TY  - JOUR
A1  - Saretia, Shivam
A1  - Machatschek, Rainhard Gabriel
A1  - Schulz, Burkhard
A1  - Lendlein, Andreas
T1  - Reversible 2D networks of oligo(epsilon-caprolactone) at the air-water interface
JF  - Biomedical Materials
N2  - Hydroxyl terminated oligo(epsilon-caprolactone) (OCL) monolayers were reversibly cross-linked forming two dimensional networks (2D) at the air-water interface. The equilibrium reaction with glyoxal as the cross-linker is pH-sensitive. Pronounced contraction in the area of the prepared 2DOCL films in dependence of surface pressure and time revealed the process of the reaction. Cross-linking inhibited crystallization and retarded enzymatic degradation of the OCLfilm. Altering the subphase pH led to a cleavage of the covalent acetal cross-links. The reversibility of the covalent acetal cross-links was proved by observing an identical isotherm as non-cross-linked sample. Besides as model systems, these customizable reversible OCL2D networks are intended for use as pHresponsive drug delivery systems or functionalized cell culture substrates.
KW  - poly(epsilon-caprolactone)
KW  - langmuir monolayer
KW  - two dimensional network
KW  - crystallization
KW  - cross-linking
Y1  - 2019
U6  - https://doi.org/10.1088/1748-605X/ab0cef
SN  - 1748-6041
SN  - 1748-605X
VL  - 14
IS  - 3
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Farhan, Muhammad
A1  - Rudolph, Tobias
A1  - Nöchel, Ulrich
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Extractable Free Polymer Chains Enhance Actuation Performance of Crystallizable Poly(epsilon-caprolactone) Networks and Enable Self-Healing
JF  - Polymers
N2  - Crosslinking of thermoplastics is a versatile method to create crystallizable polymer networks, which are of high interest for shape-memory actuators. Here, crosslinked poly(epsilon-caprolactone) thermosets (cPCLs) were prepared from linear starting material, whereby the amount of extractable polymer was varied. Fractions of 5-60 wt % of non-crosslinked polymer chains, which freely interpenetrate the crosslinked network, were achieved leading to differences in the resulting phase of the bulk material. This can be described as "sponge-like" with open or closed compartments depending on the amount of interpenetrating polymer. The crosslinking density and the average network chain length remained in a similar range for all network structures, while the theoretical accessible volume for reptation of the free polymer content is affected. This feature could influence or introduce new functions into the material created by thermomechanical treatment. The effect of interpenetrating PCL in cPCLs on the reversible actuation was analyzed by cyclic, uniaxial tensile tests. Here, high reversible strains of up to Delta epsilon = 24% showed the enhanced actuation performance of networks with a non-crosslinked PCL content of 30 wt % resulting from the crystal formation in the phase of the non-crosslinked PCL and co-crystallization with network structures. Additional functionalities are reprogrammability and self-healing capabilities for networks with high contents of extractable polymer enabling reusability and providing durable actuator materials.
KW  - shape-memory polymer actuators
KW  - soft actuators
KW  - self-healing
KW  - poly(epsilon-caprolactone)
KW  - thermoplastics
Y1  - 2018
U6  - https://doi.org/10.3390/polym10030255
SN  - 2073-4360
VL  - 10
IS  - 3
PB  - MDPI
CY  - Basel
ER  -