Polymer materials, including plastics, fibers, thin films, and membranes, are often in a non-equilibrium state. This is due to deviations in chain conformations from Gaussian statistics (which cause entropic stress), distortions of chemical bonds (which cause enthalpic stress) because of the non-equilibrium processing conditions, and sluggish dynamics induced by vitrification that prevent structure recovery during storage and use. We studied the behavior of polymers in non-equilibrium states...
The rapid development of nanotechnology in recent years has created a demand for polymer-based nano-sized devices or materials that exhibit superior performance and stability. As material size decreases to the nanoscale, approaching the typical chain coil size, molecular dynamics and associated physical properties such as glass transition, molecular diffusion, and viscosity deviate greatly from bulk behavior. This phenomenon is known as the confinement effect and severely hampers practical usage. Our research focuses on developing new methods to measure the confined polymer behavior...
Polymeric materials display distinctive structures and dynamics at their surfaces and interfaces due to effects such as the modification of neighboring interactions, symmetry breaking, and chain reflection from the boundary. Polymers located near the air surface experience enhanced mobility, reduced glass transition temperature, a gradient in segmental mobility, reduced entanglement, and an increment of local orientation.We studied how chains behave near the air surface and substrate interface of polymer materials...
