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Molecular dynamics simulation of glassy polymethylene (PM) plastic deformation is performed up to ɛ = 30% in uniaxial compression regime at a temperature of 50 K, which is ∼140 K below T g of the polymer. All atoms of PM chains are represented explisitly (all-atom model). Calculations were performed for two series of samples with different molecular mass distribution of chains: Samples have average degree of polymerization DP ≈ 212 with Mn ≈ 3000 and Mw ≈ 9500 (the first series) and DP ≈ 350, Mn ≈ 5000 and Mw ≈ 9500 (the second series). Each sample contains 12288 -CH2- monomeric units per computational sell. Nonaffine displacements of carbon atoms and conformational rearrangements in chains during deformation are visualized and analyzed. The transformation of relatively fragments of chains up to 16–20 monomer units length are basic structural units, non-conformational displacements of which controls plastic process. Relatively large nonaffine displacements are observed even in the range of low strains, which are usually interpreted as Hookean strains. In the range of yield tooth and steady plastic flow, the number of these displacements increases along with their amplitude. Conformational set of PM chains does not show a serious change during deformation. Analysis had shown that the number of conformational rearrangements of trans-gauche type in PM chains during deformation is small and such rearrangements do not play decisive role in the considered range of PM plasticity, even at ɛ > 15%, at the stage of the developed plastic flow.

A molecular-dynamics simulation of the low-temperature (∼100 K below T g) plastic deformation of glassy polymethylene (PM) was conducted. A model system consisting of 64 chains containing 100 CH2 groups (the united-atoms approach) in each computational cell with periodic boundary conditions was considered. The behavior of 32 such cells was considered. Each cell was subjected to an active isothermal uniaxial compression at a constant temperature of T def = 50 K to a strain of ɛ = 30%. An analysis showed that the inelastic deformation of glassy PM proceeded via nonaffine displacements (“gliding”) of chain fragments comprising 11–13 sites -CH2-. These displacements are correlated and directed mainly along chain axes. Only a small number of conformational rearrangements occur in chains during the deformation of the material. Conformational transitions add only small additional displacements to nonaffine atomic transformations. A free-volume analysis using Voronoi-Delaunay tessellation in the deformed polymer did not show its relation to local plastic rearrangements.

The molecular-dynamics simulation of the structure and molecular mobility of an individual macromolecule of a fourth-generation carbosilane dendrimer with terminal cyanobiphenyl groups in a highly diluted chloroform solution in the range 213–323 K is performed. Upon a change in temperature, the dendrimer undergoes structural rearrangement that depends on the ability of terminal segments to penetrate into the dendrimer. At temperatures close to the boiling point of the solvent, aliphatic spacers of terminal segments can penetrate deep into the dendrimer. As temperature decreases, the terminal segments are grouped only on the surface of the molecule; this leads to a 45% increase in the number of solvent molecules in the treelike part of the macromolecule. These results make it possible to give a new interpretation of temperature effects previously observed in NMR experiments for dilute solutions of these macromolecules.