Ketal-Modified Cellulose as a Biodegradable Bioplastic

Abstract

Polymeric plastic materials pervade every part of modern society. The vast majority of these plastics are petroleum-based; their production generates over 2 gigatons of CO₂ equivalent annually, and their waste biodegrades extraordinarily slowly. Thus, there is an urgent need to transition away from nonrenewable nonbiodegradable plastics. Biologically derived polymers hold potential to produce plastics with drastically reduced environmental impact, during both their production and waste remediation. Cellulose esters and ethers are among the oldest successful renewable plastics, but they can suffer limitations related to their processability and degradability. We report on the homogeneous phase chemical modification of cellulose to form methoxy isopropylidine acetal-modified cellulose, MiP-Cel. Chemical and materials characterization reveals a high degree of substitution and excellent solution processability. MiP-Cel forms transparent, smooth, freestanding films, which are measured for optical clarity and hydrophobicity. Finally, the pH-dependent degradation of MiP-Cel-derived materials is assessed.

1. Modification of Cellulose to Form MiP-Cel

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X–H region of ATR-FTIR spectra comparing MCC, MiP-Cel, and the product of MiP-Cel degradation.

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Powder XRD diffractogram comparing MCC, MiP-Cel, and degraded MiP-Cel.

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¹H NMR analysis of MiP-Cel shows the expected anomeric protons, ring protons, methoxy groups, and methyl groups.

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Quantitative 13C NMR of MiP-Cel.

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Analysis of MiP-Cel films. (a) Freestanding MiP-Cel film. (b) Optical transparency of a 12 μm thick film with visual spectral range annotated. (c) An advancing contact angle measured as 98°. (d) SEM micrograph of film (left) on carbon tape (right).

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Degradation of MiP-Cel films in buffer (a) or compost (b). Insets show a loss of mechanical integrity over the course of compost incubation.