Tensile properties of segmented block copolymers with monodisperse hard segments

The tensile properties of segmented block copolymers with mono-disperse hard segments were studied with respect to the hard segment content (16–44 wt.%) and the temperature (20–110 °C). The copolymers were comprised of poly(tetramethylene oxide) segments with the molecular weights of 650–2,900 Da and of mono-disperse bisester-tetra-amide segments (T6A6T) based on adipic acid (A), terephthalic acid (T) and hexamethylene diamine (6). An increasing content of T6A6T gave rise to an increased modulus, yield stress and fracture stress. The modulus could be modeled by a composite model. Moreover, a strain-softening was observed well below the yield stress, due to the shearing of the T6A6T crystallites. At strains >200%, a strain-hardening of the PTMO segments took place and this even for PTMO segments that were amorphous in the isotropic state. The strain hardening increased the tensile properties. An increase in temperature had little effect on the modulus of the copolymers, but was found to lower the yield and fracture stresses. At temperatures above the melting temperature of the oriented PTMO, no strain-hardening took place. The yield stress as a function of temperature could be described by the Eyring relationship, but a modulus–yield stress relationship could not be established

Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide) by direct coupling

Segmented copolymers with telechelic poly(2,6-dimethyl-1,4-phenylene ether) (PPE) segments and crystallizable bisester tetra-amide units (two-and-a-half repeating unit of nylon-6,T) were studied. The copolymers were synthesized by reacting bifunctional PPE with hydroxylic end groups with an average molecular weight of 3500 g/mol and bisester tetra-amide units via an ester polycondensation reaction. The bisester tetra-amide units had phenolic ester groups. By replacing part of the bisester tetra-amide units with diphenyl terephthalate units (DPT), the concentration of tetra-amide units in the copolymer was varied from 0 to 11 wt%. Polymers were also prepared from bifunctional PPE, DPT, and a diaminediamide (6T6-diamine). The thermal and thermal mechanical properties were studied by DSC and DMA and compared with a copolymer with flexible spacer groups between the PPE and the T6T6T. The copolymers had a high Tg of 180-200°C and a melting temperature that increased with amide content of 220-265°C. The melting temperature was sharp with monodisperse amide segments. The Tm - Tc was 39°C, which suggests a fast, but not very fast, crystallization. The crystallinity of the amide was 20%. The copolymers are semicrystalline materials with a high Tg and a high Tg/Tm ratio (> 0.8)