Synthesis and properties of novel polyimide-g-nylon 6 and nylon 6-b-polyimide-b-nylon 6 copolymers

This research was divided into two major parts. In the first part, the anionic polymerization of {dollar}varepsilon{dollar}-caprolactam was carried out in the presence of a small amount of several different polyimides to generate polyimide-g-nylon 6 copolymers. The polyimides, which were prepared from 2,2{dollar}spprime{dollar}-bis (4-(3,4-dicarboxyphenoxy)phenyl) propane dianhydride (BisA-DA) and commercially available diamines using a one-step method, were first dissolved in molten {dollar}varepsilon{dollar}-caprolactam. Phenylmagnesium bromide was then added at 120{dollar}spcirc{dollar}C. Under these conditions caprolactam anions were formed that attacked the 5-membered imide rings to form N-acyllactam moieties, which activated the anionic polymerization of caprolactam. In essence, nylon 6 chains grew from the polyimide backbones. Probably due to a high activation energy, the process was relatively slow, requiring 1 h at 120{dollar}spcirc{dollar}C. The introduction of 5 wt% polyimide in the graft copolymers produced significant increases in tensile modulus and tensile strength compared to those of low and high molecular weight nylon 6. The elongation to break, however, was reduced.; In the second part, polyimide-g-nylon 6 copolymers were prepared by first polymerizing phenyl 3,5-diaminobenzoate (PDB) with several diamines and dianhydrides using a one-step method. The polyimides containing pendant ester moieties were then used as activators for the anionic polymerization of molten {dollar}varepsilon{dollar}-caprolactam. Nylon 6-b-polyimide-b-nylon 6 copolymers were prepared by first using phenyl 4-aminobenzoate (PAB) as an end-capping agent in the preparation of a series of imide oligomers. The oligomers were then used to activate the anionic polymerization of {dollar}varepsilon{dollar}-caprolactam. In both the graft and copolymer syntheses, the phenyl ester groups reacted quickly with caprolactam anions at 120{dollar}spcirc{dollar}C to generate N-acyllactam moieties, which activated the anionic polymerization. All of the block copolymers had higher moduli and tensile strengths than those of nylon 6. However, their elongations at break were much lower. The graft copolymers based on BisA-DA and 2,2{dollar}spprime{dollar}-bis (4-(4-aminophenoxy)phenyl) propane (BAPP) displayed elongations comparable to that of nylon 6 and the highest moduli and tensile strengths of all the copolymers. The thermal stability, chemical resistance, moisture resistance and impact strength were dramatically increased by the incorporation of only 5 wt% polyimide in both the graft and block copolymers. The graft and block copolymers also exhibited improved melt processability.