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.
The kinetics of interface formation between poly(dimethylsiloxane) (PDMS) and poly(ethylene oxide) (PEO) with and without low molecular weight copolymer PDMS-g-PEO has been studied by interfacial tensiometry. For the PDMS/PEO interface, interfacial tension is constant with time and the interface is immediately formed. For the PDMS/PEO interface with copolymer, interfacial tension decreases slowly or goes to a minimum (unexpected) with time before reaching its equilibrium value, depending on copolymer concentration in the PEO. This kinetics of interface formation with an overshoot has been explained with two processes: adsorption of the copolymer at the interface by transfer over an energy barrier and relaxation of the interfacial layer.
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