In this work

the hydroxyl-terminated polybutadiene acrylonitrile liquid rubber (HTBN) was modified and blocked different photoactive end functional groups to prepare photoreactive telechelic polybutadiene acrylonitrile oligomers. After compounding with active small molecule and photoinitiator

as well as UV-light curing

polybutadiene acrylonitrile-based polyurethane (BNPU) dielectric elastomers with different molecular chain structures were fabricated. The results showed that with the increase of the molecular chain length in the HTBN precursor

the entanglement network density of the cured BNPU elastomers increased

further to provide a high Young’s modulus (

Y

) of utmost 1.89 MPa and a large elongation at break (

E

B

) of 112.26% to the elastomer

respectively. The long molecular chain between crosslinking points can also reduce the glass transition temperature (

T

g

) of the elastomers. The BNPU elastomer which was cured from HTBN oligomer with pentaerythritol triacrylate (PETA) end-blocked can form partial cross-linking domains with large volume steric hindrance

endowing the BNPU elastomers with increased

T

g

decreased thermal decomposition velocity and enhanced inter facial polarization between separated microphase. As a result

the dielectric properties of the BNPU elastomers with partial cross-linking regions were improved. For instance

the dielectric constant (

ε

') of BNPU elastomer sample reached a maximum value of 807 under 103 Hz

and its dielectric loss (tan

δ

) can be maintained below 1. One can make a conclusion that the synergistic effect between partial cross-linking domains with large volume hindrance and cyan side groups can guarantee the BNPU elastomer an excellent comprehensive electromechanical property

proposing a solution to the issues of high modulus and low breakdown strength for pure polyurethane and highly cross-linked nitrile rubber.