Synthesis And Formation Mechanism Of Chiral Mesoporous Conducting Polymers

Chiral conducting polymers have attracted much attention both in fundamental research and practical applications in fields as diverse as electrochemical switches, surface-modified electrodes, chiral chromatography, membrane separation technology and sensors based on the combination of conductivity, chiral selectivity and molecular recognition. Researchers working on this area have synthesized water-solution and nanafibrous chiral conducting polymers induced by small chiral organic molecules. Also, helical conducting polymer nanofibers have been prepared by chiral amphiphilic molecules templating method. To the best of our knowledge, no helical mesopores have been formed in conducting polymers.Chiral mesoporous materials with large suface areas and volumes have ordered hecical structures in meso-scale, and can be grafted with organic functional group resulting in potential applications in enantioselective adsorbents, catalysts and the synthesis of helcical nanomaterials. So the exploration and synthetic method of novel chiral mesoporous conducting polymers have been a hot topic in this area.In this paper, chiral mesoporous conducting polymers have been synthesized by the chiral lipid ribbon templating and"seeding"route. The synthesis and formation mechanism of chiral mesoporous polypyrrole (CMPP), chiral mesoporous conducing polymers (CMPANI) and chiral mesoporous poly(m-phenylenediamine) (CMPM) have been detailedly discussed by using different kinds of chiral amphiphilic molecules.In chapter 1, the background of the development and formation mechanism of chiral supermolecules assembly, chiral mesoporous materials and chiral conducing polymers, have been detailedly elaborated.In chapter 2, uniform CMPP nanofibers with controllable chiral mesopores have been synthesized by using different alkyl chains length of chiral amphiphilic molecules. The structure and chirality of helical ribbon-pores have been reconstructed by electron tomography which is the latest technology of characterization. We discussed the formation mechanism of CMPP based on the chiral lipid ribbon templating and"seeding"route in this synthetic system. Short CMPP could be first formed by chiral lipid ribbon templates in the initial stage; because the end caps of short CMPPs are relatively unstable due to the lack of geometric matching, they would be the"seed"to induce and elongate to several length scales unitl precipitating while keeping their helicity even without chiral lipid ribbon templates. Otherwise, the chiral pore size of CMPP could be effectively controlled by adjusting alkyl chains length of chiral amphiphilic molecules or the H2O/EtOH volume ratio in the synthetic system, and the structure and handedness of CMPP could also be controlled by choosing different kinds of chiral amphiphilic lipid molecules or enantiomers. CMPP could not been synthesized by small chiral molecules or achiral amphiphilic molecules. In chapter 3, we mainly discussed the synthesis of CMPANI and CMPM based on the chiral amiphiphilic molecules templating and"seeding"route, and investigated the effect of organic monomers on the synthetic system.The results showed that it was more difficult to synthesize CMPANI compared to CMPP, only in the presence of D-HSA. Two possible explanations are: a) the CMPANI backbone is very rigid and tends to linearly polymerize hard along the twisted edges of the organic templates because of small amount of chiral amphiphilic molecules leading to low electrostatic bonding between chiral anion and its chain; b) General oxidative chemical polymerization is known to yield granular PANI, so it is possible that the large part of CMPANI which are still surrounded by the monomers and oxidant species could be formed initially. They would likely become the"nucleation"centers for further PANI precipitation and finally grow into irregularly granular particles agglomerations. However, it was also found that CMPM which have been synthesized by D-HSA, C14-L-Ala and C16-L-Phe, was more easily formed than CMPANI,but less than CMPP. Though CMPM backbone similar to CMPANI's is very rigid ,m-phenylenediamine have one more amido than aniline resulting in stronger electrostatic interaction between the head carboxylic group of chiral amphiphilic molecules and amido or imine nitrogens on the poly(m-phenylenediamine) backbone. These results indicated that the molecule structures of organic monomers and the chemical structures of their polymerization products had affected the helical formation of the polymers.Chapter 4 sums up the work and proposes the outlook.