Synthesis, characterization, and thermal degradation studies on group VIA derived weak-link polymers

Abstract

Polymers containing group VIA derived weak links, viz. poly (styrene disulfide) (PSD), polystyrene 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 13C NMR spectroscopy. PSDSE, being insoluble in common organic solvents, was characterized using solid-state 13C 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 weaklink scission. A comparative study of the pyrolysis products of these polymers with that of polystyrene 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.

Synthesis and characterization of branched polymers by a free radical approach using a novel ‘macroiniferter’

“…The thermal stability of the polyperoxide and polysulfide polymers has been studied extensively [28]. It has been observed that the onset of degradation in a polysulfide polymer occurs at a higher temperature than in a polyperoxide polymer [27]. The first weight loss between 1008 and 210 8C is due to the thermal degradation of the pendant peroxide bonds and the second step of degradation from 210-350 8C corresponds to the degradation of the main chain disulfide linkages.…”

“…Either O-O or C-O cleaves to form the hydroxyl and the hydroperoxyl groups, respectively [23]. The C-S bond is known to be less stable than the S-S bond in a disulfide [27] and hence the formation of two kinds of cyclic products could be explained by considering the cleavage of the C-S bond (Scheme 3).…”

“…The yield was 90% based on 3-(t-butylperoxy)prop-1-ene. 1 Na 2 S 2 was prepared from Na 2 S. 9H 2 O (4.8 mol) and sulfur (4.8 mol) as reported [27]. To a Na 2 S 2 solution in water, t-butyl 2,3-dibromopropyl peroxide (4 mol) in CHCl 3 was added and stirred at room temperature for 24 h in the presence of the phase transfer catalyst, TBAB.…”

Synthesis and characterization of poly(p-xylylene tetrasulfide) via interfacial polycondensation in the presence of phase transfer catalysts

“…Adding TBAB as PTC caused an increase in polymerization rate in the polymer production; while adding MTBACl and BTEACl prevented the polymerization. As shown in equation 4, a stable type of benzylic carbocation will form by the reaction of the monomer with Na 2 S 4 Equation (1) ð4Þ Therefore, a chloride ion will be formed using chlorine-contained catalysts according to equation (5). This ion that is formed acts as the common ion for the first equilibrium, which prevents 1,4-bis(chloromethyl) benzene monomer separation and consequently, the polymerization will not take place…”

“…This class of materials shows great resistance against gases, organic solvents, and ozone effects [3][4][5]. Incorporation of a sulfide linkage into a polymer backbone causes an increase in solvent resistance and other properties of polymer [6][7][8][9][10].…”