Thermodynamics and Structure–Property Relationships of Charged Block Polymers

Abstract

Advancements in electronics and energy storage and conversion technologies brings with it myriads of exciting material design challenges. Charge-containing block polymers (BPs) offer unique features which can overcome some of these challenges and have thus aroused substantial interest within the field of designer soft materials. The properties of BPs are intricately coupled to the dynamic and rich nature of the nanostructured assemblies, which result from the phase separation between blocks. The introduction of strong secondary forces, such as electrostatics and hydrogen bonding (H-bonding), into BPs greatly influences their self-assembly behavior, and therefore affects their physical and electrochemical properties often in nontrivial ways. In this review, some of the prevailing research, which has expanded the understanding of structure-property relationships to include several design strategies for improving ionic conductivity and modulus in charged block polymers, is presented. The profound extent to which electrostatics and hydrogen bonding impact block polymer thermodynamics, an extent which is demonstrated by recent theoretical and experimental work, is also highlight. Insights gained from the research presented here help to lay the groundwork for a long and bright future in the field of advanced soft materials.

Microstructure development and mechanical performance of MWCNTs/GNPs filled SEBS with different block content

“…The behavior observed for these samples can be explained in terms of the competition between two parallel mechanisms: (1) enhancing effect of nanoparticles on microphase separation and (2) formation of 3D network by nanoparticles. It is well‐known that the driving force for phase‐separated domain formation, which is the thermodynamic incompatibility between the two blocks, is strong in the absence of a convective field and while cooling 31,32 . It also should be noted that the high viscosity and domain network in the S30 matrix causes further constraints for nanoparticles to move toward each other, significantly hindering particle‐particle interactions that are the driving force to form a percolated nanoparticle structure.…”

“…It is well-known that the driving force for phase-separated domain formation, which is the thermodynamic incompatibility between the two blocks, is strong in the absence of a convective field and while cooling. 31,32 It also should be noted that the high viscosity and domain network in the S30 matrix causes further constraints for nanoparticles to move toward each other, significantly hindering particle-particle interactions that are the driving force to form a percolated nanoparticle structure. In other words, favorable interaction between PS block and nanoparticles can reinforce the phaseseparated domain network by enhancing microphase separation at the expense of weakening the nanoparticles' 3D network.…”

Complex Spherical Phases in a Zwitterion-Tethered Diblock Copolymer Melt

“…In addition to conformational asymmetry, electrostatic interactions are capable of radically altering the shape and location of transition boundaries within the BP phase diagram. 19,22,23,33,42,90,91 This factor may be influencing the continued scarcity of ion-containing BPs which display complex spherical packing. 88,89,92−94 In one instance, Xie et al observed a C15 Laves phase over a narrow compositional window in a ternary blend of polystyrene (PS), poly(ethylene oxide) (PEO), and PS-b-PEO doped with lithium salts ([Li + ]/ [EO] = 0.06).…”

“…Our understanding of block polymer (BP) thermodynamics has progressed substantially alongside advancements in the underlying theoretical models. − Relative to the simplified instance of linear diblock copolymer self-assembly, , several thermodynamic driving forces have the ability to shift, deflect, flip, and unveil transition boundaries in unique fashions. − The list of modifying parameters is extensive, and each addition couples a new dimension to the phase space. While there is still much to learn about BP self-assembly, this cornucopia of factors provides a vast and broadening landscape of exciting opportunities for soft material design. − …”

“…FK and other spherical phases consume a very small portion of the phase space, making them difficult targets to hit, especially when convoluted by electrostatic interactions. In addition to conformational asymmetry, electrostatic interactions are capable of radically altering the shape and location of transition boundaries within the BP phase diagram. ,,,,,, This factor may be influencing the continued scarcity of ion-containing BPs which display complex spherical packing. ,,− In one instance, Xie et al observed a C15 Laves phase over a narrow compositional window in a ternary blend of polystyrene (PS), poly­(ethylene oxide) (PEO), and PS- b -PEO doped with lithium salts ([Li + ]/[EO] = 0.06) . In another instance, Park and co-workers observed the A15 phase with an ion-rich matrix in a few low-molecular weight, acid-tethered polystyrene- b -poly­(methylbutylene) dBPs doped with ionic liquids. ,, Samples that conformed to the A15 phase exhibited superior ion transport efficiency over those with LAM, HEX, and even BCC morphologies.…”