Syntheses of Poly[(tetraphenyl-p-silphenylenesiloxane)-co-(tetramethyl-p-silphenylenesiloxane)]s and the Physical Properties of Their Films

Abstract

ABSTRACT:In order to obtain a polysilarylenesiloxane having a high glass transition temperature (T g ), a high thermal degradation temperature (T d ), and a good solubility in common solvents to prepare a film, the copolycondensation of 1,4-bis(hydroxydiphenylsilyl)benzene with 1,4-bis(hydroxydimethylsilyl)benzene was studied. Their thermal properties were studied by using a differential scanning calorimetry and a thermogravimetry analysis. The physical properties of copolymer films were also investigated. All the copolymers exhibited the T g 's, and those increased with the increase of the molar ratio of the units based on 1,4-bis(hydroxydiphenylsilyl)benzene (PS units). The T g of one of the copolymers, CP-a, reached to 127 C. CP-c having a relatively high molecular weight showed the highest thermal stability in air, whose T d5 was 524 C. Tough self-standing films were obtained from the copolymers by the casting method. These films had much lower gas permeability coefficients than that of polydimethylsiloxanes and low surface energy similarly to the silicon-containing polymers having a phenylene moiety. The gas permeability coefficients of the films decreased, and the densities and the tensile strength of films increased with the increase of the molar ratio of PS units. These results indicated that dense and tough films were obtained from these copolymers.[doi:10.1295/polymj.PJ2006185] KEY WORDS Polysilarylenesiloxane / Thermal Degradation Temperature / Copolymerization / Glass Transition Temperature / Gas Permeability / Polysilarylenesiloxanes 1,2 and their copolymers [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have been studied as high temperature elastomers whose degradation temperature (T d ) was greatly higher than that of polydimethylsiloxane (PDMS). Poly-(tetramethyl-p-silphenylenesiloxane) (polyMS) of a typical polysilarylenesiloxane was synthesized by Merker et al. 5 and their thermal properties were investigated. According to the literature, 3-5 polyMS shows a glass transition temperature (T g ) of À20C, a melting point (T m ) of 135 C and a thermal degradation temperature (T d ) of 370-390 C under helium flow. PolyMS/PDMS and polyMS/PDMS derivatives were synthesized and their thermal and physical properties were also reported. 2-19The common characteristics of these polyMS-containing polymers are their high T d and the low T g , which resulted from their flexible tetramethyldisiloxane units in the main chain. The mechanical strength of these polymers is not enough at high temperature to use as the heat-resistant materials such as a high-temperature coating and a low dielectric insulation material in semiconductor devices. Recently, Kawakami et al.,[20][21][22] reported the polymer derived from cardo-type 9,9 0 -bis[4-(dimethylsilyl)phenyl]-fluorene using a new method of the catalytic crossdehydrocoupling polymerization, and that this polymer exhibited high T g of 160 C, 22 however, the physical properties were not reported. We reported that the fully aromatic polysilarylenesilox...

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

“…For example, poly(tetramethyl-p-silphenylenesiloxane), PTMPS, of a typical polysilarylenesiloxane showed relatively high T d10 of 475 o C and high T g of -20 o C derived from phenylene groups in the backbone. In our previous work [6,7], poly[(tetraphenyl-p-silphenylenesiloxane)-co-(tetramethyl-p-silphenylenesiloxane)], PS-co-MS, was synthesized and the thermal properties were also investigated. PS-co-MS showed 458 o C of T d and 147 o C of a softening point, T s .…”