AbstractA new method of obtaining films of aromatic heterocyclic ladder polymers has been found which circumvents casting from high‐boiling acidic solvents. The BBL ladder polymer has been formed into tough, durable films by collecting suspensions of the polymer obtained from acid reprecipitations upon a fritted glass funnel. After drying, the polymer can be removed as film, with thickness dependent upon the amount of material used. Such a film has a tensile strength of 9,600 lb/in.2as compared to a tensile strength of 16,000 lb/in.2obtained from the same polymer when cast from methanesulfonic acid solutio
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