MOLECULAR CHARACTERISTICS AND CRYSTALLINE-STRUCTURE OF ETHYLENE-DIMETHYLAMINOETHYL-METHACRYLATE COPOLYMERS

The relationship between molecular and crystalline structural characte ristics of the ethylene -dimethylaminoethylmethacrylate copolymers (ED AM) was investigated and related to melt flow index MI and average gro ss content of DAM comonomer, in comparison with low density polyethyle ne (LDPE) produced by the common high-pressure radical polymerization process. Although the average molecular weight and its distribution ar e influenced predominantly by the polymerization conditions, DAM-conte nt seems not to depend significantly on molecular weight according to the GPC-FT/IR measurement. Comonomer sequence distributions were deter mined quantitatively with the C-13-NMR spectra entirely assigned by DE PT and H-1-C-13 COSY techniques. The result suggests the alternating c opolymerization tendency and surprisingly coincides with the simulatio n out-puts based on the assumption of continuous complete mixing react or model, using Mayo-Lewis equation and the same Q-e values as previou sly reported on different types of copolymers such as EVA and St.DAM ( VA;vinylacetate, St;styrene). It was confirmed by WAXD and SAXS analys es that the crystallinity X(c) and the thickness of lamellar crystal l (c) decreased with increasing DAM-content, whereas the a-lattice and b -lattice dimensions enlarged. X(c) and l(c) can definitely be correlat ed to the heats of fusion and crystallization measured by DSC. The ave rage size of spherulites measured with light scattering photometry ten ds to be enlarged with decreasing molecular weight (increasing MI) and DAM-content.