Miniemulsion polymerizations of n-butyl cyanoacrylate via two routes: towards a control of particle degradation.

This study aimed at determining the influence of the mechanism of polymerization on the molar mass and degradation of poly(n-butyl cyanoacrylate) (PBCA) nanoparticles obtained by miniemulsion polymerization. Therefore, nanoparticles of poly(n-butyl cyanoacrylate) were synthesized via radical and/or anionic miniemulsion polymerization stabilized by Brij®78, a POE based surfactant. Polymerization conditions had little influence on the final diameter while it severely affected the final molar masses of PBCA. An increase of the temperature and of the pH of the continuous phase led to higher molar masses. A further increase was observed when a radical initiator was added in the monomer. The evolution of the molar mass of the synthesized poly(n-butyl cyanoacrylate) was followed as a function of time at pH 7.4 by Size Exclusion Chromatography. As expected, the degradation kinetics strongly depended on the polymerization mechanism (anionic or radical).

Phototransformation studies of halo-substituted cinnamates by Raman spectrometry and quantum-chemical computations.

The comprehension of the cinnamic derivative phototransformation mechanisms is particularly important when these molecules are used as addressable photosensitive layers. In this work we show that the halo-substituted cinnamate sensitivity to the phototransformation is a function of the excitation wavelength and the substituent nature and position. With this intention, we underline the existence of various isomers and rotatomers by Raman spectroscopy and we assign the observed vibrational modes with the help of quantum-chemical calculations. These various aspects of our work clarify the relative roles of the steric, inductive and mesomeric effects according to the considered substitution.