Self-Organization and Controlled Spatial Distribution of Cellulosic Nanofillers in Polymer Thin Films

Download or read book Self-Organization and Controlled Spatial Distribution of Cellulosic Nanofillers in Polymer Thin Films written by Danielle Grolman and published by . This book was released on 2017 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer nanocomposites have generated widespread interest towards the development of engineered multifunctional materials and novel hybrid assemblies for high performance applications. The addition of anisotropic nanofillers in a polymer matrix can potentially modify the material's optical, thermal, electrical, or mechanical properties due to the high surface area to volume ratio, with increasing advances and focused efforts toward the development of environmentally friendly, reinforced materials from sustainable resources. In this regard, cellulose nanocrystals (CNCs) are promising nanomaterials derived from the world's most abundant natural polymer. However, one of the key challenges and current barriers towards commercialization is controlling uniform dispersion within the polymer matrix in order to achieve effective reinforcement. The objective of this research aims to gain a fundamental understanding on how to control the dispersion and spatial organization of cellulose nanocrystals in polymer thin films by tailoring the thermodynamic interactions between the host polymer matrix and rod-like nanoparticles.The first part of this dissertation focuses on developing a facile strategy to manipulate the spatial distribution of cellulose nanocrystals in polymer thin films, which are highly susceptible to particle aggregation due to strong hydrogen bonding interactions. A model symmetric diblock copolymer poly(styrene-block-methyl methacrylate) (PS-b-PMMA) was utilized as an ideal nanostructured template to selectively sequester and organize the cellulose nanocrystals via directed self-assembly wherein the CNCs were subjected to a degree of confinement within the multilayered structure. The incorporation of anisotropic nanofillers was observed to perturb the block copolymer (BCP) morphology at relatively low nanofiller concentrations. Surface chemistry modification of the nanoparticle was employed to alter interparticle and particle-polymer interactions and subsequently control nanoparticle distribution. Furthermore, significant enhancement in the mechanical performance of these polymer nanocomposite systems were attributed to the multiscale interfacial interactions between the polymer matrix and fillers. To gain insight into the stabilization and wetting behavior of polymer nanocomposite thin films, the presence of anisotropic nanofillers in a polymer matrix was investigated on non-wetting, low surface energy substrates. Control measurements on the film morphology of homopolymer systems without nanoparticles exhibited immediate film rupture and dewetting due to unfavorable interactions between the substrate and polymer thin film. The addition of cellulose nanocrystals was observed to significantly retard dewetting kinetics and resulted in dewetting suppression where thin film stabilization was achieved at a critical particle threshold. These findings exploit the tunable wettability and nanoparticle-induced stabilization of nanoscale films without any required substrate modification which could have significant ramifications towards the development of novel functional coatings.