Synthesis And Characterization Of Novel Polyamides With Branched Structure

Recently, polyamides with branched structure, such as hyperbranched polyamides and dendronized polyamides, have drawn the attention of various research groups because of their unique physical and chemical characteristics. The branching architecture caused the unique properties of these polymers, such as good solubility, low viscosity, and strong reactivity, which showed great potential in a wide range of application, such as coatings, catalysis, liquid crystals, biomaterials, and nanoobjects. However, it still exhibits some problems in the synthesis of these two kinds of polyamides. Although the A2+B3 approach to hyperbranched polyamides holds some merit, such as facile preparation and commercial availability of monomers, it still exhibits the major problem of gelation. The synthesis of dendronized polyamides has problems such as poor yield and tedious multi- synthetic steps. New strategies are in need for the large-scale synthesis of these polyamides.The aim of this paper is to solve the problems in the synthesis of hyperbranched and dendronized polymers. The research project of this paper as followed: 1) Optimization of preparation process of hyperbranched polyamides by the A₂+B₃ approach; 2) Facile synthesis of dendronized polyamides by macromonomer approach.1. Two strategies were carried out to the synthesis of hyperbranched polyamide without gelation by the A₂+B₃ approach: 1)a series of polyamides were synthesized by direct polycondensation of aliphatic and aromatic monomers (A₂ and B₃) in the presence of CDI which can be used to activate acid (or amine) to form amide; 2) synthesis of soluble aromatic polyamide copolymers from A₂, B₃, and AB monomers. The structure of resulting polymers and copolymers was confirmed by IR, ¹H NMR measurements, and the condition of the reaction was explored, the copolymerization behavior was reviewed, too.The research on the synthesis of hyperbranched polyamides using CDI as activating agent showed that the resulting polymers could be obtained in this method without gelation. CDI had some merits over TPP/pyridine as following: more flexible in reaction; more controllable in reaction; simple process in the modification of function groups; simple disposal procedure with low-poison. The research on the synthesis of polyamide copolymers showed that the gelation was declined by the addition of AB monomer. The structure and properties were in consistent with the ratio of three monomers. IR and ¹H NMR measurements revealed that the content of the AB monomer was much lower in the early stage of polymerization. It increased with the increasing reaction time.2. Facile synthesis of dendronized polyamides by macromonomer approach. The diacid macromonomers bearing two generations of amide dendritic blocks were easily prepared by a convergent approach without protection and deprotection procedures using thionyl chloride as activating agent, the polymerization of which with 4,4'-oxydianiline led to the formation of the dendronized aromatic polyamides. The structures and properties of the resulting monomers and polymers were characterized by several instruments.The research on the synthesis of dendronized polyamides showed that the solubility of the line-dendritic polymers in organic solvents was improved with the increasing generation of dendrtic blocks. The T_g's of the novel polyamides were in a narrow range of 182-188℃. All the resulting polymers showed two decomposition stages and good thermal properties.The new synthesis strategies were carried out to solve the problems in the synthesis of hyperbranched and dendronized polyamides, which were simple and highly efficient and had a prosperous future for the industrialization.