@article{LuetzowWeigelLendlein2020,
  author    = {L{\"u}tzow, Karola and Weigel, Thomas and Lendlein, Andreas},
  title     = {Solvent-based fabrication method for magnetic, shape-memory nanocomposite foams},
  series = {MRS advances},
  volume    = {5},
  journal   = {MRS advances},
  number    = {14-15},
  publisher = {Cambridge Univ. Press},
  address   = {Cambridge},
  issn      = {2059-8521},
  doi       = {10.1557/adv.2019.422},
  pages     = {785 -- 795},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{BehlZhaoLendlein2020,
  author    = {Behl, Marc and Zhao, Qian and Lendlein, Andreas},
  title     = {Glucose-responsive shape-memory cryogels},
  series = {Journal of materials research : JMR},
  volume    = {35},
  journal   = {Journal of materials research : JMR},
  number    = {18},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {0884-2914},
  doi       = {10.1557/jmr.2020.204},
  pages     = {2396 -- 2404},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{BalkBehlLendlein2020,
  author    = {Balk, Maria and Behl, Marc and Lendlein, Andreas},
  title     = {Actuators based on oligo[(epsilon-caprolactone)-co-glycolide] with accelerated hydrolytic degradation},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {5},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {12-13},
  publisher = {Cambridge University Press},
  address   = {New York, NY},
  issn      = {2059-8521},
  doi       = {10.1557/adv.2019.447},
  pages     = {655 -- 666},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}