@article{IlnytskyiNeherSaphiannikova2011,
  author    = {Ilnytskyi, Jaroslav M. and Neher, Dieter and Saphiannikova, Marina},
  title     = {Opposite photo-induced deformations in azobenzene-containing polymers with different molecular architecture molecular dynamics study},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {135},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.3614499},
  pages     = {12},
  year      = {2011},
  abstract  = {Photo-induced deformations in azobenzene-containing polymers (azo-polymers) are central to a number of applications, such as optical storage and fabrication of diffractive elements. The microscopic nature of the underlying opto-mechanical coupling is yet not clear. In this study, we address the experimental finding that the scenario of the effects depends on molecular architecture of the used azo-polymer. Typically, opposite deformations in respect to the direction of light polarization are observed for liquid crystalline and amorphous azo-polymers. In this study, we undertake molecular dynamics simulations of two different models that mimic these two types of azo-polymers. We employ hybrid force field modeling and consider only trans-isomers of azobenzene, represented as Gay-Berne sites. The effect of illumination on the orientation of the chromophores is considered on the level of orientational hole burning and emphasis is given to the resulting deformation of the polymer matrix. We reproduce deformations of opposite sign for the two models being considered here and discuss the relevant microscopic mechanisms in both cases.},
  language  = {en}
}
@article{IlnytskyiSaphiannikovaNeheretal.2012,
  author    = {Ilnytskyi, Jaroslav M. and Saphiannikova, Marina and Neher, Dieter and Allen, Michael P.},
  title     = {Modelling elasticity and memory effects in liquid crystalline elastomers by molecular dynamics simulations},
  series = {Soft matter},
  volume    = {8},
  journal   = {Soft matter},
  number    = {43},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1744-683X},
  doi       = {10.1039/c2sm26499d},
  pages     = {11123 -- 11134},
  year      = {2012},
  abstract  = {We performed molecular dynamics simulations of a liquid crystal elastomer of side-chain architecture. The network is formed from a melt of 28 molecules each having a backbone of 100 hydrocarbon monomers, to which 50 side chains are attached in a syndiotactic way. Crosslinking is performed in the smectic A phase. We observe an increase of the smectic-isotropic phase transition temperature of about 5 degrees as compared to the uncrosslinked melt. Memory effects in liquid crystalline order and in sample shape are well reproduced when the elastomer is driven through the smectic-isotropic transition. Above this transition, in the isotropic phase, the polydomain smectic phase is induced by a uniaxial load. Below the transition, in a monodomain smectic A phase, both experimentally observed effects of homogeneous director reorientation and stripe formation are reproduced when the sample is stretched along the director. When the load is applied perpendicularly to the director, the sample demonstrates reversible deformation with no change of liquid crystalline order, indicating elasticity of the two-dimensional network of polymer layers.},
  language  = {en}
}