Study On Functionalized Amphiphilic Multistimuli Responsive Poly(Ether Amine) (PEA) Particles

During the past decades, the development of stimuli-responsive polymers has received intensive attention and many breakthroughs have been made due to its potential applications in drug delivery, biological sensors, tissue engineering, bionics, chemical separation and coating. While there are many exciting challenges in this field, there are a number of opportunities in design, synthesis, and engineering of stimuli-responsive polymeric systems. Compared with the single stimulus, the interest in multi-stimuli responsive polymers has increased due to their promising potential as intelligent materials. On the other side, molecular self-assembly and structural control of polymer particle is one of the most important research areas in the field of soft matter. The driving forces for self-assembly such as hydrogen bond, hydrophobic & electrostatic interactions, and the host-guest inclusions are important to form special structures with desirable fuctions. However, most of the polymer particles fabricated by self-assembly are not stable enough and they could disassemble by varying the environment such as temperature, solvent, additives, pH or shear force. So it is necessary to improve their stabilization for their applications. In this text, a variety of multi-stimuli responsive polymer systems with different functionality are designed and prepared based on previously synthesized poly(ether amine) (PEA). Besides, several methods are tried to improve the stability of polymer particles, from decreasing their Critical Micelle Concentration (CMC) to introducing crosslinkable moieties such as coumarin and trimethoxysilyl groups. We further investigated the host-guest interaction between PEA particles and hydrophilic dyes. Finally, potential applications of PEA particles in the controllable catalysis and smart separation were demonstrated. The contents of each part are listed as follows:(1) We synthesized a series of multi-stimuli responsive graft fluorinated poly(ether amine) (fgPEA) based on graft poly(ether amine) (gPEA). Compared with gPEA, fgPEA can self-assemble into larger micro- micelles of about 200 nm in diameter due to their much stiffer hydrophobic chain in aqueous solution. However, its aqueous solution is still transparent, which indicates the good optical property due to the low refractive indexes of fluorin-containing materials. The CMC of fgPEAs decreases with the increasing amount of fluorinated chain, which indicates their enhanced stability. The amphiphilic fgPEAs exhibit very sharp response to temperature, pH and ionic strength.(2) Novel linear PEAC or hyperbranched hPEA-EC were prepared by introducing coumarin unites into the macromolecular chain of poly(ether amine). Both of the polymers could be directly dispersed in aqueous solution and self-assemble into micelles of around 50-60 nm (PEAC) or 150 nm (hPEA-EC) in diameter. After irradiation under 365 nm light, the coumarin units could be photo-cross-linked and the nano- or micro-gels could be obtained. Compared with the former prepared micelles assembly, the stability of the particles is obviously enhanced. They do not disassemble in good organic solvent or at extreme low concentration. Moreover, the stable hPEA-diEC microgels could serve as an ideal carrier system for metal nanoparticles such as platinum (Pt@hPEA-diEC) for catalysis application. It is observed that the catalytic activity of Pt@hPEA-diEC do not follow normal Arrhenius behavior in the reduction of aromatic nitro compounds at different temperature. Deeper investigations show that the catalytic activity of Pt@hPEA-diEC could be controlled by the volume transition of the responsive hPEA-diEC.(3) We prepared novel organosilica hybrid trimethoxysilyl units containing TMS-gPEA via"thiol-ene"reaction based on graft PEA. TMS-gPEAs could be dispersed directly into water to form nanomicelles, followed by hydrolysis and condensation of trimethoxysilyl units catalyzed by tertiary amine groups. The obtained core-cross-linked hybrid nanoparticles (SiO_1.5-gPEA NPs) showed excellent stability. Besides encapsulating hydrophobic guest molecules, it is found SiO_1.5-gPEA showed selective adsorption to different hydrophilic dyes in aqueous solution. Based on the responsive property of polymers, water-soluble dyes could be transferred from water to toluene phase along with SiO_1.5-gPEA selectively and this process is reversible. In order to deeply investigate the host-guest interaction between the polymers and dyes, we further designed and prepared a series of hybrid polymer nanoparticles (SiO_1.5-hPEA NPs) based on hyperbranched poly(ether amine) (hPEA) with the different hydrophobicity and functional groups. We studied their adsorption behavior to twelve hydrophilic dyes in aqueous solution. The distribution coefficient (K = [Dye]SiO_1.5-hPEA/[Dye]aq) for partitioning of dyes between SiO_1.5-hPEA NPs and water was proposed to define the strength of the host-guest interaction between the nanoparticles and dyes. Several factors to determine the selective interaction were discussed by comparing the guest and host structures. With the increasing hydrophobicity of the host SiO_1.5-hPEAs NPs, the interaction to guest dyes increased regardless of charge state of dye and SiO_1.5-hPEAs NPs. Based on the established K, we demonstrated a methodology for the smart separation of the different mixture of dyes in water by using SiO_1.5-hPEA NPs, which can be triggered by temperature.