Synthesis, characterization, and properties of hydroxyl‐terminated copolysiloxanes containing γ‐cyanopropyl groups

Abstract

A series of random copolysiloxanes (PCDMS) containing various amount of γ‐cyanopropyl groups are prepared by a new method under mild conditions. Structures of the synthesized polymers are fully characterized by FTIR, 1H NMR, 29Si NMR, and GPC. Rheological properties of PCDMS are tested by cone and plate rheometer, and thermal properties by differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). Damping properties as well as fuel resistance of the cured PCDMS elastomers are also tested. The correlation between chemical structure, content of cyanopropyl group and properties are discussed. With the increasing amount of polar cyanopropyl group introduced, glass transition temperatures (Tg) of the synthesized PCDMS gradually increases from −121 to −65 °C, residual weight increases from 0 to 36% at 800°C, loss factor reaches as high as 1.74, mass increase under fuel immersion for 14 days can be as low as 3.6%. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1408–1421

Effect of silanol on the thermal stability of poly[methyl(trifluoropropyl)siloxane]

“…[1,2] The introduction of fluorine into the side chain of the Si O backbone provides PMTFPS products with low surface tension and a low swelling resistance to hydrocarbon solvents. [3][4][5] PMTFPS products have unparalleled advantages for use in sealants and gaskets in the astronavigation, automotive, and building fields over polysiloxanes substituted with other functional groups. [6][7][8][9][10] However, because of the strong electronwithdrawing effect of the fluorocarbon groups in the side chain, PMTFPS products suffer from poor thermal stability compared with that of polydimethylsiloxane (PDMS) and tend to degrade when exposed to temperatures above 200 C for extended periods of time.…”

Synthesis, characterization, and properties of vinyl‐terminated copolysiloxanes containing trifluoropropyl and 4‐trifluoromethylphenyl groups

“…Therefore, the polymers were hardly crosslinked when the content of P unit was high. DMA is an effective and extremely powerful method to investigate the damping properties of elastomers because the data corresponding to the damping factor (tan δ , the ratio of storage modulus to loss modulus) can be directly collected . Figure shows the temperature dependence of damping factor revealing the existence of only one transition peak for samples FSR , FSR −15PPF3 , FSR −30PPF3 , FSR −50PPF3 , located at −44.6 °C (tan δ max = 1.26), −38.3 °C (tan δ max = 1.24), −33.4 °C (tan δ max = 1.44), and −17.7 °C (tan δ max = 1.21), respectively.…”

“…Notably, the capacity of resistance to fuel could also be influenced by the crosslinking density of the matrix. Higher the crosslinking density, better is the fuel resistant properties of the elastomers . Therefore, quantitative determination of the contribution of fluorine content is difficult because of the combined effect of both crosslinking density and fluorine content.…”

“…Polysiloxanes with their unique physical and chemical properties, including exceptionally low glass transition temperature ( T g ), superior high thermal stability, and good resistance to oxidative degradation, are extensively investigated and used as potential candidates for commercial application . Currently, the copolymers with different siloxane units in main chain have attracted significant attention because different siloxane units in polysiloxanes are often necessary to obtain materials with tunable microstructures, physical properties, and required performances . For example, the thermal stability and oil resistance of conventional silicone rubber have been improved by the partial substitution of some methyl groups with phenyl and trifluoropropyl groups, respectively.…”

Synthesis of gradient copolysiloxanes by simultaneous copolymerization of cyclotrisiloxanes and mechanism for kinetics inverse between anionic and cationic ring‐opening polymerization

“…Up until now, the copolymers with different siloxane units in the main chain have always attracted significant attention because different siloxane units in polysiloxanes are often necessary to obtain materials with tunable microstructures, physical properties, and required performances . For instance, incorporation of fluorinated polysiloxane blocks into conventional vinyl polysiloxanes results in the formation of the block copolymers with thermal resistance, superior damping properties, and fuel resistance. However, in recent years, gradient copolymers of different siloxane units have gradually produced extensive concern because of their potential unique properties which are significantly different compared with the properties of block and random copolymers .…”