ULTRA-FINE STRUCTURES IN CRYSTALLINE POLYMERS FROM HIGH-RESOLUTION TEM. Masaki Tsuji, Institute for Chemical Research, Kyoto University

High-resolution TEM has become a conventional approach to clarify ultra-fine structures even in crystalline solids of radiation-sensitive polymers. In this presentation, we will show our high-resolution TEM studies mainly on fiber structure of flexible linear polymers. The specimens used here are uniaxially oriented crystalline thin films of isotactic polystyrene [i-PS](1), poly(aryl-ether-ether-ketone) [PEEK](2), polyethylene [PE](3) and poly(4-methyl-1-pentene) [P4M1P](3). For PE and P4M1P, their high-resolution images were taken at 4.2K by cryogenic TEM.

The films of PE, P4M1P and PEEK revealed stacked lamellar structure. Lattice images of PE showed (110) and/or (200) lattice fringes running in the fiber-axis [FA] direction. Each of the domains in which the fringes are observed corresponds to a so-called crystallite within a lamella, revealing crystallite size, shape and orientation. The images accordingly clarified the relationship between the lamellar structure and such domains. In some of the images, a tiny crystalline region, "tie-crystallite"(2), was identified, which connects adjacent lamellae in the FA direction. Such tie-crystallites were also recognized in the lattice images of P4M1P and PEEK films.

The i-PS film used here has basically fibrillar structure. Lattice images of the film showed (110) fringes running in the FA direction. One of the coherent regions in which the fringes are observed is about 15nm wide and reaches 200nm long. The fringes are slightly curved and partly faint, but the region seems to have no defects. Taking into account the procedure of specimen preparation, the region in question corresponds to a "shish" in the shish-kebab structure and is considered to be a kind of tie-crystallite mentioned above. Molecular chains of i-PS seem to be more or less extended in such a shish.

The fiber structure of PE, P4M1P and PEEK has two faces of lamellar and fibrillar structure. It is deduced that in ultra-drawn films/fibers of ultra-high molecular weight PE, one face, namely the lamellar structure is lost and the other face, namely the fibrillar structure consisting of a great number of tie-crystallites is enhanced. 1)Tsuji, M. et al., Sen-i Gakkaishi, 42, p.T-580 (1986). 2) Kawamura, H. et al., Bull. Inst. Chem. Res., Kyoto Univ., 68, p.41 (1990). 3)Tsuji, M. et al., Sen-i Gakkaishi, 48, p.384 (1992).