Silicon-containing polyimides: synthesis, properties, and application as optical fiber light guide coatings
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Russian Chemical Bulletin, International Edition, Vol. 69, No. 8, pp. 1486—1491, August, 2020
Silicon-containing polyimides: synthesis, properties, and application as optical fiber light guide coatings* D. A. Sapozhnikov,a A. V. Chuchalov,a,b B. A. Bayminov,a P. A. Shibaeva,a,b E. M. Chaika,a M. I. Buzin,a A. F. Kosolapov,c S. L. Semjonov,c and Ya. S. Vygodskiia аA.
N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 ul. Vavilova, 119991 Moscow, Russian Federation. Fax: +7 (499) 135 6549. E-mail: [email protected] bMendeleev University of Chemical Technology of Russia, 9 Miusskaya pl., 125047 Moscow, Russian Federation. Fax: +7 (499) 609 2964 cFiber Optics Research Center, Russian Academy of Sciences, 38 ul. Vavilova, 119333 Moscow, Russian Federation. Fax: +7 (499) 135 8139
Organosoluble polyimides with tetramethyldisiloxane fragments in the main chain were synthesized by one-step high-temperature polycondensation and their properties were studied. Heat resistant polymers (Tg = 195—240 С, T10% = 420—490 С) were tested as protective coatings for quartz optical fibers. The new developed coatings have high thermal (72 h at 300 С) and hydrolytic stability. Key words: polyimides, coatings, optical fiber light guide.
Polyimides (PIs) are one of the most important classes of high performance polymers due to their excellent thermal, mechanical, and other properties.1—6 They are used in the manufacture of flexible printed circuit boards and modules, optically transparent films for mobile screens, solar panels and electrically conductive panels, gas separation membranes and filters, etc.7—12 PIs are increasingly used as protective coatings, including for optical fibers.13—20 However, the manufacture of traditional polyimide coatings is based on the use of a precursor, polyamide acid (PAA), which have a number of disadvantages. For example, the PAA solution must be stored at low (–20 С) temperatures because of the instability. It is difficult to achieve quantitative cyclization of PAA to PIs under the conditions of fabricating the fiber coating (several seconds). Imidization proceeds at high temperatures (250—300 С) and is accompanied by water release, which can form voids, etc.21 A required coating thickness (5—10 μm) can be achieved by repeated varnishing, and a satisfactory adhesion of the coating to the fiber is achieved only with the use of a coupling agent.13 Traditional PIs tend to have poor solubility and high softening or melting points, which significantly limits their fields of application. One approach to increasing the * Based on the materials of the International Conference "Chemistry of Organoelement Compounds and Polymers 2019" (November 18—22, 2019, Moscow, Russia).
solubility and processability of PIs is the introduction of flexible bridging groups or bulky fragments.2,22 It is known that the incorporation of flexible siloxane fragments imparts some attractive properties to PIs, while retaining their characteristic features.23—26 Such (co)polymers have low water absorption,
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