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

Abstract

Understanding block copolymer (BCP) self-assembly under confi nement via conventional melt extrusion is advantageous as technology moves towards thin fi lm applications. Previous research has revealed that confi ning elastomeric BCPs in thin fi lms with polystyrene (PS) via microlayering results in an increase in ductility with decreasing layer thickness and that the interfacial region dramatically infl uences the elastic modulus. This contribution investigated the role of interfacial width and layer thickness on deformation mechanics by comparing poly(methyl methacrylate) (PMMA) and PS as wetting layers in confi ned multilayers. The interfacial region was found to be crucial to tailoring the mechanical response of composite materials.group has shown that thin fi lms of confi ned polymers exhibit unexpected physical properties, such as barrier, [ 4 ] thermal, [ 5 ] and mechanical [ 6 ] when compared to their bulk counterparts. [ 7 ] One of the most signifi cant contributions, thus far, has been utilizing forced assembly to confi ne the crystallization of semicrystalline polymers. [ 3 ] The confi ned crystallization of poly(ethylene oxide) (PEO) via microlayer co-extrusion demonstrated that in thick layers, large spherulites developed, while the PEO chains crystallized into in-plane, single lamellae in thinner layers due to the constraint of the confi ning layer. This confi ned crystallization behavior resulted in a reduction in O 2 permeability by two orders of magnitude through the thickness of the multilayer fi lm. [ 8 ] Further research revealed that the nature of the confi ning layer alters the crystal lamellae size in these PEO layered composites, which further infl uences the oxygen permeability of the multilayer fi lms. [ 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 fi lm 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

Controlling the order of triblock copolymer via confinement induced by forced self-assembly

“…SI-4). Contrary to what was observed by Burt et al [10,12,43], SAXS patterns do not show any significant change, probably due to the lack of mobility of the copolymer at this temperature (T g,PMMA + 15 • C).…”

“…In pioneering work, Baer and coworkers used what they have termed a "forced assembly" technique to combine immiscible polymer pairs into unique multilayer structures, leading to remarkable properties such as gas barrier, mechanical, and optical properties [6][7][8][9]. Recently, this forced assembly technique has been used by Korley et al to confine spherical and cylindrical ABA triblock copolymer [10][11][12]. These studies mainly focus on the relationship between the nanostructure and the mechanical properties of the resulting films, while the extrusion was carried out at a temperature below the order-disorder transition temperature (T ODT ).…”

Thin film confinement of a spherical block copolymer via forced assembly co-extrusion

“…32,33 Due to a lowered ODT (145 C), the BCP in this current study could be extruded as a homogeneous melt, which differs from our previous research on aligned microstructures from the melt. 30,31,34 Multilayer films Multilayer lms of an alternating glassy polymer and the sphere-forming BCP were produced in lms of 257 alternating layers at a constant volume composition of 50 : 50 utilizing layered co-extrusion technology. The conning layers (PS or PMMA) were extruded on the external surfaces of the lms.…”

Mechanically tunable dual-component polyolefin fiber mats via two-dimensional multilayer coextrusion

“…The coextrusion process has been described in great detail elsewhere for horizontal multilayering, vertical multi-layering, as well as the combination of the two to fabricate extruded fiber composites. [33][34][35][36][37][38] A brief summary is provided for this specific system. Three extruders were employed to produce the coextruded HDPE/PP/PS composites (Scheme 1).…”