@article{YanFangNoecheletal.2016,
  author    = {Yan, Wan and Fang, Liang and N{\"o}chel, Ulrich and Kratz, Karl and Lendlein, Andreas},
  title     = {Influence of programming strain rates on the shape-memory performance of semicrystalline multiblock copolymers},
  series = {Journal of polymer science : B, Polymer physics},
  volume    = {54},
  journal   = {Journal of polymer science : B, Polymer physics},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0887-6266},
  doi       = {10.1002/polb.24097},
  pages     = {1935 -- 1943},
  year      = {2016},
  abstract  = {Multiblock copolymers named PCL-PIBMD consisting of crystallizable poly(epsilon-caprolactone) segments and crystallizable poly[oligo(3S-iso-butylmorpholine-2,5-dione)] segments coupled by trimethyl hexamethylene diisocyanate provide a versatile molecular architecture for achieving shape-memory effects (SMEs) in polymers. The mechanical properties as well as the SME performance of PCL-PIBMD can be tailored by the variation of physical parameters during programming such as deformation strain or applied temperature protocols. In this study, we explored the influence of applying different strain rates during programming on the resulting nanostructure of PCL-PIBMD. Programming was conducted at 50 degrees C by elongation to epsilon(m)=50\% with strain rates of 1 or 10 or 50 mmmin(-1). The nanostructural changes were visualized by atomic force microscopy (AFM) measurements and investigated by in situ wide and small angle X-ray scattering experiments. With increasing the strain rate, a higher degree of orientation was observed in the amorphous domains. Simultaneously the strain-induced formation of new PIBMD crystals as well as the fragmentation of existing large PIBMD crystals occurred. The observed differences in shape fixity ratio and recovery stress of samples deformed with various strain rates can be attributed to their different nanostructures. The achieved findings can be relevant parameters for programming the shape-memory polymers with designed recovery forces. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1935-1943},
  language  = {en}
}
@article{ZhangSauterFangetal.2015,
  author    = {Zhang, Quanchao and Sauter, Tilman and Fang, Liang and Kratz, Karl and Lendlein, Andreas},
  title     = {Shape-Memory Capability of Copolyetheresterurethane Microparticles Prepared via Electrospraying},
  series = {Macromolecular materials and engineering},
  volume    = {300},
  journal   = {Macromolecular materials and engineering},
  number    = {5},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1438-7492},
  doi       = {10.1002/mame.201400267},
  pages     = {522 -- 530},
  year      = {2015},
  abstract  = {Multifunctional thermo-responsive and degradable microparticles exhibiting a shapememory effect (SME) have attracted widespread interest in biomedicine as switchable delivery vehicles or microactuators. In this work almost spherical solid microparticles with an average diameter of 3.9 +/- 0.9 mm are prepared via electrospraying of a copolyetheresterurethane named PDC, which is composed of crystallizable oligo(p-dioxanone) (OPDO) hard and oligo(e-caprolactone) (OCL) switching segments. The PDC microparticles are programmed via compression at different pressures and their shapememory capability is explored by off-line and online heating experiments. When a low programming pressure of 0.2 MPa is applied a pronounced thermally-induced shape-memory effect is achieved with a shape recovery ratio about 80\%, while a high programming pressure of 100 MPa resulted in a weak shape-memory performance. Finally, it is demonstrated that an array of PDC microparticles deposited on a polypropylene (PP) substrate can be successfully programmed into a smart temporary film, which disintegrates upon heating to 60 degrees C.},
  language  = {en}
}
@article{GhobadiHeuchelKratzetal.2013,
  author    = {Ghobadi, Ehsan and Heuchel, Matthias and Kratz, Karl and Lendlein, Andreas},
  title     = {Simulating the shape-Memory behavior of amorphous switching domains of Poly(L-lactide) by molecular dynamics},
  series = {Macromolecular chemistry and physics},
  volume    = {214},
  journal   = {Macromolecular chemistry and physics},
  number    = {11},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1022-1352},
  doi       = {10.1002/macp.201200450},
  pages     = {1273 -- 1283},
  year      = {2013},
  abstract  = {The thermally induced shape-memory effect of polymers is typically characterized by cyclic uniaxial thermomechanical tests. Here, a molecular-dynamics (MD) simulation approach of such a cyclic uniaxial thermomechanical test is presented for amorphous switching domains of poly(L-lactide) (PLLA). Uniaxial deformation of the constructed PLLA models is simulated with a Parinello-Rahman scheme, as well as a pragmatic geometrical approach. We are able to describe two subsequent test cycles using the presented simulation approach. The obtained simulated shape-memory properties in both test cycles are similar and independent of the applied deformation protocols. The simulated PLLA shows high shape fixity ratios (Rf 94\%), but only a moderate shape recovery ratio is obtained (Rr 30\%). Finally, the structural changes during the simulated test are characterized by analysis of the changes in the dihedral angle distributions.},
  language  = {en}
}