Toughness of Glassy−Semicrystalline Multiblock Copolymers

Abstract

We report a study on the mechanical properties of lamellae-forming glassy−semicrystalline block copolymers composed of poly(cyclohexylethylene) (C) and polyethylene (E). Tensile properties of polydomain CEC, ECEC, CECEC, and ECECE block copolymers, and blends of these materials, reveal a critical dependence on the connectivity of the semicrystalline E blocks. A molecular parameter directly related to the fraction of bridging E blocks is identified, which captures the fracture behavior of C/E block copolymers over a range of chain architectures. Tensile testing and small-angle X-ray scattering (SAXS) experiments on aligned block copolymers reveal the role of bridging in the glassy C block and further elucidate the mechanisms that govern the deformation of microphase-separated lamellar domains and macroscopic fracture in glassy−semicrystalline block copolymers.

Nanoscale buckling deformation in layered copolymer materials

“…This behavior was demonstrated experimentally in triblock copolymers by Small Angle Xray Scattering (SAXS) under deformation [2], and by micrographs of strongly deformed samples [3] (see figure 1). Similar effects are also observed in lamellar systems with alternating crystalline and glassy parts [4,5], and in deformed semicrystalline polymers, which form locally lamellar structures of crystalline material separated by softer amorphous parts [6].This buckling instability under strain, which is observed in many layered materials from smectic liquid crystals [7] to geological layers [8,9], is frequently described in a qualitative way by a preference to shear compared to an extension in the direction normal to the layers, in order to preserve the lamellar spacing. A different cause for buckling is the existence of a Poisson effect.…”

A New Strategy to Synthesize α,ω‐Dihydroxy Multiblock Copolymers via [CpRu(CH3CN)3]PF6/Quinaldic Acid Catalyst

“…Currently, major sy nthesis methods to get MBCs relying on polycondensation can be divided into two categories, that is, click chemistry and coupling chemistry of α,ω‐dihydroxy to form urethane, ester, or amide bonds . Although some of the MBCs have been successfully prepared and got some applications, those MBCs were mainly focused on thermoplastic materials with superior performance . Therefore, having a special terminal groups of MBCs which can be used as thermosetting material were not yet received much attention and research.…”

“…[6][7][8][9][10][11][12] Although some of the MBCs have been successfully prepared and got some applications, those MBCs were mainly focused on thermoplastic materials with superior performance. [13][14][15][16][17][18][19][20][21][22] Therefore, having a special terminal groups of MBCs which can be used as thermosetting material were not yet received much attention and research. As is well known, the preparation of α,ωdihydroxy polymers has been a hot subject of investigation for several decades owing to their diverse applications in the fields of adhesives and biomedical and elastomeric materials.…”

Phase behavior and Li + Ion conductivity of styrene‐ethylene oxide multiblock copolymer electrolytes

“…[17][18][19] The multiblock architecture has been shown to increase toughness of otherwise brittle materials as well as produce more disordered phase separation when compared with expected morphologies. [20][21][22][23] Both of these properties are advantageous for many applications, but the implementation of MBCs into common use has historically been hampered by their difficult synthesis, specifically sequential block addition by living polymerization. [16,24] Most prolifically, anionic polymerization has produced well-defined controlled MBCs that have played key roles in the fundamental understanding of MBC properties.…”