Preparation And Self-Assembly Of New Type Of Functional Molecules And Assembly Units

This thesis includes the following three sections:Section 1:Preparation of amphiphilic polymeric Janus particles and research on their self-assembly.We developed a new method to prepare polymeric Janus particles and studied self-assembly of the as-prepared Janus particles. The Janus particles were prepared by using mixed-shell micelles (MSMs) as precursor. The mixed shell of the micelles is composed of relative long uncrosslinkable polymer chains and relatively short crosslinkable chains, and the core is swollen and with a large size, which makes the micelles highly flexible. During crosslinking the crosslinkable polymer chains, they are forced to aggregate together. The relatively long uncrosslinkable chains provent intermicellar crosslinking but allow intramicellar crosslinking to occur. The highly flexibility make it possible for the crosslinked chains within one micelle to form a single domain through efficient adjustment of the conformation and position of the polymer chains. Due to the large size of the swollen core, the crosslinked chains can not form an integrated layer to cover all the surface of the core. Additionally, during the crosslinking, the uncrosslinkable polymer chains within the micelle are largely forced to the opposite side of the core. These lead to a complete intramicellar phase separation within the mixed shell, forming Janus particles. In the selective solvent for the crosslinked chains, the Janus particles self-assemble to produce 2-dimension nanofilms.Section 2:Investigation of pyridine/propargyl bromide reaction and strong fluorescence enhancements of the resultant Poly(propargyl pyridinium bromide)We made an investigation on a new method to synthesize poly(propargyl pyridium bromide) (PPPB), which is a kind of conjugated polyelectrolyte with polyacetylene as the backbone and pyridinium as side groups, via reaction between pyridine and propargyl bromide under mild conditions. A reasonable mechanism is given to account for the occurrence of spontaneous polymerization of propargyl pyridinium bromide, which is product of quaternization between pyridine and propargyl bromide. The chemical structure and molecular weight of PPPB were also well characterized. We found that the fluorescence intensity of PPPB could be enhanced up to 25 times by addition of some anions to PPPB solution in DMF or DMSO. The intensity of interactions between anions and pyridinium groups as side chains of PPPB in solvent was proved to determine the amplitude of fluorescence enhancement of PPPB. Besides, heating the polymer solution at a temperature between 70℃ and 130℃ for longer than 0.5 hour could also enhance the fluorescence intensity greatly. Furthermore, we confirmed that the fluorescence enhancement effect is resulting from the effective exciton confinement within the conjugated backbone, which is a result of a more twisted backbone by heating or interactions between anions and pyridinium groups. The fluorescence enhancement effect is very impressive because it offers a new way to make an enhancement on the fluorescence quantum yields of mono-substituted polyacetylenes, which are known to have very weak fluorescence emissions. Besides, Poly(propargyl quinolinium bromide) (PPQB) and poly(propargyl acridinium bromide) (PPAB) were also synthesized via reactions of propargyl bromide with quinoline and acridine, respectively. Compared with PPPB, PPQB and PPAB are much less hygroscopic and exhibit good conductivities in the air.Section 3:Sauerbrey equation in liquid phase:origin and potential applicationsWe gave a new equation to interpret the relation between the resonant frequency shift (△f) and mass change (△m) in the QCM technique in liquid phase. The new equation, which we name as "Sauerbrey Equation in Liquid Phase", is built based on the simplification and revision of the Voight model. The new Sauerbrey equation could be written as:△f= (-f/mq)([η]fρf)Am= C([η]fρf)Am and the ratio of △f to △m is found to be determined by the product of [η]f and pf. The new Sauerbrey equation is applicable for the characterization and analysis of properties of macromolecules adsorded or grafted with a low intensity on the solid/liquid interface. According to the new Sauerbrey equation, we could make a theoretical explanation of mass sensitivity enhancement of the QCM technique in liquid phase compared to that in gas phase. Additionally, the value of intrinsic viscosity ([η]f) of the polymeric films adsorbed on the solid/liquid interface could be calculated by application of combination of QCM and other techniques (SPR, ellipsometry, etc.). Since[η]f has a close relationship with the conformation of polymer chains, so we could make an evaluation on the conformation changes of polymer chains in the solid/liquid interface by observing the change of value of ([η]f). Besides, we confirmed that the porous PVA dried gel with GNPs (gold nanoparticles) embedded in the network, which can be prepared very conveniently, is a stable and ultrasensitive 3D SERS (surface enhanced Raman scattering) substrate. The existence of the micropores within the gel is necessary for the ultrahigh sensitivity, and embedding of GNPs in the penetrable gel results in high stability.