Frontal Polymerization of Dihydrofuran Comonomer Facilitates Thermoset Deconstruction

Abstract

Frontal ring-opening metathesis polymerization (FROMP) is a rapid, low-energy manufacturing reaction that is useful for curing thermosetting materials. FROMP of dicyclopentadiene (DCPD) results in poly­(dicyclopentadiene) (p­(DCPD)), a tough thermoset with excellent mechanical performance and chemical stability. Like most thermosets, p­(DCPD) cannot be reprocessed and is therefore difficult to recycle. Previous work demonstrated that the incorporation of a small quantity of cleavable units in the strand segments of p­(DCPD) networks enables their deconstruction. Here, we report that a commercially available multifunctional comonomer, 2,3-dihydrofuran (DHF), both acts as a potent Grubbs catalyst inhibitor during FROMP and introduces acid cleavable units. The resulting materials retain high performance characteristics, including glass-transition temperatures ranging from 115 to 165 °C and ultimate strength ranging from 35 to 40 MPa. The addition of DHF above critical loading levels enables deconstructable thermosets. We further demonstrate freeform three-dimensional (3D) printing of deconstructable thermosets via frontal polymerization.

Review of high-performance sustainable polymers in additive manufacturing

“…al. 89 p(DCPD) is a tough and chemically resistant thermoset that is often used for automotive application such as for body panels and bumpers for trucks, buses, and construction equipment. Davydovich et.…”

“…Another recent development in sustainable high-performance materials for material extrusion is the use of degradable comonomers with thermosetting poly(dicyclopentadiene) ( p(DCPD)) by Davydovich et al 89 p(DCPD) is a tough and chemically resistant thermoset that is often used for automotive application such as for body panels and bumpers for trucks, buses, and construction equipment. Davydovich et al demonstrated that the incorporation of dihydrofuran (DHF) in DCPD resins allowed the printed pDCPD to degrade into oligomeric products with product recovery around 80%.…”

Frontal Polymerizations: From Chemical Perspectives to Macroscopic Properties and Applications

“…Several examples of copolymerization under phosphite dampened FROMP exist (Scheme 3). 145,147,148,151,168 Functionalized mono-norbornene and linked di-norbornene monomers underwent random copolymerization with DCPD. The heat associated with the homopolymerization of these monomers is given in Table 2; mono-norbornenes produce more heat per gram since the reactive olefin functionality represents a larger percentage of the molecular weight.…”

“…Davydovich et al 168 described frontal copolymerizations of DCPD and 2,3-dihydrofuran (DHF). Perhaps unsurprisingly, DHF dampens νf as it forms a less reactive Fischer carbene of the type [Ru=CH2OR] after ring-opening.…”

“…In this concept, structurally robust materials undergo controlled disassembly reactions at targeted sites only in the presence of orthogonal chemistries. Indeed, Davydovich et al 168 demonstrated the feasibility of such a thermoset deconstruction strategy. Ideally, these smaller components may themselves act as monomers for future upcycling/polymerization reactions.…”