TY - THES A1 - Izraylit, Victor T1 - Reprogrammable and tunable actuation in multiblock copolymer blends T1 - Reprogrammierbare und abstimmbare Aktuation in Blenden von Multiblock Copolymeren N2 - Soft actuators have drawn significant attention due to their relevance for applications, such as artificial muscles in devices developed for medicine and robotics. Tuning their performance and expanding their functionality are frequently done by means of chemical modification. The introduction of structural elements rendering non-synthetic modification of the performance possible, as well as control over physical appearance and facilitating their recycling is a subject of a great interest in the field of smart materials. The primary aim of this thesis was to create a shape-memory polymeric actuator, where the capability for non-synthetic tuning of the actuation performance is combined with reprocessability. Physically cross-linked polymeric matrices provide a solid material platform, where the in situ processing methods can be employed for modification of the composition and morphology, resulting in the fine tuning of the related mechanical properties and shape-memory actuation capability. The morphological features, required for shape-memory polymeric actuators, namely two crystallisable domains and anchoring points for physical cross-links, were embedded into a multiblock copolymer with poly(ε-caprolactone) and poly(L-lactide) segments (PLLA-PCL). Here, the melting transition of PCL was bisected into the actuating and skeleton-forming units, while the cross-linking was introduced via PLA stereocomplexation in blends with oligomeric poly(D-lactide) (ODLA). PLLA segment number average length of 12-15 repeating units was experimentally defined to be capable of the PLA stereocomplexes formation, but not sufficient for the isotactic crystallisation. Multiblock structure and phase dilution broaden the PCL melting transition, facilitating its separation into two conditionally independent crystalline domains. Low molar mass of the PLA stereocomplex components and a multiblock structure enables processing and reprocessing of the PLLA-PCL / ODLA blends with common non-destructive techniques. The modularity of the PLLA-PCL structure and synthetic approach allows for independent tuning of the properties of its components. The designed material establishes a solid platform for non-synthetic tuning of thermomechanical and structural properties of thermoplastic elastomers. To evaluate the thermomechanical stability of the formed physical network, three criteria were appraised. As physical cross-links, PLA stereocomplexes have to be evenly distributed within the material matrix, their melting temperature shall not overlap with the thermal transitions of the PCL domains and they have to maintain the structural integrity within the strain ε ranges further applied in the shape-memory actuation experiments. Assigning PCL the function of the skeleton-forming and actuating units, and PLA stereocomplexes the role of physical netpoints, shape-memory actuation was realised in the PLLA-PCL / ODLA blends. Reversible strain of shape-memory actuation was found to be a function of PLA stereocomplex crystallinity, i.e. physical cross-linking density, with a maximum of 13.4 ± 1.5% at PLA stereocomplex content of 3.1 ± 0.3 wt%. In this way, shape-memory actuation can be tuned via adjusting the composition of the PLLA-PCL / ODLA blend. This makes the developed material a valuable asset in the production of cost-effective tunable soft polymeric actuators for the applications in medicine and soft robotics. N2 - Weiche Polymer-Aktuatoren haben, dank ihrer Bedeutung bei Anwendungen wie z.B. als künstliche Muskeln in Geräten oder in Medizin und Robotik, maßgeblich Aufmerksamkeit erregt. Das Einstellen ihrer Leistung und die Erweiterung ihrer Funktionalität werden oft mittels chemischer Modifizierung durchgeführt. Die Einführung struktureller Elemente, die durch nicht-synthetische Prozesse hervorgerufene Einstellung von Eigenschaften, sowie die Kontrolle der physikalischen Parameter und die Möglichkeit, das Material erneut zu verarbeiten, sind von besonderem Interesse für das Design von intelligenten Werkstoffen. Das Ziel dieser Doktorarbeit war es einen polymeren Formgedächtnis-Aktuator zu entwickeln, der die durch nicht-synthetische Prozesse hervorgerufene Einstellung der Aktuator Parameter mit erneuter Formgebung kombiniert. Physikalisch vernetzte Polymermatrizen stellen dafür eine solide Materialbasis dar, wobei in situ Verarbeitungsmethoden zum Ändern der Zusammensetzung und der Morphologie verwendet werden können. Die Folge davon ist eine präzise Einstellung der entsprechenden mechanischen Eigenschaften und der Formgedächtnis-Aktuator-Leistung. Die morphologischen Elemente, die für die polymeren Formgedächtnis-Aktuatoren benötig werden, nämlich zwei kristallisierbare Domänen und Verankerungspunkte für die physikalischen Cross-Links, wurden in einem Multiblock-Copolymer aus Poly(ε-Caprolakton) und Poly(L-Lactid) Segmenten (PLLA-PCL) integriert. Die Cross-Links wurden durch PLA-Stereokomplexe in Blends mit Poly(D-Lactid) Oligomer (ODLA) geformt. Um die thermomechanische Beständigkeit der hergestellten physikalischen Vernetzung einzuschätzen, wurden drei Kriterien bewertet. Die Erfüllung des morphologischen Kriteriums, gleichmäßige Verteilung innerhalb des Materials, wurde aus der Mikrophasenstruktur abgeleitet. Diese bestand aus einer kontinuierlichen PCL Phase und den isolierten PLA Domänen mit einem durchschnittlichen Domänenabstand von nm Maßstab. Die Schmelzübergänge von PLA Stereokomplexen und PCL überschnitten sich nicht, womit das thermische Kriterium erfüllt wurde. Die Gehalts- und Dehnungsbereiche der strukturelle Beständigkeit der PLA Stereokomplexe wurde in einer detaillierten Untersuchung der mechanischen Eigenschaften mittels Zug-, Dehnungsrückstellungs- und Spannungsrelaxationsversuchen definiert. Indem PCL die skelettbildende und die Aktuatorfunktion zugeordnet wurde, und die PLA Stereokomplexe die Rolle des physikalischen Netzwerks übernehmen, lassen sich in den PLLA-PCL / ODLA Polymerblends Formgedächtniseffekte ausführen. Des Weiteren wurde die Formgedächtnis-Aktuation ε′rev als eine Funktion des Gehalts an PLA Stereokomplex φc mit einem extremalen Charakter festgestellt, d.h. von der Dichte der physikalischen Cross-Links abhängt. Dadurch könnte ε′rev im PLLA-PCL / ODLA System mittels Variation der Zusammensetzung eingestellt werden. Dies verschafft dem entwickelten Polymermaterial ein wertvoller Vorteil bei der Herstellung von kosteffektiven, skalierbaren polymeren Formgedächtnis-Aktuatoren für Anwendungen in der Medizin und der Robotik. KW - Actuator KW - Shape-memory KW - Multiblock copolymer KW - Thermoplastic elastomer KW - Stereocomplex KW - Polymer physics KW - Polymer chemistry KW - Aktuator KW - Multiblock Copolymer KW - Polymerchemie KW - Polymerphysik KW - Formgedächtnis KW - Stereokomplex KW - thermoplastisches Elastomer Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-518434 ER - TY - JOUR A1 - Izraylit, Victor A1 - Gould, Oliver E. C. A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Investigating the phase-morphology of PLLA-PCL multiblock copolymer/PDLA blends cross-linked using stereocomplexation JF - MRS advances N2 - The macroscale function of multicomponent polymeric materials is dependent on their phase-morphology. Here, we investigate the morphological structure of a multiblock copolymer consisting of poly(L-lactide) and poly(epsilon-caprolactone) segments (PLLA-PCL), physically cross-linked by stereocomplexation with a low molecular weight poly(D-lactide) oligomer (PDLA). The effects of blend composition and PLLA-PCL molecular structure on the morphology are elucidated by AFM, TEM and SAXS. We identify the formation of a lattice pattern, composed of PLA domains within a PCL matrix, with an average domain spacing d0 = 12 - 19 nm. The size of the PLA domains were found to be proportional to the block length of the PCL segment of the copolymer and inversely proportional to the PDLA content of the blend. Changing the PLLA-PCL / PDLA ratio caused a shift in the melt transition Tm attributed to the PLA stereocomplex crystallites, indicating partial amorphous phase dilution of the PLA and PCL components within the semicrystalline material. By elucidating the phase structure and thermal character of multifunctional PLLA-PCL / PDLA blends, we illustrate how composition affects the internal structure and thermal properties of multicomponent polymeric materials. This study should facilitate the more effective incorporation of a variety of polymeric structural units capable of stimuli responsive phase transitions, where an understanding the phase-morphology of each component will enable the production of multifunctional soft-actuators with enhanced performance. KW - polymer KW - blend KW - nanostructure KW - morphology Y1 - 2020 U6 - https://doi.org/10.1557/adv.2019.465 SN - 2059-8521 VL - 5 IS - 14-15 SP - 699 EP - 707 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Izraylit, Victor A1 - Heuchel, Matthias A1 - Kratz, Karl A1 - Lendlein, Andreas T1 - Non-woven shape-memory polymer blend actuators JF - MRS advances : a journal of the Materials Research Society (MRS) N2 - 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. Y1 - 2021 U6 - https://doi.org/10.1557/s43580-021-00063-8 SN - 2059-8521 VL - 6 IS - 33 SP - 781 EP - 785 PB - Springer Nature Switzerland AG CY - Cham ER - TY - JOUR A1 - Izraylit, Victor A1 - Hommes-Schattmann, Paul J. A1 - Neffe, Axel T. A1 - Gould, Oliver E. C. A1 - Lendlein, Andreas T1 - Polyester urethane functionalizable through maleimide side-chains and cross-linkable by polylactide stereocomplexes JF - European polymer journal N2 - Sustainable multifunctional alternatives to fossil-derived materials, which can be functionalized and are degradable, can be envisioned by combining naturally derived starting materials with an established polymer design concept. Modularity and chemical flexibility of polyester urethanes (PEU) enable the combination of segments bearing functionalizable moieties and the tailoring of the mechanical and thermal properties. In this work, a PEU multiblock structure was synthesized from naturally derived L-lysine diisocyanate ethyl ester (LDI), poly(L-lactide) diol (PLLA) and N-(2,3-dihydroxypropyl)-maleimide (MID) in a one-step reaction. A maleimide side-chain (MID) provided a reactive site for the catalyst-free coupling of thiols shown for L-cysteine with a yield of 94%. Physical cross-links were generated by blending the PEU with poly(D-lactide) (PDLA), upon which the PLLA segments of the PEU and the PDLA formed stereocomplexes. Stereocomplexation occurred spontaneously during solution casting and was investigated with WAXS and DSC. Stereocomplex crystallites were observed in the blends, while isotactic PLA crystallization was not observed. The presented material platform with tailorable mechanical properties by blending is of specific interest for engineering biointerfaces of implants or carrier systems for bioactive molecules. KW - Functionalization KW - Polylactide stereocomplex KW - Biomolecules coupling Y1 - 2020 U6 - https://doi.org/10.1016/j.eurpolymj.2020.109916 SN - 0014-3057 SN - 1873-1945 VL - 137 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Izraylit, Victor A1 - Hommes-Schattmann, Paul Jacob A1 - Neffe, Axel T. A1 - Gould, Oliver E. C. A1 - Lendlein, Andreas T1 - Alkynyl-functionalized chain-extended PCL for coupling to biological molecules JF - European polymer journal N2 - Chemical functionalization of poly(epsilon-caprolactone) (PCL) enables a molecular integration of additional function. Here, we report an approach to incorporate reactive alkynyl side-groups by synthesizing a chain-extended PCL, where the reactive site is introduced through the covalently functionalizable chain extender 3 (prop-2-yn-1-yloxy)propane-1,2-diol (YPD). Chain-extended PCL with M-w of 101 to 385 kg.mol(-1) were successfully synthesized in a one-pot reaction from PCL-diols with various molar masses, L-lysine ethyl ester diisocyanate (LDI) or trimethyl(hexamethylene)diisocyanate (TMDI), and YPD, in which the density of functionalizable groups and spacing between them can be controlled by the composition of the polymer. The employed diisocyanate compounds and YPD possess an asymmetric structure and form a non-crystallizable segment leaving the PCL crystallites to dominate the material's mechanical properties. The mixed glass transition temperature T-g = - 60 to - 46 degrees C of the PCL/polyurethane amorphous phase maintains the synthesized materials in a highly elastic state at ambient and physiological conditions. Reaction conditions for covalent attachment in copper(I)-catalyzed azide-alkyne-cycloaddition reactions (CuAAC) in solution were optimized in a series of model reactions between the alkyne moieties of the chain-extended PCL and benzyl azide, reaching conversions over 95% of the alkyne moieties and with yields of up to 94% for the purified functionalized PCL. This methodology was applied for reaction with the azide-functionalized cell adhesion peptide GRGDS. The required modification of the peptide provides selectivity in the coupling reactions. The obtained results suggest that YPD could potentially be employed as versatile molecular unit for the creation of a variety of functionalizable polyesters as well as polyurethanes and polycarbonates offering efficient and selective click-reactions. KW - copper-catalyzed alkyne-azide cycloaddition KW - chain-extended KW - polycaprolactone KW - RGD-peptide KW - side-chains functionalization Y1 - 2020 U6 - https://doi.org/10.1016/j.eurpolymj.2020.109908 SN - 0014-3057 SN - 1873-1945 VL - 136 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Izraylit, Victor A1 - Liu, Yue A1 - Tarazona, Natalia A. A1 - Machatschek, Rainhard Gabriel A1 - Lendlein, Andreas T1 - Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers JF - MRS communications / a publication of the Materials Research Society N2 - 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. KW - Degradable KW - In situ KW - Microstructure KW - Thin film Y1 - 2021 U6 - https://doi.org/10.1557/s43579-021-00107-y SN - 2159-6859 SN - 2159-6867 VL - 11 IS - 6 SP - 850 EP - 855 PB - Springer CY - Berlin ER - TY - JOUR A1 - Neffe, Axel T. A1 - Izraylit, Victor A1 - Hommes-Schattmann, Paul J. A1 - Lendlein, Andreas T1 - Soft, formstable (Co)polyester blend elastomers JF - Nanomaterials : open access journal N2 - 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. KW - thermoplastic elastomer KW - biomaterial KW - stereocomplexes KW - mechanical KW - properties KW - form stability KW - crystallinity Y1 - 2021 U6 - https://doi.org/10.3390/nano11061472 SN - 2079-4991 VL - 11 IS - 6 PB - MDPI CY - Basel ER -