Study of the structure of polyethylene and poly(tetrafluoroethylene) radiation grafted ion-exchange copolymers

Cation- and anion-exchange copolymers were synthesized by radiation induced copolymerization of acrylic acid and 4-vinylpyridine onto polyethylene and poly(tetrafluoroethylene) (PTFE) films. The grafting was carried out by the direct method of single or multiple (discrete) irradiation by γ-rays from a ⁶⁰Co source. The grafting degree was from 10 to 121% for polyethylene and from 2.5 to 50% for poly(tetrafluoroethylene), depending on the irradiation dose (1–50 kGy). The calorimetric curves of the copolymers synthesized showed a glass transition temperature (T_g) at 333 ± 10 K. The enthalpies of melting and crystallization decreased with increasing degree of grafting. The data from wide angle X-ray analysis indicated an increase of the amorphous part with degree of grafting. At lower grafting degrees of poly(acrylic acid) and poly(4-vinylpyridine) (up to 15%) onto PTFE matrix, the size of the crystallites was found to increase. The penetration of the grafted functional monomer leads to partial deorientation of the initial LDPE film.