Crystal Structure, Thermal Properties, and Shock-Wave-Induced Nucleation of 1,2-Bis(phenylethynyl)benzene

Ren, Yi; Lee, Jaejun; Hutchins, Kristin M.; Sottos, Nancy R.; Moore, Jeffrey S.

doi:10.1021/acs.cgd.6b01119

Cited by 5 publications

(5 citation statements)

References 33 publications

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“…Current state-of-the-art materials for SWED are commercial polymers like polyurea (PUrea) composed of phase-separated hard and soft domains. The remarkable dissipative performance of PUrea has been attributed to the scattering of waves at hard/soft interfaces, dynamic hydrogen bonding, and impact-induced glass transitions. − In addition to PUrea, substantial SWED has been reported in elastomers, liquids, , and polymers, which is generally attributed to fast dynamics at relevant frequencies. Semicrystalline materials such as polyethylene possess amorphous/crystalline interfaces that scatter waves in a similar manner to the hard/soft domains of PUrea.…”

Section: Introductionmentioning

confidence: 99%

“…Semicrystalline materials such as polyethylene possess amorphous/crystalline interfaces that scatter waves in a similar manner to the hard/soft domains of PUrea. Shock-induced ordering transitions, ,, pore collapse in metal–organic frameworks, volume-reducing chemical reactions, mechanochemical reactions, and layering strategies also dissipate energy but are irreversible and limited to a single usage. New strategies are needed to molecularly design materials to dissipate more energy than current systems while also exhibiting reversibility and the capacity to absorb multiple shock waves without external intervention.…”

Section: Introductionmentioning

confidence: 99%

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Shock Wave Energy Dissipation in Catalyst-Free Poly(dimethylsiloxane) Vitrimers

et al. 2020

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Materials that absorb shock wave energy from blasts and high-speed impacts are critical for protection of structures, vehicles, and people. Incorporating dynamic bonds into polymers has enabled precise control over the time-dependent response and energydissipating modes, but this work has focused on much slower time scales and lower forces than those associated with shock waves. Here, we design polymers networks with dynamic covalent bonds, called vitrimers, where reversible exchange reactions provide a potential mechanism for shock wave energy dissipation. Increasing the density of dynamic bonds leads to a systematic increase in energy dissipation, measured by the drop in peak pressure of a laser-induced shock wave. An analogous permanent polymer network shows no dependence of dissipation on cross-link density. The vitrimers can absorb shock multiple times while maintaining performance, attributed to bond exchange and the intrinsic self-healing ability of the polymer. Our results are the first to demonstrate that vitrimers are an effective route to the design of energy-dissipating materials, particularly at the high frequencies and pressures associated with shock waves.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shock Wave Energy Dissipation in Catalyst-Free Poly(dimethylsiloxane) Vitrimers

et al. 2020

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“…According to homogeneous nucleation theory, the rate of nucleation and the rate of propagation determine crystal growth. In particular, the nucleation of dyes is governed by the intermolecular interactions in the crystal . It has been proposed previously that the out-of-plane methoxy substituent may prevent dye nucleation and therefore crystallization .…”

Section: Resultsmentioning

confidence: 99%

“…In particular, the nucleation of dyes is governed by the intermolecular interactions in the crystal. 16 It has been proposed previously that the out-of-plane methoxy substituent may prevent dye nucleation and therefore crystallization. 32 Comparison of the torsion angles of methoxy groups shows that the increased thermal stability of the amorphous state is observed for dyes when torsion angles are closer to 90°or orthogonal to the plane of the molecule.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…In fact, when substituted with alkyl chains, eight carbons in length, crystallization could be triggered by living cell attachment and cell contraction, which demonstrates its use as a highly sensitive force sensor. In addition to fluorescent systems, amorphous materials, such as SCLs, are also of interest for improved drug solubility, conducting materials for organic light-emitting diodes, nanolithography, and optical memory storage. − Therefore, new SCL materials may be used for a variety of applications.…”

Section: Introductionmentioning

confidence: 99%

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Supercooled Liquid β-Diketones with Mechanoresponsive Emission

et al. 2019

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Shear-induced crystallization of dyes in the amorphous state is an effective strategy for generating higher energy emission after mechanical perturbationa rare phenomenon in mechanoresponsive materials. Recently, we reported that a β-diketone with a 3,4,5-trimethoxy-substituted phenyl ring formed a stable supercooled liquid (SCL) phase after melting and cooling in air. To tune the lifetime of β-diketones in the SCL phase, a series of dyes with 3,4,5-trimethoxy-substituted phenyl rings were synthesized. Derivatives with naphthyl and phenyl rings were prepared in order to modulate crystallization through arene interactions. Additionally, dyes were substituted with alkoxy chains of varying length to promote crystallization through increased van der Waals interactions. Video screening in conjunction with differential scanning calorimetry and X-ray diffraction studies indicated that naphthyl-substituted derivatives exhibited increased melted state lifetimes and that increasing the alkoxy chain length can induce crystallization. Analysis of molecular packing of single crystals of PH, PC1, PC3, and PC5 revealed that the central para-substituted methoxy group of the trimethoxy-substituted ring was forced out of the molecular plane because of steric interactions with neighboring methoxy groups. The stabilities of the SCLs were generally correlated with the torsion angles of the para methoxy groups, where derivatives with smaller angles exhibited faster rates of crystallization. Mechanical perturbation of the SCL phases resulted in shear-induced crystallization of PH, PC1, PC3, and NC6 derivatives. In some cases, traditional mechanochromic luminescence with a crystalline-to-amorphous phase transition was also observed, which indicates that some trimethoxy-substituted β-diketones exhibit more than one type of mechanoresponsive luminescence.

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