TY - JOUR A1 - Zentel, Rudolf A1 - Behl, Marc A1 - Neher, Dieter A1 - Zen, Achmad A1 - Lucht, Sylvia T1 - Nanostructured polytriarylamines : orientation layers for polyfluorene Y1 - 2004 SN - 0065-7727 ER - TY - JOUR A1 - Tartivel, Lucile A1 - Behl, Marc A1 - Schröter, Michael A1 - Lendlein, Andreas T1 - Hydrogel networks based on ABA triblock copolymers JF - Journal of applied biomaterials & functional materials N2 - Background: Triblock copolymers from hydrophilic oligo(ethylene glycol) segment A and oligo(propylene glycol) segment B, providing an ABA structure (OEG-OPG-OEG triblock), are known to be biocompatible and are used as self-solidifying gels in drug depots. A complete removal of these depots would be helpful in cases of undesired side effects of a drug, but this remains a challenge as they liquefy below their transition temperature. Therefore we describe the synthesis of covalently cross-linked hydrogel networks. Method: Triblock copolymer-based hydrogels were created by irradiating aqueous solutions of the corresponding macro-dimethacrylates with UV light. The degree of swelling, swelling kinetics, mechanical properties and morphology of the networks were investigated. Results: Depending on precursor concentration, equilibrium degree of swelling of the films ranged between 500% and 880% and was reached in 1 hour. In addition, values for storage and loss moduli of the hydrogel networks were in the 100 Pa to 10 kPa range. Conclusion: Although OEG-OPG-OEG triblocks are known for their micellization, which could hamper polymer network formation, reactive OEG-OPG-OEG triblock oligomers could be successfully polymerized into hydrogel networks. The degree of swelling of these hydrogels depends on their molecular weight and on the oligomer concentration used for hydrogel preparation. In combination with the temperature sensitivity of the ABA triblock copolymers, it is assumed that such hydrogels might be beneficial for future medical applications -e.g., removable drug release systems. KW - Hydrogel KW - Rheological characterization KW - Oligo(ethylene glycol) derivatization KW - OEG-OPG-OEG triblock copolymer KW - UV crosslinking Y1 - 2012 U6 - https://doi.org/10.5301/JABFM.2012.10295 SN - 2280-8000 VL - 10 IS - 3 SP - 243 EP - 248 PB - Wichtig CY - Milano ER - TY - JOUR A1 - Melchert, Christian A1 - Yongvongsoontorn, Nunnarpas A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Synthesis and characterization of telechelic oligoethers with terminal cinnamylidene acetic acid moieties JF - Journal of applied biomaterials & functional materials N2 - Purpose: The formation of photoresponsive hydrogels were reported by irradiation of star-shaped poly(ethylene glycol)s with terminal cinnamylidene acetic acid (CAA) groups, which are capable of a photoinduced [2+2] cycloaddition. In this study we explored whether oligo(ethylene glycol) s and oligo(propylene glycol)s of varying molecular architecture (linear or star-shaped) or molecular weights could be functionalized with CAA as terminal groups by esterification or by amide formation. Methods: Oligo(ethylene glycol) (OEG) and oligo(propylene glycol) (OPG) with varying molecular architecture (linear, star-shaped) and weight average molecular weights between 1000 and 5000 g.mol(-1) were functionalized by means of esterification of hydroxyl or amine endgroups with cinnamylidene acetic acid (CAA) or cinnamylidene acetyl chloride (CAC) as telechelic endgroups. The chemical structure, thermal properties, and molecular weights of the oligoethers obtained were determined by NMR spectroscopy, UV spectroscopy, DSC, and MALDI-TOF. Results: CAA-functionalized linear and star-shaped OEGs or OPGs could be obtained with a degree of functionalization higher than 90%. In MALDI-TOF measurements an increase in Mw of about 150 g.mol(-1) (for each terminal end) after the functionalization reaction was observed. OEGCAA and OPGCAA showed an increase in glass transition temperature (T-g) from about -70 degrees C to -50 degrees C, compared to the unfunctionalized oligoethers. In addition, the melting temperature (T-m) of OEGCAA decreased from about 55 C to 30 degrees C, which can be accounted for by the hampered crystallization of the precursors because of the bulky CAA end groups as well as by the loss of the hydroxyl telechelic end groups. Conclusion: The synthesis of photoresponsive oligoethers containing cinnamylidene acetic acid as telechelic endgroup was reported and high degrees of functionalization could be achieved. Such photosensitive oligomers are promising candidates as reactive precursors, for the preparation of biocompatible high molecular weight polymers and polymer networks. KW - Biocompatible polymers KW - Cinnamylidene acetic acid KW - Photoresponsive polymers Y1 - 2012 U6 - https://doi.org/10.5301/JABFM.2012.10364 SN - 2280-8000 VL - 10 IS - 3 SP - 185 EP - 190 PB - Wichtig CY - Milano ER - TY - JOUR A1 - Melchert, Christian A1 - Behl, Marc A1 - Nöchel, Ulrich A1 - Lendlein, Andreas T1 - Influence of Comesogens on the Thermal and Actuation Properties of 2-tert-Butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone Based Nematic Main-Chain Liquid Crystalline Elastomers JF - Macromolecular materials and engineering N2 - Although the shape-changing capabilities of LCEs hold great potential for applications ranging from micropumps to artificial muscles, customization of the LCE functionality to the applications' requirements is still a challenge. It is studied whether the orientation of NMC-LCPs and NMC-LCEs based on 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone can be enhanced by copolymerization with 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone or 2,6-bis[4-(4-pentenyl-oxy)-benzoyl]anthracene. An increasing content of the comonomers stabilizes the nematic phase, which enables a tailoring of T-NI for the NMC-LCP between 45 and 68 degrees C, while for the NMC-LCE T-NI ranges between 69 and 76 degrees C. In addition, NMC-LCE show an increased actuation performance. KW - elastomers KW - liquid-crystalline polymers KW - polysiloxanes KW - stimuli-sensitive polymers KW - thermal properties Y1 - 2012 U6 - https://doi.org/10.1002/mame.201200238 SN - 1438-7492 VL - 297 IS - 12 SP - 1203 EP - 1212 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Razzaq, Muhammad Yasar A1 - Behl, Marc A1 - Frank, Ute A1 - Koetz, Joachim A1 - Szczerba, Wojciech A1 - Lendlein, Andreas T1 - Oligo(omega-pentadecalactone) decorated magnetic nanoparticles JF - Journal of materials chemistry N2 - Hybrid magnetic nanoparticles (mgNP) with a magnetite core diameter of 10 +/- 1 nm surface functionalized with oligo(omega-pentadecalactone) (OPDL) oligomers with M-n between 1300 and 3300 g mol(-1) could be successfully prepared having OPDL grafted from 200 mg g(-1) to 2170 mg g(-1). The particles are dispersible in chloroform resulting in stable suspensions. Magnetic response against an external magnetic field proved the superparamagnetic nature of the particles with a low coercivity (B-c) value of 297 mu T. The combination of the advantageous superparamagnetism of the mgNP with the exceptional stability of OPDL makes these novel hybrid mgNP promising candidates as multifunctional building blocks for magnetic nanocomposites with tunable physical properties. Y1 - 2012 U6 - https://doi.org/10.1039/c2jm16146j SN - 0959-9428 VL - 22 IS - 18 SP - 9237 EP - 9243 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Friess, Fabian A1 - Wischke, Christian A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Oligo(epsilon-caprolactone)-based polymer networks prepared by photocrosslinking in solution JF - Journal of applied biomaterials & functional materials N2 - Purpose: Polymer networks with adjustable properties prepared from endgroup-functionalized oligoesters by UV-crosslinking in melt have evolved into versatile multifunctional biomaterials. In addition to the molecular weight or architecture of precursors, the reaction conditions for crosslinking are pivotal for the polymer network properties. Crosslinking of precursors in solution may facilitate low-temperature processes and are compared here to networks synthesized in melt. Methods: Oligo(epsilon-caprolactone)-(z) methacrylate (oCL-(z) IEMA) precursors with a linear (z = di) or a four-armed star-shaped (z = tetra) architecture were crosslinked by radical polymerization in melt or in solution with UV irradiation. The thermal, mechanical, and swelling properties of the polymer networks obtained were characterized. Results: Crosslinking in solution resulted in materials with lower Young's moduli (E), lower maximum stress (sigma(max)), and higher elongation at break (epsilon(B)) as determined at 70 degrees C. Polymer networks from 8 kDa star-shaped precursors exhibited poor elasticity when synthesized in the melt, but can be established as stretchable materials with a semi-crystalline morphology, a high gel-content, and a high elongation at break when prepared in solution. Conclusions: The crosslinking condition of methacrylate functionalized precursors significantly affected network properties. For some types of precursors such as star-shaped telechelics, synthesis in solution provided semi-crystalline elastic materials that were not accessible from crosslinking in melt. KW - Crosslinking KW - Methacrylate KW - Multifunctional polyester networks KW - Poly(epsilon-caprolactone) KW - Polymer network properties Y1 - 2012 U6 - https://doi.org/10.5301/JABFM.2012.10372 SN - 2280-8000 VL - 10 IS - 3 SP - 273 EP - 279 PB - Wichtig CY - Milano ER - TY - JOUR A1 - Julich-Gruner, Konstanze K. A1 - Löwenberg, Candy A1 - Neffe, Axel T. A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Recent trends in the chemistry of shape-memory polymers JF - Macromolecular chemistry and physics N2 - Shape-memory polymers (SMPs) are stimuli-sensitive materials capable of performing complex movements on demand, which makes them interesting candidates for various applications, for example, in biomedicine or aerospace. This trend article highlights current approaches in the chemistry of SMPs, such as tailored segment chemistry to integrate additional functions and novel synthetic routes toward permanent and temporary netpoints. Multiphase polymer networks and multimaterial systems illustrate that SMPs can be constructed as a modular system of different building blocks and netpoints. Future developments are aiming at multifunctional and multistimuli-sensitive SMPs. KW - multifunctional polymers KW - networks KW - shape-memory polymers KW - stimuli-sensitive polymers KW - triple-shape effect Y1 - 2013 U6 - https://doi.org/10.1002/macp.201200607 SN - 1022-1352 VL - 214 IS - 5 SP - 527 EP - 536 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Christian A1 - Behl, Marc A1 - Lendlein, Andreas A1 - Beuermann, Sabine T1 - Synthesis of high molecular weight polyglycolide in supercritical carbon dioxide JF - RSC Advances N2 - Polyglycolide (PGA) is a biodegradable polymer with multiple applications in the medical sector. Here the synthesis of high molecular weight polyglycolide by ring-opening polymerization of diglycolide is reported. For the first time stabilizer free supercritical carbon dioxide (scCO(2)) was used as a reaction medium. scCO(2) allowed for a reduction in reaction temperature compared to conventional processes. Together with the lowering of monomer concentration and consequently reduced heat generation compared to bulk reactions thermal decomposition of the product occurring already during polymerization is strongly reduced. The reaction temperatures and pressures were varied between 120 and 150 degrees C and 145 to 1400 bar. Tin(II) ethyl hexanoate and 1-dodecanol were used as catalyst and initiator, respectively. The highest number average molecular weight of 31 200 g mol(-1) was obtained in 5 hours from polymerization at 120 degrees C and 530 bar. In all cases the products were obtained as a dry white powder. Remarkably, independent of molecular weight the melting temperatures were always at (219 +/- 2)degrees C. Y1 - 2014 U6 - https://doi.org/10.1039/c4ra06815g SN - 2046-2069 VL - 4 IS - 66 SP - 35099 EP - 35105 PB - Royal Society of Chemistry CY - Cambridge ER - TY - CHAP A1 - Behl, Marc A1 - Kratz, Karl A1 - Nöchel, Ulrich A1 - Sauter, Tilman A1 - Lendlein, Andreas T1 - Polymer networks capable of reversible shape-memory-effects T2 - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS Y1 - 2014 SN - 0065-7727 VL - 248 PB - American Chemical Society CY - Washington ER - TY - INPR A1 - Baudis, Stefan A1 - Behl, Marc A1 - Lendlein, Andreas T1 - Smart polymers for biomedical applications T2 - Macromolecular chemistry and physics Y1 - 2014 U6 - https://doi.org/10.1002/macp.201400561 SN - 1022-1352 SN - 1521-3935 VL - 215 IS - 24 SP - 2399 EP - 2402 PB - Wiley-VCH CY - Weinheim ER -