SNF - Nanoscale investigations of water effects on wood S2 layer

Natural materials, from plant origin, are ubiquitous in our daily environment, where they are exposed to environmental loading like temperature and relative humidity variations. In particular, cellulose-based materials such as wood have been used traditionally and ubiquitously, and are particularly attractive nowadays as they offer sustainable solutions and as they can be a source of inspiration for biomimetic design of new materials. Wood, an orthotropic cellular biomaterial, has the capacity of adsorbing water molecules from the surrounding environment into its hierarchical material structure. This material displays remarkable properties combining low weight, high strength and high toughness, originating from this hierarchical organization of crystalline and amorphous polymers.
The aim of this project is to understand the hygromechanical behavior of moisture-sensitive cellulose-based materials. We use wood as the base natural model and synthetize different wood polymer systems, in order to quantify the physical impact of micro-climatic conditions. We probe the systems systematically, combining experimental characterization, in vitro, and atomistic modeling, in silico, and pioneering a meticulous match of the scales of the experimental and computational investigations.

Specifically the objectives of the project are:

1. To develop a fully integrated description and understanding of the role of moisture on wood S2 cell wall layer and similar man-made lignocellulosic systems.
2. To identify the role of polymer configuration on hygromechanical behavior, investigating bulk and thin film polymers, either pure or composite, mixed or layered, and the natural material, i.e. S2.
3. To develop a robust methodology framework of MD investigations interfacing with advanced experimental results, forming “in silico/in vitro” duos, for components and composites.
4. To develop constitutive laws and phase diagrams for components and composites hygromechanical behavior towards a methodological framework for the design of bio-inspired materials.
   
   

Combining in-vitro and in-silico investigations, the project will provide a better understanding of the effects of water on each polymer and on the interactions between polysaccharides and lignin. Understanding the cell wall hygromechanical behavior is achieved by complementing its investigation by a systematic study and control of man-made wood-inspired systems. Such parametric study will allow building a phase-space of lignocellulosic polymers hygromechanical behavior for support of material design. This SNF-ANR project takes benefit of two international-level expertises related to lignocellulosic materials: the atomistic modeling of their interaction with water at Empa (Derome) and their synthesis and characterization at nano- and microscale in Reims at FARE (Chabbert, French coordinator) and at LRN URCA (Molinari).