Cellulose acetate (CA) is subjected to different aqueous environments (e.g., lake water, seawater, artificial seawater) under controlled laboratory conditions to investigate the degradation potential in natural water systems. The main changes in the CA films are detected during the first months of the 12-month study. Approximately 5% and 10% weight losses are observed during the first month of aging at RT and at 60 °C, respectively. The temperature effect is rather negligible and the weight loss also does not significantly increase on prolonged aging. A quantitative high-performance liquid chromatography analysis shows that this weight loss is mainly caused by deacetylation and depending on the aging conditions, 10–30% of the acetate groups are lost during the first 1–3 months of aging. Fourier transform infrared and nuclear magnetic resonance analyses further support this. It is well established that a high degree of substitution (DS) is the bottleneck for biodegradation of CA and a significantly higher biodegradation rate has been demonstrated for CA materials with degree of substitution, DS<2, compared to those with DS>2. The degree of deacetylation observed here is enough to decrease the DS to below 2, which can therefore have a significant effect on the subsequent biodegradation.

A fully biobased benzoxazine monomer, V-fa (using vanillin and furfurylamine) was grafted onto chitosan (CS) at different weight ratios (CXVY) using "grafting to" benign Schiff base chemistry. Incorporation of V-fa onto CS increased the tensile strength and improved chemical resistance of the CS-graft-V-fa films. Reversible labile linkages, expansion of CS galleries and leaching out of phenolic species from biobased polymer films led to an improved antibacterial activity against Staphylococcus aureus, which is similar to 125 times higher than the bare CS film, V-fa and oligomeric V-fa. The leached out species from films were analyzed extensively by NMR, FTIR, GPC, ABTS and HRMS analysis. Oxidative-stress seems to be responsible for antibacterial activity. Current work illustrates an attractive synthetic approach and the improved antibacterial performance of biobased CS-graft-poly (V-fa) films which may hold as a potential alternative for wound-healing and implant applications in future.

Chemical modification of biopolymers, before use in thermo-plastic applications, can reduce the susceptibility to open environment degradation. We demonstrate carbon dots (CDs) as green photocatalytic triggers that can render the common cellulose derivative, cellulose acetate (CA), degradable under open environment relevant conditions. CD-modified cellulose acetate (CA + CD) films were subjected to UV-A irradiation in air and simulated sea water, and the degradation process was mapped by multiple spectroscopic, chromatographic, and microscopy techniques. The addition of CDs effectively catalyzed the deacetylation reaction, the bottleneck preventing biodegradation of CA. The photocatalytically activated degradation process led to significant weight loss, release of small molecules, and regeneration of cellulose fibers. The weight loss of CA + CD after 30 days of UV-A irradiation in air or simulated sea water was 53 and 43%, respectively, while the corresponding values for plain CA films were 12 and 4%. At the same time the weight average molar mass of CA + CD decreased from 62,000 to 11,000 g/mol and 15,000 g/mol during UV-A irradiation in air and simulated sea water, respectively, and the degree of substitution (DS) decreased from 2.2 to 1.6 both in air and in water. The aging in water alone did not affect the weight average molar mass, but the DS was decreased to 1.9. Control experiments confirmed the generation of hydrogen peroxide when aqueous CD dispersion was subjected to UV-A irradiation, indicating a free radical mechanism. These results are promising for the development of products, such as mulching films, with photocatalytically triggered environmental degradation processes.

Hydrothermally carbonized cellulose and its further modifications are intriguing materials for a wide range of potential applications. Hydrothermal carbonization is a sustainable process for converting biopolymers or other biomass sources into carbonaceous materials under mild conditions in water and at relatively low temperatures. This review presents the latest progress in modification and utilization of hydrothermally carbonized cellulose and related materials in environmental, biomedical, and energy applications. Further applications presented include evaluation of cellulose-derived carbon spheres or carbon dots as catalysts, antibacterial materials, flame retardants, and functional fillers in bioplastic composites. The wide range of applications highlights the great potential and multifunctionality of hydrothermally carbonized cellulose and its derivatives. The field is expected to further expand and increase in importance as we move toward circular bioeconomy.