Sijbrandi N.J. - Synthesis, morphology and properties of segmented poly(ether ester amide)s comprising uniform glycine or b-alanine extended bisoxalamide hard segments

Niels J. Sijbrandi, Ad J. Kimenai, Edwin P.C. Mes, René Broos, Georg Bar, Martin Rosenthal, Yaroslav I. Odarchenko, Dimitri A. Ivanov, Jan Feijen, Pieter J. Dijkstra

Polymer 2012


segments are highly phase separated thermoplastic elastomers with a broad temperature independent
rubber plateau. These materials with molecular weights, Mn, exceeding 30 103 g mol1 are conveniently
prepared by polycondensation of preformed bisesterebisoxalamides and commercially available
PTHF diols. FT-IR revealed strongly hydrogen bonded and highly ordered bisoxalamide hard segments
with degrees of ordering between 73 and 99%. The morphology consists of fiber-like nano-crystals
randomly dispersed in the soft polymer matrix. The micro-structural parameters of the copolymers were
addressed by simultaneous small- and wide-angle X-ray scattering. It is shown that the crystals have
strictly identical thickness, which is close to the contour length of the hard segment. The long dimension
of the crystals is identified with the direction of the hydrogen bonds. The melting transitions of the hard
segments are sharp, with temperatures up to 170 C. The studied polymers have an elastic modulus in
the range of 139e170 MPa, a stress at break in the range of 19e31 MPa combined with strains at break of
higher than 800%. The segmented copolymer comprising the b-alanine based bisoxalamide hard segment
with a spacer of 6 methylene groups has a melting transition of 141 C which is higher than the melting
transition of its glycine analogue of 119 C. Likewise, the fracture stress increased from 22 to 31 MPa
when the glycine ester group in the hard segment was replaced with b-alanine. The improved thermal
and mechanical properties of the latter polymers is related to the crystal packing of the b-alanine based
hard segments in the copolymer compared to the packing of the hard segments comprising glycine ester