Thermal degradation of poly(tetramethyl‐p‐silphenylene) siloxane homopolymers and copolymers in nitrogen

Abstract

The thermogravimetry (TGA) in nitrogen was measured for poly(tetramethyl‐p‐silphenylene)‐siloxane (TMPS) fractions with narrow molecular weight distributions and for block copolymers of TMPS and dimethyl siloxane (DMS) with varying composition. The measurements were made with the Perkin‐Elmer DCS IB‐TGA attachment which consists of a Cahn electrobalance and a wire‐wound furnace with programmable temperature controls. The weight loss curves for heating rates of 10, 20, and 40°C/min were analyzed using the method of Flynn and Wall. The analysis indicates that thermal degradation proceeds primarily by scission of the siloxane bond with an activation energy of 44 ± 3 kcal/mole for the uncatalyzed reaction and 13 ± 2 kcal/mole for the reaction occurring in the presence of residual catalyst. The thermal stability of the TMPS–DMS copolymer is impaired through increasing the concentration of the DMS component. Cyclic DMS trimer and TMPS monomer and dimer were observed by mass spectrometry which gave results consistent with the proposed mechanism of degradation.

Preparation of Fully Aromatic Polysilarylenesiloxanes by Melt Polycondensation and Their Thermal Properties

“…It was revealed that the melt polycondensation and simultaneous cross-linking reaction were effective to obtain the polysilarylenesiloxanes which have high thermal degradation temperature and high thermomechanical stability. [doi:10.1295/polymj.PJ2006004] KEY WORDS Polysilarylenesiloxane / Melt Polycondensation / Thermal Stability / Glass Transition / Thermomechanical Stability / Polysilarylenesiloxanes 1,2 and their copolymers [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] have been investigated as high temperature elastomers. The common characteristics of these polymers are their high thermal degradation temperatures (T d 's) and low glass transition temperatures (T g 's), which are attributed to their flexible tetramethyldisiloxane units in the main chain.…”

“…The common characteristics of these polymers are their high thermal degradation temperatures (T d 's) and low glass transition temperatures (T g 's), which are attributed to their flexible tetramethyldisiloxane units in the main chain. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] These characteristics are desirable for an elastomer, and are, however, undesirable for the heat-resistant materials such as a high-temperature coating and a low dielectric insulation material in semiconductor devices because the thermomechanical stability of these polymers is not enough at high temperature. Therefore, polysilarylenesiloxanes and their copolymers have never been used nothing but elastomers.…”

Synthesis and Properties of Silicon-containing Polymers Having Cyclic Silphenylenesiloxane Moieties

“…c) A soluble part was obtained by the Soxhlet extraction method from the insoluble product. Polymer P2 [3] . It was suggested from this result that the cross-linking reaction would occur even in 0.1 M dilute solution and the part having relatively low degree of cross-linking was dissolved in THF.…”

“…. a) [3] 0 means the initial concentration of the monomer 3. b) M n (number-average molecular weight) and M w (weight-average molecular weight) were determined by GPC. c) A soluble part was obtained by the Soxhlet extraction method from the insoluble product.…”

“…Yield: 41.8 %. 1 3 CN as an eluent, equipped with a column of ODS-3. GPC analysis was conducted with a Tosoh GPC-8020 by using THF as an eluent, equipped with four columns of Tskgel SuperH5000, 3000, 2000 and 1000.…”