Physical properties, bisphenol-containing

Hilborn et al. demonstrated the synthesis of PBOs (Figure 5.29) by polymerization of bis(fluorophenyl benzoxazoles) with bisphenols. This polymerization was based on the activation of the fluoro group toward nucleophilic aromatic substitution by the oxazole component of the benzoxazole heterocyclic [51]. The TgS of the poly(arylene ether benzoxazoles) ranged from 213 to 303 °C, depending on the bisphenol and activated dihalide used in the synthesis. Generally, the TgS increased with the bulkiness of the bisphenol used. The polymers containing the >C(CF3)2 unit in both the benzoxazole and the bisphenol moiety in the monomers showed higher solubility (NMP) compared to the other PBOs. The physical properties of fluorinated poly(arylene ether benzoxazole) s are presented in Table 5.3. 

The second category of well known polyarylates contained polymers of a much softer, amorphous nature. These polymers form clear, glassy solids from Isotropic melts the polyesters tend to have high levels of relatively asymmetric monomers such as resorcinol or bIsphenol-A, The glassy polyarylates have, not surprisingly, unexceptional physical properties. 

In electronic encapsulation applications, epoxy derivatives of novolacs containing meta-bromo phenol have exhibited substantially better physical and performance properties compared to the conventional tetrabromo bisphenol-A epoxies and brominated epoxy novolacs. The meta-bromo phenol moiety contributes the expected improvements in thermal and hydrolytic stability to the formulation while providing fire retardancy properties (13). 

Miscible polymer blends offer a physical method for tailoring properties to obtain combinations that may be more desirable than those of either component polymer. The water sorption and transport behavior of miscible polymer blends have been examined in several studies. For example, Schult and Paul [12] investigated the water sorption and transport properties of homogeneous blends of PVP, a water-soluble polymer that is miscible with a relatively hydrophobic bisphenol A polysulfone (PSF) over the entire composition range. Unfortunately this study was restricted to blends containing <40% PVP, since blends containing >40% PVP would phase-separate when exposed to high water vapor activities. Such phase-separation is driven by the fact that one polymer wishes to swell or dissolve in water, while the other does not. 

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