SYNTHESIS AND ION-BINDING PROPERTIES OF POLYMERIC PSEUDOCROWN ETHERS - A MOLECULAR-DYNAMICS STUDY

A novel method for producing inexpensive polymeric pseudocrown ethers in situ during free-radical polymerizations was investigated using mol ecular dynamics simulations. This scheme is based upon a template ion and exploits the tendency of oligomeric ethylene glycol diacrylates to form intramolecular cycles during polymerization. In the scheme, a te mplate ion is used to induce the poly(ethylene glycol) diacrylates (PE GDA) to assume cyclic structures before polymerization with a comonome r. Experimental studies demonstrated that certain salts that were inso luble in nonpolar solvents were solubilized upon the addition of oligo meric poly(ethylene glycol) (PEG) due to complexation. Further evidenc e of cation binding by oligomeric PEG was obtained by H-1 NMR studies of PEG and its complexes with metal salts. To optimize the template io n synthesis approach, molecular dynamics simulations were performed on PEGDA containing between two and ten ethylene glycol repeating units, with and without the presence of cations. Simulation results indicate d that the presence of the templating cation significantly decreased t he mean end-to-end distance, thereby bringing the unsaturated endgroup s into close proximity. The PEGDA ligand that resulted in the most eff ective templatization for Na+ contained four ethylene glycol repeating units. Simulation times greater than 50 ps had little effect on the r esults for ligands containing 7 or fewer ethylene glycol repeating uni ts.