TY  - GEN
A1  - Spiekermann, Georg
A1  - Harder, M.
A1  - Gilmore, Keith
A1  - Zalden, Peter
A1  - Sahle, Christoph J.
A1  - Petitgirard, Sylvain
A1  - Wilke, Max
A1  - Biedermann, Nicole
A1  - Weis, Thomas
A1  - Morgenroth, Wolfgang
A1  - Tse, John S.
A1  - Kulik, E.
A1  - Nishiyama, Norimasa
A1  - Yavaş, Hasan
A1  - Sternemann, Christian
T1  - Persistent Octahedral Coordination in Amorphous GeO₂ Up to 100 GPa
by Kβ'' X-Ray Emission Spectroscopy
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - 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.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 699 
KW  - rutile-type
KW  - glass
KW  - crystalline
KW  - pressures
KW  - complexes
KW  - silicon
KW  - oxygen
KW  - SIO₂
KW  - MO
KW  - CU
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-427755
SN  - 1866-8372
IS  - 699
ER  - 
TY  - JOUR
A1  - Spiekermann, Georg
A1  - Harder, M.
A1  - Gilmore, Keith
A1  - Zalden, Peter
A1  - Sahle, Christoph J.
A1  - Petitgirard, Sylvain
A1  - Wilke, Max
A1  - Biedermann, Nicole
A1  - Weis, Thomas
A1  - Morgenroth, Wolfgang
A1  - Tse, John S.
A1  - Kulik, E.
A1  - Nishiyama, Norimasa
A1  - Yavaş, Hasan
A1  - Sternemann, Christian
T1  - Persistent Octahedral Coordination in Amorphous GeO₂ Up to 100 GPa
by Kβ'' X-Ray Emission Spectroscopy
JF  - Physical Review X
N2  - 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.
KW  - rutile-type
KW  - glass
KW  - crystalline
KW  - pressures
KW  - complexes
KW  - silicon
KW  - oxygen
KW  - SIO₂
KW  - MO
KW  - CU
Y1  - 2019
U6  - https://doi.org/10.1103/PhysRevX.9.011025
SN  - 2469-9926
SN  - 0556-2791
SN  - 1050-2947
SN  - 1094-1622
VL  - 9
IS  - 1
PB  - American Physical Society by the American Institute of Physics
CY  - Melville, NY
ER  - 
TY  - JOUR
A1  - Balk, Maria
A1  - Behl, Marc
A1  - Lendlein, Andreas
T1  - Actuators based on oligo[(epsilon-caprolactone)-co-glycolide] with accelerated hydrolytic degradation
JF  - MRS advances : a journal of the Materials Research Society (MRS)
N2  - 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.
KW  - actuation
KW  - shape memory
KW  - polymer
KW  - crystalline
Y1  - 2020
U6  - https://doi.org/10.1557/adv.2019.447
SN  - 2059-8521
VL  - 5
IS  - 12-13
SP  - 655
EP  - 666
PB  - Cambridge University Press
CY  - New York, NY
ER  -