Chain folding in ethylene-butylene-ethylethylene semicrystalline diblock copolymers

Abstract

X-ray pole-figure analysis and small-angle X-ray scattering were used to determine the lattice unit cell orientation with respect to the lamellar microstructure for semicrystalline diblock copolymers of ethylene-co-butylene-6-ethylethylene (EBEE). The X-ray data indicate that the orientation of the crystallized EB chains is perpendicular to the lamellar normals, unlike the chain folding which has been observed in semicrystalline homopolymers and proposed for semicrystalline diblock copolymers where the crystallized chains align roughly parallel to the lamellar normals. The unusual chain folding observed for EBEE is attributed to the influence of topological constraints on the EB blocks which crystallize within the amorphous lamellar microdomains present in the heterogeneous melt phase of the block copolymers.

The influence of melt processing on the spatial organization of polymer chains in a crystallizable diblock copolymer of nylon 6 and PDMS

“…The chains crystallize in a way that leaves the chain axes parallel to the block copolymer interfaces when crystallization occurs after microphase separation. 4,9 Findings in other groups 10,11 have verified our early observations regarding the unexpected parallel chain orientation.…”

“…An unanswered question concerns the preference for the semicrystalline periodicity of the nylon 6 to repeat selectively along FD, rather than with planar isotropy within the CD-FD plane, as observed in previous studies of polyethylene-containing diblocks. 4,9 Significant differences from polyethylene arise in the monoclinic nature of the nylon unit cell and the tendency to form hydrogen bonded sheets within its crystal structure. These two structural features may account for the resistance to inplane randomization upon slow cooling or annealing for the case of the nylon 6/PDMS diblock copolymer examined here.…”

“…Similar considerations of facilitated shear associated with preferred chain slip apply to the case of the polyethylene containing block copolymers studied earlier. 3,4,8,9 An essential consideration is the fact that semicrystalline block copolymers that crystallize from a heterogeneous melt must be viewed as a material with a preferred crystallographic texture. This texture is intimately connected to the orientation of the ordered block copolymer morphology.…”

Side-Chain Liquid Crystal Block Copolymers with Well-Defined Structures Prepared by Living Anionic Polymerization I. Thermotropic Phase Behavior and Structures of Liquid Crystal Segment in Lamellar Type of Microphase Domain

“…Such a situation has been encountered for the crystallizable block copolymers. [36][37][38] Next we consider the temperature dependence of the lamellar size. As previously observed in Figure 7, the lamellar domain size in the SA phase changed continuously from the size of the crystalline phase to that of the isotropic phase.…”

Effects of Molecular Weight and Crystallization Temperature on the Morphology Formation in Asymmetric Diblock Copolymers with a Highly Crystalline Block

“…1 Many studies have been performed so far on the final morphology of such copolymers as a function of crystallization condition and molecular characteristics. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] It is established from these studies 2 -s,i 3 -i 5 that the microdomain structure of low molecular weight copolymers is completely destroyed by the crystallization to form a lamellar morphology, an alternating structure consisting of lamellar crystals and amorphous layers, which is theoretically predicted to be favorable for crystalline block copolymers. 21 · 22 This morphological transition arises from the competition between two factors, that is, the strong crystallization force overwhelms the low stability of weakly segregated microdomains.…”