A study on the phase behavior of poly(ε-caprolactone)-poly(butadiene) diblock copolymers: The influence of relatively low-molecular-weight block copolymers on the order-disorder transition behavior

• Published in: Polymer (Guilford) Vol. 67; pp. 20 - 27
• Main Authors: Takagi, Hideaki, Yamamoto, Katsuhiro, Okamoto, Shigeru, Sakurai, Shinichi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 12.06.2015
• Subjects: Block copolymer; Copolymers; Degree of polymerization; Fluctuation; Interaction parameters; Mathematical analysis; Order disorder; Order-disorder transition; Phase diagrams; SAXS; Temperature dependence; Order-disorder transition; Fluctuation; Block copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2015.04.041

The phase behavior in relatively low-molecular-weight poly(ε-caprolactone)-poly(butadiene) diblock copolymers (PCL-PB) were investigated using small angle X-ray scattering (SAXS). The temperature dependence of χ was determined from the curve fitting of SAXS profiles using random phase approximation in the disordered state. The phase diagram for PCL-PB was constructed. Generally, according to Fredrickson-Helfand theory, the product (χN)ODT, where N is the degree of polymerization and χ is the Flory–Huggins interaction parameter at the order-disorder transition temperature, is considered to be shifted toward upper side in phase diagram due to the existence of fluctuation. However, in PCL-PB, the significant increase of (χN)ODT was not apparently observed. In order to compare (χN)ODT values with theoretical and many experimental studies, we calculated (χN)ODT which was obtained from 19 earlier reports. We picked out 69 samples which formed lamellae morphology and had nearly symmetric composition. In the region of relatively low-molecular-weight, it was found that the increase of (χN)ODT was not clearly seen in the almost all of investigated articles. [Display omitted] •The phase behavior in relatively low-molecular-weight poly(ε-caprolactone)-poly(butadiene) diblock copolymers (PCL-PB) were investigated.•We obtained the temperature dependence of χ for the PCL-PB as χ = −0.0229 + 71.65/T.•The phase diagram for the PCL-PB was constructed.•In Ñ > 103, the experimentally obtained (χN)ODT were almost consistence with the FH theory.•On the other hand, in 102 <Ñ < 103, the increase in (χN)ODT was not clearly seen in almost all of investigated articles.