Hard and Soft Confinement Effects on Nano-confined Polymer Crystallization in Cylindrical Mesophases

摘要

A lamella-forming poly(ethylene oxide)-b-polystyrene (EOS) diblock copolymer is blended with a PS homopolymer (PS, 4.6k) and a PS oligomer (PSO, 0.45k), respectively (abb. EOS/PS-32 and EOS/PSO-32), to form cylinder phases. For EOS/PS-32, the glass transition temperature for the PS phase (T_g~(PS)) is 64℃, while the T_g~(PS) is 16℃ for EOS/PSO-32. Therefore, hard confinement for the PEO crystallization can be achieved in the EOS/PS-32 blend, and soft confinement can be obtained in the EOS/PSO-32 blend. It has also been found that the crystallization kinetics for the EOS/PS-32 and EOS/PSO-32 blends are different, and at the same crystallization temperature (T_c~(PEO)) the PEO blocks in hard-confined cylinders crystallize much slower than those in the soft-confined cylinders. Differential scanning calorimetry (DSC) results show that the crystal growth dimension in the soft confinement environment is higher. This leads to a higher thermodynamic stability of the crystals formed under the soft-confined environment compared to that in the hard-confined environment.