Order−Disorder Transition, Microdomain Structure, and Phase Behavior in Binary Mixtures of Low Molecular Weight Polystyrene-block-polyisoprene Copolymers

Abstract

Order−disorder transition, microdomain structure, and phase behavior in binary mixtures of low molecular weight polystyrene-block-polyisoprene (SI diblock) copolymers were investigated. For the study, four SI diblock copolymers were synthesized, namely (i) SI-Q having a weight-average molecular weight (M w) of 2.8 × 104 and polystyrene volume fraction (f) of 0.186, (ii) SI-R having M w = 1.5 × 104 and f = 0.508, (iii) SI-S having M w = 1.76 × 104 and f = 0.372, and (iv) SI-M having M w = 1.55 × 104 and f = 0.626. Then binary mixtures of SI-Q and SI-R and binary mixtures of SI-M and SI-S, with various compositions, were prepared via solvent casting. The order−disorder transition of the binary mixtures was investigated using rheology and small-angle X-ray scattering (SAXS), respectively. Also investigated was the microdomain structure of the binary mixtures using SAXS and transmission electron microscopy (TEM). Experimentally determined phase diagrams are compared with predictions based on a self-consistent mean-field theory.

Effect of the molecular weight of the homopolymers on the morphology in ternary blends of polystyrene, polyisoprene, polystyrene-block-polyisoprene copolymer

“…For an ideal lamellar system, where the domains are perfectly well correlated, j ! 1 (or ultimately to a high value constant), whereas, for a material with domains subject to strong thermal fluctuations, j decreases well below d: The transition associated to the ODT for lamellar systems is well understood and has previously been reported to be sharp [11,19,20]. The melting of the lamellae also corresponds a tiny increase of the d-spacing at 140 8C, back to its value at 80 8C.…”

“…2 correlated (ordered phase) to un-correlated (disorder) in few degrees. The boundary between the lamellar phase and the high temperature disordered state is often identified using a temperature-controlled experiments since it is well known to be associated with a discontinuity of the SAXS peak intensity and a change in the peak shape from a Gaussian to Lorentzian function [11,19,20]. Similarly, in the microemulsion regime, the values of the characteristic length, used to map out the phase diagrams, were taken where the correlation length between the domains starts to weaken and decrease towards zero (cf.…”

Phase Behavior of Complementary Multiply Hydrogen Bonded End-Functional Polymer Blends

“…[8][9][10][11][12][13] Additionally, the phase behavior can be altered by swelling with solvent or homopolymer, [14][15][16] or two polymers with different composition can be blended. 17,18 In contrast to controlling structure through composition or chain architecture, simple thermal tunability in a polymer structure can be introduced through reversible supramolecular interactions. 19 The nature of the interaction varies widely and most commonly consists of either metal-ligand, 20,21 ionic, 22,23 or hydrogen bonding.…”

A Phase Diagram for the Binary Blends of Nearly Symmetric Diblock Copolymers. 2. Parameter Space of Temperature and Blend Composition

“…1,2 Recently, the blends of two different block copolymers, such as (A-B) R /(A-B) where A-B denotes A-block-B copolymer, also have received considerable theoretical [3][4][5][6][7][8][9] and experimental 10-29 attention due to their richness of the phase behaviors, including macrophase separation, 8,9,[13][14][15]23,27 microphase separation, 10,11,[16][17][18][19][20][21][22][23][24][25][26]29 macrophase separation induced by microphase separation, 14 OOT,4,5,[19][20][21]24,26 and modulated or superlattice structures. 15 In the previous study, 30 we investigated the interplay of macro-and microphase transitions by employing binary mixtures of polystyrene (PS)-block-polyisoprene (PI) (PS-PI) diblock copolymers which have similar molecular weights but different compositions, namely, the volume fractions of PS-block (f PS ).…”