Loli Martin

Designing hydrogel nanocomposites using TiO2 as clickable cross-linkers

Titanium dioxide (TiO2) nanoparticles with clickable functional groups were prepared to allow for the Diels–Alder “click” reaction with a furan-modified pigskin gelatin. Bifunctional dopamine-maleimide linker was employed for TiO2 functionalization with maleimide group. The obtained nanoparticles were characterized using TEM, Zeta potential and FTIR spectroscopy. Functional nanoparticles were subsequently used, together with chondroitin sulphate, as cross-linkers for gelatin hydrogels. Hydrogel controls with bare TiO2 and without nanoparticles were prepared for comparison. The swelling and rheological properties of the nanocomposite hydrogels confirmed the formation of the covalently linked heterogeneous networks. An increase in the storage moduli values was recorded when using maleimide-coated nanoparticles. At the same time, the swelling of the network was significantly reduced indicating the formation of more cross-linked networks. The participation of the surface attached maleimide functional groups through the Diels–Alder cycloaddition was thus confirmed. In addition, hydrogels responded to electrostatic forces as observed by electrostatic force microscopy.

The role of cellulose nanocrystals incorporation route in waterborne polyurethane for preparation of electrospun nanocomposites mats

Electrospinning offers the possibility of obtaining fibers mats from polymer solutions. The use of environmentally-friendly waterborne polyurethane (WBPU) allows obtaining electrospun polyurethane mats in water medium. Furthermore, the incorporation of water dispersible nanoentities, like renewable cellulose nanocrystals (CNC), is facilitated. Therefore, in this work, a WBPU was synthesized and CNC were isolated for preparing WBPU-CNC dispersions nanocomposites with 1 and 3wt% of CNC following both the classical mixing by sonication, and the innovative in-situ route. The dispersions were used for obtaining electrospun mats assisted by poly(ethylene oxide) (PEO) as polymer template. Moreover, the extraction of PEO with water resulted in continuous WBPU-CNC mats, showing different properties respect to WBPU-CNC mats containing PEO. The effective addition of CNC led to more defined cylindrical morphologies and the two alternative incorporation routes induced to different CNC dispositions in the matrix, which modified fibers diameters, and thus, mats final properties.

Innovative Systems from Clickable Biopolymer-Based Hydrogels for Drug Delivery

Biopolymer-based hydrogels have emerged as suitable systems for sustained and targeted drug delivery due to their excellent biocompatibility, biodegradability, hydrophilicity, and tunable microstructure. Even if the use of natural polymers as materials is not new, their use in hydrogel formulations has dramatically grown over the last 10 years. Owing to their chemical versatility, several synthetic approaches can be followed for the design of advanced functionalized materials. The high reactivity, orthogonality, regioselectivity, and mild reaction conditions of “click” reactions render them especially suitable for hydrogel cross-linking. These features are particularly advantageous for the design of drug delivery systems as they prevent interferences with encapsulated drugs or biomolecules while respecting the biocompatibility of the material. The use of click chemistry for the design of biopolymer-based drug delivery systems opens new avenues for the substitution of petroleum-derived polymers and the use of more environmentally friendly chemistries in the pharmaceutical industry.

Photo-Induced Optical Anisotropy and Morphological Study in Azobenzene Containing Block Copolymers

In this work, different types of nanostructured systems containing azobenzene groups were studied. With that aim, firstly, novel azo-functionalised block copolymers (BCP) were synthesized from epoxidized poly (styrene-b-butadiene-b-styrene) (SBS) modified with azobenzene units by one-step facile reaction between the epoxy groups and an azo-amine. The epoxy/amine reaction was verified by Fourier transform infrared spectroscopy. In addition, the effect of covalent attachment of the azobenzene moieties was investigated by analyzing the morphology and the optical anisotropic response of the resulting azo-containing BCP, with respect to solution mixing of the azobenzene as a guest in the BCP host without chemical bonding. On the other hand, epoxidized SBS was also used as template for the generation of nanostructured thermosetting epoxy matrices with azobenzene groups covalently linked. This BCP can self-assemble in the epoxy matrix to produce microphase-separated domains, thanks to the selective segregation of polystyrene blocks due to reaction induced microphase separation. In this case, the influence of the azobenzene content and the amount of epoxidized SBS on the generated morphologies and the photo-induced anisotropy was studied.