Cellulose nanocrystals (CNC) can be studied on a single crystal level when deposited as a submonolayer. This allows observation of effects caused by for instance exposures to different environments or crystal lattice manipulation. Submonolayers were produced by using either spin-coat or adsorption method to deposit CNCs on a cationized silica. This surface pretreatment prevents the anionic CNCs from aggregating and (3-aminopropyl)trimethoxysilane (APTS) was chosen as the cation due to its superb adsorption of CNCs according to our previous tests. The allomorph can be changed from cellulose I to cellulose III in a no. of different ways, however the use of an ethylenediamine (EDA) treatment was chosen. Surfaces were prepd. by using one of the two following methods: 1) depositing cellulose III nanocrystals, or 2) performing the allomorph change treatment on already deposited cellulose I nanocrystals. The allomorph change was detd. for samples produced for Method 1 with CP-MAS 13C-NMR, whereas for Method 2 Raman spectroscopy was utilized.The surfaces were analyzed with both AFM and TEM, and compared to non-treated cellulose I CNC and its submonolayer. The cellulose III submonolayer produced with Method 1 yielded the same dimensions for the crystals as the ref. CNC submonolayers. In contrast, the submonolayers produced via Method 2 showed distinct changes to the CNCs with the notable difference being the formation of aggregates (Figure 1). Moreover, it was obsd. that the CNCs - both in the aggregates and individually - were thinner. In fact, the crystal thickness was decreased by over 50% from around 5 nm to 2 nm. Since the allomorph transition treatment used in this work involves the breaking and re-structuring of inter- and intramol. hydrogen bonding, it is feasible that the detected redn. in crystal size results from the peeling off of the outermost layers of the crystals.
|Publication status||Published - 2016|
|Event||American Chemical Society National Meeting & Exposition - San Diego, United States|
Duration: 13 Mar 2016 → 17 Mar 2016
Conference number: 251
|Conference||American Chemical Society National Meeting & Exposition|
|Period||13/03/2016 → 17/03/2016|