Phase behavior and structure of an ABC triblock copolymer dissolved in selective solvent

Abstract

A mean-field lattice theory is applied to predict the self-assembly into ordered structures of an ABC triblock copolymer in selective solvent. More specifically, the composition-temperature phase diagram has been constructed for the system (C)14(PO)12(EO)17/water, where C stands for methylene, PO for propylene oxide and EO for ethylene oxide. The model predicts thermotropic phase transitions between the ordered hexagonal, lamellar, reverse hexagonal, and reverse cubic phases, as well as the disordered phase. The thermotropic behavior is a result of the temperature dependence of water interaction with EO- and PO-segments. The lyotropic effect (caused by changing the solvent concentration) on the formation of different structures has been found weak. The structure in the ordered phases is described by analyzing the species volume fraction profiles and the end segment and junction distributions. A "triple-layer" structure has been found for each of the ordered phases, with each layer rich in C-, PO-, and EO-segments, respectively. The blocks forming the layers are not stretched. The dependence of the domain spacing on polymer volume fraction and temperature is also considered.

Microphase separation under constraints: a molecular thermodynamic theory for polyelectrolytic amphiphilic model networks in water

“…2, where the conditions there favor swelling (high degrees of ionization and low hydrophobicities), and moving to the lower right corner, where the conditions there disfavor it, we successively encounter the disordered swollen unimer state, spheres, cylinders, lamellae, and the disordered shrunk unimer state. These transitions are in qualitative agreement with theoretical and experimental results with linear (uncross-linked) block copolymers in solution [20,21] and in the solid state [45,46], which also present transitions from the disordered state, to spheres, cylinders and lamellae. The disordered shrunk unimer state appears to be unique for networks, but there might be an analogy between this network state and macrophase separation to a polymer rich phase and to a polymer poor phase, sometimes encountered in linear block copolymer solutions [21].…”

“…cross-links located randomly along the chains) [17]. The multitude of models in the literature on segmented amphiphilic model networks concern physical (associating) rather than covalent (cross-linked) networks [18][19][20][21].…”

Behavior of block-polyampholytes near a charged surface

“…[9], scaling theories were developed to elucidate the adsorption process of a single PA chain [7] and many PA chains on a charged sphere [8]. Shusharina and Linse [10] examined grafted diblock PAs at uncharged surfaces by a mean-field lattice theory and characterized the brush structure.…”

Stimuli-responsive command polymer surface for generation of protein gradients

“…The character of switching depends on the ratio between the polyelectrolytes. 40,41 These effects are at the heart of inverse and reversible switching of the gradient of water contact angle on the surface of mixed brushes with a gradually changing ratio between the components of the brushes. 42 Here, we report on the use of such mixed-gradient grafted polyelectrolyte brushes for stimuli-sensitive generation of surface gradients of proteins.…”