Miscellaneous Graft Copolymerizations
In a rather interesting reaction, ethylene oxide can be graft-copolymerized with nylon 6,6 [406]. Formation of the graft copolymer greatly enhances flexibility of the material, while the high melting point of the nylon is still maintained. Thus, nylon 6,6 that contains as much as 50% by weight of grafted poly (ethylene oxide) still melts at 221C and has an apparent Tg below 40C. It also maintains flexibility and other useful properties over a wide range of temperatures [406]:
An entirely different procedure can be used to form graft copolymers by a step-growth polymerization [347]. Formaldehyde is condensed with either phenol, p-cresol, or p-nonyl phenol and the resin is attached to either nylon 6, nylon 6,6, nylon 6,10, or nylon 11 backbones. Initially, the formaldehyde is prereacted with an excess of phenol in the presence of the nylon, but without any catalyst, at temperatures high enough to cause condensation. This is followed by addition of toluenesulfinic acid at lower temperatures. At that point, when free formaldehyde is no longer present in the reaction mixture to cause gelation, the novolac molecules attach themselves to the nylon backbones. The excess phenol is washed away, leaving pure graft copolymers [347]. Yagci and coworkers reported a special preparation of perfectly alternating poly(p-phenylene) amphilitic graft copolymers by combination of controlled free-radical polymerization and Suzuki coupling process [345].
