2024 AIChE Annual Meeting
A Dielectric and Calorimetric Investigation of Modified Cellulose Polymers
With the depletion of fossil fuels, the potential of plant-based polymers to replace traditional synthetic plastics with equivalent eco-friendly alternatives is a beacon of hope in the field of materials engineering and environmental sustainability. These polymers, abundant and usually featuring biodegradability and biocompatibility, offer a promising future for various applications ranging from biomedicine and tissue engineering to packaging. In fact, cellulose, the most abundant polysaccharide found in nature, is easily chemically modified into various types of cellulose derivatives like methylcellulose (MC) and hydroxypropylmethylcellulose (HPMC). First, we delved into the practical applications of our research by analyzing the calorimetric Tg and the peak water loss for MC and HPMC samples using a Differential Scanning Calorimeter (DSC) equipped with an RCS90 cooler. The samples were tested using standard heating cycles from -50.000°C to 200.000°C and then to 300.000 °C. Second, we explored the real and imaginary parts of dielectric permittivity for MC and HPMC samples using broadband dielectric spectroscopy (BSD). In a temperature-controlled chamber using an Alpha analyzer, the voltage amplitude Vrms of the applied field was kept constant at 1 V, from 10 mHz to 1 MHz, to perform isothermal scans ranging from -45°C to 195°C at 5°C increments. DSC analysis identified a correlation between the MC samples' molecular weight and midpoint Tg value. A proportional relationship was found for the compressed samples. However, the powder samples showed an inverse relationship. For HPMC samples, a correlation was found between the surface hydrophobicity (SH) and the Tg, in powder samples. For all compressed MC and HPMC samples, BDS analysis located segmental relaxation caused by the Tg at higher temperatures and lower frequencies. We also found both β and σ relaxation curves in both MC and HPMC samples. The HPMC samples showed a clear positive correlation between the SH value and the dielectric constant at both the β and σ relaxation points. A small correlation was found for the MC samples between molecular weight and the dielectric constant at low frequencies.