Near-Infrared Light Triggered a High Temperature Utilizing Donor–Acceptor Cocrystals

Abstract

Developing a suitable initiation for the energetic materials that respond to a low-power near-infrared laser can aid in replacing the current expensive and bulky laser-initiation systems. Here, we report on a system of molecularly tailored 1:1 donor–acceptor (D-A) charge-transfer (CT) cocrystals that manifest ultrabroad absorption (200–2500 nm) characteristics as well as noteworthy very fast self-assembly behaviors. The very narrow highest occupied molecular orbital–lowest unoccupied molecular orbital gap enables N,N,N′,N′-tetramethyl-p-phenylenediamine and tetrahalo-1,4-benzoquinones (TMPD-TXBQ) cocrystals to have a great light-harvesting ability in the near-infrared range. When irradiated with a low-power hand-held 808 nm laser with an input energy of only 40 mJ or a power density of 260 mW·cm–2, these TMPD-TXBQ cocrystals immediately undergo an efficient photothermal conversion followed by a dramatic exothermic thermal polymerization reaction due to the face-to-face D-A-D-A stacking in these cocystals to achieve a temperature as high as 318.9 °C. This temperature is high enough for a thermal initiation of most common energetic materials, and thus this TMPD-TXBQ cocrystal can potentially act as a near-infrared laser initiator that is compact, lightweight, and cost-effective.

Organic Photothermal Cocrystals: Rational Design, Controlled Synthesis, and Advanced Application

“…Meanwhile, our group prepared a CT cocrystal based on TMPD and TCBQ via a self‐assembly method, which displays the performance of high temperatures for a novel application of laser ignition under NIR laser irradiation. [ 37 ] As shown in Figure 9e, these prepared TMPD‐TCBQ cocrystal materials could easily be triggered remotely at distances of up to 4 m. Furthermore, the superior penetration ability of the NIR laser allowed TMPD‐TBBQ encapsulated in a three‐layer polypropylene tube to be successfully triggered under an 808 nm laser (0.6 W) from the outside (Figure 9f). It suggests that the exotherm of the TMPD‐TCBQ cocrystal could be triggered when these CT cocrystal materials were encapsulated in transparent packaging.…”

“…[ 35 ] Owing to the intense CT interaction, the TMPD‐based cocrystal materials generally exhibit a narrow energy gap with a broad UV–Vis–NIR absorption, showing a wonderful potential for photothermal applications. Considering these advantages, our group successfully employed the typical electron acceptor of pyromellitic dianhydride (PMDA) and tetrachloro‐1,4‐benzoquinone (TCBQ) to rationally design and synthesize two kinds of TMPD‐based cocrystal materials of TMPD‐PMDA [ 36 ] and TMPD‐TCBQ [ 37 ] as illustrated in Figure a. Both TMPD‐PMDA and TMPD‐TCBQ have a relatively broad absorption band accompanied by a substantial absorption value in the NIR region (Figure 3b,c), which displays a promising potential for PTC.…”

“…Reproduced with permission. [ 37 ] Copyright 2022, American Chemical Society. d) The heating and cooling curves of TMPD‐PMDA at 808 nm.…”

“…Copyright 2021, American Chemical Society, c) TMPD, TCBQ, and TMPD-TCBQ cocrystals. Reproduced with permission [37]. Copyright 2022, American Chemical Society.…”

“…e) Remote trigger experiment setup and photo of successful TMPD-TBBQ triggering in this setting; f) pictures of TMPD-TBBQ before and after 808 nm laser irradiation after encapsulation; g) deflagration experiments with a handheld 808 nm laser on a mixture of KNO 3 and TMPD-TBBQ powders. Reproduced with permission [37]. Copyright 2022, American Chemical Society.…”