Understanding a novel class of thermoplastic elastomers using nanoparticles as cross-linkers
Final Report Abstract
A novel class of thermoplastic elastomers (TPE) with metal nanoparticles (NPs) as cross-linkers was studied. Employing metal nanoparticles of different shapes and size, emphasis was placed on (1) the development of novel nanocomposite preparation routes, on (2) the engineering of elastic nanocomposites with unprecedented physical properties and on (3) the underlying mechanisms. Precisely synthesized thiol-end functionalized oligo isoprene and its low molar mass block copolymers with styrene, and poly (propylene sulfide) via anionic polymerization were used as matrix materials. Shape, amount of metal NPs and matrix polymer type were some of the important parameters deciding formation and mechanical properties of the elastic composites. In contrast to conventional block copolymer thermoplastic elastomers, microphase separation of the blocks is not required. Rather, very low polymerization degrees of matrix polymer were sufficient in order to yield high tensile strengths and moduli in the cross-linked state. As a consequence of low polymerization degrees, viscosities at elevated temperatures are found to be remarkably small and independent from the block co-oligomer composition which is advantageous for processing. The use of gold nanorods together with telechelic co-oligomers provided mechano-responsive elastic nanocomposites in which the orientational alignment of gold nanorods in the solid state was achieved by mechanical stimulus. The uniaxial mechanical elongation and relaxation regulate the alignment of gold nanorods within the stretching direction in a stepless and reversible fashion. Ex situ-prepared gold nanorods in aqueous dispersion are employed in a hetero-phase ligand exchange procedure in order to obtain thermally stable hydrophobic gold nanorods. The impact of mechanical stimulation on the physical properties of these materials is demonstrated by means of absorption and scattering experiments.
Publications
- Design of soft materails from liquid triblock co-oligomers and metal nanoparticles. Chem. Mater., 2014, 26 (16), 4805–4811
Holger Pletsch, Max J. Schnepf, and Seema Agarwal
(See online at https://doi.org/10.1021/cm502322g) - Ultrasound-mediated synthesis of high molecular weight polystyrene-grafted silver nanoparticles by facile ligand exchange reactions in suspension, Small, 2014, 10 (1), 201–208
Holger Pletsch, Ling Peng, Fabian Mitschang, Andreas Schaper, Michael Hellwig, David Nette, Andreas Seubert, Andreas Greiner and Seema Agarwal
(See online at https://doi.org/10.1002/smll.201300594) - Preparing a pseudo-solid by the reinforcement of a polydentate thioether using silver nanoparticles, Nanoscale, 2015, 7, 1977-1983
Holger Pletsch, Andreas Greiner and Seema Agarwal
(See online at https://doi.org/10.1039/c4nr06834c) - Reversible gold nanorod alignment in mechanoresponsive elastomers, Polymer, 2015, 66 (1), 167-172
Holger Pletsch, Moritz Tebbe, Martin Dulle, Beate Förster, Andreas Fery, Stephan Förster, Andreas Greiner, Seema Agarwal
(See online at https://doi.org/10.1016/j.polymer.2015.04.037)
