| Janus particles are asymmetric particles comprised of two or more distinct surface regions with different chemistries or polarities. The asymmetry gives rise to unique properties such as surface activity and anisotropy, which make Janus particles potentially useful in a wide range of applications, including but not limited to chemical and biological areas, materials and colloidal chemistry. In the light of the relatively high adsorption energy of Janus particles, this thesis discusses the feasibility of Janus particles in the application field of disperse dyes, in which the large amount of conventional dispersants are used due to their thin adsorption layer. Several series of triblock terpolymers are synthesized, Janus particles of different Janus balances are prepared based on investigated morphology evolutions of the self-assemblies of the precursor polymers. Through the study of the solution behavior and the adsorption behavior at the solid/liquid(dye/water) interface of amphiphilic polymeric Janus particles with different structures, the relationship between the microstructure of Janus particles and their aggregation behavior in solution and adsorption behavior at the interface is revealed. The stability mechanism of disperse dye particles is investigated by combining Scaling Theory and the model of colloidal chemistry. In addition, the intrinsic relationship between the micro-structure of Janus particles, the conformation of the adsorbed layer of Janus particles and the stability of dye particles has been summarized. Main contents and results are as follows:(1) Several groups of amphiphilic triblock terpolymers have been synthesized via combining of sequential atom transfer radical polymerization and selective modification of the middle block, based on the architectural design of the macromolecular structure. The characterization results show that the structure of the obtained polymers is consistent with the designed, and that the molecular weight is controllable and the molecular weight distribution is narrow.(2) According to the solubility of the polymers in different solvents, the selfassembly behavior of the triblock terpolymers with different structure and molecular weight in selective solvents has been studied via dynamic laser scattering(DLS) and high resolution transmission electron microscopy(TEM), and the optimal preparation conditions have been established. The results show that the size of the core-corona micelles by self-assembly of the triblock terpolymers increase as the molecular weight grows, and the multicompartment micelles obtained by further self-assembly of these core-corona micelles have clear outlines and evident phase-separation regions. The various sizes and morphologies of these multicompartment micelles depend on the molecular weight and block fraction of the precursor triblock terpolymers and pH values of the aqueous solutions, the morphologies obtained include wormlike, Y-type, clover, dimer, hamburger and open-ring.(3) Polymeric Janus nanoparticles with adjustable sizes, micro-structures and Janus balances have been fabricated by self-assembly of triblock terpolymers of different compositions, molecular weights and block fractions. The obtained Janus particles have the size range of 27.5 ~ 79.5 nm, and their Janus balance varies from 0.8 to 15.3. The surface activity of Janus particles with that of their precursors has been compared via equilibrium surface tension method, maximum bubble pressure method and DLS. The results show that Janus particles exhibit greater surface activity that reduce that surface tension of water to around 58 mN/m at the concentration of 0.1 g/L; besides, Janus particles are tend to form dynamic clusters consisting of 2 ~ 30 individuals, which could dis-assembly at the near-surface. In addition, four types of Janus particles have been investigated on their self-aggregate behaviors and their adsorption behaviors at the water/air interface. The results show that the four types of Janus particles exhibit different surface activities – they increase as Janus balance decline; the Janus particles with the lowest Janus balance are more likely to aggregate, which results in lower surface activity. The calculation results show that the values of adsorption energy ?adsG and diffusion coefficient D of the four types of Janus particles studied fall in the same order of magnitude while the contact angle θ values vary a lot, which indicate that the main factors affecting the surface activity of the Janus particles are the differences in the aggregation tendency and adsorption stability caused by the variation in Janus balance.(4) Dye crystals of C.I. Disperse Yellow 114 have been prepared by recrystallization and slow solvent evaporation at the ambient temperature, and are used as the substrate for the investigation on the adsorption behavior of Janus particles at the solid/liquid interface. The conformation of the adsorption layer of Janus particles are obtained by Atomic Force Microscope(AFM) and explained by Scaling Theory. The intrinsic relationship between the micro-structure of Janus particles, the conformation of the adsorbed layer of Janus particles and the stability of dye particles is investigated. The results show that: a) adsorption isotherms is consistent with Langmuir type. The equilibrium adsorption amount is dependent on molecular weight and block fraction of the precursor polymers for the Janus particles. In general, the Janus particles with lower Janus balance exhibit a higher tendency to adsorb steadily at the dye/water interface. The average distance between Janus particles increases as the hydrodynamic radius increases due to the steric effect of hydration layer. b) Janus particles are distributed as spheres in uniform according to AFM observation. The adsorption layer thickness of the four Janus particles on the surface of disperse dyes are 7.208 nm, 15.374 nm, 29.557 nm and 55.380 nm, respectively, which mainly depend on the volume of the hydrophilic hemisphere of the Janus particles. The arrangements of the four Janus particles are different, the statistically average interparticle distances are 7.085 nm, 34.584 nm, 28.715 nm and 47.176 nm, respectively. c) The conformations of PDMAEMA chains of TCD1-, TCD3- and TCD4-Janus particles at the interface are brush-type, whereas that of TCD2-Janus particles is the mixture of brush-type(middle) and mushroom-type(side). The conformation of Janus particles at the interface is dependent on both of Janus balance and the length of hydrophilic chains. The thickness of the adsorption layer increases as the Janus balance increases, and the length of PDMAEMA chains on the hydrophilic hemisphere plays a major role in the thickness of the adsorption layer. d) The main factor affecting the stability of the dispersion system is the thickness of adsorption layer. At the equilibrium of adsorption, Janus particles can provide strong steric hindrance for the dye particles, and hence guarantee a good dispersion stability for the system due to the thick adsorption layer of Janus particles at the dye/water interface. |
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