Morphological Phase Behavior of Poly(RTIL)-Containing Diblock Copolymer Melts

Abstract

The development of nanostructured polymeric systems containing directionally continuous poly(ionic liquid) (poly(IL)) domains has considerable implications toward a range of transport-dependent, energy-based technology applications. The controlled, synthetic integration of poly(IL)s into block copolymer (BCP) architectures provides a promising means to this end, based on their inherent ability to self-assemble into a range of defined, periodic morphologies. In this work, we report the melt-state phase behavior of an imidazolium-containing alkyl−ionic BCP system, derived from the sequential ring-opening metathesis polymerization (ROMP) of imidazolium-and alkyl-substituted norbornene monomer derivatives. A series of 16 BCP samples were synthesized, varying both the relative volume fraction of the poly(norbornene dodecyl ester) block (f DOD = 0.42−0.96) and the overall molecular weights of the block copolymers (M n values from 5000−20 100 g mol −1 ). Through a combination of small-angle X-ray scattering (SAXS) and dynamic rheology, we were able to delineate clear compositional phase boundaries for each of the classic BCP phases, including lamellae (Lam), hexagonally packed cylinders (Hex), and spheres on a body-centered-cubic lattice (S BCC ). Additionally, a liquid-like packing (LLP) of spheres was found for samples located in the extreme asymmetric region of the phase diagram, and a persistent coexistence of Lam and Hex domains was found in lieu of the bicontinuous cubic gyroid phase for samples located at the intersection of Hex and Lam regions. Thermal disordering was opposed even in very low molecular weight samples, detected only when the composition was highly asymmetric (f DOD = 0.96). Annealing experiments on samples exhibiting Lam and Hex coexistence revealed the presence of extremely slow transition kinetics, ultimately selective for one or the other but not the more complex gyroid phase. In fact, no evidence of the bicontinuous network was detected over a 2 month annealing period. The ramifications of these results for transport-dependent applications targeting the use of highly segregated poly(IL)-containing BCP systems are carefully considered.

The change in the environment of the immiscible block stabilizes an unexpected HPC phase in a cured block copolymer/epoxy blend

“…This is the case of the peak at p 4 for the blend with 40% BCP. The suppression of this peak is expected for f cores = f PS = 0.274 [35][36][37], a value that is close to the estimated volume fraction (f PS = 0.30). The intercylinder distance can be calculated as d CYL = 4p/( p 3q 0 ) while the distance among rows of cylinders is given by d HEX = 2p/q 0 [36,38].…”

Phase Behavior of Melts of Diblock-Copolymers with One Charged Block

“…All these circumstances allow one to fine tune the properties of the system. One of the most comprehensive investigations of the phase behavior of block copolymers with one block being a poly(ionic liquid) is Reference [18]. In that work, perfectly ordered structures of various types were obtained for different fractions of the polyelectrolyte block, including lamellar, cylindrical, and spherical.…”

Elastic free-standing RTIL composite membranes for CO2/N2 separation based on sphere-forming triblock/diblock copolymer blends

“…While these systems offer an intrinsic ability to produce distinct ionic and non-ionic domains through predictable phase separation on the nanometer length scale. [24][25][26][27][28][29],the dense polymer materials have significantly lower CO 2 permeability than composite materials that contain free RTIL. [28,29] Of the few examples ofmembranes based on block copolymer/RTIL blends reported to date [21-23, 28, 29], all involvea shared fabrication strategydependent on solvent-casting of a co-solution of block copolymer and RTIL into a porous support material.Gu et al [21,22]and Rabiee et al [23]report CO 2 /N 2 separation performances of their membranesto be slightly above the 2008 Robeson plot upper bound, showing the potential of block-copolymer-based materials to be used as efficient CO 2 /N 2 separation membrane materials.…”