Cyclolinear polysiloxanes. II. Crosslinking and characterization

Abstract

The synthesis and characterization of two groups of novel networks prepared from cyclolinear polysiloxanes are described. The first group of networks from cyclolinear polysiloxanes (N-CLPSs) was synthesized by the hydrosilation of vinyl-terminated cyclolinear polyorganosiloxanes [prepared from diacetoxydiethyltetramethylcyclotetrasiloxane (D 4 Et 2 OAc 2 ) or diacetoxytriethylpentamethylcyclopentasiloxane (D 5 Et 3 OAc 2 )] with a copolymer of dimethylsiloxane and methylhydrosiloxane as the crosslinking agent. Hydrosilation was effected with a platinum carbonyl catalyst with a cyclovinylsiloxane moderator. The second group of networks (N-eCLPSs) was prepared similarly with extended cyclolinear polysiloxanes. The mechanical properties of the novel networks were comparable to those of polydimethylsiloxane networks (N-PDMS). The oxygen permeabilities were similar to or slightly higher than that of N-PDMS. The glass-transition temperatures of D 4 Et 2 OAc 2 -and D 5 Et 3 OAc 2 -based N-CLPSs were À67.8 and À90.8 8C, respectively, whereas the incorporation of polydimethylsiloxane spacers into similar N-eCLPSs lowered their glass-transition temperatures to À109.7 and À115.0 8C. Upon heating to 800 8C in air, N-CLPSs yielded more residue than N-eCLPSs, which in turn yielded more residue than N-PDMS. These results may have been due to the presence of T units in the cyclic siloxane units, which may have inhibited chain degradation or the formation of volatile products. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: [4053][4054][4055][4056][4057][4058][4059][4060][4061][4062] 2006

Synthesis Optimization of Novel Cross-Linked Polysiloxane with End-capped Epoxy Groups as Waterproofing Agent for Fabric

“…However, the cross-linked structure in CLPS polymers would restrict the rotation among backbones, which was certainly disadvantageous for the formation of the cyclic transition state, volatile cyclic oligomers and the cleavage of Si-C and C-H bonds. In other words, thermal stabilities of the cross-linked polysiloxanes in our present work were continually improved with augmentation of the degree of cross-linking compared to the linear polysiloxanes, and this result is in accordance with the reported literatures [22,30] .…”

“…Until now, the cross-linked polysiloxanes have been fabricated by heat-or photo-initiated polymerization of silicones with the pendant double bonds [16,17] , moisture curing of silicone compositions through hydrolysis=condensation reactions [18] , chemical reactions between the functional groups from different components such as chloromethyl and piperazine [19] , amino and epoxy groups [20] , amino and 1, 2, 4, 5-benzenetetracarboxylic dianhydride [10] , hydroxyl and isocyanate groups [21] , and more frequently by the hydrosilylation cross-linking method [13][14][15][22][23][24] . However, detailed information concerning their synthesis parameters using the hydrosilylation cross-linking method is still scarce.…”

Facile synthesis of cyclosiloxane-based polymers for hybrid film formation

“…Hybrid prepolymers were synthesized as viscous and soluble polymers with a linearly elongated polymeric structure under controlled hydrosilylation polymerization. The subsequent self-crosslinking of hybrid polymers by hydrolysis and condensation reactions 3,[21][22][23][24][25][26][27][28][29][30][31][32][33][34] converts the inorganic core, siloxane (RSiO 2/2 ) to silsesquioxane (RSiO 3/2 ) domain units, which make the hybrid polymer free-standing and enhance the thermal and mechanical properties. The salient benefit of this strategy is that Pt catalysts as well as monomers are removed before self-crosslinking of hybrid polymers; the removal of the catalyst results in the formation of transparent, colorless, homogeneous, and hybrid network polymer films.…”

Preparation and properties of cyanate ester/polyorganosiloxane blends with lower dielectric loss and improved toughness

“…All EPMPS‐n/BADCy resins have obvious higher char yields at 800°C than neat BADCy resin, and the EPMPS‐n/BADCy resin with more EPMPS content has higher char yield. These may be attributed to high char yield of silicone resin at high temperature 23…”