Effect of Chain Flexibility and Interlayer Interactions on the Local Dynamics of Layered Polymer Systems

Abstract

Layered polymeric systems are widely used in membrane separation applications; chain mobility in these layered systems is a key consideration in the design of the membranes. The transport properties of membrane polymers can be significantly altered by the perturbations in chain dynamics induced by the presence of an interface and also by the topological properties of the polymers constituting the layered systems. In this work, we use molecular dynamics (MD) simulations to determine the effects of polymer backbone flexibility and interlayer interactions on the glass transition and chain dynamics of polymer layers in the layered systems. We observed that the onset of glass transition of the entire layered system is governed by the stiffer polymer layer and is independent of the type of interactions between the layers. However, the interlayer interactions govern the strength of the glass transition of the entire layered system. Polymer mobility, on the other hand, exhibits a strong dependence on both the chain flexibility and the interlayer interactions. In systems with attractive interactions between the layers, the fully flexible polymer chains at the interface have a lower mobility than those in the bulk region of the layer; the behavior differs from that of rigid polymers, which have a higher mobility at the interface compared to that in the bulk. On the other hand, when the interactions between the layers are repulsive, each layer acts as a free-standing film with chains in both the layers exhibiting higher mobility at the interface.

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

“…A localized fluorescence method is used to measure the local T g ( z ) of a thin pyrene-labeled PS probe layer placed at a distance z from the PS/PDMS interface. These findings demonstrate that the breadth of the compositional interface between the two dissimilar polymers and the modulus of the neighboring domain are key factors controlling the T g ( z ) behavior, providing insight for related theoretical efforts in the field ,,,,− into the control parameters responsible for this phenomenon. Characterization of the local properties near the interface of PS/PDMS, in particular, are relevant for a range of applications from mechanical reinforcement of polymers , to the buckling-based metrology used to measure the modulus of ultrathin glassy films. − …”

“…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 .…”

Investigation of the gas permeability properties from polysulfone/polyethylene glycol composite membrane

“…In this research, by adding PEG, the field for modifying the gas separation properties of the polysulfone membrane has been provided. The type of chains' development has an important role in diffusion properties from membrane due to morphology, crystallization, compression and glass transition temperature of membrane [13][14][15]. Finding structure and properties of polymeric membranes are key factors to obtain better efficiency of gas separation from membrane.…”

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 .…”