Refine
Year of publication
- 2020 (4)
Document Type
Language
- English (4)
Has Fulltext
- yes (4)
Is part of the Bibliography
- yes (4)
Keywords
- gels an dhydrogels (1)
- polymer synthesis (1)
- polymers (1)
Scientific Unit
Living organisms share the ability to grow that allows them to absorb, transport, and integrate nutrient to continually increase in size, change in shape and modulate in strength. In contrast, synthetic polymers are constructed in fundamentally different ways and possess fixed structures after fabricated. This thesis presents various approaches to guide synthetic soft materials to grow and to mimic this fundamental growing capability: i) A photo-activation approach to probe the growth of bulky soft materials with controllable size, strength and compositions, ii) Light-induced site-specific self-growth of microstructures from the surface a dynamic soft substrate, iii) Self-growth of fully interlocked poly(disulfide)s based polycatenane elastomers with unique intermolecular interlocking topologies. These functional materials contribute to the supplement of dynamic soft substrates, providing useful information for the future both in chemistry and materials.
A solid-to-hollow evolution in macroscopic structure is challenging in synthetic materials. Herein we report a fundamentally new strategy for guiding macroscopic, unidirectional shape-evolution of materials without compromising the material’s integrity, based on the creation of a field with a “swelling pole” and a “shrinking pole” to drive polymers to disassemble, migrate, and resettle in the targeted region. We demonstrate this concept by using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+) to induce a swelling-shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects including spheres, helix tubes, and cubes with different diameters, for different applications.
Abstract Developing a novel strategy to synthesize photoresponsive polymers is of significance owing to their potential applications. We report a photoinduced strain-assisted synthesis of main-chain stiff-stilbene polymers by using ring-opening metathesis polymerization (ROMP), activating a macrocyclic π-bond connected to a stiff-stilbene photoswitch through a linker. Since the linker acts as an external constraint, the photoisomerization to the E-form leads to the stiff-stilbene being strained and thus reactive to ROMP. The photoisomerization of Z-form to E-form was investigated using time-dependent NMR studies and UV/Vis spectroscopy. The DFT calculation showed that the E-form was less stable due to a lack of planarity. By the internal strain developed due to the linker constraint through photoisomerization, the E-form underwent ROMP by a second generation Grubbs catalyst. In contrast, Z-form did not undergo polymerization under similar conditions. The MALDI-TOF spectrum of E-form after polymerization showed the presence of oligomers of >5.2 kDa.
Natural organic structures form via a growth mode in which nutrients are absorbed, transported, and integrated. In contrast, synthetic architectures are constructed through fundamentally different methods, such as assembling, molding, cutting, and printing. Here, we report a photoinduced strategy for regulating the localized growth of microstructures from the surface of a swollen dynamic substrate, by coupling photolysis, photopolymerization, and transesterification together. Photolysis is used to generate dissociable ionic groups to enhance the swelling ability that drives nutrient solutions containing polymerizable components into the irradiated region, photopolymerization converts polymerizable components into polymers, and transesterification incorporates newly formed polymers into the original network structure. Such light-regulated growth is spatially controllable and dose-dependent and allows fine modulation of the size, composition, and mechanical properties of the grown structures. We also demonstrate the application of this process in the preparation of microstructures on a surface and the restoration of large-scale surface damage.
