We synthesized rubbers including cyanoethyl groups and evaluated the effect of side-chain structures on dielectric properties, electrical properties at room temperature, and glass-transition temperatures (Tg). New monomers including cyanoethyl were synthesized via the thiol-ene reaction and esterification; these included 3-((2,4-dicyanobutyl)thio)propyl acrylate (DCEA3M) and 6-((2,4-dicyanobutyl)thio)hexyl acrylate (DCEA6M). Copolymers consisting of 2-cyanoethyl acrylate (CEA) and DCEA3M or DCEA6M were synthesized to obtain a rubber with a high dielectric constant. Reference copolymer samples with varying CN wt % consisted of CEA and acrylate monomers were also synthesized. Undesirable gelation occurred during polymerization of monomers including cyanoethyl; however, gelation could be resolved by changing the monomer concentration and reaction time. The copolymers exhibited a Tg of 5 °C or below, and the relative dielectric constant at 100 Hz was above 10. pDCEA3M exhibited the highest dielectric constant of 20.3 corresponding to a high CN wt % of 20.6%, and pDCEA6M displayed the lowest Tg of -33.2 °C due to the internal plasticization corresponding to the long side chain; however, the dielectric losses of pDCEA3M and pDCEA6M were as high as 3.2 and 7.7, respectively. On the other hand, p(CEA-DCEA3M) and p(CEA-DCEA6M) copolymerized with CEA could reduce the dielectric loss (∼2.4) while maintaining high dielectric constant (16.3-18.9) and low Tg (-22.9-3.36 °C). The copolymers also exhibited a high dielectric constant at a comparable volume resistivity (1010-1012 Ω·cm) compared to commercial rubbers. Such elastomers with high dielectric constant and low dielectric loss are expected to improve the performance of soft actuators.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry