Deformation Behavior of Weakly Segregated Block Copolymers. 1. Influence of Morphology of Poly(styrene-b-butyl methacrylate) 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 in-situ deformation device and by TEM. This allows us to describe the craze growth and propagation in block copolymers with different morphologies. The influence of shape and orientation of morphology on deformation mechanism is discussed in correlation with tensile properties. For lamellar, hexagonal, and lamellar/hexagonal structures diversion of crazes and craze stopping mechanisms are observed. The discussion of the dependence of craze initiation stress, σc, on morphology is used to correlate the micromechanical deformation processes with tensile properties. In contrast to other block copolymers, it is shown that σc exceeds the value of pure PS at 76% PS due to the hexagonal morphology, high miscibility, and broadened interface of PS-b-PBMA which explains the improved tensile properties of weakly segregated block copolymers. It is shown that microphase separated morphologies, phase behavior, and interface formation have a pronounced influence on deformation behavior of PS-b-PBMA diblock copolymers.

Morphology and micromechanical deformation behavior of SB‐block copolymers. II. Influence of molecular architecture of asymmetric star block copolymers

“…In addition, mechanisms such as craze termination, craze coalescence, and craze diversion were observed in poly(styrene-b-butyl methacrylate) (PSb-PBMA) diblock copolymers. 30 Star block copolymers investigated in this study, however, show a new homogeneous plastic deformation of PS lamellae.…”

Morphology and micromechanical deformation behavior of styrene/butadiene‐block copolymers. I. Toughening mechanisms in asymmetric star block copolymers

“…Recently, the plastic deformation of the PS matrix initiated by cavitation of PB cylinders in SB diblock copolymer was investigated 14 and accepted as a principal deformation mechanism in diblock copolymers. 5 In contrast to diblock copolymers, where a local cavitation mechanism can be observed, the investigated star block copolymers show a homogeneous deformation. As shown in Figure 2, a more diffuse cavitation in PB occurs, confirming the homogeneous characteristics of deformation in this sample.…”

“…2(a)]. In contrast to diblock copolymers, where the deformation zones are highly localized, 4,5,14 both PS and the PB lamellae are homogeneously deformed, which demonstrates that the PS lamellae show a large plastic deformation over the entire specimen. Microvoids are heavily stained by OsO 4 in different regions, as shown in Figure 2(b,c).…”

“…11,12 Block copolymers generally show different deformation mechanisms compared to those of homopolymers because of the microphase-separated morphologies (e.g., structures in the nanometer scale are often too small to initiate crazes). 5,13,14 Therefore, deformation mechanism in diblock copolymers is much different from the crazing mechanism in PS. Schwier et al 14 proposed a model for craze growth in polystyrene-b-polybutadiene diblock copolymers on the basis of a mechanism of cavitation in the PB domains under the concentrated stresses of the craze tip.…”

Chemical composition effects on the fracture of polystyrene‐block‐poly(methyl methacrylate)block copolymers

“…BCPs have a wide range of tailorable properties that are strongly affected by microphase separation, chemical composition, and chain orientation. Therefore, the fracture properties of BCPs depend not only on the molecular weight, 9 ordered structure, 10,11 and chain architecture 12 but also on the macroscopic alignment 10,13 and thermal aging. 14 Recent developments in high-performance liquid chromatography (HPLC) for BCPs have enabled the separation of BCPs by chemical composition differences.…”