Synthesis and characterization of poly(diethylsiloxane) and its copolymers with different diorganosiloxane units

Abstract

Poly(diethylsiloxane) and its copolymers with various kinds of R 1 R 2 SiO (R 1 ϭ R 2 ϭ methyl or phenyl, or R 1 ϭ methyl and R 2 ϭ phenyl) units have been prepared by the equilibrium polymerization of cyclosiloxanes. All the polymers have been characterized by 1 H and 29 Si NMR, gel permeation chromatography, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The results indicate that a random distribution of different units has been obtained in the structures of copolymers containing 50 mol % diethylsiloxane units content. DSC and DMA show that the presence of 2.5 mol % diphenylsiloxane units or 5.0 mol % methylphenylsiloxane units in the copolymer can disrupt the crystallinity and lead to noncrystalline copolymers with low glass-transition temperatures (ranging from Ϫ133 to Ϫ137°C according to DSC).

3D Printing Amorphous Polysiloxane Terpolymers via Vat Photopolymerization

“…[6,12,13] The literature provides many examples of this compositional effect. [6,[14][15][16] Surprisingly, the addition of inorganic fillers (such as silica, zinc oxide, iron oxide) is known to accelerate rather than inhibit polymer crystallization, presumably due to fillers acting as nucleating agents. [17] Recently, Zlatanic et al reported the suppression of crystallization in PDMS through inclusion of only 3.6 mol% of statistically distributed diphenylsiloxy (DiPhS) repeating units, or as low as 5 mol% of diethylsiloxy (DiEtS) units.…”

“…Thus, crystallization suppression represents an extremely attractive approach for improving low‐temperature properties of polysiloxane elastomers (e.g., for aerospace applications), which extends their application temperature range to their respective T g s. As expected, the introduction of small amounts of randomly placed, irregular repeating units sufficiently introduces asymmetry and effectively reduces crystallizability . The literature provides many examples of this compositional effect . Surprisingly, the addition of inorganic fillers (such as silica, zinc oxide, iron oxide) is known to accelerate rather than inhibit polymer crystallization, presumably due to fillers acting as nucleating agents …”

Preparation and kinetic analysis of room‐temperature vulcanized methylethylsilicone rubbers

“…Silicone rubbers have been widely used in recent years because of their excellent chemical properties, such as resistance to ozone and weathering, electrical insulating property, and excellent low‐temperature resistance . For example, high‐molecular‐weight poly(diethylsiloxane) (PDES) possesses a low glass transition temperature ( T g ) of −137°C, which is the lowest for any known polymer . However, a rigid crystal forms at temperatures below −73°C, and a conformational disorder in crystals at high temperatures limits the utilization of PDES .…”

“…Similarly, poly(diethylsiloxane‐ co ‐diphenylsiloxane) and poly(diethylsiloxane‐ co ‐3,3,3‐trifluoropropylmethylsiloxane), as well as poly(diethylsiloxane‐ co ‐ethylphenylsiloxane) and poly(diethylsiloxane‐ co ‐methylphenylsiloxane), have been reported. In addition to the aforementioned copolymers that bear two units, copolymers with three and four units have also been prepared . As mentioned above, whether PDES or PDMS possesses low T g .…”

Curing characteristics, morphology, thermal stability, mechanical properties, and irradiation resistance of methylethylsilicone/methylphenylsilicone rubber blends

“…The first approach is the synthesis of MESR‐based copolymers. Liu et al synthesized and investigated a series of MESR‐based polymers, including poly(dimethylsiloxane‐ co ‐diethylsiloxane‐ co ‐diphenylsiloxane) and poly(dimethylsiloxane‐ co ‐diethylsiloxane‐ co ‐methylphenylsiloxane). However, random copolymers with high molecular weights are difficult to obtain because comonomers have different reactivities.…”