Facile Synthesis of Natural Polymer-based Self-healing Hydrogels with Enhanced Mechanical Properties via Sacrificial Metal-ligand Bonds Interaction

Author:Imtiaz Hussain

Supervisor:guodong fu


Degree Year:2018





Natural polymer based self-healing hydrogels have attracted intense consideration due to their attributable and a wide range of applications.However,to design hydrogels having excellent self-healing efficiency and super mechanical strength is still a big challenge.Hence,the development of a mechanically robust hydrogel material with autonomous self-healing is the primary objective of hydrogel materials.In this study,we report a facile and cost-effective method for the autonomous self-healing hydrogel based on a natural polymer with enhanced mechanical properties by simple insertion of ferric ions in the physically cross-linked network via metal-ligand interactions.The mechanical properties and self-healing ability can be optimized by a variety of parameters such as natural polymers,Fe3+ ions,and AA monomer concentration We systematically studied the concentration effect of two natural polysaccharides(hydroxyethyl cellulose(HEC) and glycogen(Gly) on the mechanical properties and self-healing efficiency of hydrogels.In this work,we report the synthesis of iron(Ⅲ)containing hydroxyethyl cellulose-based hydrogel(HEC/PAA-Fe3+) through dynamic metal-ligand(M-L)interactions with enhanced self-healing and mechanical properties.The decoration of ferric ions(Fe3+) in a physically cross-linked polymer network(HEC/PAA) introduces dynamic energy dissipative coordination bonds,which dramatically enhance the overall mechanical properties and self-healing efficiency.The HEC/PAA-Fe3+ hydrogel exhibits high tensile strength(1.35 MPa),extensive fracture strain(1660%),high toughness(8.8 MJm-3) and outstanding self-healing efficiency(87%) without any external intervention.Hydroxyethyl cellulose based self-healing conducting hydrogels with enhanced mechanical properties were synthesized by the molecular engineering of Fe3+ ions among the functional groups of polyacrylic acid-polyacrylamide(P(AA-co-AAm) and hydroxyethyl cellulose(HEC) chain through supramolecular interactions.The engineered hydrogels exhibit a high mechanical strength with a tensile stress of 3.50 MPa and tensile strain of 1245%,along with compression stress of 32 MPa.These hydrogels also show about 98% self-healing efficiency as well as exhibit the conductive properties.Moreover,manipulating the various parameters,the mechanical and self-healing efficiency of the prepared hydrogel can be adjusted.We believe that this work will encourage researchers to focus on this facile technique for the synthesis of self-healing hydrogel materials with enhanced mechanical properties.Here,in this work a facile and cost-effective method is reported for the autonomous self-healing hydrogel based on Glycogen(Gly/PAA-Fe3+) with enhanced mechanical properties by simple insertion of ferric ions in the physically cross-linked network(Gly/PAA) via sacrificial bond interactions.The hydrogel exhibited excellent mechanical properties,autonomous self-healing,and high stretchability.This dual physically cross-linked hydrogel has an excellent elongation at break and self-healing properties due to the dynamic ionic cross-linking point.By optimizing the synthetic parameters,the hydrogel exhibited excellent mechanical properties with a fracture tensile stress and strain of 0.4MPa and 2110%,respectively.It sustains a compression stress of 32 MPa and has high fracture energy of 3.5 MJm-3.Healing experiment confirms that the newly formulated hydrogel(Gly/PAA-Fe3+) shows the excellent healing property with healing efficiency of 94% without any external intervention at room temperature in 24 hours.In this study,the introduction of the sacrificial bond interactions in a hybrid hydrogel of natural and synthetic polymer,give Gly-PVA/PAA-Fe3+ hydrogel with autonomous self-healing ability and tunable mechanical properties.Hydrogels were designed by sacrificial non-covalent interactions with physical cross-linking the polymer chains to trivalent metal ions.The mechanical properties and self-healing efficiency could be tuned by varying the concentration ratio of natural and synthetic polymers.Usually,the addition of natural polymers increases the mechanical strength while increasing the concentration of PVA cause the flexibility and stretchability of the hydrogels.Due to the tunable mechanical properties and excellent self-healing efficiency,it is suitable for developing advanced soft materials for several applications in biomedical fields.