Recyclability of Photoinduced Cross-Linked EPM Rubber with Anthracene-Grafted Groups: Problems and Their Solutions

Abstract

In this paper, we present the formation of reversible covalently cross-linked networks in ethylene propylene rubber with grafted anthracene groups (EPM-g-AN) based on the principles of photoinduced anthracene dimerization. First, an industrial-grade EPM rubber grafted with maleic anhydride functional groups (EPM-g-MA) was modified with 9-anthracenemethanol. By irradiating EPM-g-AN with UV light (365 nm), the anthracene moieties dimerize via [4 + 4]cycloaddition, forming a covalent network. The network cleavage proceeds at high temperatures (>170 °C), even if with considerable (chemical) degradation. Furthermore, one of the degradation routes has been identified by 1 H NMR to occur via the ester bond cleavage releasing 9anthracenemethanol. Nevertheless, the reversibility of cross-linking has been achieved by performing the reverse reaction in decalin. The UV−vis spectroscopy clearly shows that the de-cross-linking process in these conditions is due to the anthracene dimer cleavage. Although the recovery in mechanical properties upon recycling is yet to be optimized, the disclosed results pave the way toward the use of anthracene chemistry in thermally reversible networks with possible industrial perspective applications.

Reversible dual crosslinking in anthracenyl functionalized butyl elastomers based on ionic interaction and (4 + 4) cycloaddition mechanisms

“…After three recycling processes, the sample becomes heterogeneous with air bubbles. The side reaction of anthracene 22,38,56,57 ( possibility of formation of peroxide bonds) in the presence of oxygen is the reason for low reprocessiblity.…”

“…In order to achieve the state of being dynamic, the process of de-dimerization took place at a wavelength of λ = 254 nm or by applying heat over 130 °C. The [4 + 4] cycloaddition reaction has been investigated in different elastomers [37][38][39][40] such as nitrile rubber (NBR), 41 silicone elastomers, 42 etc. Here, we report a dual system of ionic interaction and dynamic [4 + 4] cycloaddition into butyl elastomers.…”

Fully Recyclable Cured Polymers for Sustainable 3D Printing

“…An alternative approach was explored to avoid UVC irradiation, based on microwave irradiation (25-38 mm), which is known to cause rapid heating through the rotation of polar molecules (C-N bonds in the present molecule, TETA-CA-based polymer). Some cycloaddition reactions, such as the [4 + 4] of anthracenes, [20][21][22] can dissociate under high temperatures that cause vibrations of the rings, leading to steric stresses, which results in conversion to the more steric stable form, which are the original molecules. Following a study by Beves et al, [23] it was hypothesized that microwave irradiation can cause a similar effect at much lower temperatures, as it effectively initiated the adducts' vibrations.…”

Chemical Recycling and Physical Tuning of Necklace‐Shaped Polydimethylsiloxanes Bearing Anthracene Dimer Units

“…[12] Anthracene dimerization systems are capable of covalent "connectdisconnect" interactions, and have been incorporated into plastics such as poly(ethylene terephthalate), [13] poly(styrene-blockmethyl methacrylate), [14] and epoxy polymers. [15] Soft elastomer systems bearing anthracene groups based on polyethylene oxide (PEO), [16,17] ethylene and propylene, [18] poly(styrenebutadiene-styrene), [19] polyurethane, [20] and polydimethylsiloxane (PDMS), [12,[21][22][23] and containing anthracene groups, have also been reported. Moreover, the photodimerization of anthracene has been utilized in the sequence-selective photochemical ligation of DNA conjugates.…”

“…Moreover, the photodimerization of anthracene has been utilized in the sequence-selective photochemical ligation of DNA conjugates. [24] These macromolecular systems exploit the photodimerization of the anthracene units and can be classified into two groups: 1) polymers in which crosslinking is controlled by introducing anthracene groups into their side chains [13,15,16,[18][19][20][21][22][23] and 2) polymers in which the molecular weight is controlled by introducing anthracene groups at the polymer terminal. [12,14] Linear-cyclic topological conversion using an anthracene-terminated polymer chain has also been demonstrated.…”