Villegas, J. A., R. Olayo, and J. Cervantes. Journal of Inorganic and Organometallic Polymers 7 (1997): 51-69.
The photodegradation of poly(phenylmethylsilane) (PPMS) was studied using two irradiation sources: a commercial mercury lamp and a neodymium:yttrium aluminum garnet (Nd:YAG) laser tuned to 266 nm. The degradation products were studied using a coupled system: gel permeation chromatography/light scattering (GPC/LS). We focus on the importance of installing a multi-angle detector on the GPC to obtain information related to molecular conformation, molecular weight, polydispersity, and mass during the photodegradation process. The results obtained are a function of the UV source. At the beginning of the photodegradation, the PPMS is strongly affected by the mercury lamp; and the molecular weight as a function of volume retention indicates the presence of at least two different species containing molecules of different shapes. In the photodegradation of PPMS using the Nd:YAG laser, the molecular weight as a function of volume retention shows a single conformation. Based on the polydispersity as a function of UV exposure time, it was observed that homolytic cleavage of the silicon-silicon bonds at the ends of the polymer chains is the main phenomenon after 10 seconds of irradiation using either the mercury lamp or the laser source. Depolymerization process. Finally, after exposure for 25 s (using a mercury lamp) and 60 s (using a laser), the polydispersity increased significantly due to random chain scission.
PPMS was dissolved in tetrahydrofuran from . THF was previously degassed. The solution was purified by filtration through a microporous membrane with a pore size of 0.20 μm. Two radiation sources were used. One was a commercial mercury lamp GL-15 with spectral lines at 254, 313.5, 365, 405, 408, 436, 546 and 576.5 nm. The corresponding energies were 112.4, 91.2, 78.4, 70.6, 70.1, 65.6, 52.4 and 49.6 kcal mol. For this source, the concentration of the solution used was 2.72 x 1 0 g m and the exposure times were 5, 10, 15, 20 and 25 s. The other light source was a HY1200 Nd:YAG laser tuned to 266 nm. The concentration of the solution used was 1.00 x 10 g m and the exposure times were 10, 15, 20, 30, 40 and 60 seconds. The PPMS solution was placed in a cylindrical quartz cell with a length of 4 cm and an optical path of 1 cm. The performance of this process was evaluated by a GPC/LS coupling system.
