Understanding the electrostatic interactions in ion-containing polymers is crucial to better design shape memory polymers and ion-conducting membranes for multiple energy storage and conversion applications. In molten polymers, the dielectric permittivity is low, generating strong ionic correlations that lead to clustering of the charges. Here, we investigate the influence of electrostatic interactions on the nanostructure of randomly charged polymers (ionomers) using coarse-grained molecular dynamics simulations. Densely packed branched structures rich in charged species are found as the strength of the electrostatic interactions increases. Polydispersity in charge fraction and composition combined with ion correlations leads to percolated nanostructures with long-range fluctuations. We identify the percolation point at which the ionic branched nanostructures percolate and offer a rigorous investigation of the statistics of the shape of the aggregates. The extra degree of freedom introduced by the charge polydispersity leads to bicontinuous structures with a broad range of compositions, similar to neutral A-B random copolymers, as well as to desirable percolated ionic structure in randomly charged-neutral diblock copolymers. These findings provide insight into the design of conducting and robust nanostructures in ion-containing polymers.

Polymer aggregation plays a critical role in miscibility of materials and the performance of allpolymer solar cells (APSCs). However, many aspects of how polymer texturing and aggregation affect photoactive blend film microstructure and photovoltaic performance are poorly understood.Here we study the effects of aggregation in donor-acceptor blends in which the number-average molecular weights (M n s) of both an amorphous donor polymer poly [4,8-bis(5-(2ethylhexyl)This article is protected by copyright. All rights reserved.3 alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) are systematically varied. The photovoltaic performance is correlated with active layer microstructural and optoelectronic data acquired by indepth transmission electron microscopy (TEM), grazing incidence wide-angle X-ray scattering (GIWAXS), thermal analysis, and optical spectroscopic measurements. Coarse-grained modeling provides insight into the effects of polymer aggregation on the blend morphology. Notably, the computed average distance between the donor and the acceptor polymers correlates well with solar cell photovoltaic metrics such as short-circuit current density (J sc ) and represents a useful index for understanding/predicting active layer blend material intermixing trends. Importantly, these results demonstrate that for polymers with different texturing tendencies (amorphous/semicrystalline), key for optimal APSC performance, photovoltaic blend morphology can be controlled via both donor and acceptor polymer aggregation.

Solid polymer electrolytes are considered a promising alternative to traditional liquid electrolytes in energy storage applications because of their good mechanical properties, and excellent thermal and chemical stability. A gap, however, still exists in understanding ion transport mechanisms and improving ion transport in solid polymer electrolytes. Therefore, it is crucial to bridge composition-structure and structure-property relationships. Here we demonstrate that size asymmetry, λ , represented by the ratio of counterion to charged monomer size, plays a key role in both the nanostructure and in the ionic dynamics. More specifically, when the nanostructure is modified by the external electric field such that the mobility cannot be described by linear response theory, two situations arise. The ionic mobility increases as λ decreases (small counterions) in the weak electrostatics (high dielectric constant) regime.Whereas in systems with strong electrostatic interactions, ionomers with higher size symmetry (λ ≈ 1) display higher ionic mobility. Moreover, ion transport is found to be dominated by the 1 arXiv:1907.03946v1 [cond-mat.mtrl-sci] 9 Jul 2019 hopping of the ions and not by moving ionic clusters (also known as "vehicular" charge transport). These results serve as a guide for designing ion-containing polymers for ion transport related applications. IntroductionIon-containing polymers are a class of materials which have generated great interest over the past few decades, due to their various applications such as solid polymer electrolytes for ion batteries and fuel cells, organic field-effect transistors, and water purification membranes. 1-5 Ion transport properties in such materials are of interest in many of these applications and has been extensively investigated through experimental, theoretical, and computational approaches. 6-12 Evidently, the structural features of the assembled nanostructures, particularly the morphology of the ionic aggregates formed in ion-containing polymers, strongly influence the dynamics of coand counterions with and without an external electric field. 13,14 Therefore, understanding both the structure-property relationship and composition-structure relationship contributes to better design of ion-containing polymeric materials tailored for different applications.Charge fraction has been shown to be a very effective tuning parameter to achieve different morphologies in ion-containing polymers. [15][16][17][18][19][20] For instance, Sing et al. demonstrated that the Coulombic interaction between charged monomers and counterions lead to nontrivial effects in the phase behavior of polymer blends and block copolymers. 15,16 Shim and coworkers discovered a superlattice morphology by varying the charge content of charged block copolymers. 18 Our previous work demonstrated that ionic correlations in random ionomers lead to nanostructures with composition polydispersity, which are desired for ion battery and fuel cell applications. 21 Random ionomers, whose fraction and sequence of ch...

A wearable device that responds to sweat vapor can switch between radiative heating and evaporative cooling.

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