6533b82bfe1ef96bd128e043

RESEARCH PRODUCT

Characterization of semicrystalline random copolymers by small-angle neutron scattering

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A new method is introduced to determine the degree of partitioning of noncrystallizable comonomer units (B units) between the two phases of a semicrystalline random copolymer. The method is based on the comparison of the intensities of small-angle neutron and x-ray scattering (SANS and SAXS, respectively). By this technique two quantities can be evaluated: the difference Δρ of the mass densities between the crystalline and the disordered regions, and the concentration fluctuations of the B units in the two phases. It is found that SANS is very sensitive to the presence of small amounts of B units if their scattering length is sufficiently different from that of the A units. This will be the case for copolymers with B units, in which a hydrogen is substituted by another atom. But in addition it can also be achieved generally by deuteration of the comonomer units. So a wide range of copolymer systems can be studied by this method. The capability of the method was proved by measurements on chlorinated polyethylene and on 1,3,5-trioxane–1,3-dioxolane copolymers. Both copolymers are distinguished by a random distribution of the co-units. The results show that even at relatively low concentrations xB of the comonomer units a remarkable fraction of the B units is incorporated into the crystalline A phase and that this fraction rises if xB is increased.