Initiation of the radical cation polymerization of propene has been observed following the selective ionization of benzene in the gas phase by resonance two-photon ionization−high-pressure mass spectrometry (R2PI−HPMS) and by selected ion flow tube (SIFT) techniques. In this system, the aromatic initiator (C6H6) has an ionization potential (IP) between those of the reactant's monomer (C3H6) and its covalent dimer (C6H12), i.e, IP(C3H6) > IP(C6H6) > IP(C6H12). Therefore, direct charge transfer from C6H6 •+ to C3H6 is not observed due to the large endothermicity of 0.48 eV, and only the adduct C6H6 •+(C3H6) is formed. However, coupled reactions of charge transfer with covalent condensation are observed according to the overall process C6H6 •+ + 2C3H6 → C6H12 •+ + C6H6, which results in the formation of a hexene product ion, C6H12 •+. The formation of this ion can make the overall process of charge transfer and covalent condensation significantly exothermic. At higher concentrations of propene, the reaction products are the propene oligomers (C3H6) n •+ with n = 2−7 and the adduct series C6H6 •+(C3H6) n with n ≤ 6. The significance of the coupled reactions is that the overall process leads exclusively to the formation of the condensation product (C3H6) n •+ and avoids other competitive channels in the ion/molecule reactions of propene. Gas-phase nominal second-order rate coefficients for the overall reaction into both channels are in the range of (1−3) × 10-12 cm3 s-1. The rate coefficients into both channels, especially for the formation of the C6H12 •+ dimer, have large negative temperature dependencies. Consistent with the gas-phase results, the intracluster reactions of C6H6 •+ produced selectively by R2PI of mixed benzene/propene clusters also do not form the monomer ion C3H6 •+ but form higher propene clusters (C3H6) n •+ that contain at least the C6H12 •+ hexene ion. The similarity of the reaction mechanisms in the gas phase and in preformed clusters suggests that the mechanism may also apply in the condensed phase in common aromatic solvents such as benzene and toluene.

No abstract

We report the results of joint beam expansion and thermochemical studies of clusters containing ionic hydrogen bonds between water (W), trimethylamine (T), and methanol (M). The cluster distributions H+W,T, show magic numbers for (n, m) = (1, 3), (2,4), and (3, 5), where the solvent shells are completed by blocking groups around a H30+ core ion. Larger clusters with n > 3 show deviation from the n + 2 rule, suggesting structural changes. In H+M,T, clusters, the H+M,T2 sequence is always more predominant than the H+M,,T series independent of expansion or ionization conditions. In the three component clusters, the predominant series is H+W,MmT,+2. The cluster distributions from the beam expansion are quite sensitive to the clusters' binding energies as measured by high-pressure mass spectrometry. Even though ionization involves large excess energies, the observed cluster distributions show sensitivity to thermochemical differences as small as 1-3 kcal/mol.

No abstract

As a closed space, the functional requirements of the tunnel pavement are very different from ordinary pavements. In recent years, with the increase of requirements for tunnel pavement safety, comfort and environmental friendliness, asphalt pavement has become more and more widely used in long tunnels, due to its low noise, low dust, easy maintenance, and good comfort. However, conventional tunnel asphalt pavements cause significant safety and environmental concerns. The innovative polyurethane thin overlay (PTO) has been developed for the maintenance of existing roads and constructing new roads. Based on the previous study, the concept of PTO may be a feasible and effective way to enrich the innovative functions of tunnel pavement. In this paper, the research aims to evaluate the functional properties of PTO, such as noise reduction, solar reflection and especially combustion properties. Conventional asphalt (Open-graded Friction Course (OGFC) and Stone Mastic Asphalt (SMA)) and concrete pavement materials were used as control materials. Compared with conventional tunnel pavement materials, significant improvements were observed in functional properties and environmental performance. Therefore, this innovative wearing layer can potentially provide pavements with new eco-friendly functions. This study provides a comprehensive analysis of these environmentally friendly materials, paving the way for the possible application in tunnels, as well as some other fields, such as race tracks in stadiums.