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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 (EOm-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 EOm-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 (TDOT) to higher temperature, whereas a higher molecular weight leads to a lower TDOT. 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 EOm-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 EOm-b-(IL-X)n BCPs, which can be attributed to the cooperative effects of temperature rising and LDOT. [ABSTRACT FROM AUTHOR]

ABSTRACT Glassy polymer nanofibers with spatially confined poly(ethylene oxide) (PEO) were fabricated by coaxial electrospinning of PEO with polyacrylonitrile (PAN) or polystyrene. The effect of melt-annealing on the crystallization behavior of the confined PEOs was studied using differential scanning calorimetry. It is found that the crystallization behavior of the confined PEOs varies with annealing temperature ( Ta), annealing time ( ta), and molecular weight of PEO. Notably, it is observed that the crystallization temperature ( Tc) and melting temperature ( Tm) of PEO increase with prolongation of ta, for PEO600K/PAN and PEO2K/PAN coaxial electrospun fibers. This phenomenon can be interpreted by the annealing-induced demixing at the core-sheath interface. After the coaxial electrospinning, the core and sheath of the PEO/PAN coaxial fibers are partially compatible due to the miscible solvents used for the core and sheath polymers. Upon annealing, demixing occurs at the core-sheath interface, leading to improved crystallizability of PEO. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45760. [ABSTRACT FROM AUTHOR]

Concomitant double crystallization processes widely occur in semicrystalline polymers and their blends because of structural and morphological heterogeneity. In this work, a generalized kinetics model was established for the isothermal crystallization in the presence of concomitant double crystallization processes, based on the Avrami theory for single crystallization process. The different situations of the double crystallization processes, including independent, competitive, and composite types, are considered in the model by introducing the concept of "domains". This model was applied to crystallization of triblock terpolymer with morphological defects, polymorphic poly(vinylidene fluoride)/nanoclay nanocomposite, isotactic polypropylene with a broad isotacticity distribution, and poly(ethylene terephthalate) ultrathin film. It is found that, besides the information on crystallization kinetics, other information such as morphological defect, nucleation density, cocrystallization, and structure of ultrathin film can also be provided by this model. [ABSTRACT FROM AUTHOR]

In the present work, crystallization-driven coassembly of micrometric polymer single crystals and nanometric block copolymer micelles was achieved. The hybrid single crystals are first formed by cocrystallization of polyethylene (PE) homopolymer and polyethylene-b-poly(tert-butyl acrylate) (PE-b-PtBA) block copolymer (BCP) in DMF or DMF/o-xylene mixed solvent. The morphology of the obtained hybrid single crystals can be regulated via changing the solvent composition, crystallization temperature and mass ratio of BCP/homopolymer. Because of the difference in crystallization rate, the distribution of PE-b-PtBA BCP in the hybrid single crystals may be inhomogeneous, leading to a concave gradient surface structure. The hybrid single crystals have a double-layer structure, in which PE homopolymer chains adopt extended conformation and the PE blocks in PE-b-PtBA are probably once-folded. After the PE homopolymer is consumed, cylindrical micelles of PE-b-PtBA can further epitaxially grow on the lateral surface of the hybrid single crystals and "ciliate paramecium-like" coassemblies are yielded. The single crystal/micelles coassemblies can be prepared either by one-step method, in which PE and PE-b-PtBA are added together in a single step, or by two-step method, in which the hybrid single crystals are prepared in the first step and extra PE-b-PtBA is added in the second step to grow BCP micelles. This work provided a simple route to construct hierarchical assemblies composed of objects with different scales by using crystallization as the key driving force. [ABSTRACT FROM AUTHOR]