@article{FolikumahBehlLendlein2021,
  author    = {Folikumah, Makafui Yao and Behl, Marc and Lendlein, Andreas},
  title     = {Thiol-Thioester exchange reactions in precursors enable pH-triggered hydrogel formation},
  series = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences},
  volume    = {22},
  journal   = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences},
  number    = {5},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1525-7797},
  doi       = {10.1021/acs.biomac.0c01690},
  pages     = {1875 -- 1884},
  year      = {2021},
  abstract  = {Bio-interactive hydrogel formation in situ requires sensory capabilities toward physiologically relevant stimuli. Here, we report on pH-controlled in situ hydrogel formation relying on latent cross-linkers, which transform from pH sensors to reactive molecules. In particular, thiopeptolide/thio-depsipeptides were capable of pH-sensitive thiol-thioester exchange reactions to yield a,co-dithiols, which react with maleimide-functionalized multi-arm polyethylene glycol to polymer networks. Their water solubility and diffusibility qualify thiol/thioester-containing peptide mimetics as sensory precursors to drive in situ localized hydrogel formation with potential applications in tissue regeneration such as treatment of inflamed tissues of the urinary tract.},
  language  = {en}
}
@article{MachatschekHeuchelLendlein2021,
  author    = {Machatschek, Rainhard Gabriel and Heuchel, Matthias and Lendlein, Andreas},
  title     = {Thin-layer studies on surface functionalization of polyetherimide},
  series = {Journal of materials research : JMR / Materials Research Society},
  volume    = {37},
  journal   = {Journal of materials research : JMR / Materials Research Society},
  number    = {1},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {0884-2914},
  doi       = {10.1557/s43578-021-00339-7},
  pages     = {67 -- 76},
  year      = {2021},
  abstract  = {Among the high-performance and engineering polymers, polyimides and the closely related polyetherimide (PEI) stand out by their capability to react with nucleophiles under relatively mild conditions. By targeting the phthalimide groups in the chain backbone, post-functionalization offers a pathway to adjust surface properties such as hydrophilicity, solvent resistance, and porosity. Here, we use ultrathin PEI films on a Langmuir trough as a model system to investigate the surface functionalization with ethylene diamine and tetrakis(4-aminophenyl)porphyrin as multivalent nucleophiles. By means of AFM, Raman spectroscopy, and interfacial rheology, we show that hydrolysis enhances the chemical and mechanical stability of ultrathin films and allows for the formation of EDC/NHS-activated esters. Direct amidation of PEI was achieved in the presence of a Lewis acid catalyst, resulting in free amine groups rather than cross-linking. When comparing amidation with hydrolysis, we find a greater influence of the latter on material properties.},
  language  = {en}
}
@article{NeffeLoewenbergJulichGruneretal.2021,
  author    = {Neffe, Axel T. and L{\"o}wenberg, Candy and Julich-Gruner, Konstanze K. and Behl, Marc and Lendlein, Andreas},
  title     = {Thermally-induced shape-memory behavior of degradable gelatin-based networks},
  series = {International journal of molecular sciences},
  volume    = {22},
  journal   = {International journal of molecular sciences},
  number    = {11},
  publisher = {Molecular Diversity Preservation International},
  address   = {Basel},
  issn      = {1422-0067},
  doi       = {10.3390/ijms22115892},
  pages     = {15},
  year      = {2021},
  abstract  = {Shape-memory hydrogels (SMH) are multifunctional, actively-moving polymers of interest in biomedicine. In loosely crosslinked polymer networks, gelatin chains may form triple helices, which can act as temporary net points in SMH, depending on the presence of salts. Here, we show programming and initiation of the shape-memory effect of such networks based on a thermomechanical process compatible with the physiological environment. The SMH were synthesized by reaction of glycidylmethacrylated gelatin with oligo(ethylene glycol) (OEG) alpha,omega-dithiols of varying crosslinker length and amount. Triple helicalization of gelatin chains is shown directly by wide-angle X-ray scattering and indirectly via the mechanical behavior at different temperatures. The ability to form triple helices increased with the molar mass of the crosslinker. Hydrogels had storage moduli of 0.27-23 kPa and Young's moduli of 215-360 kPa at 4 degrees C. The hydrogels were hydrolytically degradable, with full degradation to water-soluble products within one week at 37 degrees C and pH = 7.4. A thermally-induced shape-memory effect is demonstrated in bending as well as in compression tests, in which shape recovery with excellent shape-recovery rates R-r close to 100\% were observed. In the future, the material presented here could be applied, e.g., as self-anchoring devices mechanically resembling the extracellular matrix.},
  language  = {en}
}
@article{NieWangXuetal.2021,
  author    = {Nie, Yan and Wang, Weiwei and Xu, Xun and Ma, Nan and Lendlein, Andreas},
  title     = {The response of human induced pluripotent stem cells to cyclic temperature changes explored by BIO-AFM},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {31},
  publisher = {Springer},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00110-4},
  pages     = {745 -- 749},
  year      = {2021},
  abstract  = {Human induced pluripotent stem cells (hiPSCs) are highly sensitive to extrinsic physical and biochemical signals from their extracellular microenvironments. In this study, we analyzed the effect of cyclic temperature changes on hiPSCs behaviors, especially by means of scanning force microscopy (BIO-AFM). The alternation in cellular mechanics, as well as the secretion and pattern of deposition of extracellular matrix (ECM) protein in hiPSCs were evaluated. The arrangement of the actin cytoskeleton changed with the variation of the temperature. The rearranged cytoskeleton architecture led to the subsequent changes in cell mechanics (Young's modulus of hiPSCs). With the exposure to the cyclic cold stimuli, an increase in the average surface roughness (Ra) and roughness mean square (RMS) was detected. This observation might be at least in part due to the upregulated secretion of Laminin alpha 5 during repeated temporary cooling. The expression of pluripotent markers, NANOG and SOX2, was not impaired in hiPSCs, when exposed to the cyclic cold stimuli for 24 h. Our findings provide an insight into the effect of temperature on the hiPSC behaviors, which may contribute to a better understanding of the application of locally controlled therapeutic hypothermia.},
  language  = {en}
}
@article{FriessLendleinWischke2021,
  author    = {Frieß, Fabian and Lendlein, Andreas and Wischke, Christian},
  title     = {Switching microobjects from low to high aspect ratios using a shape-memory effect},
  series = {Soft matter},
  volume    = {17},
  journal   = {Soft matter},
  number    = {41},
  publisher = {Royal Society of Chemistry},
  address   = {London},
  issn      = {1744-6848},
  doi       = {10.1039/d1sm00947h},
  pages     = {9326 -- 9331},
  year      = {2021},
  abstract  = {Spherical particles from shape-memory polymers (SMP) can be stretched to ellipsoids with high aspect ratio (AR) and temporarily stabilized. They can switch back to low AR upon thermal stimulation. Here, the creation of an alternative shape-switching capability of particles from low to high AR is introduced, where a SMP matrix from polyvinyl alcohol (PVA) is used to create crosslinked high AR particles and to program the embedded micrometer-sized particles from a second SMP (oligo(epsilon-caprolactone) micronetworks, MN) with a low switching temperature T-sw. This programming proceeds through shape-recovery of the PVA matrix, from which the MN are harvested by PVA matrix dissolution. The use of a dissolvable SMP matrix may be a general strategy to efficiently create systems with complex moving capabilities.},
  language  = {en}
}
@article{TungSunWangetal.2021,
  author    = {Tung, Wing Tai and Sun, Xianlei and Wang, Weiwei and Xu, Xun and Ma, Nan and Lendlein, Andreas},
  title     = {Structure, mechanical properties and degradation behavior of electrospun PEEU fiber meshes and films},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {10},
  publisher = {Springer Nature Switzerland AG},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-020-00001-0},
  pages     = {276 -- 282},
  year      = {2021},
  abstract  = {The capability of a degradable implant to provide mechanical support depends on its degradation behavior. Hydrolytic degradation was studied for a polyesteretherurethane (PEEU70), which consists of poly(p-dioxanone) (PPDO) and poly(epsilon-caprolactone) (PCL) segments with a weight ratio of 70:30 linked by diurethane junction units. PEEU70 samples prepared in the form of meshes with average fiber diameters of 1.5 mu m (mesh1.5) and 1.2 mu m (mesh1.2), and films were sterilized and incubated in PBS at 37 degrees C with 5 vol\% CO2 supply for 1 to 6 weeks. Degradation features, such as cracks or wrinkles, became apparent from week 4 for all samples. Mass loss was found to be 11 wt\%, 6 wt\%, and 4 wt\% for mesh1.2, mesh1.5, and films at week 6. The elongation at break decreased to under 20\% in two weeks for mesh1.2. In case of the other two samples, this level of degradation was achieved after 4 weeks. The weight average molecular weight of both PEEU70 mesh and film samples decreased to below 30 kg/mol when elongation at break dropped below 20\%. The time period of sustained mechanical stability of PEEU70-based meshes depends on the fiber diameter and molecular weight.},
  language  = {en}
}
@article{NeffeIzraylitHommesSchattmannetal.2021,
  author    = {Neffe, Axel T. and Izraylit, Victor and Hommes-Schattmann, Paul J. and Lendlein, Andreas},
  title     = {Soft, formstable (Co)polyester blend elastomers},
  series = {Nanomaterials : open access journal},
  volume    = {11},
  journal   = {Nanomaterials : open access journal},
  number    = {6},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2079-4991},
  doi       = {10.3390/nano11061472},
  pages     = {18},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{FriessLendleinWischke2021,
  author    = {Friess, Fabian and Lendlein, Andreas and Wischke, Christian},
  title     = {Size control of shape switchable micronetworks by fast two-step microfluidic templating},
  series = {Journal of materials research},
  volume    = {36},
  journal   = {Journal of materials research},
  number    = {16},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {0884-2914},
  doi       = {10.1557/s43578-021-00295-2},
  pages     = {3248 -- 3257},
  year      = {2021},
  abstract  = {Shape-memory polymer micronetworks (MN) are micrometer-sized objects that can switch their outer shape upon external command.This study aims to scale MN sizes to the low micrometer range at very narrow size distributions. In a two-step microfluidic strategy, the specific design of coaxial class capillary devices allowed stabilizing the thread of the dispersed phase to efficiently produce precursor particles in the tip-streaming regime at rates up to similar to 170 kHz and final sizes down to 4 mu m. In a subsequent melt-based microfluidic photocrosslinking of the methacrylate-functionalized oligo(epsilon-caprolactone) precursor material, MN could be produced without particle aggregation. A comprehensive analysis of MN properties illustrated successful crosslinking, semi-crystalline morphology, and a shape-switching functionality for all investigated MN sizes (4, 6, 9, 12, 22 mu m). Such functional micronetworks tailored to and below the dimension of cells can enable future applications in technology and medicine like controlling cell interaction.},
  language  = {en}
}
@article{LendleinHeuchel2021,
  author    = {Lendlein, Andreas and Heuchel, Matthias},
  title     = {Shape-memory polymers designed in view of thermomechanical energy storage and conversion systems},
  series = {ACS central science},
  volume    = {7},
  journal   = {ACS central science},
  number    = {10},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {2374-7951},
  doi       = {10.1021/acscentsci.1c01032},
  pages     = {1599 -- 1601},
  year      = {2021},
  language  = {en}
}
@article{FolikumahBehlLendlein2021,
  author    = {Folikumah, Makafui Y. and Behl, Marc and Lendlein, Andreas},
  title     = {Reaction behaviour of peptide-based single thiol-thioesters exchange reaction substrate in the presence of externally added thiols},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6859},
  doi       = {10.1557/s43579-021-00041-z},
  pages     = {402 -- 410},
  year      = {2021},
  abstract  = {Identification of patterns in chemical reaction pathways aids in the effective design of molecules for specific applications. Here, we report on model reactions with a water-soluble single thiol-thioester exchange (TTE) reaction substrate, which was designed taking in view biological and medical applications. This substrate consists of the thio-depsipeptide, Ac-Pro-Leu-Gly-SLeu-Leu-Gly-NEtSH (TDP) and does not yield foul-smelling thiol exchange products when compared with aromatic thiol containing single TTE substrates. TDP generates an alpha,omega-dithiol crosslinker in situ in a 'pseudo intramolecular' TTE. Competitive intermolecular TTE of TDP with externally added "basic" thiols increased the crosslinker concentration whilst "acidic" thiols decreased its concentration. TDP could potentially enable in situ bioconjugation and crosslinking applications.},
  language  = {en}
}
@article{DengWangXuetal.2021,
  author    = {Deng, Zijun and Wang, Weiwei and Xu, Xun and Ma, Nan and Lendlein, Andreas},
  title     = {Polydopamine-based biofunctional substrate coating promotes mesenchymal stem cell migration},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {31},
  publisher = {Springer Nature Switzerland AG},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00091-4},
  pages     = {739 -- 744},
  year      = {2021},
  abstract  = {Rapid migration of mesenchymal stem cells (MSCs) on device surfaces could support in vivo tissue integration and might facilitate in vitro organoid formation. Here, polydopamine (PDA) is explored as a biofunctional coating to effectively promote MSC motility. It is hypothesized that PDA stimulates fibronectin deposition and in this way enhances integrin-mediated migration capability. The random and directional cell migration was investigated by time-lapse microscopy and gap closure assay respectively, and analysed with softwares as computational tools. A higher amount of deposited fibronectin was observed on PDA substrate, compared to the non-coated substrate. The integrin beta 1 activation and focal adhesion kinase (FAK) phosphorylation at Y397 were enhanced on PDA substrate, but the F-actin cytoskeleton was not altered, suggesting MSC migration on PDA was regulated by integrin initiated FAK signalling. This study strengthens the biofunctionality of PDA coating for regulating stem cells and offering a way of facilitating tissue integration of devices.},
  language  = {en}
}
@article{BehlBalkMansfeldetal.2021,
  author    = {Behl, Marc and Balk, Maria and Mansfeld, Ulrich and Lendlein, Andreas},
  title     = {Phase morphology of multiblock copolymers differing in sequence of blocks},
  series = {Macromolecular materials and engineering},
  volume    = {306},
  journal   = {Macromolecular materials and engineering},
  number    = {3},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1439-2054},
  doi       = {10.1002/mame.202000672},
  pages     = {9},
  year      = {2021},
  abstract  = {The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. It is hypothesized that a strictly alternating sequence should impact phase segregation. A library of well-defined MBC obtained by coupling oligo(epsilon-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification results in strictly alternating (MBCalt) or random (MBCran) MBC. The three different series has a weight average molecular weight (M-w) of 65 000, 165 000, and 168 000 g mol(-1) for MBCalt and 80 500, 100 000, and 147 600 g mol(-1) for MBCran. When the chain length of OCL building blocks is increased, the tendency for phase segregation is facilitated, which is attributed to the decrease in chain mobility within the MBC. Furthermore, it is found that the phase segregation disturbs the crystallization by causing heterogeneities in the semi-crystalline alignment, which is attributed to an increase of the disorder of the OCL semi-crystalline alignment.},
  language  = {en}
}
@article{XuNieWangetal.2021,
  author    = {Xu, Xun and Nie, Yan and Wang, Weiwei and Ma, Nan and Lendlein, Andreas},
  title     = {Periodic thermomechanical modulation of toll-like receptor expression and distribution in mesenchymal stromal cells},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6859},
  doi       = {10.1557/s43579-021-00049-5},
  pages     = {425 -- 431},
  year      = {2021},
  abstract  = {Toll-like receptor (TLR) can trigger an immune response against virus including SARS-CoV-2. TLR expression/distribution is varying in mesenchymal stromal cells (MSCs) depending on their culture environments. Here, to explore the effect of periodic thermomechanical cues on TLRs, thermally controlled shape-memory polymer sheets with programmable actuation capacity were created. The proportion of MSCs expressing SARS-CoV-2-associated TLRs was increased upon stimulation. The TLR4/7 colocalization was promoted and retained in the endoplasmic reticula. The TLR redistribution was driven by myosin-mediated F-actin assembly. These results highlight the potential of boosting the immunity for combating COVID-19 via thermomechanical preconditioning of MSCs.},
  language  = {en}
}
@article{FarhanBehlKratzetal.2021,
  author    = {Farhan, Muhammad and Behl, Marc and Kratz, Karl and Lendlein, Andreas},
  title     = {Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6859},
  doi       = {10.1557/s43579-021-00058-4},
  pages     = {476 -- 482},
  year      = {2021},
  abstract  = {Active fibers can serve as artificial muscles in robotics or components of smart textiles. Here, we present an origami hand robot, where single fibers control the reversible movement of the fingers. A recovery/contracting force of 0.2 N with a work capacity of 0.175 kJ kg(-1) was observed in crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, which could enable the bending movement of the fingers by contraction upon heating. The reversible opening of the fingers was attributed to a combination of elastic recovery force of the origami structure and crystallization-induced elongation of the fibers upon cooling.},
  language  = {en}
}
@article{IzraylitHeuchelKratzetal.2021,
  author    = {Izraylit, Victor and Heuchel, Matthias and Kratz, Karl and Lendlein, Andreas},
  title     = {Non-woven shape-memory polymer blend actuators},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {33},
  publisher = {Springer Nature Switzerland AG},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00063-8},
  pages     = {781 -- 785},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{ZhangRešetičBehletal.2021,
  author    = {Zhang, Pengfei and Rešetič, Andraž and Behl, Marc and Lendlein, Andreas},
  title     = {Multifunctionality in polymer networks by dynamic of coordination bonds},
  series = {Macromolecular chemistry and physics},
  volume    = {222},
  journal   = {Macromolecular chemistry and physics},
  number    = {3},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1521-3935},
  doi       = {10.1002/macp.202000394},
  pages     = {11},
  year      = {2021},
  abstract  = {The need for multifunctional materials is driven by emerging technologies and innovations, such as in the field of soft robotics and tactile or haptic systems, where minimizing the number of operational components is not only desirable, but can also be essential for realizing such devices. This study report on designing a multifunctional soft polymer material that can address a number of operating requirements such as solvent resistance, reshaping ability, self-healing capability, fluorescence stimuli-responsivity, and anisotropic structural functions. The numerous functional abilities are associated to rhodium(I)-phosphine coordination bonds, which in a polymer network act with their dynamic and non-covalently bonded nature as multifunctional crosslinks. Reversible aggregation of coordination bonds leads to changes in fluorescence emission intensity that responds to chemical or mechanical stimuli. The fast dynamics and diffusion of rhodium-phosphine ions across and through contacting areas of the material provide for reshaping and self-healing abilities that can be further exploited for assembly of multiple pieces into complex forms, all without any loss to material-sensing capabilities.},
  language  = {en}
}
@article{ZhouXuMaetal.2021,
  author    = {Zhou, Shuo and Xu, Xun and Ma, Nan and Jung, Friedrich and Lendlein, Andreas},
  title     = {Influence of sterilization conditions on sulfate-functionalized polyGGE},
  series = {Clinical hemorheology and microcirculation : blood flow and vessels},
  volume    = {79},
  journal   = {Clinical hemorheology and microcirculation : blood flow and vessels},
  number    = {4},
  publisher = {IOS Press},
  address   = {Amsterdam},
  issn      = {1386-0291},
  doi       = {10.3233/CH-211241},
  pages     = {597 -- 608},
  year      = {2021},
  abstract  = {Sulfated biomolecules are known to influence numerous biological processes in all living organisms. Particularly, they contribute to prevent and inhibit the hypercoagulation condition. The failure of polymeric implants and blood contacting devices is often related to hypercoagulation and microbial contamination. Here, bioactive sulfated biomacromolecules are mimicked by sulfation of poly(glycerol glycidyl ether) (polyGGE) films. Autoclaving, gamma-ray irradiation and ethylene oxide (EtO) gas sterilization techniques were applied to functionalized materials. The sulfate group density and hydrophilicity of sulfated polymers were decreased while chain mobility and thermal degradation were enhanced post autoclaving when compared to those after EtO sterilization. These results suggest that a quality control after sterilization is mandatory to ensure the amount and functionality of functionalized groups are retained.},
  language  = {en}
}
@article{BehlBalkLuetzowetal.2021,
  author    = {Behl, Marc and Balk, Maria and L{\"u}tzow, Karola and Lendlein, Andreas},
  title     = {Impact of block sequence on the phase morphology of multiblock copolymers obtained by high-throughput robotic synthesis},
  series = {European polymer journal : EPJ},
  volume    = {143},
  journal   = {European polymer journal : EPJ},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0014-3057},
  doi       = {10.1016/j.eurpolymj.2020.110207},
  pages     = {9},
  year      = {2021},
  abstract  = {The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. We hypothesized that a strictly alternating sequence should favour phase segregation and in this way the elastic properties. A library of well-defined MBCs composed of two different hydrophobic, semi-crystalline blocks providing domains with well-separated melting temperatures (T(m)s) were synthesized from the same type of precursor building blocks as strictly alternating (MBCsalt) or random (MBCsran) MBCs and compared. Three different series of MBCsalt or MBCsran were synthesized by high-throughput synthesis by coupling oligo(e-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification in which the molar ratio of the reaction partners was slightly adjusted. Maximum of weight average molecular weight (M-w) were 65,000 g center dot mol(-1), 165,000 g center dot mol(-1), and 168,000 g center dot mol(-1) for MBCsalt and 80,500 g center dot mol(-1), 100,000 g center dot mol(-1), and 147,600 g center dot mol(-1) for MBCsran. When Mw increased, a decrease of both Tms associated to the melting of the OCL and OTHF domains was observed for all MBCs. T-m (OTHF) of MBCsran was always higher than Tm (OTHF) of MBCsalt, which was attributed to a better phase segregation. In addition, the elongation at break of MBCsalt was almost half as high when compared to MBCsran. In this way this study elucidates role of the block length and sequence structure in MBCs and enables a quantitative discussion of the structure-function relationship when two semi-crystalline block segments are utilized for the design of block copolymers.},
  language  = {en}
}
@article{MachatschekHeuchelLendlein2021,
  author    = {Machatschek, Rainhard Gabriel and Heuchel, Matthias and Lendlein, Andreas},
  title     = {Hydrolytic stability of polyetherimide investigated in ultrathin films},
  series = {Journal of materials research : JMR / Materials Research Society},
  volume    = {36},
  journal   = {Journal of materials research : JMR / Materials Research Society},
  number    = {14},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {0884-2914},
  doi       = {10.1557/s43578-021-00267-6},
  pages     = {2987 -- 2994},
  year      = {2021},
  abstract  = {Increasing the surface hydrophilicity of polyetherimide (PEI) through partial hydrolysis of the imide groups while maintaining the length of the main-chain was explored for adjusting its function in biomedical and membrane applications. The outcome of the polymer analogous reaction, i.e., the degree of ring opening and chain cleavage, is difficult to address in bulk and microstructured systems, as these changes only occur at the interface. Here, the reaction was studied at the air-water interface using the Langmuir technique, assisted by atomic force microscopy and vibrational spectroscopy. Slow PEI hydrolysis sets in at pH > 12. At pH = 14, the ring opening is nearly instantaneous. Reduction of the layer viscosity with time at pH = 14 suggested moderate chain cleavage. No hydrolysis was observed at pH = 1. Hydrolyzed PEI films had a much more cohesive structure, suggesting that the nanoporous morphology of PEI can be tuned via hydrolysis.},
  language  = {en}
}
@article{NeffeLoewenbergLendlein2021,
  author    = {Neffe, Axel T. and L{\"o}wenberg, Candy and Lendlein, Andreas},
  title     = {Hydrogel networks by aliphatic dithiol Michael addition to glycidylmethacrylated gelatin},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {33},
  publisher = {Springer Nature Switzerland AG},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00136-8},
  pages     = {796 -- 800},
  year      = {2021},
  abstract  = {Functionalization of gelatin with glycidylmethacrylate (GMA-gelatin) enables network formation employing the double bond, so that the reaction is orthogonal to the inherent functional groups in the biomacromolecule. Here, network formation by crosslinking of GMA-gelatin with hexane 1,6-dithiol or nonane 1,9-dithiol to tailor properties and enable a shape-memory effect is shown by H-1 NMR and FT-IR spectroscopy. Hydrogel swelling (460-1900 vol\%) and mechanical properties (Young's modulus E = 59-512 kPa, elongation at break epsilon(b) = 44-127\%) depended on the molecular composition of the networks and temperature. Increased crosslinker length, thiol:methacrylate molar ratio, and precursor concentrations led to denser networks. Change of properties with temperature suggested adoption of triple helices by gelatin chains, forming physical netpoints at lower temperatures (< 20 degrees C). However, the limited freedom of the gelatin chains to move allowed only a minimal extent of triple helices formation, as it became apparent from the related signal in wide-angle X-ray scattering and the thermal transition associated to triple helices in some networks by DSC. The presented strategy is likely transferable to other biomacromolecules, and the results suggest that too short crosslinkers may result in a significant amount of grafting rather than network formation.},
  language  = {en}
}
@article{XuNieWangetal.2021,
  author    = {Xu, Xun and Nie, Yan and Wang, Weiwei and Ullah, Imran and Tung, Wing Tai and Ma, Nan and Lendlein, Andreas},
  title     = {Generation of 2.5D lung bud organoids from human induced pluripotent stem cells},
  series = {Clinical hemorheology and microcirculation : blood flow and vessels},
  volume    = {79},
  journal   = {Clinical hemorheology and microcirculation : blood flow and vessels},
  number    = {1},
  publisher = {IOS Press},
  address   = {Amsterdam},
  issn      = {1386-0291},
  doi       = {10.3233/CH-219111},
  pages     = {217 -- 230},
  year      = {2021},
  abstract  = {Human induced pluripotent stem cells (hiPSCs) are a promising cell source to generate the patient-specific lung organoid given their superior differentiation potential. However, the current 3D cell culture approach is tedious and time-consuming with a low success rate and high batch-to-batch variability. Here, we explored the establishment of lung bud organoids by systematically adjusting the initial confluence levels and homogeneity of cell distribution. The efficiency of single cell seeding and clump seeding was compared. Instead of the traditional 3D culture, we established a 2.5D organoid culture to enable the direct monitoring of the internal structure via microscopy. It was found that the cell confluence and distribution prior to induction were two key parameters, which strongly affected hiPSC differentiation trajectories. Lung bud organoids with positive expression of NKX 2.1, in a single-cell seeding group with homogeneously distributed hiPSCs at 70\% confluence (SC 70\% hom) or a clump seeding group with heterogeneously distributed cells at 90\% confluence (CL 90\% het), can be observed as early as 9 days post induction. These results suggest that a successful lung bud organoid formation with single-cell seeding of hiPSCs requires a moderate confluence and homogeneous distribution of cells, while high confluence would be a prominent factor to promote the lung organoid formation when seeding hiPSCs as clumps. 2.5D organoids generated with defined culture conditions could become a simple, efficient, and valuable tool facilitating drug screening, disease modeling and personalized medicine.},
  language  = {en}
}
@article{SauterKratzHeucheletal.2021,
  author    = {Sauter, Tilman and Kratz, Karl and Heuchel, Matthias and Lendlein, Andreas},
  title     = {Fiber diameter as design parameter for tailoring the macroscopic shape-memory performance of electrospun meshes},
  series = {Materials and design},
  volume    = {202},
  journal   = {Materials and design},
  publisher = {Elsevier},
  address   = {Amsterdam [u.a.]},
  issn      = {1873-4197},
  doi       = {10.1016/j.matdes.2021.109546},
  pages     = {10},
  year      = {2021},
  abstract  = {Fibrous shape-memory polymer (SMP) scaffolds were investigated considering the fiber as basic microstructural feature. By reduction of the fiber diameter in randomly oriented electrospun polyetherurethane (PEU) meshes from the micro-to the nano-scale, we observed changes in the molecular orientation within the fibers and its impact on the structural and shape-memory performance. It was assumed that a spatial restriction by reduction of the fiber diameter increases molecular orientation along the orientation of the fiber. The stress-strain relation of random PEU scaffolds is initially determined by the 3D arrangement of the fibers and thus is independent of the molecular orientation. Increasing the molecular orientation with decreasing single fiber diameter in scaffolds composed of randomly arranged fibers did not alter the initial stiffness and peak stress but strongly influenced the elongation at break and the stress increase above the Yield point. Reduction of the single fiber diameter also distinctly improved the shape-memory performance of the scaffolds. Fibers with nanoscale diameters (< 100 nm) possessed an almost complete shape recovery, high recovery stresses and fast relaxation kinetics, while the shape fixity was found to decrease with decreasing fiber diameter. Hence, the fiber diameter is a relevant design parameter for SMP.},
  language  = {en}
}
@article{NeffeZhangHommesSchattmannetal.2021,
  author    = {Neffe, Axel T. and Zhang, Quanchao and Hommes-Schattmann, Paul J. and Lendlein, Andreas},
  title     = {Ethylene oxide sterilization of electrospun poly(L-lactide)/poly(D-lactide) core/shell nanofibers},
  series = {MRS advances},
  volume    = {6},
  journal   = {MRS advances},
  number    = {33},
  publisher = {Springer},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00058-5},
  pages     = {786 -- 789},
  year      = {2021},
  abstract  = {The application of polymers in medicine requires sterilization while retaining material structure and properties. This demands detailed analysis, which we show exemplarily for the sterilization of PLLA/PDLA core-shell nanofibers with ethylene oxide (EtO). The electrospun patch was exposed to EtO gas (6 vol\% in CO2, 1.7 bar) for 3 h at 45 degrees C and 75\% rel. humidity, followed by degassing under pressure/vacuum cycles for 12 h. GC-MS analysis showed that no residual EtO was retained. Fiber diameters (similar to 520 +/- 130 nm) of the patches remained constant as observed by electron microscopy. Young's modulus slightly increased and the elongation at break slightly decreased, determined at 37 degrees C. No changes were detected in H-1-NMR spectra, in molar mass distribution (GPC) or in crystallinity measured for annealed samples with comparable thermal history (Wide Angle X-Ray Scattering). Altogether, EtO emerged as suitable sterilization method for polylactide nanofibers with core-shell morphology.},
  language  = {en}
}
@article{LauLiuMaieretal.2021,
  author    = {Lau, Skadi and Liu, Yue and Maier, Anna and Braune, Steffen and Gossen, Manfred and Neffe, Axel T. and Lendlein, Andreas},
  title     = {Establishment of an in vitro thrombogenicity test system with cyclic olefin copolymer substrate for endothelial layer formation},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {5},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6867},
  doi       = {10.1557/s43579-021-00072-6},
  pages     = {559 -- 567},
  year      = {2021},
  abstract  = {In vitro thrombogenicity test systems require co-cultivation of endothelial cells and platelets under blood flow-like conditions. Here, a commercially available perfusion system is explored using plasma-treated cyclic olefin copolymer (COC) as a substrate for the endothelial cell layer. COC was characterized prior to endothelialization and co-cultivation with platelets under static or flow conditions. COC exhibits a low roughness and a moderate hydrophilicity. Flow promoted endothelial cell growth and prevented platelet adherence. These findings show the suitability of COC as substrate and the importance of blood flow-like conditions for the assessment of the thrombogenic risk of drugs or cardiovascular implant materials.},
  language  = {en}
}
@article{BalkBehlNoecheletal.2021,
  author    = {Balk, Maria and Behl, Marc and N{\"o}chel, Ulrich and Lendlein, Andreas},
  title     = {Enzymatically triggered Jack-in-the-box-like hydrogels},
  series = {ACS applied materials \& interfaces / American Chemical Society},
  volume    = {13},
  journal   = {ACS applied materials \& interfaces / American Chemical Society},
  number    = {7},
  publisher = {American Chemical Society},
  address   = {Washington, DC},
  issn      = {1944-8244},
  doi       = {10.1021/acsami.1c00466},
  pages     = {8095 -- 8101},
  year      = {2021},
  abstract  = {Enzymes can support the synthesis or degradation of biomacromolecules in natural processes. Here, we demonstrate that enzymes can induce a macroscopic-directed movement of microstructured hydrogels following a mechanism that we call a "Jack-in-the-box" effect. The material's design is based on the formation of internal stresses induced by a deformation load on an architectured microscale, which are kinetically frozen by the generation of polyester locking domains, similar to a Jack-in-thebox toy (i.e., a compressed spring stabilized by a closed box lid). To induce the controlled macroscopic movement, the locking domains are equipped with enzyme-specific cleavable bonds (i.e., a box with a lock and key system). As a result of enzymatic reaction, a transformed shape is achieved by the release of internal stresses. There is an increase in entropy in combination with a swelling-supported stretching of polymer chains within the microarchitectured hydrogel (i.e., the encased clown pops-up with a pre-stressed movement when the box is unlocked). This utilization of an enzyme as a physiological stimulus may offer new approaches to create interactive and enzyme-specific materials for different applications such as an optical indicator of the enzyme's presence or actuators and sensors in biotechnology and in fermentation processes.},
  language  = {en}
}
@article{LauMaierBrauneetal.2021,
  author    = {Lau, Skadi and Maier, Anna and Braune, Steffen and Gossen, Manfred and Lendlein, Andreas},
  title     = {Effect of endothelial culture medium composition on platelet responses to polymeric biomaterials},
  series = {International journal of molecular sciences},
  volume    = {22},
  journal   = {International journal of molecular sciences},
  number    = {13},
  publisher = {Molecular Diversity Preservation International},
  address   = {Basel},
  issn      = {1422-0067},
  doi       = {10.3390/ijms22137006},
  pages     = {13},
  year      = {2021},
  abstract  = {Near-physiological in vitro thrombogenicity test systems for the evaluation of blood-contacting endothelialized biomaterials requires co-cultivation with platelets (PLT). However, the addition of PLT has led to unphysiological endothelial cell (EC) detachment in such in vitro systems. A possible cause for this phenomenon may be PLT activation triggered by the applied endothelial cell medium, which typically consists of basal medium (BM) and nine different supplements. To verify this hypothesis, the influence of BM and its supplements was systematically analyzed regarding PLT responses. For this, human platelet rich plasma (PRP) was mixed with BM, BM containing one of nine supplements, or with BM containing all supplements together. PLT adherence analysis was carried out in six-channel slides with plasma-treated cyclic olefin copolymer (COC) and poly(tetrafluoro ethylene) (PTFE, as a positive control) substrates as part of the six-channel slides in the absence of EC and under static conditions. PLT activation and aggregation were analyzed using light transmission aggregometry and flow cytometry (CD62P). Medium supplements had no effect on PLT activation and aggregation. In contrast, supplements differentially affected PLT adherence, however, in a polymer- and donor-dependent manner. Thus, the use of standard endothelial growth medium (BM + all supplements) maintains functionality of PLT under EC compatible conditions without masking the differences of PLT adherence on different polymeric substrates. These findings are important prerequisites for the establishment of a near-physiological in vitro thrombogenicity test system assessing polymer-based cardiovascular implant materials in contact with EC and PLT.},
  language  = {en}
}
@article{LiangBehlLendlein2021,
  author    = {Liang, Xiao and Behl, Marc and Lendlein, Andreas},
  title     = {Dihydroxy terminated teroligomers from morpholine-2,5-diones},
  series = {European polymer journal : EPJ},
  volume    = {143},
  journal   = {European polymer journal : EPJ},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0014-3057},
  doi       = {10.1016/j.eurpolymj.2020.110189},
  pages     = {9},
  year      = {2021},
  abstract  = {Oligodepsipeptides (ODPs) attract increasing attention as degradable materials in controlled drug delivery or as building blocks for nano-carriers. Their strong intermolecular interactions provide high stability. Tailoring the side groups of the amino acid repeating units to achieve a strong affinity to particular drugs allows a high drug-loading capacity. Here we describe synthesis and characterization of dihydroxy terminated teroligodepsipeptides (ter-ODPs) by ring-opening copolymerization (ROP) of three different morpholine-2,5-diones (MDs) in bulk in order to provide a set of teroligomers with structural variation for drug release or transfection. Ter-ODPs with equivalent co-monomer feed ratios were prepared as well as ter-ODPs, in which the co-monomer feed ratio was varied between 9 mol\% and 78 mol\%. Ter-ODPs were synthesized by ROP using 1,1,10,10-tetra-n-butyl-1,10-distanna-2,9,11,18-tetraoxa-5,6,14,15-tetrasulfur-cyclodecane (tin(IV) alkoxide) that was obtained by the reaction of dibutyl tin(II) oxide with 2-hydroxyethyl disulfide. The number average molecular weight (M-n) of ter-ODPs, determined by H-1 NMR and gel permeation chromatography (GPC), ranged between 4000 g center dot mol(-1) and 8600 g center dot mol(-1). Co-monomer compositions in ter-ODPs could be controlled by changing the feed ratio of co-monomers as observed by H-1 NMR spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The amount of remaining monomers as determined by H-1 NMR could be kept below 1 wt\%. Macrocycles as main sources of byproducts as determined from MALDI-TOF-MS measurements were significantly lower as compared to polymerization by Sn(Oct)(2). Glass-transition temperature (T-g) of ter-ODPs ranged between 59 degrees C and 70 degrees C.},
  language  = {en}
}
@article{LauGossenLendlein2021,
  author    = {Lau, Skadi and Gossen, Manfred and Lendlein, Andreas},
  title     = {Designing cardiovascular implants taking in view the endothelial basement membrane},
  series = {International journal of molecular sciences},
  volume    = {22},
  journal   = {International journal of molecular sciences},
  number    = {23},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {1422-0067},
  doi       = {10.3390/ijms222313120},
  pages     = {26},
  year      = {2021},
  abstract  = {Insufficient endothelialization of cardiovascular grafts is a major hurdle in vascular surgery and regenerative medicine, bearing a risk for early graft thrombosis. Neither of the numerous strategies pursued to solve these problems were conclusive. Endothelialization is regulated by the endothelial basement membrane (EBM), a highly specialized part of the vascular extracellular matrix. Thus, a detailed understanding of the structure-function interrelations of the EBM components is fundamental for designing biomimetic materials aiming to mimic EBM functions. In this review, a detailed description of the structure and functions of the EBM are provided, including the luminal and abluminal interactions with adjacent cell types, such as vascular smooth muscle cells. Moreover, in vivo as well as in vitro strategies to build or renew EBM are summarized and critically discussed. The spectrum of methods includes vessel decellularization and implant biofunctionalization strategies as well as tissue engineering-based approaches and bioprinting. Finally, the limitations of these methods are highlighted, and future directions are suggested to help improve future design strategies for EBM-inspired materials in the cardiovascular field.},
  language  = {en}
}
@article{BochoveGrijpmaLendleinetal.2021,
  author    = {Bochove, Bas van and Grijpma, Dirk W. and Lendlein, Andreas and Sepp{\"a}l{\"a}, Jukka},
  title     = {Designing advanced functional polymers for medicine},
  series = {European polymer journal : EPJ},
  volume    = {155},
  journal   = {European polymer journal : EPJ},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0014-3057},
  doi       = {10.1016/j.eurpolymj.2021.110573},
  pages     = {2},
  year      = {2021},
  language  = {en}
}
@article{SaretiaMachatschekLendlein2021,
  author    = {Saretia, Shivam and Machatschek, Rainhard Gabriel and Lendlein, Andreas},
  title     = {Degradation kinetics of oligo(ε-caprolactone) ultrathin films},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {33},
  publisher = {Springer Nature Switzerland AG},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00067-4},
  pages     = {790 -- 795},
  year      = {2021},
  abstract  = {The potential of using crystallinity as morphological parameter to control polyester degradation in acidic environments is explored in ultrathin films by Langmuir technique. Films of hydroxy or methacrylate end-capped oligo(epsilon-caprolactone) (OCL) are prepared at the air-water interface as a function of mean molecular area (MMA). The obtained amorphous, partially crystalline or highly crystalline ultrathin films of OCL are hydrolytically degraded at pH similar to 1.2 on water surface or on silicon surface as-transferred films. A high crystallinity reduces the hydrolytic degradation rate of the films on both water and solid surfaces. Different acceleration rates of hydrolytic degradation of semi-crystalline films are achieved either by crystals complete melting, partially melting, or by heating them below their melting temperatures. Semi-crystalline OCL films transferred via water onto a solid surface retain their crystalline morphology, degrade in a controlled manner, and are of interest as thermoswitchable coatings for cell substrates and medical devices.},
  language  = {en}
}
@article{IzraylitLiuTarazonaetal.2021,
  author    = {Izraylit, Victor and Liu, Yue and Tarazona, Natalia A. and Machatschek, Rainhard Gabriel and Lendlein, Andreas},
  title     = {Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {6},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6859},
  doi       = {10.1557/s43579-021-00107-y},
  pages     = {850 -- 855},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{LiangBehlLuetzowetal.2021,
  author    = {Liang, Xiao and Behl, Marc and L{\"u}tzow, Karola and Lendlein, Andreas},
  title     = {Cooligomers from morpholine-2,5-dione and para-dioxanone and catalyst complex SnOct(2)/2-hydroxyethyl sulfide},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {32},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00082-5},
  pages     = {764 -- 768},
  year      = {2021},
  abstract  = {Complexes from catalysts and initiator can be used to insert a specific number of additional chemical functional groups in (co)polymers prepared by ring-opening polymerization (ROP) of lactones. We report on the synthesis of cooligomers from sec-butyl-morpholine-2,5-dione (SBMD) and para-dioxanone (PDX) by ROP with varied feed ratios in the bulk using the catalyst complex SnOct(2)/2-hydroxyethyl sulfide. M-n of the cooligomers (determined by GPC) decreased with decreasing SBMD feed ratio from 4200 +/- 420 to 800 +/- 80 g mol(-1). When the feed ratio was reduced from 80 to 50 mol\% the molar ratio of SBMD of the cooligomers (determined by H-1-NMR) remained nearly unchanged between 81 and 86 mol\% and was attributed to a higher reactivity of SBMD. This assumption was confirmed by fractionation of GPC, in which an increase of SBMD with increasing molecular weight was observed. The catalyst/initiator system provides a high potential to create orthogonal building blocks by cleavage of the sulfide bond.},
  language  = {en}
}
@article{BaeckemoLiuLendlein2021,
  author    = {B{\"a}ckemo, Johan Dag Valentin and Liu, Yue and Lendlein, Andreas},
  title     = {Bio-inspired and computer-supported design of modulated shape changes in polymer materials},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6867},
  doi       = {10.1557/s43579-021-00056-6},
  pages     = {462 -- 469},
  year      = {2021},
  abstract  = {The Venus flytrap is a fascinating plant with a finely tuned mechanical bi-stable system, which can switch between mono- and bi-stability. Here, we combine geometrical design of compliant mechanics and the function of shape-memory polymers to enable switching between bi- and mono-stable states. Digital design and modelling using the Chained Beam Constraint Model forecasted two geometries, which were experimentally realized as structured films of cross-linked poly[ethylene-co-(vinyl acetate)] supported by digital manufacturing. Mechanical evaluation confirmed our predicted features. We demonstrated that a shape-memory effect could switch between bi- and mono-stability for the same construct, effectively imitating the Venus flytrap.},
  language  = {en}
}
@article{MachatschekSaretiaLendlein2021,
  author    = {Machatschek, Rainhard Gabriel and Saretia, Shivam and Lendlein, Andreas},
  title     = {Assessing the influence of temperature-memory creation on the degradation of copolyesterurethanes in ultrathin films},
  series = {Advanced materials interfaces},
  volume    = {8},
  journal   = {Advanced materials interfaces},
  number    = {6},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2196-7350},
  doi       = {10.1002/admi.202001926},
  pages     = {8},
  year      = {2021},
  abstract  = {Copolyesterurethanes (PDLCLs) based on oligo(epsilon-caprolactone) (OCL) and oligo(omega-pentadecalactone) (OPDL) segments are biodegradable thermoplastic temperature-memory polymers. The temperature-memory capability in these polymers with crystallizable control units is implemented by a thermomechanical programming process causing alterations in the crystallite arrangement and chain organization. These morphological changes can potentially affect degradation. Initial observations on the macroscopic level inspire the hypothesis that switching of the controlling units causes an accelerated degradation of the material, resulting in programmable degradation by sequential coupling of functions. Hence, detailed degradation studies on Langmuir films of a PDLCL with 40 wt\% OPDL content are carried out under enzymatic catalysis. The temperature-memory creation procedure is mimicked by compression at different temperatures. The evolution of the chain organization and mechanical properties during the degradation process is investigated by means of polarization-modulated infrared reflection absorption spectroscopy, interfacial rheology and to some extend by X-ray reflectivity. The experiments on PDLCL Langmuir films imply that degradability is not enhanced by thermal switching, as the former depends on the temperature during cold programming. Nevertheless, the thin film experiments show that the leaching of OCL segments does not induce further crystallization of the OPDL segments, which is beneficial for a controlled and predictable degradation.},
  language  = {en}
}