Role of “Hard” and “Soft” Confinement on Polymer Dynamics at the Nanoscale

Abstract

We investigated the segmental dynamics of asymmetrically confined polymer films and report an unusual phenomenon in which the presence and thickness of a soft confining layer are responsible for significant changes in the segmental dynamics of the confined films. Specifically, the segmental dynamics of poly(vinyl alcohol) (PVA) thin films asymmetrically confined between hard aluminum (Al), and soft polystyrene (PS) films are shown to shift by as much as half an order of magnitude upon changes in the thicknesses of the confining PS layer. These effects are more significant than those due to symmetric confinement between hard Al substrates or exposure to a free surface. These observations, partially rationalized in terms of recent simulations and theory, implicate the role of the moduli of the confining layers.

Local Glass Transition Temperature Tg(z) Within Polystyrene Is Strongly Impacted by the Modulus of the Neighboring PDMS Domain

“…High-performance multicomponent materials have nanostructured morphologies where the desired global properties are obtained from an amalgam of local property changes caused by the multitude of internal interfaces. Studies on thin polymer films have demonstrated a host of property changes with decreasing film thickness attributed to interface effects, − including polymer–polymer interfaces. − The efficient design of multicomponent materials requires the understanding of how these interface effects perturb local properties. Glassy–rubbery interfaces between polymer domains impart material toughness and flexibility , and can be used to tune phononic transport .…”

Enhanced Dynamics of Confined Polymers near the Immiscible Polymer–Polymer Interface: Neutron Reflectivity Studies

“…11,[15][16][17][18][19]22 Lang et al also perfomed molecular dynamics (MD) simulation study regarding the effects of polymer−polymer interaction energy and hardness of confining polymer on change in T g of confined polymers. i v i d u a l n o t d i r e c t l y a s s o c i a t e d w i t h s c i t e i s p r o h i b i t e d .…”

“…In addition to polymer–solid and polymer–air interfaces, studies have recently focused on polymer structure and properties, such as T g and dynamics of nanoconfined polymers, near polymer–polymer interfaces. − The contribution of the region near the polymer–polymer interface in polymer blend systems is not ignorable if the domain size is sub-100 nm, and the interface predominantly influences the overall blend structure and properties. , In this respect, understanding the local dynamics is clearly necessary. We have previously investigated the diffusion dynamics of PMMA/ d PMMA confined between graphene oxide (GO) sheets (GO/PMMA/ d PMMA/GO) using the neutron reflectivity (NR) technique .…”

“…The importance of this research topic for practical applications has resulted in numerous theoretical and experimental studies of changes in the structure, dynamics, and T g of thin polymer films on various polymer surfaces with different interfacial structures, mechanical softness, and interfacial energies. ,− , Lang et al also perfomed molecular dynamics (MD) simulation study regarding the effects of polymer–polymer interaction energy and hardness of confining polymer on change in T g of confined polymers . They found that as the polymer–polymer interfacial adhesion energy decreases, there is no difference between soft and hard confinement effect on the T g changes.…”

Polymer–Polymer Interfacial Perturbation on the Glass Transition of Supported Low Molecular Weight Polystyrene Thin Films

“…Compared with free surface and polymer–substrate interface, more complicated factors determine the polymer–polymer interfacial perturbation due to the diversity of polymers. Polymer–polymer interfacial perturbation has been studied mainly by stacking different polymer thin films − or dispersing polymer nanoparticles in blends . Rharbi investigated the T g of emulsion polymerized PS nanospheres confined in cross-linked poly­(butyl methacrylate) matrices, and T g depression was observed when the particle size was decreased to below 50 nm .…”