TY  - JOUR
A1  - Sauter, Tilman
A1  - Kratz, Karl
A1  - Heuchel, Matthias
A1  - Lendlein, Andreas
T1  - Fiber diameter as design parameter for tailoring the macroscopic shape-memory performance of electrospun meshes
JF  - Materials and design
N2  - Fibrous shape-memory polymer (SMP) scaffolds were investigated considering the fiber as basic microstructural feature. By reduction of the fiber diameter in randomly oriented electrospun polyetherurethane (PEU) meshes from the micro-to the nano-scale, we observed changes in the molecular orientation within the fibers and its impact on the structural and shape-memory performance. It was assumed that a spatial restriction by reduction of the fiber diameter increases molecular orientation along the orientation of the fiber. The stress-strain relation of random PEU scaffolds is initially determined by the 3D arrangement of the fibers and thus is independent of the molecular orientation. Increasing the molecular orientation with decreasing single fiber diameter in scaffolds composed of randomly arranged fibers did not alter the initial stiffness and peak stress but strongly influenced the elongation at break and the stress increase above the Yield point. Reduction of the single fiber diameter also distinctly improved the shape-memory performance of the scaffolds. Fibers with nanoscale diameters (< 100 nm) possessed an almost complete shape recovery, high recovery stresses and fast relaxation kinetics, while the shape fixity was found to decrease with decreasing fiber diameter. Hence, the fiber diameter is a relevant design parameter for SMP.
KW  - Nanofiber
KW  - Shape-memory polymer
KW  - Electrospinning
KW  - Function by design
KW  - Molecular orientation
Y1  - 2021
U6  - https://doi.org/10.1016/j.matdes.2021.109546
SN  - 1873-4197
VL  - 202
PB  - Elsevier
CY  - Amsterdam [u.a.]
ER  - 
TY  - JOUR
A1  - Cui, Qianling
A1  - Xia, Bihua
A1  - Mitzscherling, Steffen
A1  - Masic, Admir
A1  - Li, Lidong
A1  - Bargheer, Matias
A1  - Moehwald, Helmuth
T1  - Preparation of gold nanostars and their study in selective catalytic reactions
JF  - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects
N2  - In this work, gold nanostars (AuNSs) with size around 90 nm were prepared through an easy one-step method. They show excellent catalytic activity and large surface-enhanced Raman scattering (SERS) activity at the same time. Surprisingly, they exhibited different catalytic performance on the reduction of aromatic nitro compounds with different substituents on the para position. To understand such a difference, the SERS spectra were recorded, showing that the molecular orientation of reactants on the gold surface were different. We anticipate that this research will help to understand the relationship of the molecular orientation with the catalytic activity of gold nanoparticles.
KW  - Nanoparticles
KW  - Gold
KW  - Catalytic reaction
KW  - Surface enhanced Raman scattering (SERS)
KW  - Molecular orientation
Y1  - 2015
U6  - https://doi.org/10.1016/j.colsurfa.2014.10.028
SN  - 0927-7757
SN  - 1873-4359
VL  - 465
SP  - 20
EP  - 25
PB  - Elsevier
CY  - Amsterdam
ER  -