Appearance of this peak is also concomitant with an increase in %CTA selectivity for the 3 representative samples (Figure ) from low to high . Considering that topochemical conversion to crystalline CTA has been observed for the Sassi & Chanzy acidcatalysed system ) and that we do not observe drastic changes in the relative intensities of the cellulose I peaks at high DS (Figure ), it seems logical that a similar topochemical conversion of whole fibrils is occurring in our case. From these results it is clear that the soil biodegradability of the macro-papers suffers drastically with the formation of CTA (Figure & b), at least over these short time periods. Even the 62.5 vol% nano-paper sample, with a DS of 0.20 and no CTA formation, shows poor biodegradability at 3 months. Thus, CTA formation is only one factor in significantly reducing soil biodegradability. The lower DS 6-acetylated macro-paper sample does indicate some potential resistance to degradation, compared to the reference sample, but is almost completely consumed by the 3-month mark. Surprisingly, the mDMDHEU cross-linked BSK paper sample also shows strong resistance after 1 month in soil but shows clear signs of degradation, in comparison to the CTA-containing samples, after 3 months. Due to the higher expected 'hydrophobicity' of the CTA-containing samples, it is clear that both hydrophobicity and cross-linking can prevent significant swelling of the sample, which may affect the initial penetration of the matrices with degrading microorganisms or enzymes.