Deformation Behavior of Weakly Segregated Block Copolymers. 2. Correlation between Phase Behavior and Deformation Mechanisms of Diblock Copolymers

Abstract

The deformation behavior of poly(styrene-b-butyl methacrylate) diblock copolymers, PS-b-PBMA, is studied by high-voltage electron microscopy (HVEM) with an in-situ tensile device. While in the first part the phase behavior of PS-b-PBMA diblock copolymers is investigated via small-angle neutron scattering (SANS), in the second part the deformation behavior depending on composition and molecular weight is discussed. Disordered block copolymers have the same deformation mechanism as the corresponding homopolymers, while microphase-separated block copolymers undergo a cavitation mechanism. At the order-disorder transition, ODT, a transition from crazing to cavitation mechanism is found via HVEM. Moreover, a sharp increase of the diameter of craze fibrils occurs at the ODT, demonstrating that the craze microstructure is strongly influenced by phase behavior. As the incompatibility increases with increasing molecular weight, deformation mechanisms such as diversion and termination of crazes are observed for intermediately segregated block copolymers. The discussed correlation between phase behavior and deformation mechanisms indicates the existence of a unified scheme for deformation behavior of diblock copolymers depending on the strength of segregation, N.

Mechanical properties of gradient copolymers of styrene and n -butyl acrylate

“…More interestingly, both LG and DI own similar tensile strength. In the case of DI, it is believed that the cavitation in soft phase should be the dominating mechanism for the quick break of the specimen, as a result of the lack of crosslinks in the rubbery phase of PnBA . It is evidenced that the soft phase cavitation to catastrophic failure should not occur in LG.…”

Influence of Thin Film Confinement on Surface Plasticity in Polystyrene and Poly(2-vinylpyridine) Homopolymer and Block Copolymer Films

“…Block copolymers are facinating materials with a richness of mechanical behavior emerging from the organized nanostructures which can form within. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Over the past several decades, many block copolymer systems have been industrialized and much has been learned about the details of their bulk mechanical behavior. Studies have largely focused on hard-soft material combinations, driven by attempts to toughen materials while maintaining other desirable properties (optical transparency, for example).…”

“…Studies have largely focused on hard-soft material combinations, driven by attempts to toughen materials while maintaining other desirable properties (optical transparency, for example). [3][4][5][6][7][8][9][10] There is also some precedent for the study of hard-hard systems in attempts to compatiblize homopolymer mixtures or attempts to add crystallinity. [11][12][13][14] As one might imagine, material properties are found to depend on almost all of the features governing the nanostructure of the materials (volume fraction, 6,7,9 chain-chain interactions, 4,16 chain orientation and alignment, 7,8,10,12 thermal history 12 ).…”

Simulation study of the morphologies of energetic block copolymers based on glycidyl azide polymer

“…In fact, several empirical or semiempirical methods can calculate the mechanical properties on the basis of the chemical composition and molecular structure for copolymer systems, such as the relationships (adapted to small‐strain behavior, i.e., small deformations) developed by Seitz,13 which obviously ignore the effect of the morphology of copolymer systems 14. It is the morphology (5–100 nm) from the microphase separation that can significantly influence the mechanical properties of block copolymer materials 15–18. To understand the influence of their structures on the properties of energetic block copolymers, we need information on their morphologies and to take them as a bridge linking the microstructures and the macroproperties.…”