@article{SpiekermannHarderGilmoreetal.2019,
  author    = {Spiekermann, Georg and Harder, M. and Gilmore, Keith and Zalden, Peter and Sahle, Christoph J. and Petitgirard, Sylvain and Wilke, Max and Biedermann, Nicole and Weis, Thomas and Morgenroth, Wolfgang and Tse, John S. and Kulik, E. and Nishiyama, Norimasa and Yava{\c{s}}, Hasan and Sternemann, Christian},
  title     = {Persistent Octahedral Coordination in Amorphous GeO₂ Up to 100 GPa by Kβ'' X-Ray Emission Spectroscopy},
  series = {Physical Review X},
  volume    = {9},
  journal   = {Physical Review X},
  number    = {1},
  publisher = {American Physical Society by the American Institute of Physics},
  address   = {Melville, NY},
  issn      = {2469-9926},
  doi       = {10.1103/PhysRevX.9.011025},
  pages     = {10},
  year      = {2019},
  abstract  = {We measure valence-to-core x-ray emission spectra of compressed crystalline GeO₂ up to 56 GPa and of amorphous GeO₂ up to 100 GPa. In a novel approach, we extract the Ge coordination number and mean Ge-O distances from the emission energy and the intensity of the Kβ'' emission line. The spectra of high-pressure polymorphs are calculated using the Bethe-Salpeter equation. Trends observed in the experimental and calculated spectra are found to match only when utilizing an octahedral model. The results reveal persistent octahedral Ge coordination with increasing distortion, similar to the compaction mechanism in the sequence of octahedrally coordinated crystalline GeO₂ high-pressure polymorphs.},
  language  = {en}
}
@article{BalkBehlLendlein2020,
  author    = {Balk, Maria and Behl, Marc and Lendlein, Andreas},
  title     = {Actuators based on oligo[(epsilon-caprolactone)-co-glycolide] with accelerated hydrolytic degradation},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {5},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {12-13},
  publisher = {Cambridge University Press},
  address   = {New York, NY},
  issn      = {2059-8521},
  doi       = {10.1557/adv.2019.447},
  pages     = {655 -- 666},
  year      = {2020},
  abstract  = {Polyester-based shape-memory polymer actuators are multifunctional materials providing reversible macroscopic shape shifts as well as hydrolytic degradability. Here, the function-function interdependencies (between shape shifts and degradation behaviour) will determine actuation performance and its life time. In this work, glycolide units were incorporated in poly(epsilon-caprolactone) based actuator materials in order to achieve an accelerated hydrolytic degradation and to explore the function-function relationship. Three different oligo[(epsilon-caprolactone)-co-glycolide] copolymers (OCGs) with similar molecular weights (10.5 +/- 0.5 kg center dot mol(-1)) including a glycolide content of 8, 16, and 26 mol\% (ratio 1:1:1 wt\%) terminated with methacrylated moieties were crosslinked. The obtained actuators provided a broad melting transition in the range from 27 to 44 degrees C. The hydrolytic degradation of programmed OCG actuators (200\% of elongation) resulted in a reduction of sample mass to 51 wt\% within 21 days at pH = 7.4 and 40 degrees C. Degradation results in a decrease of T-m associated to the actuating units and increasing T-m associated to the skeleton forming units. The actuation capability decreased almost linear as function of time. After 11 days of hydrolytic degradation the shape-memory functionality was lost. Accordingly, a fast degradation behaviour as required, e.g., for actuator materials intended as implant material can be realized.},
  language  = {en}
}