TY - JOUR A1 - Goebel, Ronald A1 - Hesemann, Peter A1 - Friedrich, Alwin A1 - Rothe, Regina A1 - Schlaad, Helmut A1 - Taubert, Andreas T1 - Modular thiol-ene chemistry approach towards mesoporous silica monoliths with organically modified pore walls JF - Chemistry - a European journal N2 - The surface modification of mesoporous silica monoliths through thiol-ene chemistry is reported. First, mesoporous silica monoliths with vinyl, allyl, and thiol groups were synthesized through a sol-gel hydrolysis-poly-condensation reaction from tetramethyl orthosilicate (TMOS) and vinyltriethoxysilane, allyltriethoxysilane, and (3-mercaptopropyl) trimethoxysilane, respectively. By variation of the molar ratio of the comonomers TMOS and functional silane, mesoporous silica objects containing different amounts of vinyl, allyl, and thiol groups were obtained. These intermediates can subsequently be derivatized through radical photoaddition reactions either with a thiol or an olefin, depending on the initial pore wall functionality, to yield silica monoliths with different pore-wall chemistries. Nitrogen sorption, small-angle X-ray scattering, solid-state NMR spectroscopy, elemental analysis, thermogravimetric analysis, and redox titration demonstrate that the synthetic pathway influences the morphology and pore characteristics of the resulting monoliths and also plays a significant role in the efficiency of functionalization. Moreover, the different reactivity of the vinyl and allyl groups on the pore wall affects the addition reaction, and hence, the degree of the pore-wall functionalization. This report demonstrates that thiol-ene photoaddition reactions are a versatile platform for the generation of a large variety of organically modified silica monoliths with different pore surfaces. KW - mesoporous materials KW - photochemistry KW - sol-gel processes KW - surface chemistry Y1 - 2014 U6 - https://doi.org/10.1002/chem.201403982 SN - 0947-6539 SN - 1521-3765 VL - 20 IS - 52 SP - 17579 EP - 17589 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Löbbicke, Ruben A1 - Chanana, Munish A1 - Schlaad, Helmut A1 - Pilz-Allen, Christine A1 - Günter, Christina A1 - Möhwald, Helmuth A1 - Taubert, Andreas T1 - Polymer Brush Controlled Bioinspired Calcium Phosphate Mineralization and Bone Cell Growth JF - Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences N2 - Polymer brushes on thiol-modified gold surfaces were synthesized by using terminal thiol groups for the surface initiated free radical polymerization of methacrylic acid and dimethylaminotheyl methacrylate, respectively. Atomic force microscopy shows that the resulting poly(methacrylic acid (PMAA) and poly(dimethylaminothyl methacrylate) (PDM- AEMA) brushes are homogeneous. Contact angle measurements show that the brushes are pH responsive and can reversibly be protonated and deprotonated. Mineralization of the brushes with calcium phosphate at different pH yields homogeneously mineralized surfaces, and preosteoblastic cells proliferate-on be number of living cells on the mineralized hybrid surface is ca. 3 times (P corresponding nonmineralized brushes. Y1 - 2011 U6 - https://doi.org/10.1021/bm200991b SN - 1525-7797 VL - 12 IS - 10 SP - 3753 EP - 3760 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Chandran, Sivasurender A1 - Dold, Stefanie A1 - Buvignier, Amaury A1 - Krannig, Kai-Steffen A1 - Schlaad, Helmut A1 - Reiter, Günter A1 - Reiter, Renate T1 - Tuning Morphologies of Langmuir Polymer Films Through Controlled Relaxations of Non-Equilibrium States JF - Langmuir N2 - Langmuir polymers films (LPFs) frequently form non-equilibrium states which are manifested in a decay of the surface pressure with time when the system is allowed to relax. Monitoring and manipulating the temporal evolution of these relaxations experimentally helps to shed light on the associated molecular reorganization processes. We present a systematic study based on different compression protocols and show how these reorganization processes impact the morphology of LPFs of poly(gamma-benzyl-L-glutamate) (PBLG); visualized by means of atomic force microscopy. Upon continuous compression, a fibrillar morphology was formed with a surface decorated by squeezed-out islands. By contrast, stepwise compression promoted the formation of a fibrillar network with a bimodal distribution of fibril diameters, caused by merging of fibrils. Finally, isobaric compression induced in-plane compaction of the monolayer. We correlate these morphological observations with the kinetics of the corresponding relaxations, described best by a sum of two exponential functions with different time scales representing two molecular processes. We discuss the observed kinetics and the resulting morphologies in the context of nucleation and growth, characteristic for first-order phase transitions. Our results demonstrate that the preparation conditions of LPFs have tremendous impact on ordering of the molecules and hence various macroscopic properties of such films. Y1 - 2015 U6 - https://doi.org/10.1021/acs.langmuir.5b01212 SN - 0743-7463 VL - 31 IS - 23 SP - 6426 EP - 6435 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Knecht, Volker A1 - Reiter, Guenter A1 - Schlaad, Helmut A1 - Reiter, Renate T1 - Structure Formation in Langmuir Peptide Films As Revealed from Coarse-Grained Molecular Dynamics Simulations JF - Langmuir N2 - Molecular dynamics simulations in conjunction with the Martini coarse-grained model have been used to investigate the (nonequilibrium) behavior of helical 22-residue poly(gamma-benzyl-L-glutamate) (PBLG) peptides at the water/vapor interface. Preformed PBLG mono- or bilayers homogeneously covering the water surface laterally collapse in tens of nanoseconds, exposing significant proportions of empty water surface. This behavior was also observed in recent AFM experiments at similar areas per monomer, where a complete coverage had been assumed in earlier work. In the simulations, depending on the area per monomer, either elongated clusters or fibrils form, whose heights (together with the portion of empty water surface) increase over time. Peptides tend to align with respect to the fiber axis or with the major principal axis of the cluster, respectively. The aspect ratio of the cluster observed is 1.7 and, hence, comparable to though somewhat smaller than the aspect ratio of the peptides in alpha-helical conformation, which is 2.2. The heights of the fibrils is 3 nm after 20 ns and increases to 4.5 nm if the relaxation time is increased by 2 orders of magnitude, in agreement with the experiment. Aggregates with heights of about 3 or 4.5 nm are found to correspond to local bi- or trilayer structures, respectively. Y1 - 2017 U6 - https://doi.org/10.1021/acs.langmuir.7b01455 SN - 0743-7463 VL - 33 SP - 6492 EP - 6502 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Noack, Sebastian A1 - Schanzenbach, Dirk A1 - Koetz, Joachim A1 - Schlaad, Helmut T1 - Polylactide-based amphiphilic block copolymers BT - Crystallization-Induced Self-Assembly and Stereocomplexation JF - Macromolecular rapid communications N2 - The aqueous self-assembly behavior of a series of poly(ethylene glycol)-poly(l-/d-lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm-like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm-like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self-assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular-shaped clusters of spherical micelles and pearl-necklace-like structures. KW - crystallization KW - polylactide KW - self-assembly KW - stereocomplexation Y1 - 2018 U6 - https://doi.org/10.1002/marc.201800639 SN - 1022-1336 SN - 1521-3927 VL - 40 IS - 1 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Matic, Aleksandar A1 - Hess, Andreas A1 - Schanzenbach, Dirk A1 - Schlaad, Helmut T1 - Epoxidized 1,4-polymyrcene JF - Polymer chemistry N2 - 1,4-Polymyrcene was synthesized by anionic polymerization and epoxidized using meta-chloroperbenzoic acid. Samples with different degrees of epoxidation (25%, 49%, 74%, and 98%) were prepared and examined according to their chemical and thermal properties. Epoxidation was found to increase the glass transition temperature (T-g = 14 degrees C for the 98% epoxidized 1,4-polymyrcene) as well as the shelf live (>10 months). The trisubstituted epoxide groups were remarkably stable against nucleophiles under basic conditions but cross-linked or hydrolyzed in the presence of an acid. Also, highly epoxidized 1,4-polymyrcene readily cross-linked upon annealing at 260 degrees C to produce an epoxy resin. KW - comb poly(beta-myrcene)-graft-poly(l-lactide) copolymers KW - thermoplastic elastomer synthesis KW - myrcen KW - polymerization KW - epoxidation Y1 - 2020 U6 - https://doi.org/10.1039/c9py01783f SN - 1759-9954 SN - 1759-9962 VL - 11 IS - 7 SP - 1364 EP - 1368 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Glatzel, Julia A1 - Noack, Sebastian A1 - Schanzenbach, Dirk A1 - Schlaad, Helmut T1 - Anionic polymerization of dienes in ‘green’ solvents JF - Polymer international N2 - Isoprene and beta-myrcene were polymerized by anionic polymerization in bulk and in the 'green' ether solvents cyclopentyl methyl ether and 2-methyltetrahydrofuran and, for comparison, in cyclohexane and tetrahydrofuran. The polydienes produced in bulk and in cyclohexane contained high amounts of 1,4 units (>90%) whereas those produced in ether solvents were rich in 1,2 and 3,4 units (36%-86%). Comparison of the microstructures and glass transition temperatures of the polydienes obtained in the various solvents suggests that conventionally used solvents can be substituted by environmentally more friendly alternatives. KW - isoprene KW - β‐myrcene KW - anionic polymerization KW - green KW - solvents KW - microstructure KW - glass transition Y1 - 2020 U6 - https://doi.org/10.1002/pi.6152 SN - 0959-8103 SN - 1097-0126 VL - 70 IS - 2 SP - 181 EP - 184 PB - Wiley CY - Hoboken ER -