Syntheses, Characterization Of Hyperbranched Polymers Based On Amino Acids Formed By Michael Addition

Dendritic Polymer is a kind of macromolecule with fractal characteristics, and it has been widely considered to be a hot spot of research succeeding linear, branched, and cross-linked polymer. Comparing to the multi-step preparation of the dendrimers, hyperbranched polymers can be prepared by one-step synthesis. Although the hyperbranched polymers have defects in molecular structure, they are suitable for large-scale preparation. Also, compare to dendrimers, hyperbranched polymers have similar properties, more structural control parameters, and abilities to prepare high molecular weight polymers easily. Because of these features, hyperbranched polymers have both great theoretical and practical value in research and in actual production.The function of complexing substrates of protein molecular is not only related to its three-dimensional shape of the molecule, but also related to multi-functional environment, zwitterionic characteristics and chiral environments constituted by peptide chain which composed of a variety of amino acid side groups. This would be an attractive feature if these properties of proteins can be transferred to the hyperbranched polymer. Specific studies are as follows:(1) Novel polymer are obtained form Michael addition polymerizations of L-cysteine with an equimolar methylene-bis-acrylamide as raw materials. The intermediates were formed fleetly during the initial reaction stage through "thiol-ene" Michael reaction. An amino group has the the addition capacity of two double bonds, therefore the system satisfies the condition of the formation of hyperbranched polymer. In order to demonstrate the structure of the polymer, we built some molecule models which have the similar structure units as macromolecule. Camparing to the 13C-NMR spectrum of molecule models, the strcture of polymers can be identified by using this method easily. Finally, we found that the polymer macromolecules were mainly linear structure. The reason why they formed the linear polymers is that two types of amines have different reactivity.(2)We try to change the polymerization process and replace the polymerized monomer structure by using L-lysine as skeleton material synthesis AB2 type monomers. Comparing to the molecule models, the strcture of branched units still can not be found on 13C-NMR spectrum. The result shows that polymerization of AB2 monomer needs keeping the reactivity, and if the reactivity markedly decreases with the increase of the steric hindrance, it would not meet the conditions of hyperbranched structure’s production.(3) We synthesised several A2 and B3 monomers with equi-activity groups, and polymerize polymers with them. Due to the reactivity would not change during the polymerization, the problem of different activtity no longer exists. The molecule models with different structure units have been made to analyze the position of all the carbon atoms in 13C-NMR spectrum. The result shows polymers with hyperbranched structure are obtained form Michael addition polymerizations of N,N-bis(acryloyl)-(L)-cystine with an equimolar 1,3,5-(Tris-piperazine)-triazine as raw materials. Finally, we calculated the polymer’s degree of branching by 13C-NMR directly.