Synthesis and thermally responsive properties of novel Pluronic F87/polycaprolactone (PCL) block copolymers with short PCL blocks

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AbstractPolycaprolactone (PCL) was successfully grafted to both ends of Pluronic F87 block copolymers (PEO‐PPO‐PEO) to obtain novel amphiphilic PCL‐F87‐PCL block copolymers with short PCL blocks. The block composition and structure of PCL‐F87‐PCL block copolymers were studied by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetric (DSC), and wide angle X‐ray diffraction (WXRD) techniques. Several kinds of particles consisting of small micelles and medium and large aggregates were observed by laser light scattering (LLS) measurements because of the complicated structure of these copolymers. Importantly, PCL‐F87‐PCL block copolymers exhibit temperature‐sensitive behavior similar to that found in Pluronic systems. Compared with Pluronics, the critical micellization temperature (CMT) values of PCL‐F87‐PCL block copolymers obtained from surface tension measurements are significantly lower due to the enhanced hydrophobicity of PCL segments. A fully reversible sol–gel transition was detected for the PCL‐F87‐PCL hydrogels. Preliminary results show that there is no burst release for hydrophobic model drug, 9‐(methylaminomethyl) anthracene (MAMA), from PCL‐F87‐PCL hydrogel and the initial release rate is almost constant. This indicates that PCL‐F87‐PCL hydrogels possess attractive release profiles, which are beneficial for application in controlled release systems. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4163–4172, 2006