Pyridine containing polymers thermal

Having found the proton carrier, the next step is to find a suitable host polymer that possesses the appropriate thermal stability and compatibility with phosphoric acid in the desired temperature range. Using a basic polymer is a general practice via acid-base interactions with the acid. For this, the most successful polymers are PBIs, a large family of heterocyclic polymers with excellent thermal, chemical, and mechanical stabilities. PBI variants, their blends as well as analogues such as pyridine containing aromatic polymers are chosen as the focal point of this book. 

Poly(benzimidazole)s possess excellent thermal stability, flame resistance, and outstanding chemical resistance. The solubility of hexafluoroisopropyli-dene-unit-containing poly(benzimidazole)s is remarkably improved.24 They are readily soluble in strong acids such as formic acid, concentrated sulfuric acid, and methanesulfonic acid and in aprotic polar solvents such as DMAc and NMP. The polymer from tetramine (23) is soluble even in m-cresol and pyridine. 

Thermally stable copolymers of 3-(trimethylsiloxyl)- and 3,5-bis(trimethylsiloxyl)benzoyl chloride (4A) or 3-acetoxy- and 3,5-diace-toxy-benzoic acid (4B) were prepared with mole ratios of AB AB2 monomer ranging from 160-5.32 Polymers containing 10-20 mole % of branching monomers were insoluble in CHC13 but soluble in polar solvents, such as A,A-dimethylformamide (DMF) or a mixture of pyridine and benzene. Compared to the linear homopolymer of 3-hydroxy-benzoic acid, the branched polymer showed lower crystallinity and slower crystallization. There was an inverse linear relationship between percent crystallinity and the number of branches in the chain. Similarly, in an attempt to improve moldability and decrease anisotropy of rigid aromatic polyesters, 0.3-10 mole % of 1,3,5-trihydroxybenzene, 3,5-di-hydroxybenzoic acid, and 5-hydroxyisophthalic acid were copolymerized with p-hydroxybenzoic acid/terephthalic acid/4,4 -dihydroxy-diphenyl.33 The branched polymer showed a lower orientation and possessed improved flex properties. 

Mallakpour S, Zarei M. Novel, thermally stable and chiral poly(amide-imide)s derived from a new diamine containing pyridine ring and various amino acid-based diacids fabrication and characterization. High Perform Polym 2013 25(3) 245-53. 

The second general approach for the covalent cross-linking was the use of side double bond functionalized copolymers [24]. In this case the synthesis of aromatic polyethers containing polar pyridine units in the main chain and side cross-linkable propenyl groups was the key step. These polymers were subjected to thermal cross-linking with the use of a cross-linker. The effect of the cross-linking on the thermal and mechanical... 

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