The conformers of α-serine were investigated by matrix-isolation IR spectroscopy combined with NIR laser irradiation. This method, aided by 2D correlation analysis, enabled unambiguously grouping the spectral lines to individual conformers. On the basis of comparison of at least nine experimentally observed vibrational transitions of each conformer with empirically scaled (SQM) and anharmonic (GVPT2) computed IR spectra, six conformers were identified. In addition, the presence of at least one more conformer in Ar matrix was proved, and a short-lived conformer with a half-life of (3.7 ± 0.5) × 10(3) s in N2 matrix was generated by NIR irradiation. The analysis of the NIR laser-induced conversions revealed that the excitation of the stretching overtone of both the side chain and the carboxylic OH groups can effectively promote conformational changes, but remarkably different paths were observed for the two kinds of excitations.

Lubricants are complex fluids consisting of a base oil and many different additives, and are used to control friction and wear between solid inorganic surfaces in relative motion. A review of recent work on molecular simulations of lubricants is given. It is shown that simulations can be used to uncover a lot of interesting behaviour, including additive adsorption, additive self-assembly, and a competition between the two. The specific examples to be discussed are: the adsorption of stearic acid and oleic acid in squalane on iron-oxide surfaces; the self-assembly of glycerol monooleate in bulk n-heptane; the adsorption and friction of glycerol monooleate in squalane on iron-oxide surfaces; and the conformations of functionalised copolymers in bulk n-heptane. The structures adopted by the additives can be correlated with the observed frictional properties, opening up the possibility of molecular-level design of new lubricants.

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The first observation of the higher-energy conformer of tribromoacetic acid (trans-TBAA) is reported. The conformer was produced in cryogenic matrices (Ar, Kr, and N) by in situ selective narrowband near-infrared excitation of the lower-energy cis-TBAA conformer and characterized both structurally and vibrationally. The novel trans-TBAA conformer is shown to spontaneously decay to the most stable cis-TBAA form in all studied matrix media, by tunneling, and the measured decay rates in the different matrices were compared with those of the trans conformers of other carboxylic acids in similar experimental conditions. In the N matrix, where trans-TBAA establishes a specific stabilizing intermolecular interaction with the host N molecules via its OH group and is about 11 times more stable than in rare gas matrices, the effect of changing the irradiation wavenumber within the 2νOH absorption profile was investigated in detail. An interesting phenomenon of matrix-site changing mediated by conformational conversion was observed in the N matrix: vibrational excitation of cis-TBAA in the 2νOH wavenumber range predominantly converts the molecules located in a specific "matrix site" into trans-TBAA; then, relaxation (by tunneling) of the produced higher-energy conformer back to the cis form populates almost exclusively another "matrix site." The experimental studies received support from quantum chemistry calculations, which allowed a detailed characterization of the relevant regions of the potential energy surface of the molecule and the detailed assignment of the infrared spectra of the two conformers in the various matrices.

The sizes and structures of isolated functionalised polymers in a hydrocarbon solvent are studied using atomistic molecular dynamics simulations and Monte Carlo simulations of coarse-grained chains. A specific functionalised polyethylene-polypropylene random copolymer in n-heptane is studied using atomistic simulations. The functional groups contain aromatic and polar groups, and 8 of them are distributed on an 8 kDa polymer backbone in several different ways. It is shown that the radius of gyration and the end-to-end distance depend sensitively on the functionalgroup distribution. A random distribution of functional groups gives the most compact polymer structure, but other distributions gives values up to 50% larger; the largest values are when the functional groups are split evenly between both ends of the polymer. This is shown to be due to the association of the polar, and hence solvophobic, functional groups. A coarse-grained bead-spring model is then studied that includes solvophilic beads (representing unfunctionalised units) and solvophobic beads (representing functionalised units). Monte Carlo simulations are used to survey functional-group concentration and distribution. The results show that the collapse of a polymer with increasing solvophobicity depends sensitively on the distribution of different beads. Form factors are presented for both the atomistic and coarse-grained models, and are analysed as if they were experimental scattering measurements. The apparent radii of gyration are in good agreement with those determined directly from simulation.