Surface Modification of Cellulose Nanocrystals with Glycidyl Methacrylate for UV-crosslinking COST FP1205 13.04.16 Yuval Nevo The Robert H. Smith Faculty of Agriculture, Food and Environment, the Hebrew University of Jerusalem

Introduction

Surface functionalization of CNCs via methacrylation Chemical modification of CNC surface with methacrylate groups will allow the crosslinking of CNC particles and can lead to the formation of crosslinked films, hydrogels and aerogels. This modification will also allow crosslinking of CNC inside acrylic matrices, resulting in composite materials with improved mechanical properties Films Hydrogels Foams Stability in water Improved mechanical properties Improved physical properties

Methacrylation of CNCs MA-CNCs have available methacrylate groups that can be crosslinked via free radical reactions Crosslinking can happen between adjacent particles Crosslinking can be more efficient using a linker (i.e. PEG-diacrylate) MA-CNCs can also be polymerized inside acrylic polymers OH C=C SO3- Covalent crosslinking

Methacrylation of CNCs using Glycidyl methacrylate Reaction conducted in DMSO 4-Dimethylaminopyridine (DMAP) was used as a catalyst Butylated hydroxytoluene (BHT) was used as inhibitor (protecting C=C bonds) + R = H or (DMAP) DMSO CNC CNC

Methacrylation confirmation FTIR analysis Raman analysis

MA-CNC characterization Atomic force microscopy (AFM) CNC’s crystal structure was not destroyed by the reaction 0.01% wt. 0.001% wt.

MA-CNC characterization X-ray diffraction (XRD) Corresponds to cellulose I structure Modification did not change the native cellulose form of the crystals MA-CNC CNC

Thermogravimetric analysis CNC MA-CNC

MA-CNC characterization Solid-state NMR New peaks corresponding to GMA appears Degree of substitution needed to be calculated

Hydrogel formation Irgacure2959 was added to ~1% wt. MA-CNC and 365 nm UV-light was shone Adjacent CNCs were crosslinked to form a stable gel Gel was transferred to water

Aerogel formation Critical point evaporation was used to form aerogels The inner architecture is of ~10 µm wide, long pores (“tunnels”)

Hydrogel formation with linker Crosslinking was conducted with the addition of PEGDA Gels appear to be more stable than those without PEGDA = = PEGDA

MA-CNCs/Acrylamide composites MA-CNCs were crosslinked together with acrylamide, in DMSO 10% acrylamide, 0.75% bis-acrylamide Acrylamide Bis-acrylamide

MA-CNCs/Acrylamide hydrogels Gels with MA-CNCs are much more opaque Gels with MA-CNCs swell less Gels with CNCs are less opaque and swell more

MA-CNCs/Acrylamide hydrogels properties Mechanical properties of gels were tested MA-CNCs mechanically reinforce acrylamide gels Average curves

MA-CNCs/Acrylamide hydrogels CNC/Acrylamide MA-CNC/Acrylamide

Conclusions CNC’s surface was successfully modified with GMA, resulting in methacrylated CNC particles The methacrylation procedure did not change the crystal structure of CNCs MA-CNCs were crosslinked using UV light to form porous gels MA-CNCs were crosslinked along with acrylamide to form reinforced polyacrylamide gels with higher crosslinking density

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