Effect of Hydrophilicity of the Sidechains on the Amorphous Structure of Polypropylene Derivatives Studied by Positronium Lifetime Measurements

摘要

Polypropylene (PP) derivatives, prepared with different α-olefin comonomers of hexene and hexenol, were investigated using the positron annihilation lifetime technique. The free-volume hole sizes for the present polymers were quantified from the long-lived ortho-positronium (o-Ps) lifetimes. In contrast to the case of the nonpolar hexene, introduction of the polar hexenol into PP decreased the o-Ps lifetimes, signifying the reduction of the free-volume hole sizes. This indicates that the interchain interaction due to the hydrogen bonds in the amorphous region is much stronger than the enhancement of the segmental motion due to the butyl long branch. A comparison of the o-Ps lifetimes with the corresponding tensile strength suggested significant contribution of the subnanostructure in the amorphous region to the mechanical property.