Photo‐oxydation des polyéther‐bloc‐polyamides, 2. Influence de la composition des polymères multiséquencés

Analytical and kinetical aspects of the photooxidation in the solid state of two polyether‐block‐polyamides 1c and 1d are described. The block copolymers studied contain different polyether sequences at different percentages. In copolymer 1d as well as in copolymers 1a and 1b, previously studied, the photooxidation concerns mainly the ether groups. High maximal concentrations of hydroperoxy groups, CH(OOH)OCH2, are observed (0,12 mol.kg−1). These hydroperoxides are converted into hemi‐acetals, CH(OH)OCH2, saturated esters and formate through photolysis or thermolysis above 60°C. The hemi‐acetal groups are thermo‐unstable too and decompose into alcohol and aldehyde groups. The photooxidation of copolymer 1c presents different features. At long wavelengths, low stationary concentration of hydroperoxy groups are observed (0,02 mol.kg−1). Hydroperoxidation of the polyamide 6 sequences is revealed by the formation of imide groups. Hydroperoxidation of the poly(propylene glycol) sequences are surprisingly located on the ether methylene groups. Excitation of polyamide 6 sequences at short wavelength (254 nm) induces the formation of crotonized aldehyde groups.