Allomorph transformation in cellulose nanocrystals from cellulose I to cellulose III on a 2D-​surface submonolayer

Reeta Salminen, Eero Kontturi

    Research output: Contribution to conferencePaperScientific

    Abstract

    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.
    Original languageEnglish
    Publication statusPublished - 2016
    EventAmerican Chemical Society National Meeting & Exposition - San Diego, United States
    Duration: 13 Mar 201617 Mar 2016
    Conference number: 251

    Conference

    ConferenceAmerican Chemical Society National Meeting & Exposition
    Abbreviated titleACS
    CountryUnited States
    CitySan Diego
    Period13/03/201617/03/2016

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