Synchronously improved toughness and dielectric properties of cyanate ester resins via modification with biobased poly(N‐phenylmaleimide‐co‐limonene)

Abstract High‐performance cyanate ester (CE) resins have attracted intensive interests due to low‐k and heat resistant properties. However, the extreme high curing temperature and inherent brittleness severely limit their practical application. Herein, novel biobased poly(N‐phenylmaleimide‐co‐limonene) (PML) microspheres were specially designed and synthesized by self‐stabilized precipitation polymerization, which could simultaneously serve as effective curing agents and toughening modifiers for 2,2‐bis(4‐cyanatophenyl) propane (BADCy). The high density of unreacted endocyclic vinyl groups in PML could effectively react with BADCy, leading to lower curing temperature and good interfacial compatibility. Benefitting from both the weakly polarizable flexible chains and the highly crosslinked semi‐interpenetrating network formed during the curing process, BADCy/PML resins exhibited highly enhanced toughness and reduced dielectric constant (ε). Specifically, the BADCy/PML resins showed minimum values of ε and dielectric loss of 2.61 and 0.0032 at 10 6 Hz, much lower than BADCy resins (2.88, 0.0052). More importantly, a maximum impact strength of 15.6 kJ/m 2 was achieved at 10 wt% loading of PML, which was 86% higher than BADCy resin. In summary, this work developed a novel strategy to simultaneously improve toughness and dielectric properties of CE resins using bio‐based PML copolymer, which have great potential in the fields of electronics and information technology.