Coarsening Dynamics in Co-Continuous Polymer Blends and Composites
Co-continuous polymer blends find extensive use across multiple industries. However, the morphology of these blends is thermodynamically unstable, which causes coarsening during processing. As a result, it is essential to understand the coarsening mechanism to improve their performance. Unfortunately, the current literature lacks a comprehensive explanation of the microstructural changes that occur during coarsening. To address this issue, the study employs 4D laser scanning confocal microscopy coupled with rotational rheometry to observe the coarsening dynamics in real-time. The aim is to understand the interplay between viscoelasticity and morphology during coarsening. The results show that when the ratio of interfacial tension to viscosity of blends exceeds a critical value, they tend to break down into droplet-matrix structures. The study also focuses on improving the stability and functionality of blends by incorporating solid particles. In literature, particle surfaces are often chemically modified, requiring complex and costly treatments. Therefore, this study examines the stability of co-continuous blends with pristine particles and how particle size and size distribution affect the stability. The study investigates the coarsening dynamics of blends filled with five different silica particles of diameters ranging from 5 nm to 490 nm. The results show that particle size does not play a role in blend stability when particles are thermodynamically driven to their preferred polymer phase. However, a striking effect is achieved when particles are kinetically trapped at the interface. The interparticle interaction governs their extent of agglomeration and, consequently, their ability to stabilize the morphology. The most effective, 140 nm and 250 nm particles are then added into blends under different loading ratios to simulate polydispersity in four different blends. The study demonstrates that polydispersity in particle size does not negatively affect blend stability. The efficacy of particles to suppress coarsening is dependent on their initial localization in the blend, which is determined by polymer characteristics. Overall, the study's findings provide a better understanding of the coarsening mechanism and stabilization of co-continuous morphology in polymer blends using particles. The results contribute to the fundamental knowledge of these materials and can aid in improving their design in various industries.
confocal microscopy, rheology, microstructure
Shah, R. S. (2023). Coarsening dynamics in co-continuous polymer blends and composites (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.