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- ItemA block copolymer templated approach for the preparation of nanoporous polymer structures and cellulose fiber hybrids by ozone treatment(Cambridge : RSC Publ., 2022) Gemmer, Lea; Hu, Qiwei; Niebuur, Bart-Jan; Kraus, Tobias; Balzer, Bizan N.; Gallei, MarkusFunctional amphiphilic block copolymers (BCPs) are versatile, smart, and promising materials that are often used as soft templates in nanoscience. BCPs generally feature the capability of microphase-separation leading to various interesting morphologies at the nanometer length scale. Materials derived from BCPs can be converted into porous structures while retaining the underlying morphology of the matrix material. Here, a convenient and scalable approach for the fabrication of porous functional polyvinylpyridines (P2VP) is introduced. The BCP polyisoprene-block-P2VP (PI-b-P2VP) is obtained via sequential anionic polymerization of the respective monomers and used to form either BCP films in the bulk state or a soft template in a composite with cellulose fibers. Cross-linking of the BCPs with 1,4-diiodobutane is conducted and subsequently PI domains are selectively degraded inside the materials using ozone, while preserving the porous and tailor-made P2VP nanostructure. Insights into the feasibility of the herein presented strategy is supported by various polymer characterization methods comprising nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). The resulting bulk- and composite materials are investigated regarding their morphology and pore formation by scanning electron microscopy (SEM), atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS). Furthermore, chemical conversions were examined by energy dispersive X-ray spectroscopy (EDS), attenuated total reflection Fourier-transformation infrared spectroscopy (ATR-FTIR) and water contact angle (WCA) measurements. By this convenient strategy the fabrication of functional porous P2VP in the bulk state and also within sustainable cellulose composite materials is shown, paving the synthetic strategy for the generation of a new family of stimuli-responsive sustainable materials.
- ItemSelf-Healing Iron Oxide Polyelectrolyte Nanocomposites: Influence of Particle Agglomeration and Water on Mechanical Properties(Basel : MDPI, 2023) Oberhausen, Bastian; Plohl, Ajda; Niebuur, Bart-Jan; Diebels, Stefan; Jung, Anne; Kraus, Tobias; Kickelbick, GuidoSelf-healing nanocomposites can be generated by organic functionalization of inorganic nanoparticles and complementary functionalization of the polymer matrix, allowing reversible interactions between the two components. Here, we report on self-healing nanocomposites based on ionic interactions between anionic copolymers consisting of di(ethylene glycol) methyl ether methacrylate, sodium 4-(methacryloyloxy)butan-1-sulfonate, and cationically functionalized iron oxide nanoparticles. The materials exhibited hygroscopic behavior. At water contents < 6%, the shear modulus was reduced by up to 90%. The nanoparticle concentration was identified as a second factor strongly influencing the mechanical properties of the materials. Backscattered scanning electron microscopy and small-angle X-ray scattering measurements showed the formation of agglomerates in the size range of 100 nm to a few µm in diameter, independent of concentration, resulting in the disordering of the semi-crystalline ionic polymer blocks. These effects resulted in an increase in the shear modulus of the composite from 3.7 MPa to 5.6 MPa, 6.3 Mpa, and 7.5 MPa for 2, 10, and 20 wt% particles, respectively. Temperature-induced self-healing was possible for all composites investigated. However, only 36% of the maximum stress could be recovered in systems with a low nanoparticle content, whereas the original properties were largely restored (>85%) at higher particle contents.