Cellulose, the most abundant and important biopolymer, deserves a special position among the industrially used raw materials. The annual yield of cellulosic matter resulting from photoinitiated biosynthesis amounts to approximately 10¹¹ -10¹² tons. Cellulose is one of the main cell wall constituents of all major plants. It is found in nonlignified (such as cotton) and lignified (such as wood) secondary plant cells. In wood it constitutes 40-50% by weight, while nearly 90% in cotton. Cellulose is a macromolecule consisting of ß-1,4-linked anhydro D-glucopyranose structural units.

The raw material sources for industrially used cellulose are cotton, flax, hemp, jute, ramie, bagasse, sisal and - the most important renewable natural resource in terms of quantity - wood. In wood, cellulose is part of an ingeniously constructed fiber-reinforced composite in which long, stiff cellulose chain molecules organized in thin fibrils constitute the plant reticulum material held together and protected by hydrophobic lignin acting as binder and encasement. To isolate cellulose from wood for industrial applications, the wooden composite must be broken up by so-called pulping processes. In these treatments, other wood constituents, such as lignin (20-30%) and hemicelluloses (20-40%), are to a large extent degraded and dissolved. The greatest portion of industrially used wood cellulose by far is used after partial removal of the noncellulosic constituents in its original fiber form for the production of paper, board and nonwovens. The same applies to most of the long-haired cotton fibers and their use in the manufature of textiles. Only a minor portion is used in form of high-alpha-cellulose wood pulps or cotton linters as starting material for the production of synthetic cellulosic fibers , primarily viscose and acetate fibers, or regenerated cellulose films, and cellulose derivatives, especially esters and ethers. Cellulose esters are usually applied as so-called primary components (plastics, fibers), whereas cellulose ethers are used as auxiliaries (detergent additives, thickening, suspending and binding agents, adhesive improvers). Cellulose ethers such as methylcellulose, hydroxyethylcellulose and the corresponding mixed ethers are widely used as concrete additives in the building industry. They improve the dispersion of sand or cement, intesify the adhesiveness and act as moisture-retaining agents. Novel plasticizers based on cellulose were obtained by selective functionalization of cellulose, varying the molecular weight in a broad range. Synthesis was carried out under heterogeneous reaction conditions analogously to common industrial processes. Advantages of chemical reactions in heterogeneous systems are avoidance of problems with high viscosity at high polymer concentrations, easy removal of by-products and maintainance of the fibrous or particulate state of the starting material throughout the reactions. Main disadvantages are non-uniform degrees of substitution and uneven substituent distribution among and along the cellulose molecules. The degree of uniformity of partially substituted cellulose derivatives has a profound effect on the resulting properties, above all on the solubility of the products. To overcome these problems, reactions can be carried out homogeneously in a number of sovents developed for cellulose which yield true cellulosic solutions. We used DMA/LiCl for the synthesis of amino-functionalized cellulose and liquid crystalline cellulose esters , resp., under homogeneous reaction conditions.

Hyaluronic acid (HA), or hyaluronan, is a versatile building block of novel biomaterials for tissue engineering and regenerative medicine. As the major component of extracellular matrix (ECM), HA is widely distributed in most connective tissues (skin, cartilage, etc.) and plays an important role in wound repair process. However, the native HA is far beyond the direct use in certain preclinical studies (e.g., articular cartilage regeneration) because it lacks of mechanical strength and long-enough duration in vivo. To address these problems, researchers have explored the (meth)acrylated HA as polymerizable hydrogel precursors which are injectable and biomechanically robust. 

We are particularly interested in developing cytocompatible and (photo)polymerizable HA derivatives that are injectable and suitable for potential clinical applications. Specifically, we focus on the synthesis of low toxicity derivatives of HA by introducing cell-friendly functional groups (e.g., vinyl esters). Compared to acrylate, the vinyl ester chemistry shows much more promise due to its unique degradation products (FDA-approved poly(vinylalkohol) and easy-removable acetaldehyde)