Synthesis of copolymers based on divinylbenzene and dibenzocyclobutyldimethylsilane and a study of their functional characteristics

Objectives. To create new polymer materials based on organosilicon derivatives of benzocyclobutene and to study the possibility of their use as insulating dielectric layers in micro- and microwave electronics devices.

Methods. The synthesis of the dibenzocyclobutyldimethylsilane (diBCB-DMS) monomer was carried out from 4-brombenzocyclobutene through the production stage of the Grignard reagent. Copolymers based on divinylbenzene and dibenzocyclobutyldimethylsilane were obtained by means of thermal polymerization. The properties and structure of the copolymers thus obtained were studied using the following methods: thermogravimetric analysis, infrared spectroscopy, nuclear magnetic resonance (NMR), mass spectroscopy, and by means of high-frequency measurements of volt-ampere characteristics and volumetric resonator.

Results. diBCB-DMS was synthesized with a yield of 81.5%. The composition and structure were confirmed by ¹H and ¹³C NMR spectroscopy. The dielectric constant of the diBCB-DMS homopolymer is ~2.6. The tangent of the dielectric loss angle at 1 GHz of the diBCB-DMS homopolymer is 2.3∙10⁻⁴. The tangent of the dielectric loss angle at 10 GHz of the diBCB-DMS homopolymer is 2.6∙10⁻⁴. The study of divinylbenzene and diBCB-DMS copolymers in different molar ratios on a thermogravimetric analyzer showed that the copolymers are able to withstand temperatures up to 470°C. The dielectric permittivity of diBCB-DMS and divinylbenzene copolymers in a molar ratio of 1 : 1 was 2.6. The values of the loss tangent at 1 and 10 GHz of copolymers in a molar ratio of 1 : 1 were 4.0∙10−4 and 5.6∙10⁻⁴, respectively.

Conclusion. Analysis of the obtained results shows that the samples of the diBCB-DMS homopolymer have the same dielectric characteristics as the samples based on diBCB-DMS and divinylbenzene, therefore, the introduction of divinylbenzene into the polymer structure does not worsen the dielectric parameters and such polimer materials can be used at high temperatures.

1. Zuniga C.A., Abdallah J., Haske W., Zhang Y., Coropceanu I., Barlow S., Kippelen B., Marder S.R. Crosslinking using rapid thermal processing for the fabrication of efficient solutionprocessed phosphorescent organic light‐emitting diodes. Adv. Mater. 2013;25(12):1739–1744. https://doi.org/10.1002/adma.201204518

2. Cao L., Grimault-Jacquin A.S., Zerounian N., Aniel F. Design and VNA-measurement of coplanar waveguide (CPW) on benzocyclobutene (BCB) at THz frequencies. Infrared Phys. Technol. 2014;63:157–164. https://doi.org/10.1016/j.infrared.2013.12.023

3. Chen Q., Yu W., Huang C., Tan Z., Wang Z. Reliability of through-silicon-vias (TSVs) with benzocyclobutene liners. Microelectron. Reliab. 2013;53(5):725–732. https://doi.org/10.1016/j.microrel.2012.12.012

4. Hyeon I.J., Park W.Y., Lim S., Baek C.W. Ku-band bandpass filters using novel micromachined substrate integrated waveguide structure with embedded silicon vias in benzocyclobutene dielectrics. Sens. Actuators A: Phys. 2012;188(12):463–470. https://doi.org/10.1016/j.sna.2012.02.012

5. Makihata M., Tanaka S., Muroyama M., Matsuzaki S., Yamada H., Nakayama T., Esashi M. Integration and packaging technology of MEMS-on-CMOS capacitive tactile sensor for robot application using thick BCB isolation layer and backsidegrooved electrical connection. Sens. Actuators A: Phys. 2012;188:103–110. https://doi.org/10.1016/j.sna.2012.04.032

6. Yang J., Sun M., Cheng Y., Xiao F. Study of benzocyclobutenefunctionalized siloxane thermoset with a cyclic structure. In: 2011 12th International Conference on Electronic Packaging Technology and High Density Packaging. IEEE. 2011. https://doi.org/10.1109/ICEPT.2011.6066841

7. Yang J., Cheng Y., Xiao F. Synthesis, thermal and mechanical properties of benzocyclobutene-functionalized siloxane thermosets with different geometric structures. Eur. Polym. J. 2012;48(4):751–760. https://doi.org/10.1016/j.eurpolymj.2012.01.006

8. Zuo X., Yu R., Shi S., Feng Z., Li Z., Yang S., Fan L. Synthesis and characterization of photosensitive benzocyclobutenefunctionalized siloxane thermosets. J. Polym. Sci. A: Polym. Chem. 2009;47(22):6246–6258. https://doi.org/10.1002/pola.23668

9. Rabanzo-Castillo K.M., Kumar V.B., Söhnel T., Leitao E.M. Catalytic synthesis of oligosiloxanes mediated by an air stable catalyst, (C6F5)3B(OH2). Front. Chem. 2020;8:477. https://doi.org/10.3389/fchem.2020.00477

10. Li J., Zhang Z., Zhu T., Li Z., Wang J., Cheng Y. Multibenzocyclobutene functionalized siloxane monomers prepared by Piers-Rubinsztajn reaction for low-k materials. Eur. Polym. J. 2020;126:109562. https://doi.org/10.1016/j.eurpolymj.2020.109562

11. Chen X., Wang J., Sun J., Fang Q. High performance low dielectric polysiloxanes with high thermostability and low water uptake. Mater. Chem. Front. 2018;2(7):1397–1402. https://doi.org/10.1039/C8QM00104A

12. Shi Q., Pen, Q., Wu S., Long Q., Deng Y., Huan, Yang J. Benzocyclobutene‐containing carbosilane monomers as a route to low‐κ dielectric and low dielectric loss materials. ChemistrySelect. 2022;7(15):e202104413. https://doi.org/10.1002/slct.202104413

13. Yang J., Liu S., Zhu F., Huang Y., Li B., Zhang L. New polymers derived from 4‐vinylsilylbenzocyclobutene monomer with good thermal stability, excellent film‐forming property, and low‐dielectric constant. J. Polym. Sci. A: Polym. Chem. 2011;49(2):381–391. https://doi.org/10.1002/POLA.24437

14. Sakellariou G., Ji H., Mays J.W., Baskaran D. Enhanced polymer grafting from multiwalled carbon nanotubes through living anionic surface-initiated polymerization. Chem. Mater. 2008;20(19):6217–6230. https://doi.org/10.1021/cm801449t

15. Levchenko K.S., Adamov G.E., Demin D.Y., Chicheva P.A., Chudov K.A., Shmelin P.S., Grebennikov E.P. Di(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)dimethylsilane. Molbank. 2020;2020(4): M1160. https://doi.org/10.3390/M1160