Poly(ethylene oxide-b-isoprene) Diblock Copolymer Phase Diagram

Abstract

The phase state of 25 poly(ethylene oxide-b-isoprene) (PEO-PI) diblock copolymers spanning the composition range 0.05 < f PEO < 0.8 has been studied using small-angle X-ray scattering and rheology. In addition, the thermal and thermodynamic properties have been obtained from differential scanning calorimetry and pressure-volume-temperature measurements. Twenty of the diblocks exhibit at least one order-to-order transition, and two show four ordered phases. The phase diagram consists of four equilibrium phases in the melt; lamellar (Lam), hexagonally packed cylinders (Hex), spheres packed in a body centered cubic lattice (bcc) and a bicontinuous cubic phase with the Ia3 hd space group symmetry known as the gyroid phase. The latter is formed for the range of compositions 0.4 < f PEO < 0.45 which are the highest ever reported for a stable gyroid phase. The high asymmetry in the present phase diagram is attributed to the high conformational asymmetry of the PEO and PI ( ) 2.72). At low temperatures, upon PEO crystallization, all phases revert to the crystalline lamellar structure (Lc). Within the composition range 0.66 < fPEO < 0.7 another intermediate phase is formed known as perforated layers (PL) which is clearly not an equilibrium phase. The thermal expansion coefficient was found to be a sensitive probe of the ordered microstructures.

Linking experiment and theory for three-dimensional networked binary metal nanoparticle–triblock terpolymer superstructures

“…While the periodic G D network structure is accessible via di-BCP self-assembly, the G A structure is only accessible via triblock terpolymers, which provides three distinct periodic block volumes. Triply periodic network phases formed by triblock terpolymers also form over much wider composition windows (4-14 vol%) 22,23 than the G D structure found in diBCPs (2-6 vol%) 24,25 . Furthermore, mesoporous materials derived from the G A phase typically have larger pore volume than those from the G D phase.…”

Supramolecular Block Copolymers with Cucurbit[8]uril in Water

“…Their combination allows for the formation of an amphiphilic block copolymer that is expected to exhibit higher order nanostructures in solution. [36] Treatment of a 5000 g mol À1 methylviologen-terminated poly(ethylene glycol) monomethyl ether (1) with one equivalent of CB [8] in D 2 O resulted in an upfield shift and broadening of the signals in the 1 H NMR spectrum arising from the aromatic protons on the viologen moiety. This result indicates the complexation of a methylviologen guest inside the cavity of the CB [8] host.…”

Effect of interacting nanoparticles on the ordered morphology of block copolymer/nanoparticle mixtures

“…[6][7][8] Because of their synergistic interaction of individual constituents, block copolymer/NP hybrids can produce a wealth of novel structural features, [9][10][11] and the rational design of hybrid morphology can be based on the current understanding of the phase behavior of block copolymers and copolymer-homopolymer mixtures. [12][13][14][15][16][17] When block copolymer/NP hybrids are prepared by the blending of presynthesized NPs with a block copolymer, 18,19 not by in situ reduction of metal ions within one of the block domains, [20][21][22][23][24][25] the surface of NPs can be decorated with surfactant molecules with a chemical structure similar to that of a selected block, and those NPs will diffuse into the compatible block domain. In this case, the addition of NPs can alter the characteristic dimension or sometimes even the morphology of the ordered block copolymer structure 26,27 because the miscibility of NPs with a polymer matrix (or with one of the blocks) and the resulting NP stability are crucial factors.…”