Thermoresponsive cellulose-based composites by polymer modification

Sammanfattning: The interest in utilizing cellulose based materials has grown rapidly in recent years, due to the growing environmental concerns about utilizing fossil based material. One potential application of cellulose is in thermoresponsive materials, which are attracting attention due to their ability of altering conformation when exposed to changes in external temperature. In this study, a variation of cellulose substrates have been utilized; both as the main component and as reinforcing fillers in thermoresponsive composites.Photoinduced controlled radical polymerization was utilized to graft the thermoresponsive polymer poly(di(ethylene glycol) ethyl ether acrylate) (PDEGA)  from the surface of filter paper. The method showed to be efficient to graft large amounts of polymer from the cellulose surface in short reaction times, while utilizing smaller amounts of catalyst than typically employed in controlled radical polymerizations.Di-, tri, and star block copolymers of quaternized poly(2-(dimethylamino)ethyl methacrylate) (qPDMAEMA) and poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) were synthesized by atom transfer radical polymerization (ATRP), and adsorbed to cellulose nanofibrils (CNFs) in a water dispersion. This provided a simple route for the preparation of thermoresponsive CNF based composites.Thermoresponsive cryogels of poly(N-isopropylacrylamide) (PNIPAAm), synthesized by free radical polymerization (FRP), were reinforced by the addition of cellulose nanocrystals (CNCs). Two types of CNCs were investigated: neat CNC and CNC with acrylic, polymerizable,  groups attached to its structure. The CNC addition showed to be an efficient way to modify the mechanical properties of the cryogels.All materials synthesized in this project displayed thermoresponsive properties. Cellulose can therefore be considered to be a promising material for the production of more environmentally friendly thermoresponsive composites.