TY  - JOUR
A1  - Neffe, Axel T.
A1  - Izraylit, Victor
A1  - Hommes-Schattmann, Paul J.
A1  - Lendlein, Andreas
T1  - Soft, formstable (Co)polyester blend elastomers
JF  - Nanomaterials : open access journal
N2  - High crystallization rate and thermomechanical stability make polylactide stereocomplexes effective nanosized physical netpoints. Here, we address the need for soft, form-stable degradable elastomers for medical applications by designing such blends from (co)polyesters, whose mechanical properties are ruled by their nanodimensional architecture and which are applied as single components in implants. By careful controlling of the copolymer composition and sequence structure of poly[(L-lactide)-co-(epsilon-caprolactone)], it is possible to prepare hyperelastic polymer blends formed through stereocomplexation by adding poly(D-lactide) (PDLA). Low glass transition temperature T-g <= 0 degrees C of the mixed amorphous phase contributes to the low Young's modulus E. The formation of stereocomplexes is shown in DSC by melting transitions T-m > 190 degrees C and in WAXS by distinct scattering maxima at 2 theta = 12 degrees and 21 degrees. Tensile testing demonstrated that the blends are soft (E = 12-80 MPa) and show an excellent hyperelastic recovery R-rec = 66-85% while having high elongation at break epsilon(b) up to >1000%. These properties of the blends are attained only when the copolymer has 56-62 wt% lactide content, a weight average molar mass >140 kg center dot mol(-1), and number average lactide sequence length >= 4.8, while the blend is formed with a content of 5-10 wt% of PDLA. The devised strategy to identify a suitable copolymer for stereocomplexation and blend formation is transferable to further polymer systems and will support the development of thermoplastic elastomers suitable for medical applications.
KW  - thermoplastic elastomer
KW  - biomaterial
KW  - stereocomplexes
KW  - mechanical
KW  - properties
KW  - form stability
KW  - crystallinity
Y1  - 2021
U6  - https://doi.org/10.3390/nano11061472
SN  - 2079-4991
VL  - 11
IS  - 6
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Izraylit, Victor
A1  - Heuchel, Matthias
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Non-woven shape-memory polymer blend actuators
JF  - MRS advances : a journal of the Materials Research Society (MRS)
N2  - The hierarchical design approach provides various opportunities to adjust the structural performance of polymer materials. Electrospinning processing techniques give access to molecular orientation as a design parameter, which we consider here in view of the shape-memory actuation performance. The aim of this work is to investigate how the reversible strain epsilon'(rev) can be affected by a morphology change from a bulk material to an electrospun mesh. epsilon'(rev) could be increased from 5.5 +/- 0.5% to 15 +/- 1.8% for a blend from a multiblock copolymer with poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA) segments with oligo(D-lactide) (ODLA). This study demonstrates an effective design approach for enhancing soft actuator performance, which can be broadly applied in soft robotics and medicine.
Y1  - 2021
U6  - https://doi.org/10.1557/s43580-021-00063-8
SN  - 2059-8521
VL  - 6
IS  - 33
SP  - 781
EP  - 785
PB  - Springer Nature Switzerland AG
CY  - Cham
ER  - 
TY  - JOUR
A1  - Izraylit, Victor
A1  - Liu, Yue
A1  - Tarazona, Natalia A.
A1  - Machatschek, Rainhard Gabriel
A1  - Lendlein, Andreas
T1  - Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers
JF  - MRS communications / a publication of the Materials Research Society
N2  - Supporting the wound healing of soft tissues requires fixation devices becoming more elastic while degrading. To address this unmet need, we designed a blend of degradable multiblock copolymers, which is cross-linked by PLA stereocomplexation combining two soft segments differing substantially in their hydrolytic degradation rate. The degradation path and concomitant structural changes are predicted by Langmuir monolayer technique. The fast hydrolysis of one soft segment leads to a decrease of the total polymer mass at constant physical cross-linking density. The corresponding increase of the average spacing between the network nodes suggests the targeted increase of the blend's flexibility.
KW  - Degradable
KW  - In situ
KW  - Microstructure
KW  - Thin film
Y1  - 2021
U6  - https://doi.org/10.1557/s43579-021-00107-y
SN  - 2159-6859
SN  - 2159-6867
VL  - 11
IS  - 6
SP  - 850
EP  - 855
PB  - Springer
CY  - Berlin
ER  -