The correlation between crystalline behavior of polyethylene segments and hydrogen bonds among carboxyl groups in ethylene–Acrylic Acid copolymers

The fine structure of the methylene rocking bands obtained by high resolution and cryogenic FTIR spectroscopy was utilized to characterize the crystalline behavior of polyethylene (PE) segments in an ethylene-acrylic acid copolymers. The hydrogen bonds among the carboxyl groups play a cross-linking role and prevent the PE segments from adopting the stable orthorhombic form. As a result, a lower content of the orthorhombic form and higher contents of the monoclinic form and amorphous region of PE segments are found in the samples. Quenching treatment of the samples strengthens this effect. On the other hand, the crystallization of the PE segments causes strain on the hydrogen bonds among carboxyl groups. Consequently, the distorted carboxyl dimers are easy to break at elevated temperature.