Polyamide , covalently bound

Apart from natural materials, oxidoreducates have been used to modify synthetic polymers. For example, using peroxidase, poly(4-hydroxystyrene) has been functionalized with aniline while poly(p-phenylene-2,6-benzobisthiazole) has been rendered more hydrophilic [22, 23]. Other authors have demonstrated that phenolics can be covalently bound to amino-functionalized polymers by using laccase resulting in increased fire resistance [13]A large number of scientific reports are available on enzymatic functionalization of poly(alkyleneterephthalate)s. Polyester fibers account for 73% of all synthetic fibers on the market with an annual production of approx. 27 million tons [24]. Similarly, polyamides and polyacrylonitriles have significant market shares. In contrast to natural polymers discussed above, hydrolases have shown higher potential for modification of these synthetic materials than oxidoreducates. 

CONTEXT The distinction between plastics that bend and stretch (elastomers such as rubber) and plastics that bend but don t stretch (fibers such as nylon) is that the dipole-dipole attraction gives fibers great tensile strength without the rigidity that we associate with covalent bonds. Nylon is composed of polyamide chains, bound by the dipole-dipole attraction of the C=0 bond fx 2.3 D) and the N—H bond fjL 1.3D), forming a hydrogen bond. 

The availability of sequence-specific DNA binding molecules led to the development of bifunctional polyamides that covalently react with the minor groove of DNA. Two classes of alkylating agents were conjugated to the hairpin turn unit and bound proximal to their alkylation sites by a DNA-binding polyamide [58, 59]. 

Exhaustive solvent extraction of the extruder blended products with triflouroethanol (TFE), a polyamide solvent, indicated that a substantial amount of unextractable PA6 was usually bound to the reactive rubbers via the graft-coupling reactions. In the case of PA6/ maleated EPR (80/20) blend, >20% of PA6 is bound to the rubber as a graft copolymer. In the case of the PA6 blend compounded with 20% zinc ionomer of ethyiene-methacrylic acid copolymer (E-MAAZn), the TFE extraction indicated only <3% bound PA6. However, the blend showed a moderate torque increase in the Rheomixer experiment. These results indicate that the E-MAAZn ionomer does not bond covalently with the polyamide chains, but more likely interacts via a simple associative interaction occurring at the interface. 

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