Tuning Polymer Blends to Cocontinuous Morphology by Asymmetric Diblock Copolymers as the Surfactants

Abstract

We investigated the influence of the chain asymmetry of the styrene (S)Àmethyl methacrylate (MMA) copolymer (surfactant) on the morphology of the polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends. It was, for the first time, demonstrated that the chain asymmetry of the block copolymer surfactant would have significant influence on the structure of the polymer blend in the melt mixing process. In the PS/PMMA = 30/70 blends, the addition of asymmetric AB diblock copolymers tuned the morphology from the droplet-in-matrix structure to the cocontinuous structure. At 20 wt % asymmetric AB block copolymer (PMMA 110 -block-PS 430 ) dosage, the onset of the cocontinuous interval of the PS/PMMA blends was lowered to PS/PMMA = 20/80 and the cocontinuous interval was broadened to PS/PMMA = 20/80À30/70, compared with the onset at PS/PMMA = 45/55 and the interval at PS/PMMA = 45/55À50/50 of the PS/PMMA blends without the copolymers. The reason was that the packing of the asymmetric block copolymer on the interface provided the bending energy being against the interfacial energy when the longer block of the copolymer was in the minor phase side, suppressing the breakup of the minor phase fibers during melt mixing. With the addition of 20 wt % AC block copolymer (P(S-ran-MMA) 220 -block-PS 320 ), which was more asymmetric than the AB block copolymer (PMMA 110 -block-PS 430 ) of the same molecular weight and monomer composition, the PS/PMMA blends showed an even wider cocontinuous interval at PS/PMMA = 10/90À30/70.

Morphology of polystyrene/poly(methyl methacrylate) blends: Effects of carbon nanotubes aspect ratio and surface modification

“…Fillers and especially nanofillers can change the morphology type and phase size mostly because of a combination of changed viscosity ratios during morphology creation and reduced coalescence due to steric hindrance. Examples of such fillers include nanoclay, carbon black, copolymers, and nanoparticles . For example, Filippone et al have incorporated organoclay into poly(ethylene)/poly (amide) 6 (PA6) blends and found that the clay changes the sea‐island structure of the blends to the cocontinuous morphology, and the rubbery modulus of the composites increased.…”

“…Carbon black and nanoparticles have also been found to change blend morphology. Copolymers and Janus particles can be located at the interface, and can reduce the domain size of the minor polymer phase as well as possibly increasing the interfacial adhesion.…”

Effect of a dual compatibilizer on the formation of co-continuous morphology of immiscible po`lymer blends

“…Recently, Luo et al [47] successfully prepared co-continuous PS/ PMMA blends with only 20 wt% of the minor phase by using asymmetric PS-b-PMMA diblock copolymers as compatibilizers. They assumed that when the longer block of the asymmetric block copolymer was packed on the minor phase side of the interface between the PS and PMMA homopolymers, the bending stress of the copolymer layer could be against the interfacial tension to suppress the breakup of the minor phase fibers during melt mixing, which promoted the formation of the co-continuous morphology.…”

Critical adsorption of an end-grafted diblock copolymer on a flat surface

“…2 Therefore, understanding the physics of adsorption and desorption of the polymer with one end tethered to a surface is useful to design special surfaces with improved biocompatibility. 1 Surfaces coated with polymers are also relevant to many applications in industrial and biological technologies such as chromatography, 5,6 polymer compatibilization, 7,8 medical implants and bioaffinity sensors. 9 The behavior of polymers near attractive surfaces has been extensively studied in theory and by computer simulation.…”