Hydrogen Bonding-Induced Crystal Orientation Changes in Confined Microdomains Constructed by Block Copolymer Blends

Abstract

This study examined crystal orientation confined within a lamellar microdomain morphology formed by the blends of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) and polystyrene-block-poly(acrylic acid) (PS-b-PAA) through wide-angle X-ray diffraction. The hydrogen-bonding interaction between PEO and PAA molecules enabled block copolymers to co-organize into a microphase-separated morphology without inducing macrophase separation, but it hampered PEO crystallization. PEO crystallization that occurred at −20 °C resulted in the nucleation mechanism to be dominant, thus leading to the formation of small crystals. Small crystals allowed them to be free from spatial confinement, and they tended to be oriented with their c-axis parallel to the microdomain interface. By contrast, when PEO was crystallized at 40 °C, the high temperature facilitated PEO crystals to exhibit large crystallite sizes, which aligned perpendicularly to the microdomain interface. An increase in the PS-b-PAA concentration considerably reduced the crystallizability of PEO. The presence of a low amount of crystals and additional lateral confinement formed by hydrogen-bonded PEO/PAA reduced the degree of orientation regardless of the crystallization temperature.

Compositional asymmetry in a crystalline–amorphous block copolymer influences the phase and crystallization behaviors of its blend with an amorphous block copolymer

“…However, the growth of crystals was strongly influenced by the geometric confinement afforded by the common PEO/PAA microdomains, leading to a preferential crystal alignment normal to the microdomain interface. 29 By contrast, a low crystallization temperature increased the preponderance of nucleation, resulting in small crystal formation. The small crystals were unaffected by confinement; thus, they were oriented randomly.…”

Surface Nucleation-Induced Raspberry-like PVDF@P(St-co-MPS-co-AA) Core–Shell Latex Particles via Seeded Emulsion Polymerization and Their High Efficiency for Confined Crystallization of PVDF in Nanospheres

“…3−6 In addition, nanoconfinement has been shown to influence phase transitions, such as crystal melting, leading to a decrease in melting temperature, 7,8 change in Curie temperature, and other related effects. 9 Various methods have been employed to achieve the confined crystallization of polymers, including the formation of core−shell composite particles, 10,11 polymers in nanopores, 12,13 multilayer polymer films, 14 microphase-separated crystalline block copolymers, 15,16 and well-dispersed immiscible polymer blends. 17 Among these strategies, the encapsulation of a crystalline polymeric core within a polymeric shell represents a particularly unique approach.…”

“…This approach holds great promise for the development of novel applications, as the resulting physical properties usually differ significantly different from those observed in their bulk materials. , Notably, the confinement can lead to remarkable alterations in their crystallization behavior, including changes in crystallization temperature ( T c ) and kinetics, crystal orientation, polymorphism, and crystalline of semicrystalline polymers. − In addition, nanoconfinement has been shown to influence phase transitions, such as crystal melting, leading to a decrease in melting temperature, , change in Curie temperature, and other related effects . Various methods have been employed to achieve the confined crystallization of polymers, including the formation of core–shell composite particles, , polymers in nanopores, , multilayer polymer films, microphase-separated crystalline block copolymers, , and well-dispersed immiscible polymer blends . Among these strategies, the encapsulation of a crystalline polymeric core within a polymeric shell represents a particularly unique approach.…”