TY  - JOUR
A1  - Ghobadi, Ehsan
A1  - Heuchel, Matthias
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Atomistic simulation of the shape-memory effect in dry and water swollen Poly[(rac-lactide)-co-glycolide] and copolyester urethanes thereof
JF  - Macromolecular chemistry and physics
N2  - An atomistic molecular dynamics simulation approach is applied to model the influence of urethane linker units as well as the addition of water molecules on the simulated shape-memory properties of poly[(rac-lactide)-co-glycolide] (PLGA) and PLGA-based copolyester urethanes comprising different urethane linkers. The shape-memory performance of these amorphous packing models is explored in a simulated heating-deformation-cooling-heating procedure. Depending on the type of incorporated urethane linker, the mechanical properties of the dry copolyester urethanes are found to be significantly improved compared with PLGA, which can be attributed to the number of intermolecular hydrogen bonds between the urethane units. Good shape-memory properties are observed for all the modeled systems. In the dry state, the shape fixation is found to be improved by implementation of urethane units. After swelling of the copolymer models with water, which results in a reduction of their glass transition temperatures, the relaxation kinetics during unloading and shape recovery are found to be substantially accelerated.
KW  - molecular dynamics simulations
KW  - polyesterurethane
KW  - shape-memory effect
Y1  - 2014
U6  - https://doi.org/10.1002/macp.201300507
SN  - 1022-1352
SN  - 1521-3935
VL  - 215
IS  - 1
SP  - 65
EP  - 75
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - CHAP
A1  - Behl, Marc
A1  - Kratz, Karl
A1  - Nöchel, Ulrich
A1  - Sauter, Tilman
A1  - Lendlein, Andreas
T1  - Polymer networks capable of reversible shape-memory-effects
T2  - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS
Y1  - 2014
SN  - 0065-7727
VL  - 248
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schöne, Anne-Christin
A1  - Schulz, Burkhard
A1  - Richau, Klaus
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Characterization of Langmuir films prepared from copolyesterurethanes based on oligo(omega-pentadecalactone) and oligo(epsilon-caprolactone)segments
JF  - Macromolecular chemistry and physics
N2  - A series of multiblock copolymers (PDLCL) synthesized from oligo(omega-pentadecalactone) diol (OPDL) and oligo(epsilon-caprolactone) diol (OCL), which are linked by 2,2(4), 4-trimethyl-hexamethylene diisocyanate (TMDI), is investigated by the Langmuir monolayer technique at the air-water interface. Brewster angle microscopy (BAM) and spectroscopic ellipsometry are employed to characterize the polymer film morphologies in situ. PDLCL containing >= 40 wt% OCL segments form homogeneous Langmuir monofilms after spreading. The film elasticity modulus decreases with increasing amounts of OPDL segments in the copolymer. In contrast, the OCL-free polyesterurethane OPDL-TMDI cannot be spread to monomolecular films on the water surface properly, and movable slabs are observed by BAM even at low surface pressures. The results of the in situ morphological characterization clearly show that essential information concerning the reliability of Langmuir monolayer degradation (LMD) experiments cannot be obtained from the evaluation of the pi-A isotherms only. Consequently, in situ morphological characterization turns out to be indispensable for characterization of Langmuir layers before LMD experiments.
KW  - brewster angle microscopy
KW  - ellipsometry
KW  - Langmuir layers
KW  - morphology
KW  - polyesterurethanes
Y1  - 2014
U6  - https://doi.org/10.1002/macp.201400377
SN  - 1022-1352
SN  - 1521-3935
VL  - 215
IS  - 24
SP  - 2437
EP  - 2445
PB  - Wiley-VCH
CY  - Weinheim
ER  -