A series of amorphous and semicrystalline poly(ary1 ether-bisketone)s have been synthesized from bisphenols and 4,4'-bis(p-fluorobenzoyl)biphenyl via nucleophilic aromatic substitution reactions. Model compound studies were carried out with a variety of substituted phenols, 4,4'-bis( p-fluorobenzoyl)biphenyl and 4,4'-bis( p-chloroben-zoy1)biphenyl. The bishalide monomers were synthesized by the reaction of biphenyl-4,4'-dicarboxylic acid with thionyl chloride followed by Friedel-Crafts acylation with the appropriate aryl halide. Potassium carbonate mediated reaction of these monomers in dimethylacetamide or diphenyl sulphone gave high-molecular-weight polymers in excellent yield. Polymers with semicrystalline morphologies were synthesized from soluble highmolecular-weight amorphous precursors with removable bulky substituents. Unlike the corresponding monoketone analogues, the amorphous poly(ary1 ether-bisketone)s exhibited poor solubility in a wide variety of solvents, indicative of improved solvent resistance. The glass-transition and melting temperatures of the polymers are among the highest known for poly(ary1 ether-ketone)s. In addition, the polymers exhibit excellent thermal stability and afford tough films by compression moulding.
ABSTRACT:A series of amorphous and semicrystalline poly(aryl ether-bisketone)s have been synthesized from bisphenols and 3,3' -( 4-fluorobenzoyl)biphenyl via nucleophilic aromatic substitution reactions. Model compound studies were carried out with a variety of substituted phenols, 3,3' -( 4-fluorobenzoyl)biphenyl and 3,3' -( 4-chlorobenzoyl)biphenyl. The bishalide monomers were prepared by the reaction of 3,3' -bi phenyl dicarboxylic acid with thionyl chloride followed by Friedel-Crafts reaction with the appropriate aryl halide. Potassium carbonate mediated reaction of these monomers with a variety of bisphenols in dimethylacetamide or diphenylsulfone gave moderate to high molecular weight polymers in excellent yield. The high molecular weight polymers afforded tough films by compression molding. The glass transition temperatures, melting points and the thermal behaviors of the polymers were compared with the corresponding polymers derived from 4,4'-(4-fluorobenzoyl)biphenyl.KEY WORDS Nucleophilic Aromatic Substitution / Glass-Transition Temperatures / Annealing / Poly(aryl ether-ketone)s belong to a class of materials known as engineering thermoplastics.1·2 The introduction of crystallinity into a poly(aryl ether-ketone) backbone results in improving the solvent resistance and modulus. PEEK™, (1, poly(ether ether ketone)) an aromatic poly(ether-ketone) exhibits a relatively high degree of crystallinity and a melting point (Tm) of 335°C. 3 a, 4 , 5 On the other hand, PEEK suffers from poor creep behavior above its relatively low glass transition temperature (Tg) of 145°C. 6 Therefore, attempts have been made to either increase the glass transition temperature or to introduce crosslink sites into the PEEK backbone. 7 -9 The amorphous poly(aryl ether-ketone)s, characterized by backbones containing sp 3 or sp 3 d 2 hybridized atoms (e.g., 2 and 3, respectively), exhibit lower glass transition temperatures than the analogous amorphous poly(aryl ether-sulfone)s, 4 and 5. 10 · 11 In order to achieve higher Tgs and/or higher Tms, two carbonyl groups, (in contrast to PEEK which contain one such group) have been incorporated into the polymer repeat unit (e.g., 6a and 6b). 2 • 12 -15 Polymer 6a was synthesized by the reaction of bisphenol-A with either 7a or 7b via nucleophilic aromatic substitution reactions. Electrophilic aromatic substitution reactions have been used also for the synthesis of poly(aryl ether-ketone)s (e.g., Sa and Sb) containing two keto substituents. 16 • 17
A series of high-molecular-weight amorphous and semicrystalline poly(ary1 ether bisketone)s were prepared from bisphenols and 3,4'-bis(4-fluorobenzoyl)biphenyl via nucleophilic aromatic substitution reactions. Model compound studies were carried out with several substituted monohydric phenols, 3,4'-bis(4-fluorobenzoyl)biphenyl and 3,4'-bis(4-~hlorobenzoyl)biphenyl. The dihalo-substituted aromatic ketones were synthesized by the reaction of 3,4'-biphenyldicarboxylic acid with thionyl chloride, followed by Friedel-Crafts acylation with the appropriate aryl halide. The required dicarboxylic acid was prepared starting from 4-bromotoluene and 3-methylcyclohexanone. Potassium carbonate mediated reaction of the monomers in dimethylacetamide or diphenyl sulfone gave high-molecular-weight polymers in excellent yield. The glass transition temperatures of the polymers are in the 170 to 190°C range. In addition, the polymers exhibit excellent thermal stability, as evidenced by both dynamic and isothermal thermogravimetric analysis, and afford tough films by compression molding. Scheme I:
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