Kannan Ganesh

Thermal degradation products of poly(styrenesulfides) investigated by direct pyrolysis—mass spectrometry and flash pyrolysis—gas chromatography/mass spectrometry

The thermal degradation products of two sulfur polymers, poly(styrenedisulfide) (PSD) and poly(styrenetetrasulfide) (PST), were investigated in parallel by direct pyrolysis-mass spectrometry (DPMS) and by flash pyrolysis-GC/MS (Py-GC/MS). The time-scale of the two pyrolysis techniques is quite different, and therefore they were able to detect significantly different products in the pyrolysis of PSD and PST because of the thermal lability of sulfur-containing compounds. However, the results obtained are not contradictory, and satisfactory mechanisms for the thermal degradation of PSD and PST have been derived from the overall evidence available. Pyrolysis compounds containing sulfur, styrene, and a number of cyclic styrene sulfides and diphenyldithianes have been observed by DPMS. However, in flash pyrolysis-GC/MS, styrene, sulfur, only one cyclic styrene sulfide, and two isomers of diphenylthiophene have been detected. These thiophene derivatives were indeed absent among the compounds obtained by DPMS because they were the terminal (most thermally stable) species arising from further decomposition of the cyclic styrene sulfides formed in the primary thermal degradation processes of PSD and PST.

End-group analysis of vinyl polyperoxides by MALDI-TOF-MS, FT-IR technique and thermochemical calculations

A first comprehensive investigation has been made to unequivocally analyze the end groups of two vinyl polyperoxide polymers namely, poly(α-methylstyrene peroxide), and poly(methylmethacrylate peroxide), using matrix-assisted laser desorption ionization-time of flight-mass spectrometry, Fourier transform-infra red techniques and thermochemical calculations. In both the polymers, the end groups formed due to chain transfer reactions were found in large concentrations. Detail mechanism of the formation of end groups has been presented.

Stabilization of thermal degradation of poly(methyl methacrylate) by polysulfide polymers

The thermal degradation of poly(methyl methacrylate) (PMMA) in the presence of polysulfide polymers, namely, poly( styrene disulfide) (PSD) and poly(styrene tetrasulfide) (PST) was studied using thermogravimetry (TG) and direct pyrolysis-mass spectrometric (DP-MS) analysis. Both PSD and PST were found to stabilizethe PMMA degradation, which was explained by both radical recombination and a chain-transfer mechanism

Poly(styrene disulfide) and poly(styrene tetrasulfide) as chain transfer agents in the radical polymerization of styrene

This is a first report on the chain transfer behaviour of polysulfide polymers, namely poly(styrene disulfide) (PSD) and poly(styrene tetrasulfide) (PST), in the radical polymerization of styrene. It was observed that while PSD acts as a conventional chain transfer agent, PST acts as a retardant. Comparison of the chain transfer constants of PSD and PST with that of the corresponding simple sulfides indicates that polysulfide polymers are better chain transfer agents.

Determination of end groups in poly(methylmethacrylate peroxide) by fast atom bombardment mass spectrometry and IR spectroscopy

SummaryA detailed comprehensive investigation has been made to unequivocally analyse the end groups of a vinyl polyperoxide polymer namely, poly(methylmethacrylate peroxide), PMMAP, using Fast Atom Bombardment Mass Spectrometric (FABMS) technique. Further evidence to FABMS analysis has been sought from IR spectroscopic analysis on the same polymer. It has been found that PMMAP contains both hydroxyl and hydroperoxide end groups which has been explained by the chain transfer reaction of growing chain with the degradation product of PMMAP.

Studies on model oligosulfides to understand polysulfide polymers

Abstract1-bromo-1-phenylethane was reacted with aqueous sodium disulfide or sodium tetrasulfide to form the 1-phenylethyl polysulfides of sulfur rank 2 or 4 respectively. The distribution of the 1-phenylethyl polysulfides thus formed was studied using1H NMR and GC-MS analysis. Apart from 1-phenylethyl disulfide and 1-phenylethyl tetrasulfide being produced in large amounts when aqueous sodium disulfide and sodium tetrasulfide were used respectively, the formation of 1-phenylethyl monosulfide in the former case and both mono and disulfide in the latter case, in minor amounts, is also observed. Also, it was found that the undetection of the molecular ion peaks of 1-phenylethyl polysulfides having rank above 2 is due to their thermal decomposition to elemental sulfur, 1-phenylethyl mono and disulfide, under the heating conditions employed for GC-MS analysis.