Forced Assembly of Polymer Nanolayers Thinner Than the Interphase

Abstract

When two polymers are brought into intimate contact, the interface is not perfectly sharp. Instead, localized molecular mixing produces an interphase with thickness on the order of 10 nm. Forced assembly by layer multiplying coextrusion makes it possible to create films that are entirely interphase. The new interphase materials can be characterized using conventional tools of polymer analysis. In this study we vary the ratio of poly(methyl methacrylate) (PMMA) to polycarbonate (PC) in the coextrusion process in order to obtain very thin PMMA nanolayers sandwiched between thicker (∼50 nm) PC layers. We use oxygen permeability to probe the nature of the interphase as the PMMA layer thickness is reduced below the interphase thickness to the limit of layer stability. If the PMMA nanolayers are made thinner than the 12 nm interphase dimension, they more closely resemble a thin interphase region sandwiched between thicker PC layers than they do discrete PMMA layers. The interphase region becomes progressively thinner with decreasing PMMA layer thickness until the limit in melt stability of the PMMA layer is reached. Efforts to obtain PMMA nanolayers thinner than 5 nm resulted in layer instability and breakup. Oxygen permeability suggested that the nanolayer fragments had a very high aspect ratio.

Design and development of microbioreactors for long-term cell culture in controlled oxygen microenvironments

“…We fabricated the gas and culture channels in PMMA sheets due to its low permeability to oxygen (4.3×10 −17 mol/ s cm mmHg (Liu et al 2005;Hess et al 2009)). In addition, PMMA is optically transparent (i.e.…”

Investigating Interfacial Contributions on the Layer‐Thickness‐Dependent Mechanical Response of Confined Self‐Assembly via Forced Assembly

“…Further research revealed that the nature of the confining layer alters the crystal lamellae size in these PEO layered composites, which further influences the oxygen permeability of the multilayer films 9, 10. Similar research utilizing microlayering technology investigated the effect of layer thickness on the glass transition temperature ( T g ) of two immiscible polymers and revealed a critical layer thickness at which the film becomes completely “interphase region,” resulting in a merging of the two material T g s into a single T g for the composite 5, 11. The understanding of structure–property relationships of polymers under thin film confinement has become increasingly important with the push towards utilizing smaller quantities of raw materials.…”

“…Manipulation of materials via microlayer co‐extrusion has been utilized to systematically study the effect of confinement on composite material responses 3. Previous work by the Baer research group has shown that thin films of confined polymers exhibit unexpected physical properties, such as barrier,4 thermal,5 and mechanical6 when compared to their bulk counterparts 7. One of the most significant contributions, thus far, has been utilizing forced assembly to confine the crystallization of semicrystalline polymers 3.…”

Dielectric response of structured multilayered polymer films fabricated by forced assembly

“…The layered materials are readily fabricated by forced assembly techniques. 4, 5 The motivation for a multilayered structure is to take advantage of the barrier effect. [6][7][8][9] It is well known that introducing a component that presents a barrier to the propagation of the electrical breakdown channel can increase the dielectric strength of the material.…”