Heat Flow in Solvent-Free, Dense Amorphous and Semi-Crystalline Cellulose Derivatives

Polymers are essential in our everyday life due to their versatility and tunable properties, but common synthetic polymers pose significant environmental challenges. This has led to growing interest in natural, biodegradable alternatives such as cellulose. For cellulose to serve as a viable alternative, it must match or ideally exceed materials properties of synthetic polymers. Thermal conductivity, κ, is one such critical property that often determines the suitability of polymers for a wide range of applications. In this study, we employ large-scale molecular dynamics simulations to investigate heat transport in dense, solvent-free cellulose and cellulose acetate systems. Our focus is on the amorphous phases of both materials, as well as the semi-crystalline phase of pure cellulose. By analyzing the vibrational density of states, g(ν), we report quantum-corrected estimates of the heat capacity, c, and consequently κ, enabling reasonable comparison with experimental data. Our results show that, over the temperature, T, range of 280-400 K, κ of amorphous cellulose varies between approximately 0.14 and 0.26 Wm^-1 K^-1, while slightly lower values, around 0.12 to 0.22 Wm^-1 K^-1, are observed for amorphous cellulose acetate. Within a similar temperature range, our experimental data for amorphous cellulose acetate give κ ≃ 0.15-0.21 Wm^-1 K^-1. In semi-crystalline cellulose samples, depending on T, κ can increase by approximately 20-35% when the degree of crystallinity reaches d ≃ 20%. These values are comparable to those of standard synthetic polymers, highlighting cellulose as a promising alternative. This study demonstrates that cellulose offers a natural, sustainable alternative to common synthetic polymers, while also providing insight into the thermal behavior of cellulose-based materials.