TY  - JOUR
A1  - Lützow, Karola
A1  - Weigel, Thomas
A1  - Lendlein, Andreas
T1  - Solvent-based fabrication method for magnetic, shape-memory nanocomposite foams
JF  - MRS advances
N2  - This paper presents shape-memory foams that can be temporarily fixed in their compressed state and be expanded on demand. Highly porous, nanocomposite foams were prepared from a solution of polyetherurethane with suspended nanoparticles (mean aggregate size 90 nm) which have an iron(III) oxide core with a silica shell. The polymer solution with suspended nanoparticles was cooled down to -20 degrees C in a two-stage process, which was followed by freeze-drying. The average pore size increases with decreasing concentration of nanoparticles from 158 mu m to 230 mu m while the foam porosity remained constant. After fixation of a temporary form of the nanocomposite foams, shape recovery can be triggered either by heat or by exposure to an alternating magnetic field. Compressed foams showed a recovery rate of up to 76 +/- 4% in a thermochamber at 80 degrees C, and a slightly lower recovery rate of up to 65 +/- 4% in a magnetic field.
KW  - composite
KW  - foam
KW  - polymer
KW  - magnetic
KW  - shape memory
Y1  - 2020
U6  - https://doi.org/10.1557/adv.2019.422
SN  - 2059-8521
VL  - 5
IS  - 14-15
SP  - 785
EP  - 795
PB  - Cambridge Univ. Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Behl, Marc
A1  - Zhao, Qian
A1  - Lendlein, Andreas
T1  - Glucose-responsive shape-memory cryogels
JF  - Journal of materials research : JMR
N2  - Boronic ester bonds can be reversibly formed between phenylboronic acid (PBA) and triol moieties. Here, we aim at a glucose-induced shape-memory effect by implementing such bonds as temporary netpoints, which are cleavable by glucose and by minimizing the volume change upon stimulation by a porous cryogel structure. The polymer system consisted of a semi-interpenetrating network (semi-IPN) architecture, in which the triol moieties were part of the permanent network and the PBA moieties were located in the linear polymer diffused into the semi-IPN. In an alkaline medium (pH = 10), the swelling ratio was approximately 35, independent of C-glu varied between 0 and 300 mg/dL. In bending experiments, shape fixity R-f approximate to 80% and shape recovery R-r approximate to 100% from five programming/recovery cycles could be determined. R-r was a function of C-glu in the range from 0 to 300 mg/dL, which accords with the fluctuation range of C-glu in human blood. In this way, the shape-memory hydrogels could play a role in future diabetes treatment options.
KW  - shape memory
KW  - polymer
KW  - porosity
Y1  - 2020
U6  - https://doi.org/10.1557/jmr.2020.204
SN  - 0884-2914
SN  - 2044-5326
VL  - 35
IS  - 18
SP  - 2396
EP  - 2404
PB  - Springer
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Balk, Maria
A1  - Behl, Marc
A1  - Lendlein, Andreas
T1  - Actuators based on oligo[(epsilon-caprolactone)-co-glycolide] with accelerated hydrolytic degradation
JF  - MRS advances : a journal of the Materials Research Society (MRS)
N2  - Polyester-based shape-memory polymer actuators are multifunctional materials providing reversible macroscopic shape shifts as well as hydrolytic degradability. Here, the function-function interdependencies (between shape shifts and degradation behaviour) will determine actuation performance and its life time. In this work, glycolide units were incorporated in poly(epsilon-caprolactone) based actuator materials in order to achieve an accelerated hydrolytic degradation and to explore the function-function relationship. Three different oligo[(epsilon-caprolactone)-co-glycolide] copolymers (OCGs) with similar molecular weights (10.5 +/- 0.5 kg center dot mol(-1)) including a glycolide content of 8, 16, and 26 mol% (ratio 1:1:1 wt%) terminated with methacrylated moieties were crosslinked. The obtained actuators provided a broad melting transition in the range from 27 to 44 degrees C. The hydrolytic degradation of programmed OCG actuators (200% of elongation) resulted in a reduction of sample mass to 51 wt% within 21 days at pH = 7.4 and 40 degrees C. Degradation results in a decrease of T-m associated to the actuating units and increasing T-m associated to the skeleton forming units. The actuation capability decreased almost linear as function of time. After 11 days of hydrolytic degradation the shape-memory functionality was lost. Accordingly, a fast degradation behaviour as required, e.g., for actuator materials intended as implant material can be realized.
KW  - actuation
KW  - shape memory
KW  - polymer
KW  - crystalline
Y1  - 2020
U6  - https://doi.org/10.1557/adv.2019.447
SN  - 2059-8521
VL  - 5
IS  - 12-13
SP  - 655
EP  - 666
PB  - Cambridge University Press
CY  - New York, NY
ER  -