Recovery as a measure of oriented crystalline structure in poly(ether ester)s based on poly(ethylene oxide) and poly(ethylene terephthalate) used as shape memory polymers

Poly(ether ester)s consisting of poly(ethylene oxide) and poly(ethylene terephthalate) segments, EOET copolymers, could be used as shape memory polymers (SMP). Crystalline structural characters of the copolymers during the memory process were investigated by dynamic mechanical analysis, differential scanning calorimeter, wide-angle X-ray diffraction, polarizing microscopy, and recovery measurements. PEO crystals in stretched EOET copolymer preferentially oriented along fiber axis or stretch direction. During stretching, the structure of the copolymer undertake a transformation from spherulite to fiber, resulting in a crystalline morphology similar to shish-kebab, and recovery properties of stretched EOET samples were dependent on as-described crystalline structural characters that can be influenced by draw ratio. Driving forces for contraction come from the oriented chains, and only oriented or extended chains can be contributive to the recovery of deformation; these extended chains involve both crystalline and amorphous segments. The recovery process in shape memory behavior was noticed to be deorientation of oriented chains due to thermodynamic entropy effect, and was divided into three stages.

[1]  U. Göschel,et al.  Thermally stimulated structural changes in highly oriented glassy poly(ethylene terephthalate) , 1996 .

[2]  Mao Xu,et al.  Thermally stimulated shape-memory behavior of ethylene oxide-ethylene terephthalate segmented copolymer , 1997 .

[3]  S. Ota.  Current status of irradiated heat-shrinkable tubing in Japan , 1981 .

[4]  T. Pakula,et al.  Thermally stimulated shrinkage forces in oriented polymers: 1. Temperature dependence , 1985 .

[5]  T. Pakula,et al.  The influence of internal stresses on viscoelastic and thermal properties of oriented and aged glassy polymers , 1988 .

[6]  Shunichi Hayashi,et al.  Structure and properties of shape-memory polyurethane block copolymers , 1996 .

[7]  Z. Pelzbauer,et al.  Relationship between thermal shrinkage and morphology of zone-drawn polyethylene , 1991 .

[8]  Mingtai Wang,et al.  Shape Memory Properties in Poly(ethylene oxide)–Poly(ethylene terephthalate) Copolymers , 1997 .

[9]  T. Vigo,et al.  Temperature-Adaptable Fabrics , 1985 .

[10]  Mingtai Wang,et al.  Dynamic mechanical behavior in the ethylene terephthalate-ethylene oxide copolymer with long soft segment as a shape memory material , 1998 .

[11]  I. R. Harrison,et al.  A criterion for craze formation , 1982 .

[12]  D. Coleman.  Block copolymers: Copolymerization of ethylene terephthalate and polyoxyethylene glycols , 1954 .

[13]  I. Ward,et al.  Shrinkage, shrinkage force and the structure of ultra high modulus polyethylenes , 1982 .

[14]  W. James,et al.  Poly(ethylene terephthalate). I. Study of crystallization kinetics , 1965 .

[15]  P. Barham,et al.  Self‐hardening of highly oriented polyethylene , 1977 .

[16]  Anton Peterlin,et al.  Plastic deformation of crystalline polymers , 1977 .

[17]  N. Kalfoglou.  Thermomechanical studies of semicrystalline polyether–ester copolymers. Effect of thermal, mechanical, and solvent treatment , 1977 .

[18]  C. Booth,et al.  Interpretation of melting data for low molecular weight poly(ethylene oxide) , 1972 .