Periodic Reporting for period 1 - DisMolGels (Dissipative Self-Assembly: A powerful but unexplored tool to create temporary supramolecular hydrogels) Período documentado: 2017-05-01 hasta 2019-04-30 Resumen del contexto y de los objetivos generales del proyecto The main purpose of this proposal was to develop molecular temporary hydrogels coupled to an energy dissipating chemical reaction. Until now, most molecular self-assembled materials operate close to thermodynamic equilibrium and are far from the interesting features biological living “materials” display like adaptivity, self-healing or temporal control. Biological materials are thermodynamically open and are kept far from equilibrium by a constant input of energy. This mode of self-assembly, one of the requirements of life, is referred to as dissipative or dynamic self-assembly. Over the last decade, in order to overcome this gap between synthetic and biologicals materials, several researchers are trying to recreate part of such dissipative processes and translate them into the already known static materials. We envision for these materials unique properties which will expand their current applications. As an example, biomedical implants that would autonomously degrade after performing their function would diminish the need for a post-treatment surgery to remove the implant. Or, a detergent that would degrade hours after usage would be less harmful to the environment. However, the topic is still in its infancy and therefore, design rules are still missing and hampering the development of these interesting systems. In this way, our proposal aims not only at creating dynamic hydrogels with entirely new properties but also at setting new design guidelines and requirements to pave the way for the further development of dissipative materials. Our strategy is based on coupling chemical reactions to self-assembled hydrogels. Such hydrogels are maintained far from the equilibrium by the constant input of fuel and therefore endowed with tunable lifetime and stiffness. In order to be successful, the following four specific objectives were tackled: 1. Develop chemical reaction networks that can drive the transient formation of assemblies. 2. Design and synthesize precursor building blocks that can self-assemble into hydrogels.3. Develop transient dissipative molecular hydrogels by coupling chemical reaction networks to precursor building blocks.4. Study the relation between the kinetics of the chemical reaction networks and material properties.By the end of the project the main objectives of the proposal were achieved and published in peer review journals. Moreover, the same approach was applied to different kind of molecules which allowed us to develop a larger library of dissipative systems and explore their unique properties Trabajo realizado desde el comienzo del proyecto hasta el final del período abarcado por el informe y los principales resultados hasta la fecha "Following the objectives of the proposal, a new chemical reaction network was successfully developed (Figure 1). The chemical reaction network converts carboxylates into metastable anhydrides in aqueous media upon consumption of carbodiimide fuels. The anhydrides rapidly hydrolyze to the original carboxylates, therefore, closing the cycle. The reactions involved work in buffered water at pH values around pH=6. The carboxylate precursor carries negative charges under the described conditions which are neutralized by the formation of the anhydride. This hydrophobization process driven by our chemical reaction network is a crucial step since it changes completely the solubility of the precursor and induces the self-assembly of the anhydride product. The next step was the design and synthesis of precursor building blocks able to self-assemble into hydrogels. As described in our proposal we satisfactory used small peptide molecules endowed with aromatic motifs, ß-sheet amino acid directors and carboxylate groups as building blocks for our chemical reaction network. When combining the chemical reaction network previously described with the appropriate building blocks, temporary hydrogels were obtained. Crucially, the lifetimes of these hydrogels could be predicted and tuned by controlling the amount of fuel and/or precursor present in the chemical reaction network. Also relevant was to discover the reusability of these materials by the addition of subsequent batches of fuel. Due to the versatility of the chemical reaction network, other different fuels and precursor building blocks were explored therefore developing other types of dissipative materials (Figure 2). Particularly interesting were the formation of temporary colloids upon self-assembly and their application for the sequentially release of hydrophobic agents and the formation of spherulites and their use for temporary inks. The applications of all these materials were possible due to the dissipative nature of the system. Most likely such applications could not be achieved by using the classical thermodynamic materials developed so far. The main results have been published in two papers: ""Non-equilibrium dissipative supramolecular materials with a tunable lifetime"" (Nat Commun 2017) and ""Self-selection of dissipative assemblies driven by primitive chemical reaction networks"" (Nat Commun 2018). Both publications were followed by press releases in TUM news. The results of this research have been presented in several scientific meetings and international conferences. For instance, I had the opportunity to make oral presentations in ""Suprachem 2019"" (February 2019, Würzburg), ""Women in Science"" (2018, Erlangen) and during the ""Gordon Research Seminar"" (May 2017-Les Diablerets). Poster contribution was also possible in ""Molecular Origins of Life 2018"" (October 2018, Munich), in the ""International Symposium of Macrocyclic and Supramolecular Chemistry"" (2018, Quebec) and during the Young Chemist Researchers 2017 (2017, Badajoz).I was also invited to give a talk at the Universitat Jaume I 2018 (Castellón-Spain). The dissemination of the results was also expanded to the general public by the performance of outreach activities. For instance, I co-organise an exhibition activity included at the ""Open Door Day"" at TUM (2018-Garching) and a science communication event called ""15x4 Share your knowledge"" sponsored by sponsored the Marie Curie Alumni Association (February 2019, Munich) " Avances que van más allá del estado de la técnica e impacto potencial esperado (incluida la repercusión socioeconómica y las implicaciones sociales más amplias del proyecto hasta la fecha) The development of the chemical reaction network and the design of different building blocks allowed the creation of materials with tunable lifetime and reusability properties. Kinetic models can predict the lifetime and extend our experimental conditions have been also successfully developed. The experimental conditions employed avoid the use of toxic or hazardous reagents and work under mild conditions in aqueous media. Thus will facilitate the potential use of our dissipative materials in ecologically friendly, mass-production industrial or biomedical applications. Moreover the versatility of our dissipative system allowed us to translate them into topics like origin of life which were not envisioned at the beginning of the project. For instance, we show that such a simple process like phase-separation (due to the self-assembly) could offer a mechanism for the selection of dissipative products from a library of reacting molecules. The formation of the anhydrides that phase separate into droplets can protect themselves from hydrolysis which make them more persistent than the non-assembling ones. The simplicity of this mechanism will enable the further design of reaction schemes to self-select assemblies with more life-like features from molecular libraries driven out of equilibrium.
