Effect of block number on multiblock copolymer lamellae alignment under oscillatory shear
(a) Illustration of coordinate system for oscillatory shear alignment and orientated lamellae. (b) Illustration of complexity of chain conformations for triblock and pentablock copolymers.
(a) SAXS patterns and (b) TEM micrograph for parallel-aligned SISIS. (c) SAXS patterns and (d) TEM micrograph for perpendicular-aligned SISISISISIS. 2D SAXS patterns are illustrated in three-dimensional reciprocal space, and related to the shear coordinate system. Poly(isoprene) domains were preferentially stained with and appear dark in the TEM images.
Alignment behavior mapped with shear frequency and strain amplitude for (a) SI at , (b) SIS at , (c) SISI at , (d) SISIS at , (e) SISISISI at , and (f) SISISISISIS at . Open and filled circles denote parallel and perpendicular orientations, respectively. Partially filled circles denote the mixtures of parallel and perpendicular orientations; cross symbols represent the observation of edge failure. The dashed lines indicate either the critical frequency for SI or the crossover frequency for other multiblock samples, identified from viscoelastic properties [Wu et al. (2004a)].
Master curves for (a) perpendicular- and (b) parallel-aligned samples at a reference temperature of . Solid symbols and open symbols denote elastic modulus and loss modulus , respectively. The inset of (a) shows the shift factor as a function of temperature for all aligned samples. (c) Comparison of complex modulus between perpendicular and parallel orientations at . Open squares and triangles denote parallel- and perpendicular-aligned samples, respectively. For clarity, data for SIS, SISI, SISIS, SISISIS and SISISISISIS are vertically shifted by one, two, three, four, and five decades, respectively.
(a) Stress response and (b) with increasing strain amplitude at for aligned and unaligned SISISIS during dynamic strain sweeps at . Open squares, triangles, and circles denote parallel, perpendicular, and unoriented SISISIS, respectively.
2D SAXS patterns at specific times for (a) unoriented SIS sheared at and ; (b) unoriented SIS sheared at and ; and (c) perpendicular-aligned SIS sheared at and . All three tests were conducted at .
2D SAXS patterns at specific times for (a) unoriented SISIS sheared at and ; and (b) unoriented SISIS sheared at and . Both tests were conducted at . Note that the scale of intensity is three times larger than that in Fig. 6.
Amplitude of the complex modulus , Herman’s orientation factor and integrated intensity as a function of time for (a) unoriented SIS sheared at and ; (b) unoriented SIS sheared at and ; and (c) perpendicular-aligned SIS sheared at and . All three tests were conducted at . Open triangles, circles, and squares denote , , and , respectively. was rescaled by dividing by counts.
Amplitude of the complex modulus , Herman’s orientation factor and integrated intensity as a function of time for (a) unoriented SISIS sheared at and ; and (b) unoriented SISIS sheared at and . Both tests were conducted at . Open triangles, circles, and squares denote , , and , respectively. was rescaled by dividing by counts.
Schematic chain conformations within (a) parallel- and (b) perpendicular-aligned heptablock lamellae. The parallel orientation contains predominantly looping chains, weaving back and forth across interfaces, whereas block junctions are placed on a common plane of shear in perpendicular arrangement. Note that both chain configurations localize the block junctions in a single shear plane, and accommodate a 2D (random) walk. The deformation profiles are shown on the plane for both parallel and perpendicular orientations: Slip occurs at the center of lamellae at large strains for the parallel configuration, whereas the perpendicular oriented lamellae deform uniformly along the direction.
Characteristics of multiblock copolymer samples.
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