Preparation And Application Of Boronic Acid-Containing Optically Active Substituted Polyacetylenes

Functional boronic acid groups can react with alcohols, sugars and phenols containing cis polyols to form reversible boronate bonds, and this dynamic, reversible complex is affected by external pH. In recent years,the synthesis of intelligent responsive polymers based on reversible boronate bonds has raised much attention. Boronic acid-containing polymers are widely used in controlled released of insulin, specific recognition of glycoproteins, response materials, biosensors, drug carriers,targeted controlled release, etc. Boronic acid, as an important functional unit for the construction of intelligent polymer materials and supramolecular materials, has been widely concerned by researchers.As an important form of chirality, helical structure is ubiquitous in nature and life, such as the genetic material DNA, the protein structure,the snail's shell. There is no doubt that chirality and life are closely related. Helical substituted polymers not only include functional groups,but also remain the special helical structure of polymer chains. In the present study, we prepared a substituted acetylene monomer containing boronic acid group, used it to prepare optically active polymer microspheres and gels, and applied the materials to chiral adsorption and chirally controlled release toward enantiomers. The main research contents are as follows:1. Synthesis of the boronic acid-containing substituted acetylene monomers, and copolymerization with chiral monomer by suspension polymerization method. The prepared boronic acid-containing microspheres were 425 ± 75 ?m in diameter and uniform in particle size.The X-ray photoelectron spectroscopy shows that the boronic acid group is enriched on the surface of the polymer microspheres, which is due to the hydrophilicity of the boronic acid groups. The circular dichroism and UV-vis spectra show the copolymer chains in microspheres formed helical conformations of predominantly one-handed screw sense, which enabled the polymer microspheres to exhibit optical activity. When the external pH is alkaline, the polymer microspheres exhibit chiral adsorption toward DOPA enantiomers, that is, preferentially adsorb L-DOPA. When the pH is acidic, the microspheres also exhibit a significant chiral controlled release effect on the DOPA enantiomers,giving priority to the release of D-DOPA. Adsorption and controlled release experiments confirmed synergistic effects occurring between the helical polymer main chains and the pendant boronic acid moieties in the process of chiral adsorption and controlled release.2. Two kinds of substituted polyacetylene copolymers bearing boronic acid and catechol moieties respectively were prepared. The circular dichroism and UV-vis spectra indicate these two copolymers formed helical conformation of predominantly one-handed screw sense.Under basic conditions, boronic acid groups react with catechol groups,so that the polymer chains are cross-linked to each other to form polymer gels. Circular dichroism and UV-vis spectroscopy suggest that the copolymer gels remained optical activity. Under acidic conditions, the alanine enantiomers encapsulated in polymer gels are slowly released by the dissociation of the boronate bonds thus polymer gels exhibit chiral controlled release toward alanine enantiomers, that is, giving priority to the release of D-alanine.