TY  - JOUR
A1  - Debsharma, Tapas
A1  - Behrendt, Felix Nicolas
A1  - Laschewsky, Andre
A1  - Schlaad, Helmut
T1  - Ring-opening metathesis polymerization of biomass-derived levoglucosenol
JF  - Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker
N2  - The readily available cellulose-derived bicyclic compound levoglucosenol was polymerized through ring-opening metathesis polymerization (ROMP) to yield polylevoglucosenol as a novel type of biomass-derived thermoplastic polyacetal, which, unlike polysaccharides, contains cyclic as well as linear segments in its main chain. High-molar-mass polyacetals with apparent weight-average molar masses of up to 100kgmol(-1) and dispersities of approximately 2 were produced despite the non-living/controlled character of the polymerization due to irreversible deactivation or termination of the catalyst/active chain ends. The resulting highly functionalized polyacetals are glassy in bulk with a glass transition temperature of around 100 degrees C. In analogy to polysaccharides, polylevoglucosenol degrades slowly in an acidic environment.
KW  - degradable polymers
KW  - metathesis
KW  - ring-opening polymerization
KW  - sustainable chemistry
KW  - thermoplastics
Y1  - 2019
U6  - https://doi.org/10.1002/anie.201814501
SN  - 1433-7851
SN  - 1521-3773
VL  - 58
IS  - 20
SP  - 6718
EP  - 6721
PB  - Wiley-VCH
CY  - Weinheim
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  -