Photopatternable, Degradable, and Performant Polyimide Network Substrates for E-Waste Mitigation

Abstract

The continuous accumulation of electronic waste is reaching alarming levels necessitating sustainable solutions to mitigate environmental impact. Fabrication of the commercial electronic substrates also requires high heat. As an alternative, we propose a series of reprocessible electronic substrates based on photopolymerizable polyimides containing degradable ester linkages. We synthesize imide-containing diallyl monomers derived from readily available chemical feedstocks to produce high-quality substrates via rapid photopolymerization. Such materials possess exceptional thermal properties (thermal conductivity, K = 0.37-0.54 WmK-1; degradation temperature, Td > 300 °C), dielectric (dielectric constant, Dk = 2.81-3.05; dielectric loss, Df < 0.024) and mechanical properties (Strength ~ 50 MPa ; ultimate elongation, dL/L0 > 5%) needed in flex electronic applications. When utilized as electronic substrates, we demonstrate mild depolymerization via transesterification reactions to recover and reuse the functional components. Moreover, these photopolymer resins remain compatible with commercial workflows and enable fabrication of next-generation, dense multilayered circuits.

Ductile Glassy Polymer Networks Capable of Large Plastic Deformation and Heat-Induced Elastic Recovery

“…We found all three diallyl phthalamide compounds to be crystalline solids (Figure S2), though we were able to prepare photopolymerizable liquid resin by melting the phthalamides in the thiol monomers (Figure B). Photopolymerization of a stoichiometric functional group mixture of diallyl phthalamides and a mixture of commercially available thiols, namely ethylene bis­(3-mercaptopropionate) (EBMP) and tris­[2-(3-mercaptopropionyloxy)­ethyl]­isocyanurate (TEMPIC) (Scheme E), proceeded smoothly with a catalytic amount of photoinitiator (2,4,6-trimethylbenzoylphenyl phosphinate, TPO) and 405 nm LED irradiation at 80 °C (Scheme C) . The three polymers were found to be glassy materials at ambient conditions (Figure C).…”