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On the Crystal Structure of Isotactic cis-1,4-Poly(1,3-Pentadiene)
No full textA comparison between the crystal structure of isotactic cis-1,4-poly(1,3-pentadiene) previously predicted by molecular mechanics calculations and that successively determined by other authors by experimental data is reported. The agreement between the two structures is very good as far as the space group, the unit cell parameters and the conformation of the polymer chain are concerned. The mode of packing of the chains proposed in the experimental crystal structure is very similar to that found as relative minimum in the previous energy calculations. The coexistence, in different amounts, of these two modes of packing is suggested by the analysis of the simulated X-ray spectra and by the results of new energy calculations
Studies of Adjacent Re-Entry Folds of Chains of Syndiotactic 1,2-Poly(1,3-butadiene) by Molecular Mechanics Calculations
No full textThe mode of packing and the adjacent re-entry folds of chains of syndiotactic 1,2-poly(1,3-butadiene) have been studied by molecular mechanics calculations with the use of various sets of potential functions. The results of the packing analysis indicate that the crystal grows preferentially along the [100] and [110] directions. Models of fold have been built up on an infinite ab surface completely covered by adjacent re-entry folds in the (100) and (110) planes. The results of energy minimizations show that several almost isoenergetic folds, constituted by four monomeric units, can be realized in the (100) planes, while the fold in the (110) planes has higher energy. The calculated value of the work of fold is in satisfactory agreement with that derived by crystallization kinetics reported in literature
CRYSTAL STRUCTURE AND ADJACENT REENTRY FOLDS AF THE A FORM OF SYNDIOTACTIC POLYSTIRENE. CONFORMATIONAL AND PACKING ANALYSIS BY MOLECULAR MECHANISM
No full textModels of Adjacent Re-Entry Folds in the b Form of Syndiotactic Polystyrene. Conformational and Packing Analysis by Molecular Mechanics
No full textANALYSIS BY MOLECULAR MECHANICS OF THE CRYSTAL STRUCTURE AND MODELS OF ADJACENT RE-ENTRY FOLDS IN THE A FORM OF SYNDIOTACTIC POLYSTYRENE
No full textThe role of molecular mechanics in the prediction of the chain conformation of polymers in the crystalline state: Syndiotactic polymers
No full textANALISI DELL'IMPACCHETTAMENTO E MODELLI DI CHAIN FOLDING NEL 1,2-POLI(1,3-BUTADIENE) SINDIOTATTICO MEDIANTE L'USO DELLA MECCANICA MOLECOLARE
No full textMolecular mechanics calculations have been performed on syndiotactic l,2-poly(1,3 -butadiene) with the aim to give a prediction on the direction of crystal growth and to find models of adjacent re-entry fold. Packing energy calculations indicate that the best interactions are found between chains related by inversion centers and that the triplet of chains having the lowest energy is consistent with the hypothesis that the crystal growth is along the b direction of the unit cell. Conformational and packing energy calculations on models of chain folding give low-energy folds which connect the chains of the best triplet
The role of molecular mechanics in the prediction of the chain conformation of polymers in the crystalline state: Syndiotactic polymers
No full text
Models of Adjacent Re-Entry Folds in the b Form of Syndiotactic Polystyrene. Conformational and Packing Analysis by Molecular Mechanics
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