Blends Based on Polystyrene and Styrene Copolymers

Polystyrene and styrene containing copolymers have been the subject of countless investigations, due at least in part to the wide variety of monomers available for copolymerization. These copolymers are particularly useful for testing the concept of the binary interaction model and various examples of these studies will be noted. 

Poly(cyclohexyl acrylate) was shown to be miscible with PS with ucst behavior [720]. Random copolymers of cyclohexyl acrylate with n-butyl acrylate showed miscibility with PS above 50% cyclohexyl acrylate[721]. Poly(cyclohexyl methacrylate)/isotactic PS blends showed miscibility based on calorimetry and NMR studies [722]. The NMR results showed homogeneous behavior at a scale of 2.5-3.5 nm. Poly(4-trimethylsilyl styrene) miscibility with polyisoprene was observed with a lest behavior (critical temperature = 172 ° C at degree of polymerization of 370) [723]. The interaction parameter, showed the following relationship = 0.027—9.5/T. Isotactic and syndiotactic polystyrene both exhibit crystallinity, whereas atactic polystyrene is amorphous. Atactic PS/isotactic PS blends exhibited crystallization kinetics, which decreased linearly with atactic PS addition indicating miscibility [724]. The TgS of aPS and iPS are identical, thus Tg methods could not be employed to assess miscibility. Atactic PS/syndiotactic PS blends were also noted to be miscible with rejection of atactic PS in the interfibrillar region between the lamellar stacks of sPS [725]. 

The miscibility mapping of SMA copolymers with SAN and SMMA copolymers was determined by Gan and Paul [740], showing significant miscible composition ranges as illustrated in Figs. 4.23 and 4.24 for the SMA/SMMA and SMA/SAN blends. Two set of B,j values were employed to fit the experimental observations as noted in the figures. The spinodal decomposition of miscible blends of SMA (32 wt% MA) and a MMA-EA (10 wt%EA) copolymer was studied, showing a lest minimum at 190 °C [741]. 

Poly(a-methyl styrene) was shown to be miscible with poly(cyclohexyl methacrylate) with /cst behavior [742]. The copolymer of a-methyl styrene and acrylonitrile (31 wt%AN) exhibited miscibility with PMMA when determined by dielectric spectroscopy and calorimetric measurements [743]. The same amS-AN/PMMA blend showed lest behavior and spinodal decomposition phase separation when heated above 180 °C [744]. 

Styrene-acryhc acid (SAA) copolymers have been noted in Section 4.4.1 to exhibit miscibility with polyamides. Miscibility has also been observed with SAA and various polymethacrylates (PMMA, PEMA, PnPMA) at low AA content in SAA [745]. The miscibility window of SAA with SMMA copolymers was defined, showing a narrow miscibility range as a function of AA and MMA in the respective copolymers. The miscibility was explained using the mean field approach (copolymer repulsion mechanism). Similar results were reported for SAA copolymer blends with PEMA, with immiscibility for SAA with poly(isobutyl methacrylate) [746]. Ckjpolymerization of isobutyl methacrylate with 4-vinyl pyridine yielded miscible compositions with SAA, as would be expected based on the strong specific interaction. 

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