Morphology of a Crystalline/Amorphous Diblock Copolymer:  Poly((ethylene oxide)-b-butadiene)

Abstract

The bulk morphology of a crystalline/amorphous diblock copolymer under different thermal conditions was studied. The diblock copolymer, poly((ethylene oxide)-b-1,4-polybutadiene), forms a microphase-separated lamellar morphology in the molten state. For samples crystallized within the range of 20−50 °C, TEM coupled with electron diffraction revealed a microphase-separated, alternating lamellar morphology with the PEO crystalline chains oriented perpendicular to the interface between the PEO and PBD domains. A significant increase in the microphase-separated, lamellar domain spacing was observed upon crystallization. On the length scale of tens of microns, as probed by polarizing optical microscopy, a nonspherultic crystalline texture (with the absence of the Maltese cross), corresponding to the microphase-separated lamellar grain morphology, was observed. In contrast to the integral chain folding observed in PEO homopolymer, the increase in PEO lamellar thickness with decreasing undercooling is continuous in the block copolymer. In addition, the equilibrium melting temperature and lamellar spacing were determined.

A Novel Crystallization Scheme in Poly[styrene‐block‐(ferrocenyl dimethylsilane)] Diblock Copolymers

“…Block copolymers containing crystallizing segments provide a deep insight into the mechanisms of nucleation and crystal growth 1–27. Quite often, the number of individually crystallizing entities such as spheres, cylinders, or lamellae is much larger than the overall number of heterogeneities inside the samples.…”

Pathway‐Dependent Melting in a Low‐Molecular‐Weight Polyethylene‐block‐Poly(ethylene oxide) Diblock Copolymer

“…It was found that, depending on the phase segregation strength ( χ N where χ is the Flory‐Huggins interaction parameter and N is the total degree of polymerization), the crystallization of the crystalline blocks could exhibit three different modes: confined, templated, and breakout (unconfined) 4,5. The crystallization kinetics for these three modes were quite different, depending on a number of chemical and physical parameters, such as domain connectivity,6,7 morphology,5,8–10 matrix hardness,11 and domain size 12. Very often, the crystallization kinetics were influenced by more than one of the above factors occurring simultaneously in the system.…”

Micelles of polybutadiene-b-poly(ethylene oxide) in deuterated methanol and deuterated cyclohexane

“…In the partially miscible mixture of methanol + cyclohexane, only spherical micelles form over a wide temperature range in the methanolrich phase, but form only near the critical solution point in the cyclohexane-rich phase. While the assembly of poly(ethylene oxide)-b-polybutadiene has been studied extensively in water [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], we are aware of no work other than that of Ploetz and Greer in non-aqueous solvents.…”