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 106 Hz, much lower than BADCy resins (2.88, 0.0052). More importantly, a maximum impact strength of 15.6 kJ/m2 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.

Bismaleimide and Biobased Limonene Copolymer Microspheres as Reactive Fillers to Fabricate Low-k, High-Toughness Cyanate Ester Resin Composites

“…The decrease of ε and tan δ could be tentatively explained as follows: (1) BMIP and BADCy have a similar chemical structure (bisphenol A backbone), so they are more compatible and present a lower interfacial polarization; (2) the unreacted endocyclic double bonds on the surface of BMPL chemically react with –OCN groups during the curing process to form a highly cross-linked network, which effectively inhibits the dipole motion and reduces the polarization; and (3) the BMPL contains a large number of alkane and benzene ring groups, the BMPL/BADCy composite has more rigid groups and fewer triazine rings, which reduce the dipole density per unit volume, and the free volume of the molecule increases, which is favorable for the reduction of ε and tan δ . In short, the cross-linked network structure formed by the reaction of intraring double bonds with –OCN groups and the introduction of rigid benzene ring groups promote the low dielectric properties of BADCy resins …”

“…Pure BADCy itself has good hygroscopicity, mainly due to the absence of dipoles and hydrogen bonds, and the cyclotrimerization of the cyanate group allows the formation of a highly symmetrical triazine ring structure and an intact cross-linked polymer network with excellent hygroscopicity. 48 The excellent hygroscopicity of the polymer is due to the absence of dipoles and hydrogen bonds. The addition of highly cross-linked polymer microspheres BMPL has a large number of benzene rings, making the modified resin more hydrophobic.…”

“…47 In short, the cross-linked network structure formed by the reaction of intraring double bonds with −OCN groups and the introduction of rigid benzene ring groups promote the low dielectric properties of BADCy resins. 48…”