Polystyrene microphases

The observed Tgs of the polystyrene microphases in all of the work quoted above (1,2,3,4,5) were lower than those expected for polystyrene homopolymers having the same molecular weights as the blocks in the block copolymers. We present a detailed comparison of such data below. 

DSC data for SSEBS gave a large broad endotherm at about 0 °C which was unattributed. T for the SSEBS hard block (sulphonated polystyrene) was at about 64 °C and decreased to 54 °C on addition of 27 wt % PCL to the copolymer Tg of the ethylene-butylene block was about -40 °C. This change in Tg of the hard block was attributed to disruption of ionic interactions in the sulphonated polystyrene microphase. It was also suggested that swelling of the sulphonated polystyrene blocks by PCL also allowed more facile development of a well-ordered lamellar morphology. 

Figure C2.1.11. Morjrhologies of a microphase-separated di-block copolymer as function of tire volume fraction of one component. The values here refer to a polystyrene-polyisoprene di-block copolymer and ( )pg is tire volume fraction of the polystyrene blocks. OBDD denotes tire ordered bicontinuous double diamond stmcture. (Figure from [78], reprinted by pemrission of Annual Reviews.)...

LeiblerL., Theory of microphase separation in block copolymers. Macromolecules, 13, 1602, 1980. Eoerster S., Khandpur A.K., Zhao J., Bates E.S., Hamley I.W., Ryan A.J., and Bras W. Complex phase behavior of polyisoprene-polystyrene diblock copolymers near the order-disorder transition. Macromolecules, 21, 6922, 1994. 

Fig. 17. Monolayer of arborescent graft macromolecules consisting of a polystyrene core and poly(2-vlnylplrldlne) shell. Microphase separation between the blocks and strong interaction of the PVP block with mica resulted In lateral arrangement of the PS and PVP domains [89]...

Various types of well-defined block copolymers containing polypropylene segments have been synthesized by Doi et al. on the basis of three methods (i) sequential coordination polymerization of propylene and ethylene 83-m>, (ii) transformation of living polypropylene ends to radical or cationic ones which initiate the polymerization of polar monomers 104, u2i, and (iii) coupling reaction between iodine-terminated monodisperse polypropylene and living polystyrene anion 84). In particular, the well-defined block copolymers consisting of polypropylene blocks and polar monomer unit blocks are expected to exhibit new characteristic properties owing to the effect of microphase separation. 

The concept of using block copolymers for preparation of nanoscopically structured material and surfaces was advanced further by introducing a third block in the chain structure [29]. One of the consequences of the multiphilicity and versatility of the ABC triblock copolymers is their tremendous richness and diversity in morphology. One of the most peculiar structures is shown in Fig. 28 where the helices of a polybutadiene microphase are wound around columns of polystyrene which are embedded in a matrix of polymethylmethacrylate. Complementary to the TEM studies of the bulk morphology (Fig. 28a,b), SFM has been used to image the surface structure of the triblock copolymer films. Figure 28c shows the wrapped PS cylinders oriented parallel to the surface, where one... 

The system with which we have begun our investigations is the styrene-dimethylsiloxane system. The dimethylsiloxane blocks should be considerably less compatible with polystyrene blocks than either polybutadiene or polyisoprene since the solubility parameter of dimethylsiloxane is much farther from that of polystyrene than are the solubility parameters of polybutadienes or of polyisoprenes (17), no matter what their microstructure. Furthermore, even hexamers of polystyrene and of polydimethylsiloxane are immiscible at room temperature and have an upper critical-solution temperature above 35°C (18). In addition, the microphases in this system can be observed without staining and with no ambiguity about the identity of the phases in the transmission electron microscope (TEM) silicon has a much higher atomic number than carbon or oxygen, making the polydimethylsiloxane microphases the dark phases in TEM (19,20). 

Demonstier-Champagne et al. used atomic force microscopy (AFM) to observe microphase separation within cast films of PS-PMPS-PS/ PS-PMPS block copolymer mixtnre [43] that were nsed to compatibilize a blend of PMPS and PS. The fractnre snrface of blend films with the block copolymer incorporated show a far finer dispersion of particle sizes than those without. Matyjaszewski et al. studied PMPS-PS thin films by SFM (scanning force microscopy) and TEM (transmission electron microscopy) and Fig. 8 shows a TEM picture of a thin section of a film which was prepared by slow evaporation from THE, which is slightly selective for the polystyrene block [73]. 

The self assembly of polymers in the solid state, using polystyrene scaffolds with pendant 2,6-diamino-pyridine (DAP) units has been extensively described by Rotello et al. [224] (Sect. 3.3). Two different polymers were investigated either a homopolymer, functionalized with the pendant DAP units, or a PS-PS diblock copolymer, in which one block only was functionalized with the DPA units via a p-chloromethylstyrene block (Fig. 67). In order to study the effect exerted by the hydrogen-bonding moieties onto the microphase separation, a series of polymers with different fractions of... 

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