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Lower disorder-to-order transition (LDOT) phase behavior is seldom observed in block copolymers (BCPs). Design of LDOT BCPs is important for broadening the applications and improving the high temperature properties of BCPs. In this work, the LDOT phase behavior was first achieved in the strongly interacting BCPs consisting of poly(ethylene oxide) (PEO) and poly(ionic liquid) (PIL) blocks (EO m -b-(IL-X) n , X: counterion) by introducing two extra strong forces (hydrogen-bonding and Coulombic interaction) with different temperature dependences. It is also found that the LDOT phase behavior of the EO m -b-(IL-X) n BCPs can be regulated by molecular weight (related to mixing entropy), counterion, and salt doping. Increasing counterion size and salt content shifts the disorder-to-order transition temperature (T DOT ) to higher temperature, whereas a higher molecular weight leads to a lower T DOT . Based on our findings, some general rules for design of LDOT phase behavior in the strongly interacting BCPs were proposed. Moreover, the conductivity of the EO m -b-(IL-X) n BCPs was correlated with the LDOT phase behavior. A remarkable increase in conductivity after LDOT, i.e., a thermo-activated transition, is observed for the EO m -b-(IL-X) n BCPs, which can be attributed to the cooperative effects of temperature rising and LDOT.

Superior toughness has been achieved in the nylon-6/PVDF blends with semicrystalline PVDF component as the dispersed particles. Morphological observations on the impact tested specimens unambiguously reveal the formation of voids and microfibrils across the fracture surface, suggesting that some extent of plastic deformation occurs within ductile PVDF particles. It is further confirmed by the structural evolution at crack tips through micro-FTIR studies on the quasi-static stretching of precracked films. During fracture R f β phase transformation of dispersed PVDF particles first takes place, followed by the extensive plastic deformation and fibrillation of new-formed β-crystals. It is believed that the R f β phase transformation and fibrillation of β-crystals of the dispersed PVDF particles are responsible for the toughness enhancement in the nylon-6/PVDF blends with good interfacial adhesion.

A comparative study of cold crystallization behavior in poly(L-lactide) (PLLA) annealed below and just above the glass transition temperature (T(g)) has been conducted. Annealing benefits the generation of local order and the subsequent cold crystallization process, which becomes significant in PLLA annealed just above T(g). Surprisingly, morphological observation reveals high density nuclei in PLLA annealed below T(g), contrary to its relatively slow crystallization kinetics. This unusual crystallization behavior in physically aged PLLA arises from the retarded crystal growth rate because of incomplete recovery of reduced segmental mobility above T(g). In contrast, annealing just above T(g) has little influence on the crystal growth rate, and the increased nucleation density alone accounts for the accelerated crystallization rate.

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