Self-healing Hydrogels for Nanomedicine: Understanding the Fundamentals through Neutron & X-ray Scattering combined with Model Systems

Biological systems have a fascinating ability to repair themselves, i.e. to undergo self-healing. A familiar example is simple skin cuts. Mimicking similar properties in synthetic compounds is an extremely attractive goal for material sciences, life sciences and medicine. Injectable hydrogels, i.e. materials that are solid-like without and liquid-like under shear (e.g. in a syringe) is a convenient way of administrating drugs or other functional substances in the body. In order to design such features, there is a need for a fundamental understanding on how molecules are capable to reorganize themselves and diffuse back to its original form. In this work, we designed a set of minimalistic, very simple model systems that is able to self-repair and heal after deformation and used neutron and X-ray scattering to get insight into the microscopic structure and dynamics. The system of choice was a well-defined model system consisting of simple self-assembling polymers that forms hydrogels consisting of nanostructured micellar-like network. In the study, we combined state-of-the art time-resolved scattering techniques to decipher the dynamics of the polymer, with rheological methods to determine the mechanical strength. In the study, we showed that the rheological properties, including the self-healing, are decided almost solely by the lifetime of the ?bridges? which is controlled by the size of the hydrophobic molecular patches. Moreover, we have gained a profound understanding of the chemical design rules to achieve full control of both structure and mechanical properties. This insight is crucial for intelligent design of self-healing polymer matrices useful for example for biomedical applications.

Biological systems have a fascinating ability to repair themselves, i.e. to undergo self-healing. A familiar example is simple skin cuts. Mimicking similar properties in synthetic compounds is an extremely attractive goal for material sciences, life scie nces and medicine. Injectable hydrogels, i.e materials that are solid-like without and liquid-like under shear (e.g. in a syringe) is a convenient way of administrating drugs or other functional substances in the body. In order to design such features, th ere is a need for a fundamental understanding on how molecules are capable to reorganize themselves and diffuse back to their original form. In this work we design a set of minimalistic, very simple model systems that are able to self-repair and heal afte r deformation and use neutron and X-ray scattering to get insight into the microscopic structure and dynamics. The systems of choice is self-assembling block copolymers that forms hydrogels. In this way a nanostructured micellar-like network is formed whe re the hydrophobic patches connect and bind the micelles together. The mechanical strength (rheological properties) is here expected to be decided solely by the polymers spanning the micelles and their lifetime. Here we show how neutron scattering can be used to directly measure the microscopic dynamics- the kinetics of molecular exchange, which can be directly correlated with the macroscopic rheological properties. In this study we will systematically study the kinetics and mechanical properties of suc h systems by combining state-of-the art time-resolved scattering techniques with rheological methods. We will also provide studies on how scattering techniques can be used to study the stability and role of molecular exchange on the properties related nan o-carriers for drug-like molecules. Apart from the scientific insight expected, we believe that this project will give valuable methodology useful for areas such as life science, nanotechnology and materials science