SYNTHESIS, CHARACTERIZATION, AND THERMAL-DEGRADATION STUDIES ON GROUP VIA DERIVED WEAK-LINK POLYMERS

Polymers containing group VIA derived weak links, viz. poly(styrene disulfide) (PSD), poly(styrene tetrasulfide) (PST), and poly(styrene diselenide) (PSDSE), have been synthesized. The polymers PSD and PST were characterized by NMR, IR, UV, TGA, and fast atom bombardment mass spectrometric (FABMS) techniques. The presence of different configurational sequences in PSD and PST were identified by C-13 NMR spectroscopy. PSDSE, being insoluble in common organic solvents, was characterized using solid-state C-13 NMR (CP-MAS) spectroscopy. Thermal degradation of polymers under direct pyrolysis-mass spectrometric (DP-MS) conditions revealed that all the polymers undergo degradation through the weak-link scission. A comparative study of the pyrolysis products of these polymers with that of poly(styrene peroxide) (PSP) revealed a smooth transformation down the group with no monomer (styrene or oxygen) formation in PSP to only styrene and selenium metal in PSDSE. This trend of group VIA is explained from the energetics of the C-X bond (X = O, S, and Se) which also seems to be important in addition to the weak X-X bond cleavage. In PSP and PSD, the behavior is also explained from the energetics of the alkoxy and thiyl radicals. The unique exothermic degradation in PSP compared to endothermic degradation in PSD and PSDSE is explained from the nature of the products of degradation.