Abstract
It is known that 2-oxazoline compounds react with amines at higher temperatures to produce aminoamides5, 6) , but there has been no attempt to prepare polymers from bis-oxazolines and diamines. We investigated the reactions of 2, 2'- (1, 3-phenylene) -bis-2-oxazoline [1] or 2-phenyl-2-oxazoline with amines and found the following; (1) 2-oxazolines reacted easily with aromatic amines in the presence of a catalyst, (2) in that case a primary amine acted as a bifunctional group, (3) the reaction products were aminoamides as reported, and (4) effective catalysts were strong acids (sulfuric acid, hydrogen halides, and p-toluenesulfonic acid) and compounds that produced strong acids by reaction with the amine in the reaction system (aliphatic halides and alkyl p-toluene-sulfonates). After an induction period the reaction proceeded rapidly with generation of a large amount of heat (Figure 1).
The activities of hydrogen halides as catalysts can be explained by a series of reaction mechanisms which include opening of an oxazoline ring activated by a proton, the formation of a halo compound, and the reaction of a 2-oxazoline ring with the halo compound.
From the above information it was predicted that cross-linked polyaminoamides would be formed by the reaction of bis-2-oxazolines with aromatic diamines in a molar ratio of between 1 : 1 and 2 : 1. Thus a new group of cross-linked polymers was made by using [1] and 4, 4'-diaminodiphenylmethane as the reactants, and noctyl bromide as the catalyst, and the physical properties of these polymers were measured (Table 4).
These new thermoset resins had higher impact strengths, much higher deflection temperatures under load, and lower water absorption rates than those of the polyesteramides reported before4) .
