Polymerization of styrenes with pendant aminophosphazenes and fluorescence behaviors of their Eu 3+ complexes

Abstract

Radical polymerizations of novel styrenes with pendant penta(3-dimethylaminopropylamino)-(SPDAP) and penta(2-dimethyl aminoethoxy)cyclotriphosphazene (SEAP) in various solvents and the fluorescence behavior of complexes of Eu 3+ with these cascade materials were studied. The conversion of SEAP increased on going from THF to ethanol, whereas the conversion of SPDAP in ethanol showed the lowest value. The application of the Kamlet-Taft equation to the conversion suggested that the polymerization of SPDAP and SEAP is primarily affected by the hydrogen bond interaction. 13C NMR spectra of SEAP showed that the peak of the β-carbon in the vinyl group shifted downfield as the conversion increased. This suggests that the interaction between the monomer and solvents brings about a change of polymerizability of SEAP. A similar downfield shift was observed for SPDAP in ethanol, suggesting that SPDAP also has a high polymerizability. The inherent viscosities of poly(SEAP) and poly(SPDAP) in ethanol were found to be considerably higher than those in THF. This result and the kinetic treatment of polymerization suggest that the side arms on the phosphazene ring in ethanol are expanded due to the hydrogen bond interactions with the solvent, and that the propagation is sterically hindered, especially for the polymerization of SPDAP with relatively long side arms. This might be responsible for the low conversion observed for the polymerization of SPDAP in ethanol. When Eu 31 ions were added to SPDAP, a significant increase in fluorescence intensity of Eu 3+ was observed. The plot of fluorescence intensity vs the concentration of SPDAP suggests the formation of a 2:1 SPDAP-Eu 3+ complex. For the polymer-Eu 3+ complex, a similar increment of the intensity was observed. From the chemical shifts of side arms in the monomer-Eu 3+ complex, the structure of the complex is discussed.