Preparation and properties of brominated poly(arylcarboxylate)s via interfacial polycondensation

Abstract

The interfacial polycondensation method has been used for the preparation of brominated poly(arylcarboxylate)s. Brominated poly(arylcarboxylate)s can be prepared easily by mixing a solution of diacid chloride in a water‐immiscible organic solvent with an aqueous alkaline solution of bisphenol in the presence of catalyst such as quaternary ammonium salts. First, in a dichloromethane‐water system using triethylbenzylammonium chloride (TEBAC) as the catalyst a series of 2,2‐bis(4‐hydroxy‐3,5‐dibromophenyl)propane (3,3′,5,5′‐tetrabromobisphenol A, TBBPA) with isophthaloyl (I) and terephthaloyl chlorides (T) has been prepared and some properties as inherent viscosity, solubility, crystallinity, and flammability have been measured. Copolymers prepared from TBBPA and mixed T/I with 33/67–67/33 molar ratios show good solubility and amorphous nature, and can be cast into transparent and tough films with limiting oxygen index of 58–59 (ANSI/ASTM D2683‐77). Second, the effects of some variables as the nature of organic phase and catalysts, concentration of reactants, and basicity of aqueous phase on the interfacial polycondensation of TBBPA with equal parts of T and I [T/I (50/50)] was investigated in some detail. Among the solvents tested dichloromethane was found to be the best solvent and quaternary ammonium salts such as TEBAC and tetra‐n‐butylammonium bromide (TBAB) were highly efficient catalysts. Poly(arylcarboxylate)s with the highest molecular weights were obtained at an acid chloride concentration of 0.2 mol/L in dichloromethane and a concentration of TBBPA of 0.1 mol/L in alkali when TEBAC was used as catalyst. A maximum of inherent viscosity was obtained at two equivalent amounts of alkali corresponding to bisphenol. Polycondensation of several combinations of T/I (50/50) with some other tetrabromobisphenols, such as 3,3′,5,5′‐tetrabromo‐4,4′‐biphenol, 3,3′,5,5′‐tetrabromobisphenol S, 3,3′,5,5′‐tetrabromo‐4,4′‐thiodiphenol, and 3,3′,5,5′‐tetrabromophenolphthalein, were carried out with limited success. Whereas, a more favorable result could be obtained by the mixed copolycondensation of these tetrabromobisphenols and bisphenol A (BPA) with T/I (50/50). Finally, the copoly(arylcarboxylate)s from TBBPA, BPA, T, and I were prepared and characterized. The incorporation of bromine on the polymer backbone caused a decrease of inherent viscosity, glass transition temperature, crystallinity, and thermal stability of copolyarylates, whereas it caused a great enhancement of flame retardancy.