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The structural evolution with pressure of icy mixtures of simple molecules is a poorly explored field despite the fundamental role they play in setting the properties of the crustal icy layer of the outer planets and of their satellites. Water and ammonia are the two major components of these mixtures, and the crystal properties of the two pure systems and of their compounds have been studied at high pressures in a certain detail. On the contrary, the study of their heterogeneous crystalline mixtures whose properties, due to the strong N–H⋯O and O–H⋯N hydrogen bonds, can be substantially altered with respect to the individual species has so far been overlooked. In this work, we performed a comparative Raman study with a high spatial resolution of the lattice phonon spectrum of both pure ammonia and water–ammonia mixtures in a pressure range of great interest for modeling the properties of icy planets’ interiors. Lattice phonon spectra represent the spectroscopic signature of the molecular crystals’ structure. The activation of a phonon mode in plastic NH3-III attests to a progressive reduction in the orientational disorder, which corresponds to a site symmetry reduction. This spectroscopic hallmark allowed us to solve the pressure evolution of H2O–NH3–AHH (ammonia hemihydrate) solid mixtures, which present a remarkably different behavior from the pure crystals likely to be ascribed to the role of the strong H-bonds between water and ammonia molecules characterizing the crystallites’ surface.

The direct chemical reactivity between phosphorus and nitrogen was induced under high-pressure and high-temperature conditions (9.1 GPa and 2000-2500 K), generated by a laser-heated diamond anvil cell and studied by synchrotron X-ray diffraction, Raman spectroscopy, and DFT calculations. α-P

High pressure reactivity of phosphorus and hydrogen is relevant to fundamental chemistry, energy conversion and storage, and materials science. Here we report the synthesis of (PH3)2H2, a crystalline van der Waals (vdW) compound (I4cm) made of PH3 and H2 molecules, in a Diamond Anvil Cell by direct catalyst-free high pressure (1.2 GPa) and high temperature (T ≲ 1000 K) chemical reaction of black phosphorus and liquid hydrogen, followed by room T compression above 3.5 GPa. Group 15 elements were previously not known to form H2-containing vdW compounds of their molecular hydrides. The observation of (PH3)2H2, identified by synchrotron X-ray diffraction and vibrational spectroscopy (FTIR, Raman), therefore represents the discovery of a previously missing tile, specifically corresponding to P for pnictogens, in the ability of non-metallic elements to form such compounds. Significant chemical implications encompass reactivity of the elements under extreme conditions, with the observation of the P analogue of the Haber-Bosch reaction for N, fundamental bond theory, and predicted high pressure superconductivity in P-H systems., Chemical elements at high pressure may behave more consistently with their periodic properties than they do at ambient conditions. The authors report the synthesis of PH3 from black phosphorous and hydrogen, and the crystallization of the van der Waals compound (PH3)2H2 which fills a gap in the chemistry of adjacent elements in the periodic table.

The formation of a clathrate hydrate crystal is characterized by several steps, each of them distinguished by a different structural arrangement and temporal duration. A precise definition of these different forms is a challenging task, because the entirety of the formation dynamics spans over a time interval ranging from few nanoseconds to several days. Computational methods are powerful and essential to define the nucleation step, but they fail in providing a reliable picture of the long-range order establishment. On the other side, the experimental methods employed in the study of the growth dynamics usually monitor the hydrate growth at the interface with the fluid and thus are limited by the diffusion of the guest molecules through the newly formed hydrate phase. This problem is overcome here by the confinement of an argon hydrate sample in a sapphire anvil cell, allowing monitoring of the melting and crystallization of hydrates under moderate pressures by FTIR and Raman spectroscopies. This approach, besides providing a spectroscopic characterization of this hydrate, allowed the time windows characteristic of the formation of a macroscopic amorphous phase to be identified, possibly coincident with the so-called blob, and its rapid evolution toward the achievement of the local structure. Long-range ordering takes place on a longer time scale, most of it is realized in few hours but still evolving for weeks. No hints for supporting the so-called memory effect are gained through this study.

The nature of hydrogen bond (HB) interactions is still far from being understood despite intense experimental and theoretical studies on this subject carried out by the leading research centers. In this paper, by a combination of unique high-pressure infrared, dielectric and volumetric data, the intramolecular dynamics of hydroxyl moieties (which provides direct information about Hbonds) was studied along various isolines, i.e., isotherms, isobars, isochrones, and isochores, in a simple monohydroxy alcohol (2-ethyl-1-hexanol). This allowed us to discover that the temperature controls the intermolecular hydrogen bonds, which then affect the intramolecular dynamics of O-H units. Although the role of density fluctuations gets stronger as temperature rises. We also demonstrated a clear connection between the intra- and intermolecular dynamics of the associating liquid at high pressure. The data reported herein open a new perspective to explore this important aspect of the glass transition phenomenon and understand H-bonding interactions at varying thermodynamic conditions.

Chemical reactivity between As and N2 , leading to the synthesis of crystalline arsenic nitride, is here reported under high pressure and high temperature conditions generated by laser heating in a Diamond Anvil Cell. Single crystal synchrotron X-ray diffraction at different pressures between 30 and 40 GPa provides evidence for the synthesis of a covalent compound of AsN stoichiometry, crystallizing in a cubic P213 space group, in which each of the two elements is single-bonded to three atoms of the other and hosts an electron lone pair, in a tetrahedral anisotropic coordination. The identification of characteristic structural motifs highlights the key role played by the directional repulsive interactions between non-bonding electron lone pairs in the formation of the AsN structure. Additional data indicate the existence of AsN at room temperature from 9.8 up to 50 GPa. Implications concern fundamental aspects of pnictogens chemistry and the synthesis of innovative advanced materials.

A comparison between the high-pressure (0.8 GPa) photo-induced reactivity of black and red phosphorus at ambient temperature in the presence of ammonia has been conducted in Diamond Anvil Cells (DAC), using spectroscopy (IR and Raman) and X-ray diffraction (XRD). Reactivity has been triggered exploiting the two-photon absorption of near-UV radiation by ammonia. The infrared characterization showed a very complex reactivity in the case of red phosphorus, proceeding to a much more extent with respect to the black allotrope. Furthermore, Raman spectra showed the formation of molecular hydrogen and phosphine besides of three different solid products. Whereas one of them is air sensitive, the other two are recoverable at ambient conditions. IR, Raman and XRD data for the obtained products have been compared to those acquired on known HxPyNz compounds: for one of the two stable products, a fair matching was found with the XRD pattern and the IR spectrum of P3N3(NH2)6 ·(NH3)0.5, whereas for the other one only the functional groups actually involved in the structure could be evinced from accurate Raman mapping of the sample, with no further information about composition or stoichiometry. High density conditions in combination with near-UV laser irradiation were thus proved to be effective in the formation of two stable reaction products featuring new P-N functionalities, both recoverable at ambient pressure. For the first time, a cyclic triphosphazene has been synthesized through the reaction of red phosphorus and ammonia triggered by UV light under moderate high pressure conditions, possibly opening new perspectives about this topic.

The insertion of oxygen and nitrogen molecules in the one-dimensional (1D) pore system of the zeolite TON was studied at high pressure by vibrational spectroscopy, X-ray diffraction, and Monte Carlo (MC) molecular modeling. Rietveld refinements and MC modeling indicate that, on average, six diatomic molecules per unit cell enter the pores of the zeolite. This induces changes in compressibility and distortion related to the Cmc21-to-Pbn21 phase transition compared to the empty-pore material. The filling behavior with N2 and O2 under pressure is similar to that of argon, suggesting that the kinetic diameter, which is very close in these three systems, plays a major role. The orientation of the diatomic molecules appears to have a rather minor effect on filling occurring at a slightly higher pressure for N2, which has a larger kinetic diameter. Both inserted molecules, initially not showing any marked orientation, begin to exhibit a degree of orientational order above 2 GPa.

We present a study on the phase stability of dense carbon dioxide (${\mathrm{CO}}_{2}$) at extreme pressure-temperature conditions, up to 6200 K within the pressure range $37\ifmmode\pm\else\textpm\fi{}9$ to $106\ifmmode\pm\else\textpm\fi{}17\text{ }\text{ }\mathrm{GPa}$. The investigations of high-pressure high-temperature in situ x-ray diffraction patterns recorded from laser-heated ${\mathrm{CO}}_{2}$, as densified in diamond-anvil cells, consistently reproduced the exclusive formation of polymeric tetragonal ${\mathrm{CO}}_{2}$-V at any condition achieved in repetitive laser-heating cycles. Using well-considered experimental arrangements, which prevent reactions with metal components of the pressure cells, annealing through laser heating was extended individually up to approximately 40 min per cycle in order to keep track of upcoming instabilities and changes with time. The results clearly exclude any decomposition of ${\mathrm{CO}}_{2}$-V into the elements as previously suggested. Alterations of the Bragg peak distribution on Debye-Scherrer rings indicate grain coarsening at temperatures $g4000\text{ }\text{ }\mathrm{K}$, giving a glimpse of the possible extension of the stability of the polymeric solid phase.

Black phosphorus was studied by state-of-the-art synchrotron X-ray diffraction in a Diamond Anvil Cell during room temperature compression in the presence of He, H2, N2 and Daphne Oil 7474. The data demonstrate that the existence of the pseudo simple-cubic (p-sc) structure above 10.5 GPa is an intrinsic feature of P independent from the pressure transmitting medium. In the case of He, the pressure evolution of the lattice parameters and unit cell volume of P across the A17, A7 and p-sc structures was obtained and the corresponding EOS derived, providing a deeper insight on the recently reported p-sc structure. The results presented in this letter highlight the key role of the s-p orbital mixing in the formation and stabilization of the p-sc structure up to ~30 GPa, solving apparent contradictions emerging from previous literature and finally bringing order to the sequence of the high pressure A7 layered structure in group 15 elements.

International audience; Condensed O2 tends to form clusters, even with a long-range order. In particular, in solid oxygen, strong intermolecular charge transfer at high pressures leads to the formation of (O2)4 tetramers above 10 GPa, in the ε-O2 phase, with weak O2–O2 chemical bonds. Indeed, ε-O2 is entirely made of these tetramers. We conducted experimental investigations on strongly densified O2 in a different environment, that is to say in the form of a subnano phase build up within the 1D microchannels of a purely siliceous, inert zeolite, TON, at pressures of 0.5–20 GPa, by means of diamond anvil cells. Our X-ray diffraction and infrared and Raman spectroscopy results consistently show that oxygen forms clusters in this nanophase, above 10 GPa, similar to ε-O2, except that the clusters are rather of the type of weakly bonded (O2)2 dimers in this case. Also, by analogy with bulk oxygen, we show that the O2 spin within the dimers departs from S = 1 toward lower values, upon increasing pressure. Our findings thereby add to the general view on essential properties of highly dense oxygen.

The crystalline A17 layered structure of Phosphorus, commonly indicated as black Phosphorus, was synthesized for the first time at high pressure by Bridgman back in 1914 [1] and is currently attracting a growing attention from chemists, physicists and materials scientists due to the appealing properties of its monolayer counterpart named Phosphorene [2]. Recently, high pressure studies have reported the observation of a pseudo simple cubic (p-sc) structure in the phase diagram of Phosphorus up to 30 GPa, significantly raising the pressure limit for the layered structures of P and opening new perspectives for their stabilization and functionalization [3-4]. On the other side, the experimental report of superconductivity in compressed PH 3 [5], with no structural characterization so far, has stimulated experimental and theoretical efforts to investigate the high pressure stability of different systems containing Phosphorus and Hydrogen, which can be responsible for such behavior in analogy with H 2 S [6,7]. In this study we investigated the chemical reactivity of black Phosphorus and molecular Hydrogen under high pressure and high temperature conditions, which were generated using a membrane Diamond Anvil Cell (DAC) in combination with laser heating. The sample was probed by means of synchrotron X-ray diffraction at ESRF-ID27 and by FTIR and Raman spectroscopy at LENS. The visual inspection of the sample after laser heating clearly showed the consumption of Phosphorus. Correspondingly, the analysis of the experimental XRD and spectroscopic data indicated the formation of different reaction products containing P-H bonds, particularly PH 3 , H-functionalized Phosphorus fragments and a solid product identified as a van der Waals compound made of PH 3 and H 2 , whose crystal structure was accurately determined from single crystal data. The identification of this compound, representing so far a missing piece, consistently fills a gap in the periodic table for Phosphorus, in agreement with analogous compounds reported in literature formed by the hydrides of Carbon (CH 4 ), Sulphur (H 2 S), Selenium (H 2 Se) and Iodine (HI) in the presence of H 2 [8-11]. Furthermore, the observation of this compound provides new experimental evidence for the formation of unexpected chemical species originating from the high pressure chemistry of Phosphorus and Hydrogen, possibly shedding new light on the high pressure superconductivity of Phosphorus-Hydrogen systems. Acknowledgments: Thanks are expressed to EC through the European Research Council (ERC) for funding the project PHOSFUN "Phosphorene functionalization: a new platform for advanced multifunctional materials" (Grant Agreement No. 670173) through an ERC Advanced Grant. References [1] P. W. Bridgman, J. Am. Chem. Soc. 1914, 36, 1344. [2] M. Peruzzini et al., Eur. J. Inorg. Chem. 2019, 1476. [3] D. Scelta et al., Angew. Chem. Int. Ed. 2017, 56, 14135. [4] D. Scelta et al., Chem. Commun. 2018, 54, 10554. [5] A. P. Drozdov et al., arXiv:1508.06224 (2015). [6] T. Bi et al., Angew. Chem. Int. Ed. 2017, 56, 10192. [7 M. Liu et al. J. Raman Spectrosc. 2018, 49, 721. [8] M. S. Somayazulu et al., Science 1996, 271, 1400. [9] T. A. Strobel et al. Phys. Rev. Lett. 2011, 107, 255503 .[10] E. J. Pace et al., J. Chem. Phys. 2017, 147, 184303. [11] Binns J. et al., Phys. Rev. B 2018, 97, 024111. Keywords: Phosphorus, Hydrogen, high pressure chemistry

A pressure induced lattice expansion of Graphite Oxide (GO) in presence of NH 3 was observed by X-ray diffraction during room temperature compression and decompression up to 7 GPa in a diamond anvil cell (DAC). A remarkable increase ( ∼ 11%) of the interlayer d-spacing of GO was observed between 0.2 and 1.1 GPa in the liquid phase of NH 3 , indicating the occurrence of molecular insertion between the GO layers. The expansion is reversible with the release of pressure, thus leading to a pressure induced breathing of the GO lattice. The presence of high density NH 3 between the GO layers opens new perspectives for N-doping and chemical functionalization of GO and for designing new advanced carbon based nanostructured materials.

The recent synthesis of Phosphorene [1,2] and the theoretical predictions of a variety of related 2D allotropes [3] have raised a growing interest from the scientific community about the layered structures of Phosphorus. Indeed, black Phosphorus (bP, A17), formed by the ordered stacking of Phosphorene layers in a similar way as graphene is related to graphite, is actually the starting material for the synthesis of Phosphorene by exfoliation techniques. However, while the synthesis and stabilization of Phosphorene are still challenging tasks, its chemistry and functionalization represent frontier research topics. Within this perspective, pressure has been shown to be a very effective tool. Besides bP, another layered structure of P, rhombohedral A7, made by the stacking of blue Phosphorene layers, is indeed experimentally accessible by pressure. Remarkably, pressure has recently allowed to gain fundamental insight about the mechanism ruling the formation of chemical bonds between P layers, unveiling the existence of an intermediate p-sc structure between the layered rhombohedral A7 and the non-layered simple-cubic phases of P, significantly raising the pressure limit where the layers of P can be observed up to at least 30 GPa [4]. In this study we report the high pressure and high temperature chemistry of Phosphorus in the presence of N2 by means of state-of-the-art synchrotron X-ray diffraction (at ESRF-ID27), FTIR and Raman spectroscopy, using membrane Diamond Anvil Cell for the generation of static high pressure and laser heating for in situ generation of high temperature. Besides the N- functionalization of Phosphorene layers, this study is relevant to the substantially unexplored chemistry of the lowest Z pnictogens and to the synthesis of new PN compounds. Crystalline black Phosphorus was laser heated under different pressure and temperature conditions, corresponding to different crystalline structures of Phosphorus (A17, A7 and sc), above and below the melting line of N2. The results indicate a pressure dependent chemical reactivity, leading to different reaction products, according to the applied pressure. The low pressure data demonstrated the first direct synthesis of gamma-P3N5 from the elements, avoiding any precursor or byproduct [5]. Raman spectra and XRD patterns were acquired at high and ambient pressure, tracing the equation of state of the material, and providing new experimental input about the existence of the predicted delta- P3N5 phase [6-7]. References [1] Liu, H.; Neal, A. T.; Zhu, Z.; Luo, Z.; Xu, X.; Tománek, D.; Ye, P. D. Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility, ACS Nano 2014, 8, 4033-4041. [2] Li, L.; Yu, Y.; Ye, G. J.; Ge, Q.; Ou, X.; Wu, H.; Feng, D.; Chen, X. H.; Zhang, Y. Black phosphorus field-effect transistors, Nat. Nanotechnol. 2014, 9, 372-377. [3] Woo Hyun Han, W.H. Sunghyun Kim, S.; Lee, I-H.; Chang, L.J. Prediction of Green Phosphorus with Tunable Direct Band Gap and High Mobility, J. Phys. Chem. Lett. 2017, 8, 4627-4632. [4] Scelta, D.; Baldassarre, A.; Serrano-Ruiz, M.; Dziubek, K.; Cairns, A. B.; Peruzzini, M.; Bini, R.; Ceppatelli, M. Interlayer Bond Formation in Black Phosphorus at High Pres- sure, Angew. Chem. Int. Ed. 2017, 56, 14135-14140. [5] Landskron, K.; Huppertz, H.; Senker, J. and Schnick, W. High-Pressure Synthesis of gamma- P3N5 at 11 GPa and 1500 °C in a Multianvil Assembly: A Binary Phosphorus (V) Nitride with a Three-Dimensional Network Structure from PN4 Tetrahedra and Tetragonal Pyramids Angew. Chem. Int. Ed. 2001, 40, 2643-2645. [6] Dong, J.; Kinkhabwala, A. A.; McMillan, P. F. , High-pressure polymorphism in phosphorus nitrides Physica Status Solidi B, 2004, 210, 2319-2325. [7] Kroll, P.; Schnick, W. A Density Functional Study of Phosphorus Nitride P3N5 : Refined Geometries, Properties, and Relative Stability of alpha-P3N5 and gamma-P3N5 and a Further Possible High-Pressure Phase delta-P3N5 with Kyanite-Type Structure Chem. Eur. J. 2002, 8, 3530- 3537.

Black Phosphorus (bP), which is made by the periodic stacking of Phosphorene [1], has a layered orthorhombic A17 structure, stable at room conditions, that transforms into a layered rhombohedral A7 above ~5 GPa, which is reported to further convert into a non-layered simple cubic structure at ~11 GPa. The sequence of the high pressure (HP) structures of P at room T presents two striking anomalies if compared to the other group 15 elements with higher Z: first, the A17 structure is an isolated exception and second, whereas the HP limit for the A7 decreases in group 15 with increasing Z, according to current literature its pressure value in P (11 GPa) is located below that of As (25 GPa) [2]. A recent experiment [3], in agreement with theoretical predictions [4], has revealed a two-step mechanism for the A7 to sc transition and the existence of a previously unreported, intermediate pseudo simple-cubic (p-sc) structure from 10.5 up to at least 30 GPa, which significantly raised the HP limit for the layered structures of P and provided new experimental evidences to account for the long debated anomalous pressure behaviour of the superconducting critical temperature, T c. In this study we performed synchrotron X-ray diffraction (ID27, ESRF) during room T compression of bP up to 30 GPa in Diamond Anvil Cell (DAC) in the presence of He, H2, N2 and Daphne Oil 7474. Our data demonstrated that the p-sc structure is an intrinsic feature of P, independent from the pressure transmitting media. Furthermore, we derived the EOS's of A17, A7 and p-sc phases and demonstrated the first order mechanism of the A7 to p-sc transition. Highlighting the structural relations between A7 and p-sc, here we finally solved the apparent contradictions from previous literature bringing order to the sequence of HP A7 layered structures in group 15 elements [2,5]. Acknowledgements: Thanks are expressed to EC through the European Research Council (ERC) for funding the project PHOSFUN "Phosphorene functionalization: a new platform for advanced multifunctional materials" (Grant Agreement No. 670173) through an ERC Advanced Grant. References: [1] M. Batmunkh et al., Adv. Mater. 28, 8586 (2016) [2] H. Katzke et al., Phys. Rev. B, 2008, 77, 024109 [3] D. Scelta et al., Angew. Chem. Int. Ed. 56, 14135 (2017) [4] K. T. Chan et al., Phys. Rev. B 88, 064517 (2013) [5] D. Scelta et al., submitted (2018)

Black phosphorus was compressed at room temperature across the A17, A7 and simple‐cubic phases up to 30 GPa, using a diamond anvil cell and He as pressure transmitting medium. Synchrotron X‐ray diffraction showed the persistence of two previously unreported peaks related to the A7 structure in the pressure range of the simple‐cubic phase. The Rietveld refinement of the data demonstrates the occurrence of a two‐step mechanism for the A7 to simple‐cubic phase transition, indicating the existence of an intermediate pseudo simple‐cubic structure. From a chemical point of view this study represents a deep insight on the mechanism of interlayer bond formation during the transformation from the layered A7 to the non‐layered simple‐cubic phase of phosphorus, opening new perspectives for the design, synthesis and stabilization of phosphorene‐based systems. As superconductivity is concerned, a new experimental evidence to explain the anomalous pressure behavior of Tc in phosphorus below 30 GPa is provided.

An efficient loading technique has been developed for flammable, toxic, or explosive gases which can be condensed at liquid nitrogen temperature and ambient pressure in membrane diamond anvil cells (DACs). This cryogenic technique consists in a deposition of small quantities of the desired gas directly into the sample chamber. The deposition is performed using a capillary that reaches the space between the diamond anvils. The DAC is kept under inert gas overpressure during the whole process, in order to avoid contamination from atmospheric O2, CO2, and H2O. This technique provides significant advantages over standard cryo-loading and gas-loading when the condensation of dangerous samples at liquid nitrogen temperature raises safety concerns because it allows dealing with minimum quantities of condensed gases. The whole procedure is particularly fast and efficient. The "spray-loading" has been successfully used in our laboratory to load several samples including acetylene, ammonia, ethylene, and carbon dioxide/water or red phosphorus/NH3 mixtures.

The high pressure structural and reactive beahvior of graphene oxide (GO) in the presence of Ar, N2, and NH3 was studied in diamond anvil cells (DAC) by X-ray diffraction (XRD) and vibrational spectroscopy (FTIR and Raman), with the purpose of investigating the use of pressure for N-doping and functionalization of GO in high-density conditions. The pressure evolution of the interlayer d-spacing of GO during room temperature compression and decompression indicates the pressure-induced insertion of the selected systems between the GO layers and the stability of the GO layered structure at high pressure. Thermal and photoinduced reactivity was studied in GO with N2 and in GO with NH3 in different pressure conditions. The comparison of the infrared spectra of the recovered samples at ambient conditions with respect to the starting GO provides evidence for the occurrence of chemical reactivity of N2 and NH3 with GO, leading to N incorporation and GO functionalization, as also confirmed by the Raman spectra. The observed reactivity opens new perspectives for the high-pressure chemistry of GO and carbon-based nanostructured systems.

Recently, simple carbon based polymers have been synthesized at high pressures in silicalite, a pure SiO2 zeolite with a 3D system of mutually interconnected microchannels. These protocols permitted otherwise unstable polymers to be stabilized and protected from the atmosphere and to obtain an entirely novel class of nanocomposites with modified physical properties. In these 3-D systems, channel interconnection may prevent ideal, isolated polymer chains to be obtained. In this work, the :high pressure (5-10 GPa) synthesis of two archetypal, linear polymers polyacetylene (PA) and polycarbonyl (pCO) in the 1D channel system of the pure SiO2 zeolite ZSM-22 (TON) has been performed. The two resulting nano composites PA/TON and pCO/TON are organic/inorganic composite materials, which are good candidates as highly directional semiconductors and high energy density materials, respectively. The synthesis was performed in diamond anvil cells, starting from dense C2H2 and CO, confined in ZSM-22, and the nanocomposites were recovered at ambient conditions. The monomer polymerization was proven by IR spectroscopy and synchrotron X-ray diffraction measurements. DFT calculations were performed in order to obtain insight about the configurations of the 1D embedded polymers.

The spontaneous polymerization of fluid ethylene under high temperature and pressure conditions has been characterized by using FTIR absorption spectroscopy. The fluid has been isobarically heated at pressures ranging between 0.4 and 1.5 GPa by means of a resistively heated membrane diamond anvil cell. Besides tracing the instability boundary for spontaneous polymerization in the fluid, we have also measured the reaction kinetics at 1.5 GPa and temperatures ranging between 340 and 423 K. From the rate constants the activation energy of the overall reaction could be computed, information that joined to the molecularity of the initiation step provides some insight about the reaction mechanism. The polymers recovered from the different reactions have been characterized by FTIR, Raman, and X-ray diffraction revealing in all the cases a crystalline material of astonishing quality, likely related to the growth of the polymer in the hot fluid monomer.

No abstract available.

A study was conducted to demonstrate the synthesis of high pressure synthesis of all-transoid polycarbonyl [-(C=O)]n in a zeolite. The study also demonstrated the feasibility of inducing the self-assembly of dense CO in the spatially subnano-confined region of the channels of an electrically neutral, non-catalytic, hydrophobic, and all SiO2 zeolite silicalite. It was observed that the insertion of simple guest molecules, such as Ar and CO2 in the channels of this zeolite deactivated the pressure induced amorphization of the framework up to at least 25 GPa.