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This work is funded by National Funds through FCT-Portuguese Foundation for Science and Technology, Reference UID/CTM/50025/2013 and FEDER funds through the COMPETE 2020 Program under the project number POCI-01-0145-FEDER-007688. C. Echeverria acknowledges the Juan de la Cierva contract (IJCI-2015-26432) from MINECO-Spanish Ministry of Economy, Industry and Competitiveness. One strategy that has gained much attention in the last decades is the understanding and further mimicking of structures and behaviours found in nature, as inspiration to develop materials with additional functionalities. This review presents recent advances in stimuli-responsive gels with emphasis on functional hydrogels and microgels. The first part of the review highlights the high impact of stimuli-responsive hydrogels in materials science. From macro to micro scale, the review also collects the most recent studies on the preparation of hybrid polymeric microgels composed of a nanoparticle (able to respond to external stimuli), encapsulated or grown into a stimuli-responsive matrix (microgel). This combination gave rise to interesting multi-responsive functional microgels and paved a new path for the preparation of multi-stimuli "smart" systems. Finally, special attention is focused on a new generation of functional stimuli-responsive polymer hydrogels able to self-shape (shape-memory) and/or self-repair. This last functionality could be considered as the closing loop for smart polymeric gels. publishersversion published

Composite ferrogels were obtained by encapsulation of magnetic nanoparticles at two different concentrations (2.0 and 5.0 % w/v) within mixed agarose/chitosan hydrogels having different concentrations of agarose (1.0, 1.5 and 2.0% (w/v)) and a fixed concentration of chitosan (0.5% (w/v)). The morphological characterization carried out by scanning electron microscopy showed that dried composite ferrogels present pore sizes in the micrometer range. Thermogravimetric measurements showed that ferrogels present higher degradation temperatures than blank chitosan/agarose hydrogels without magnetic nanoparticles. In addition, measurements of the elastic moduli of the composite ferrogels evidenced that the presence of magnetic nanoparticles in the starting aqueous solutions prevents to some extent the agarose gelation achieved by simply cooling chitosan/agarose aqueous solutions. Finally, it is shown that composite chitosan/agarose ferrogels are able to heat in response to the application of an alternating magnetic field so that they can be considered as potential biomaterials to be employed in magnetic hyperthermia treatments., Vanessa Zamora-Mora thanks CSIC for a JAE predoc fellowship. Rebeca Hernández acknowledges MINECO for a Ramon y Cajal fellowship. Financial support from MINECO (MAT 2011-24797 and MAT 2014-53437-C2-1) is gratefully acknowledged. Paula I.P. Soares and Coro Echeverria acknowledge support from the Portuguese Science and Technology Foundation through grants SFRH/BD/81711/2011, SFRH/BPD/88779/2012 and project UID/CTM/500025/2013., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

Cellulose is the world’s most abundant, biocompatible, non-toxic, biodegradable polymer obtained from renewable sources. However its dissolution problems hampers a more generalized application. ILs are generally defined as organic/inorganic salts with a melting point lower than 100 C which present a good solubility for polar and non-polar compounds such as organic, inorganic or polymeric materials like cellulose. Cellulose solvents are scarce and, as such, the modification of its properties is a challenge. In this dissertation the main goal was to combine some of the unique IL’s properties with the intrinsic cellulose features. Thus, our strategy was to synthesize cellulose derivatives that enable the dissolution process in order to, later on, obtain a polymer gel. In the first stage we obtained ionic liquid grafted cellulose derivatives. Afterwards, we performed an extensive solubilization study to select the appropriate conditions to obtain the gel state. To further understand the solvents’ dynamics and their relevance in the gelation process, these conditions were followed by NMR and Rheology. The obtained results allowed the proposal of a gelation model for these cellulosic polymers. The proposed strategy could be a starting point to design and produce Ionic Liquid Paper (ILP), a material that could have potential for electrochemical applications.