimethylpentane (TMP). This system yielded conditions that allowed for a spherical drop to be stable at that interface while the polymerization occurred. This approach was used to synthesize particles composed of pNIPAM and poly(2-hydroxyethyl methacrylate). Furthermore, the polymer particles could easily be doped with a variety of nanoparticles and small molecules simply by adding the components to the monomer/crosslinker solution prior to polymerization. This route is advantageous because it only appears to depend on the ability to form a water drop at the PTFE-TMP interface, thus this approach can be used to synthesize particles with a variety of different functionalities and compositions. This can lead to direct applications in oral drug delivery and tissue engineering.