Studies On The Self-Assembly Of Dendron Based On The H-Bonding And The Supramolecular Multi-block Copolymer Based On The Inclusion Complexation

Molecular self-assembly is one of the most active areas in current scientific research. It is a very important and effective way to realize the multi-scale ordered structures containing functional units. Therefore, studies on self-assembly possess tremendous values in both theory and practice in exploring the mechanisms in life processes and preparing advanced functional materials. Since 1980s, scientists have found that block copolymers could self-assemble to micelle or micelle-like aggregates in selective solvents with diverse morphologies such as spheres, rods, vesicles, tubes and compounded micelles etc. Along with the rapid progress of the research, a plenty of new macromolecular building-blocks with sophisticated structures are introduced into the studies of self-assembly. Abundant experimental results concluded that the architecture of the building blocks has obvious impact on the processes and resultant objects of the self-assembly. Among such new-type building blocks, macromolecular dendrimers have drawn special attention since they have regular and diaphanous structures and their molecular volume, shape and functions can be accurately controlled. In fact, more and more experiments reveal that the dendrimers distinguish themselves significantly from the corresponding linear polymers in the self-assembly processes.In the long-term research of our group on macromolecular self-assembly to construct non-covalent connected micelle (NCCM) via hydrogen bonding, only linear macromolecules as building blocks were used in the past. On the view that molecular architecture of the building blocks could intensively affect the self-assembly behavior and the morphology of the resultant micelles, in this thesis, efforts have been made to use dendrimers and its derivatives as building blocks to construct our NCCM. In the thesis, firstly, we investigated the self-assembly of Frechet-type dendron and linear polymers in solution driven by hydrogen bonding. Afterwards, we tried to acquire C60 "Nanowire" by using liquid crystals of Perece-type dendrons as structural director component. Finally, the research was extended to the field of constructing supramolecular polymers by the inclusion complexion between cyclodextrin and admantane.This thesis focuses on the following four parts:1.) The Frechet-type dendrons (G1-G4) with single carboxylic focus were synthesized through the convergent method and characterized in details. Through RAFT method, we acquired P4VP (Mn=36K) with a narrow molecular weight distribution. Self-assembly of the dendrons and P4VP in their common solvent chloroform was realized due to hydrogen-bonding interaction between the carboxyl and pyridine groups. We found that the structure and morphology of the assemblies relied on the composition of the building blocks. By changing the molar ratio of the two building blocks, "watermelon micellers", large thin-shell vesicles and small thick-shell vesicles were attained. Such morphologies were explored and confirmed by SEM, TEM, AFM, DLS and SLS studies. For the thin-shell vesicles, crosslinking the shell could improve the strength and then prevent deformation and collapse of the vesicles during the TEM and SEM sample preparation. Therefore reliable images of the vesicles could be attained. Due to the structural asymmetry of two building blocks, phase separation takes place forming layers in the vesicles shell, thus such vesicles may possess more ordered structure compared to the previously acquired ones.2.) The third generation dendrimer were synthesized and modified with carboxyl on the surface by means of F-C reaction and oxygenation. Meanwhile, liner polymer P2VP was synthesized by RAFT method. Self-assembly of this modified dendrimer and P2VP in selective solvents due to hydrogen bonding between the carboxyl and pyridine groups were completed. Adjusting the proportion of the dendrimer and liner polymer, we gained typical solid micelles as well as "bowl" micelles. The latter was supposed to form as the collapse of the liner P2VP chains induced grafted dendrimers to take an ordered arrangement. Such assemblies provide broad possibilities for further functionalization on the surface to meet different requirements in a variety of applications.3.) Taking Percec-type dendron as a liquid-crystal director component, we tried to realize one-dimension regular arrangement of C60 to acquire C60 "Nanowire" with good conductance properties. For this purpose, we synthesized a new compound of C60 connected with two Percec dendrons. But probably due to the steric hindrance of C60, the target compound did not form liquid crystal phase. However, It is interesting that the compound formed long stripes in ordered arrangement on HOPG These stripes can be regarded as C60 nanowires. Based on this work, we designed a new strategy of taking liquid-crystal denpols (dendronazed polymer) as C60 vehicle, i.e. C60 is chemically attached to the denpol chains so that the steric effect could be prevented.4.) Supramolecular polymers (SupP) have been intensively studied as an important field in molecular assembly. However, few reports on using low-molecular weight polymers as building blocks to construct SupPs. In this chapter we synthesized low-molecular-weight polymers, i.e. Ad-PNIPAm-CD, CD-PNIPAm-CD and Ad-PEG-Ad with end groups of host (CD) and guest (Ad), via ATRP and click reaction. They are used as building blocks to form SupPs driven by the inclusion complexation between the host and guest. The formation of SupPs in solution was studies and characterized by LS, NOSEY, fluorescence spectrum. Particularly, we carried out the kinetic study on the SupP formation from CD-PNIPAm-CD and Ad-PEG-Ad by Stopped-Flow spectroscopy. We found that there are two steps in the formation of the SupPs. In the first step which occurs instantly, relatively low-molecular-weight SupPs formed. Then, in the second step, such formed SupPs connected each other to form much longer SupPs. This finding not only has theoretical significance in understanding the physical process of the formation of SupPs but also provide a guide for designing polymers used for supramolecular studies.