Polymer/Silicate Intercalated Nanocomposites: Confinement Induced Segmental Dynamics in 2nm Slits

Introduction Layered-silicate based polymer nanocomposites have become an attractive set of organic-inorganic materials not only for their obvious potential as technological materials, but also for providing a convenient macroscopic system to study fundamental scientific issues concerning confined polymers [1]. Studying the formation, structure and dynamics of these nanocomposites can lead to a better understanding of organic-inorganic hybrids, polymers in a confined environment or at a solid interface, and at the same time provide the necessary fundamental level knowledge to design polymer/inorganic hybrid materials with enhanced properties. Fluids in nanoscopic confinements possess a variety of unusual properties, and in particular remarkable dynamical heterogeneities which vary on length scales as short as a few Ångstroms. While the Surface Forces Apparatus provides an experimental probe of macroscopic properties of a single fluid film between two atomically smooth solid surfaces, few experimental probes are available which test the microscopic origins of these heterogeneities in nanoscopically confined films. However, ultra-thin (~20Å) polymer films confined between solid surfaces can be created by intercalating high molecular weight polymers inbetween allumino-phyllosilicates (micatype layered crystals). Especially where well-defined synthetic silicates –such as fluorohectorite (FH)– are used to form intercalated nanocomposites, very homogeneous ultra-thin confined polymer structures are developed throughout the hybrid composite. In such cases, careful design of the polymer/inorganic hybrid material can provide macroscopic quantities of self-assembled multilayer nanostructured systems that contain huge numbers of identical nanoconfined films. This offers great opportunity to study the properties of polymers and liquids in extreme confinements (1-2nm) by employing conventional analytical techniques [1]. Here, we report selected experimental findings and comparative atomistic modeling efforts aiming in obtaining insight into the confinement induced dynamical processes of ultra-thin polymer films (typically 2nm) observed in polymer/silicate intercalated systems.