With the popularization of 4G communication technology and the continuous development of 5G communication technology, the higher frequency communication technology will be the future development trend, and the corresponding high frequency and low dielectric materials demand is also growing day by day.High frequency low dielectric materials need to meet the Low dielectric constant and dielectric loss under high frequency conditions, in addition, the material itself should meet the application conditions of low water absorption, high heat resistance, mechanical properties and processability, etc. The fluoropolymer has Good low dielectric properties, such as polytetrafluoroethylene (PTFE), but because of its molecular inertness, resulting in poor processing performance, you need to be on the surface of the etching treatment to increase the adhesion with the copper foil in order to For the next step, it is important to develop easily machinable, high-performance fluorine-containing low-dielectric materials.
Fang Qiang, Key Laboratory of Organic Synthesis and Assembly, School of Organic Chemistry, Chinese Academy of Sciences, CAS conducted a systematic research in this field. By utilizing the heat-cyclability of trifluorovinyl ethers and developing heat-crosslinkable Fluoropolymers, and have recently achieved a series of research results.Through the design of multi-functional (> 3) macromonomer strategy, the polymer chain growth in many directions, to effectively prevent the formation of trifluorovinyl ether monomer is difficult to High molecular weight polymer defects.This strategy can not only improve the processability of the fluoropolymer, but also get good insulation, heat resistance and transparency, etc .. In trifluoro vinyl ether synthesis method, cleverly Alkaline strong and weakly nucleophilic 2,6-dimethylpiperidine lithium (LTMP) for the elimination of tetrafluoroethyl ether reaction, a simple and high yield of tetra-substituted tetrafluorotrifluoroether ether tetraphenyl Methane (TPM-TFVE) .This molecule has a tetrahedron skeleton and can be obtained by thermal cross-linking of a fluoropolymer with a microporous structure. The polymer exhibits excellent dielectric properties with a dielectric constant below 10 MHz Dielectric constant at 2.29 at 5 GHz And dielectric losses of 2.36 and 1.29 × 10 -3, respectively, outperform traditional commercial low dielectric materials (Macromolecules 2016, 49, 7314).
Silsesquioxanes (POSS) are nanomaterials with unique cage structures that are often incorporated as additives into polymers to improve their mechanical and dielectric properties, etc. POSS has less functionalization of fluorine, primarily due to the lack of direct The effective method of fluorination.After exploration, the group using efficient platinum-hydrosilylation reaction, one-step reaction is to introduce fluorine-containing groups into the POSS POSS to achieve fluoroalkylation and functionalization.This method makes difficult Soluble and refractory POSS dissolves, melts, thermally polymerizes novel organic-inorganic hybrid sheets and films, exhibiting superior transparency and excellent dielectric properties at high frequency (at 5 GHz An electrical constant of 2.51 and a dielectric loss of 3.1 x 10-3.) The hybrid material maintains stable dielectric properties even in humid environments, setting the stage for its potential application in high frequency communications (ACS Applied Materials & Interfaces 2017, 9, 12782).
The group found that Si-OH groups are generated in the hydrolysis and condensation of organosiloxanes and that -Si-CH2-CH2- segments are also produced in the hydrosilylation reaction. The presence of these groups and segments In order to solve this problem, the research group through a one-step Piers-Rubinsztajn reaction, the basic industrial raw material tetraethoxysilane (TEOS) for fluorine functionalization , The in situ formed fluorine-containing organosiloxane macromonomer can form a transparent film after thermal polymerization, and the film shows the excellent performance of a dielectric constant of 2.50 and a dielectric loss of 4.0 × 10-3 at ultra-high frequency of 10 GHz, While common non-porous silicon dioxide films and polyorganosiloxanes typically have dielectric constants greater than 3.0 (Macromolecules 2017, 50, 9394).
The research work was supported by the Ministry of Science and Technology, the National Natural Science Foundation of China, and the Strategic Pilot Project of Science and Technology of the Chinese Academy of Sciences (Category B).
Figure 1. Synthesis of tetra-functional trifluorovinyl ether monomers and polymers.
Figure 2. Preparation of organic-inorganic hybrid fluorinated POSS.
Figure 3. Preparation of TEOS-based fluorinated organosiloxane macromonomers and polymers.
