Poly interface with polystyrene, interfacial

The interfacial properties of an amphiphilic block copolymer have also attracted much attention for potential functions as polymer compatibilizers, adhesives, colloid stabilizers, and so on. However, only a few studies have dealt with the monolayers o well - defined amphiphilic block copolymers formed at the air - water interface. Ikada et al. [124] have studied monolayers of poly(vinyl alcohol)- polystyrene graft and block copolymers at the air - water interface. Bringuier et al. [125] have studied a block copolymer of poly (methyl methacrylate) and poly (vinyl-4-pyridinium bromide) in order to demonstrate the charge effect on the surface monolayer- forming properties. Niwa et al. [126] and Yoshikawa et al. [127] have reported that the poly (styrene-co-oxyethylene) diblock copolymer forms a monolayer at the air - water... 

The first set of experiments that will be considered has examined the ability of random copolymers of styrene and methyl methacrylate to improve the interfacial strength between polystyrene and poly(methyl methacrylate). Using the asymmetric double cantilever beam technique, the researchers have found that a diblock copolymer (50/50 composition, Mw = 282,000) creates an interface with strength of400 J/m2. When utilizing a random copolymer however, it was found that the strongest interface (70% styrene, Mw =... 

Experiments in which interfacial widths were directly measured have been summarised by Stamm and Schubert (1995). The most studied pair has been polystyrene and poly(methyl methacrylate), whose interfacial width has been measured directly using neutron reflectivity. The initial experiments were done by two groups, Anastasiadis, Russell and co-workers (Anastasiadis et al. 1990) and Fernandez, Higgins and co-workers (Fernandez et al. 1988) both obtained the virtually identical result that the interface was described by a tanh profile with a width of 25 A This result is consistent with the interfacial tension measurement, but the prediction of equation (4.3.11) using an independently measured value of % (Russell et al. 1990) is for a width of 14.9 A. 

SBM) as a compatibilizer. As a result of the particular thermodynamic interaction between the relevant blocks and the blend components, a discontinuous and nanoscale distribution of the elastomer at the interface, the so-called raspberry morphology, is observed (Fig. 15). Similar morphologies have also been observed when using triblock terpolymers with hydrogenated middle blocks (polystyrene-W<9ck-poly(ethylene-C0-butylene)-Wock-poly(methyl methacrylate), SEBM). It is this discontinuous interfacial coverage by the elastomer as compared to a continuous layer which allows one to minimize the loss in modulus and to ensure toughening of the PPE/SAN blend [69],... 

One might wonder whether it is possible to correlate the interfacial fracture energy of an incompatible polymer pair more precisely to the width of the interface. Such a correlation clearly exists at a qualitative level. For example, polystyrene is substantially less miscible with poly(2-vinyl pyridine) (PVP) than it is with PMMA. This is reflected via equation (4.2.4) in the width of the... 

Figure 7.9. Interfacial reinforcement of a polystyrene/poly(vinyl pyridine) interface by a high relative molecular mass deuterated styrene-vinyl pyridine block copolymer, with degrees of polymerisation of each block 800 and 870, respectively. Circles (right-hand axis) show the measured interfacial fracture energy as a function of the areal chain density of the block copolymer 2, whereas crosses show the fraction of dPS found on the polystyrene side of the interface after fiacture. The discontinuity in the curves at 2 = 0.03 nm is believed to reflect a transition from failure by chain scission to failure by crazing. After Kramer et al. (1994).

Styrene has also been polymerized under dispersion conditions in CO2. However, the poly(FOA) homopolymer and the PDMS macromonomer were not the best stabilizers for this monomer. Polystyrene (PS) was polymerized efficiently under dispersion conditions using a PS/poly(FOA) diblock stabilizer (48). The PS segment anchored to the growing PS particle, while the poly(FOA) block provided steric stabilization in CO2. Indeed, it has been shown that the block copolymer reduces the interfacial tension at the PS-CO2 interface (49). As was shown previously, added stabilizer increased both the yield and molecular weight of the PS when compared with polymerizations without stabilizer. The mean particle diameter and the particle size dispersity decreased as the length of both the PS and the poly(FOA) blocks increased. Poly(FOA) homopolymer did offer some stabilization to the dispersion polymerization of PS when compared with no added stabilizer, but the presence of the PS block greatly enhanced the stabilization of the PS particles. 

The molecular weight of the reactive polymers, thus of the constitutive blocks of the compatibilizer, is also critical for efficient entanglements with the phases to be compa-tibilized. Indeed, good interfacial adhesion is essential for stress transfer from one phase to the other one to be efficient and for cracks initiated at the interface to be prevented from growth until catastrophic failure occurs. Kramer et al. studied the fracture mechanism of the polystyrene/poly(2-vinylpyridine) interface modified by the parent di-block copolymer. They found that the minimum degree of polymerization of PVP for entanglement (Npvp) was 255, below which the PVP block was pulled out in slow crack opening experiment [93, 94]. 

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