Pressure-Induced Crystallization and Phase Transformation of Para-xylene

Abstract

Static pressure is an alternative method to chemical pressure for tuning the crystal structure, bonds, and physical properties of materials, and is a significant technique for the synthesis of novel materials and fundamental research. In this letter, we report the crystallization and phase transformation of p-xylene under high pressure. Our optical micrographic observations and the appearance of lattice modes in the Raman and infrared (IR) spectra indicated that p-xylene crystallizes at ∼0.1 GPa. The X-ray diffraction (XRD) pattern at 0.84 GPa suggests that the crystallized p-xylene had a monoclinic phase with the Cc(9) space group. The sharp shrinkage of the lattice at ~13 GPa and the solid state of the decompressed sample we observed suggests a new crystalline phase of p-xylene. The in situ XRD showed that the new crystalline phase was still a monoclinic structure but with a different space group of C2(5), indicating that a phase transition occurred during further compression. The mass spectrometry experiment confirmed phase transition polymerization, with mainly trimer and tetramer polymers. Our findings suggest an easy and efficient method for crystallizing and polymerizing p-xylene under high pressure.

Para‐xylene under extreme conditions: A Raman spectroscopic study

“…In the second set of experiments, the delay between pump and probe beam is fixed to 52 ns, and the pump beam energy (and hence the pressure) is varied from 100 (1.2 GPa) to 1,340 mJ (4.1 GPa) in steps. We also compare the dynamically shocked p-xylene results with the static compression results reported by Bai et al [23] The para-xylene sample used in these experiments is procured from M/s Sigma-Aldrich (purity 99%).…”

“…In this manuscript, we present laser-driven shock studies on the p-xylene sample and its comparison with static compression data published in Bai et al [23] We have also performed a one-dimensional (1-D) radiation hydrodynamic simulation to validate our experimental results. A brief discussion on experimental setup is presented in Section 2; in situ time-resolved Raman spectroscopy (TRRS) of shocked sample to deduce shock velocity and its comparison with simulation is shown in Section 3.1.…”

“…The Raman spectrum has fairly good signal-to-noise (S/N) ratio because the total recording time is 2 × 40 = 80 ns. The Raman modes are identified with the data presented in Bai et al and Lindenmaier et al [23,27] The details of the modes along with the data provided by Lindenmaier et al and Bai et al are present in Table S1.…”

“…The effect of laser-driven shock pressure on the Raman modes of p-xylene in the spectral range 500-1,300 and 2,400-3,300 cm −1 has been studied in the pressure range 1.2-4.6 GPa by changing the laser energy from 100 to 1340 mJ in the step of 200 mJ and compared with the static pressure data presented in Bai et al [23] In these measurements, the delay between pump and probe beams is kept fixed at 52 ns to get a reasonable amount of signal from the shocked region. At 100-mJ laser energy (corresponding pressure 1.2 GPa), a broadened signal is observed.…”

“…solid phase transition and polymerization at 0.1 and 13 GPa, respectively, using Raman spectroscopy and X-ray diffraction. [23] However, as per our knowledge, no studies on dynamically shocked p-xylene at gigapascal pressure and temperature up to 1,300 K have been performed.…”