Synthesis of phosphorus-containing polyurethanes without use of isocyanates

Phosphorus-containing polyurethanes were synthesized by reacting phosphonic acid diesters (RO)₂P(O)X (X = H, CH₃, Ph) with hydroxycarbamates. These phosphorus-containing polyurethanes were characterized by a combination of molecular-weight determination (GPC) and NMR spectroscopy. The thermal stability of the polymers was evaluated by a combination of TGA and DTA techniques. These polymers are readily soluble in highly polar solvents like DMF and DMSO. The phosphorus-containing polyurethanes are water soluble. © 1996 John Wiley & Sons, Inc.     

Synthesis of poly(oxyethylene phosphonate)s bearing oxirane groups in the side chain

The interaction between poly(oxyethylene phosphonate)s and 1,2-epoxy-7-octene has been investigated. It has been established that in the presence of benzoyl peroxide there proceeds a selective addition of the P( )H group to the C()C double bond. Poly(oxyethylene phosphonate)s bearing oxirane groups in the side chain have been synthesized. The new polymers can be used as polymer carriers of drugs. © 1997 John Wiley & Sons, Inc.     

Cooperative behavior between oscillatory and excitable units: the peculiar role of positive coupling-frequency correlations

We study the collective dynamics of noise-driven excitable elements, so-called active rotators. Crucially here, the natural frequencies and the individual coupling strengths are drawn from some joint probability distribution. Combining a mean-field treatment with a Gaussian approximation allows us to find examples where the infinite-dimensional system is reduced to a few ordinary differential equations. Our focus lies in the cooperative behavior in a population consisting of two parts, where one is composed of excitable elements, while the other one contains only self-oscillatory units. Surprisingly, excitable behavior in the whole system sets in only if the excitable elements have a smaller coupling strength than the self-oscillating units. In this way positive local correlations between natural frequencies and couplings shape the global behavior of mixed populations of excitable and oscillatory elements.