Interface poly polystyrene

Figure 6.16. Segregation of a deuterium-labelled styrene-vinyl pyridine block copolymer to an interface between polystyrene and poly(vinyl pyridine), revealed by forward recoil spectrometry. The block copolymer was initially imiformly distributed in the upper, polystyrene film after annealing for 8 h at 178 °C an interfacial excess of 100 A has developed. After Shull etal. (1990).

The self-consistent field theory also allows one to calculate the segment density profiles of each homopol)maer and each block of the copolymer. Forward recoil spectrometry is unable to resolve the details of these concentration profiles — the apparent finite width of the copolymer layer shown in figure 6.6 is entirely due to the instrumental resolution - but from neutron reflectivity measurements on a series of differently labelled samples one is able to extract all four segment density profiles. Figure 6.20 shows an example of this, for a styrene/methyl methacrylate copolymer at an interface between polystyrene and poly(methyl methacrylate). 

Figure 6.20. Segment distributions of a styrene-(methyl methacrylate) block copolymer (relative molecular masses of each block were in the range 48 000-65 000) at an interface between polystyrene (relative molecular mass in the range 110000-127 000) and poly(methyl methacrylate) (relative molecular mass in the range 107000-146 000), revealed by a series of neutron reflection experiments in which various parts of the copolymer and/or one of the homopolymers was labelled with deuterium. The bold lines are the segment density profiles for all styrene and methyl methacrylate segments, summed over both the homopolymer and the copolymer the solid lines are the homopolymers, and the dotted lines are the styrene and methyl methacrylate blocks of the copolymer. After Russell et al. (1991).

Figure 7.3. Fracture energies of interfaces between polystyrene and poly(/)-methyl styrene) of various relative molecular masses (A, PS 1 250 000 and PpMS 570 000 o, PS 310 000 and PpMS 570 000 and O, PS 862 000 and PpMS 157 000) as functions of their interfacial widths, measured by neutron reflectivity. After Schnell et al. (1998).

Addition of poly(styrene-block-butadiene) block copolymer to the polystyrene-polybutadiene-styrene ternary system first showed a characteristic decrease in interfacial tension followed by a leveling off. The leveling off is indicative of saturation of the interface by the solubilizing agent. 

Fig. 10. X-ray reflectivity curves of polystyrene (PS)/poly-p-bromostyrene (PBrS) on a glass substrate before (solid line) and after annealing for 13 h at 130 °C (dashed tine) [191]. The width of the interface changes from 1.3 nm to 2.0 nm due to interfacial mixing of components. The X-ray wavelength is 0.154 nm and films have a thickness of 37.8 nm (PS) and 45.0 nm (PBrS), respectively...

Emulsion polymerization is used for 10-15% of global polymer production, including such industrially important polymers as poly(acrylonitrile-butadiene-styrene) (ABS), polystyrene, poly(methyl methacrylate), and poly (vinyl acetate) [196]. These are made from aqueous solutions with high concentrations of suspended solids. The important components have unsaturated carbon-carbon double bonds. Raman spectroscopy is well-suited to address these challenges, though the heterogeneity of the mixture sometimes presents challenges. New sample interfaces, such as WAI and transmission mode, that have shown promise in pharmaceutical suspensions are anticipated to help here also. 

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],... 

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... 

Such hydrophilic macromonomers (DPn=7-9) were radically homopolymer-ized and copolymerized with styrene [78] using AIBN as an initiator at 60 °C in deuterated DMSO in order to follow the kinetics directly by NMR analysis. The macromonomer was found to be less reactive than styrene (rM=0.9 for the macromonomer and rs=1.3 for styrene). Polymerization led to amphiphilic graft copolymers with a polystyrene backbone and poly(vinyl alcohol) branches. The hydrophilic macromonomer was also used in emulsion polymerization and copolymerized onto seed polystyrene particles in order to incorporate it at the interface. 

One of the potential applications of these ABC triblock copolymers was explored by Hillmyer and coworkers in 2005 [118]. They have prepared nanoporous membranes of polystyrene with controlled pore wall functionality from the selective degradation of ordered ABC triblock copolymers. By using a combination of controlled ring-opening and free-radical polymerizations, a triblock copolymer polylactide-/j-poly(A,/V-dimethylacrylamide)-ib-polystyrene (PLA-h-PDMA-h-PS) has been prepared. Following the self-assembly in bulk, cylinders of PLA are dispersed into a matrix of PS and the central PDMA block localized at the PS-PLA interface. After a selective etching of the PLA cylinders, a nanoporous PS monolith is formed with pore walls coated with hydrophilic PDMA. 

Extensive neutron reflectivity studies on surfactant adsorption at the air-water interface show that a surfactant monolayer is formed at the interface. Even for concentration cmc, where complex sub-surface ordering of micelles may exist,the interfacial layer remains a monolayer. This is in marked contrast to the situation for amphiphilic block copolymers, where recent measurements by Richards et al. on polystyrene polyethylene oxide block copolymers (PS-b-PEO) and by Thomas et al. on poly(2-(dimethyl-amino)ethylmethacrylamide-b-methyl methacrylate) (DMAEMA-b-MMA) show the formation of surface micelles at a concentration block copolymer, where an abrupt change in thickness is observed at a finite concentration, and signals the onset of surface micellisation. 

---