TY  - JOUR
A1  - Ghobadi, Ehsan
A1  - Heuchel, Matthias
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Simulating the shape-Memory behavior of amorphous switching domains of Poly(L-lactide) by molecular dynamics
JF  - Macromolecular chemistry and physics
N2  - 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.
KW  - molecular modeling
KW  - polyesters
KW  - shape-memory properties
KW  - stimuli-sensitive polymers
KW  - thermomechanical properties
Y1  - 2013
U6  - https://doi.org/10.1002/macp.201200450
SN  - 1022-1352
VL  - 214
IS  - 11
SP  - 1273
EP  - 1283
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Rüder, Constantin
A1  - Sauter, Tilman
A1  - Kratz, Karl
A1  - Haase, Tobias
A1  - Peter, Jan
A1  - Jung, Friedrich
A1  - Lendlein, Andreas
A1  - Zohlnhöfer, Dietlind
T1  - Influence of fibre diameter and orientation of electrospun copolyetheresterurethanes on smooth muscle and endothelial cell behaviour
JF  - Clinical hemorheology and microcirculation : blood flow and vessels
N2  - Polymers exhibiting cell-selective effects represent an extensive research field with high relevance for biomedical applications e.g. in the cardiovascular field supporting re-endothelialization while suppressing smooth muscle cell overgrowth. Such an endothelial cell-selective effect could be recently demonstrated for a copolyetheresterurethane (PDC) containing biodegradable poly(p-dioxanone) and poly(epsilon-caprolactone) segments, which selectively enhanced the adhesion of human umbilical vein endothelial cells (HUVEC) while suppressing the attachment of smooth muscle cells (SMC).
 In this study we investigated the influence of the fibre orientation (random and aligned) and fibre diameter (2 mu m and 500 nm) of electrospun PDC scaffolds on the adhesion, proliferation and apoptosis of HUVEC and SMC.
 Adhesion, viability and proliferation of HUVEC was diminished when the fibre diameter was reduced to a submicron scale, while the orientation of the microfibres did only slightly influence the cellular behaviour. In contrast, a submicron fibre diameter improved SMC viability. In conclusion, PDC scaffolds with micron-sized single fibres could be promising candidate materials for cell-selective stent coatings.
KW  - Endothelialization
KW  - drug eluting stent
KW  - degradable polymer
KW  - electrospinning
KW  - cell selectivity
Y1  - 2013
U6  - https://doi.org/10.3233/CH-131787
SN  - 1386-0291
SN  - 1875-8622
VL  - 55
IS  - 4
SP  - 513
EP  - 522
PB  - IOS Press
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Sauter, Tilman
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Pore-size distribution controls shape-memory properties on the macro- and microscale of polymeric foams
JF  - Macromolecular chemistry and physics
N2  - Open porous foams with identical foam density but different pore-size distributions (bimodal or monomodal) are prepared from a shape-memory polyetherurethane (PEU) by thermally induced phase separation. The shape-memory effect of the two PEU foams is explored by cyclic thermomechanical compression tests and microstructural analysis. The obtained results reveal that the PEU foam with a bimodal pore-size distribution exhibits an increased shape-recovery under stress-free conditions, both on the macro- (foam level) as well as the microscale (pore level). While bimodal pore-size distributions induce microscale bending during compression, buckling occurs in foams with monomodal pore-size distributions, leading to both a reduced and delayed shape recovery.
KW  - microstructure
KW  - morphology
KW  - polymer foams
KW  - pore-size distribution
KW  - shape-memory polymers
Y1  - 2013
U6  - https://doi.org/10.1002/macp.201300062
SN  - 1022-1352
VL  - 214
IS  - 11
SP  - 1184
EP  - 1188
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - CHAP
A1  - Sauter, Tilman
A1  - Lützow, Karola
A1  - Schossig, Michael
A1  - Kosmella, Hans
A1  - Weigel, Thomas
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Pore morphology as structural parameter to tailor the shape-memory effect of polyuetherurethane foams
T2  - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS
Y1  - 2013
SN  - 0065-7727
VL  - 245
PB  - American Chemical Society
CY  - Washington
ER  -