Probing the interfacial region of microphase-separated block copolymers by differential scanning calorimetry

Abstract

A region of broad nonlinear curvature is observed in DSC traces of ABA copolymers during temperature sweeps between the glass transition temperatures of the two principal microphases. This curvature is attributed to a smoothly varying composition profile through the interfacial region lying between microphases. The shape of the DSC curve is proposed to be a fingerprint for a given profile. This curvature is, however, shown to be a possible source of uncertainty in precise evaluation of Tg for the microphases and the reported enhanced breadth of these transitions. In addition, microphase separation temperatures are readily identifiable from DSC traces, and their values correspond well to the predictions of Leary‐Williams theory. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 267–274, 1999

Synthesis and Characterisation of Styrene Butadiene Styrene Based Grafted Copolymers for Use in Potential Biomedical Applications

“…As presented in Figure 6, a T g value at -92°C was located in the butadiene rich microphase domain which coincides with the T g (-90°C) of pure PB and this result is in agreement with the findings of Spaans et al,(1999) and Kennedy et al, (2009). The glass transition of the PS domain in SBS copolymer can be detected at around 67°C which corresponds with the findings of Spaans et al,(1999) , Kennedy et al, (2009) and Mohammady et al,(2005). This value was significantly lower than the T g at 100°C for a PS homopolymer of comparable molecular weight.…”

“…These elements, rich in one block, take the form of either spherical, cylindrical or lamellar domains (as previously discussed) dispersed in a continuous matrix of the other component. The phase-separated structure for SBS contains two homogeneous, nearly pure phases and a third diffuse interphase (Spaans et al, 1999). A schematic of these phases is illustrated in Figure 4.…”

“…Schematic representation of SBS molecule embedded in a phase separated microstructure consisting of matrix B, core S and a broad interphase of mixed S and B. S represents styrene and B represents butadiene (Spaans et al, 1999). Spaans et al, (1999) has correlated this information with a typical DSC thermograph of SBS to represent the locations of these microphase domains.…”

“…S represents styrene and B represents butadiene (Spaans et al, 1999). Spaans et al, (1999) has correlated this information with a typical DSC thermograph of SBS to represent the locations of these microphase domains. A graphical representation illustrating Spaans concept is shown in Figure 5.…”

“…5. A graphical representation of a DSC thermograph illustrating the Tg changes in the local heat capacity at a sequence of positions through the interfacial region, as the sample experiences a broad temperature range (Spaans et al, 1999).…”