Water plays a central role in the assembly and the dynamics of charged systems such as proteins, enzymes, DNA, and surfactants. Yet it remains a challenge to resolve how water affects relaxation at a molecular level, particularly for assemblies of oppositely charged macromolecules. Here, the molecular origin of water’s influence on the glass transition is quantified for several charged macromolecular systems. It is revealed that the glass transition temperature (Tg) is controlled by the number of water molecules surrounding an oppositely charged polyelectrolyte–polyelectrolyte intrinsic ion pair as 1/Tg ∼ ln(nH2O/nintrinsic ion pair). This relationship is found to be “general”, as it holds for two completely different types of charged systems (pH- and salt-sensitive) and for both polyelectrolyte complexes and polyelectrolyte multilayers, which are made by different paths. This suggests that water facilitates the relaxation of charged assemblies by reducing attractions between oppositely charged intrinsic ion pairs. This finding impacts current interpretations of relaxation dynamics in charged assemblies and points to water’s important contribution at the molecular level.

Here, we present the thermal behavior of polyelectrolyte complexes (PECs) containing weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) as influenced by water content and complexation pH. Modulated differential scanning calorimetry (MDSC) reveals a glass-transition-like thermal transition (T tr ) that decreases in value with increasing hydration and with decreasing complexation pH. We show the collapse of all T tr values into a single master curve when plotted against the ratio of water molecules per intrinsic (PAH + −PAA − ) ion pair for all pH values explored. Remarkably, this master curve is linear when the natural log of the water to intrinsic ion pair ratio is plotted against the inverse of T tr . This strongly indicates that the thermal transition is heavily influenced by water at the intrinsic ion pair site. Other water−solvent mixtures are also explored, for which T tr appears to depend only on water content, regardless of the added solvent. These results suggest that water plays a dual role in PAH−PAA complex: first by participating in the hydrogen-bonding network within and second by plasticizing the PEC. A hypothesis for the thermal transition is proposed in which hydrated PECs undergo a two-step thermal transition caused by an initial restructuring of the water−polyelectrolyte hydrogen-bonding network, followed by chain relaxation.

Figure S1. Size exclusion chromatography (SEC) traces of block copolymer P4 at different temperatures (CHCl 3 , 1 mL/min, RI).

We report a facile way to synthesize polythiophenes carrying pendant 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) radicals, here called PTATs, by electropolymerization in boron trifluoride diethyl etherate (BFEE). The spacing between the TEMPO radical and the polythiophene backbone is varied by an alkyl spacer (n = 2, 4, 6), and the electronic and electrochemical properties are examined using UV–vis spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Film morphologies are also studied via scanning electron microscopy (SEM) and atomic force microscopy (AFM), which show that the longer octyl chain placed between thiophene and TEMPO effectively suppresses aggregation. The highest conductivity and electroactivity are observed for n = 4 and n = 6, respectively. Such morphology differences provide an opportunity to better understand the charge transport and energy storage properties in electronic materials.

A novel methodology of precisely constructing stable and controllable conjugated polymer (CP)/fullerene nanostructures is presented. By building in noncovalent interactions between CP nanofibers (NFs) and fullerene derivatives, supramolecular polymer/ fullerene composite NFs are obtained in solution for the first time. Specifically, a conjugated block copolymer having poly(3-hexylthiophene) (P3HT) backbone selectively functionalized with polar isoorotic acid (IOA) moieties, P1, is used as the building block. Selfassembly of P1 in mixed solvents leads to well-defined NFs decorated with IOA groups on the periphery, onto which phenyl-C61-butyric acid methyl ester (PCBM) molecules are subsequently attached noncovalently. Formation of such complex structures are studied in detail and confirmed by UV−vis absorption spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray scattering measurements. Application of these composite NFs in organic photovoltaic (OPV) devices not only leads to superior performance but also much improved thermal stability and better defined and controllable morphology, when compared with conventional bulk heterojunction (BHJ) devices.

Nitroxide-containing organic radical polymers (ORPs) have captured attention for their high power and fast redox kinetics. Yet a major challenge is the polymer's aliphatic backbone, resulting in a low electronic conductivity. Recent attempts that replace the aliphatic backbone with a conjugated one have not met with success. The reason for this is not understood until now. We examine a family of polythiophenes bearing nitroxide radical groups, showing that while both species are electrochemically active, there exists an internal electron transfer mechanism that interferes with stabilization of the polymer's fully oxidized form. This finding directs the future design of conjugated radical polymers in energy storage and electronics, where careful attention to the redox potential of the backbone relative to the organic radical species is needed.

The design and electrochemical synthesis of a conjugated radical polymer (CRP), poly(dithieno[3,2-b:2′,3′d]pyrrole) bearing pendant nitroxide radicals, is reported. Conjugated radical polymers potentially offer simultaneous conductivity and redox activity in the context of organic energy storage. One challenge is understanding the internal electron transfer that occurs in CRPs, which affects the electrochemical energy storage properties. The CRP here is purposefully designed to examine the case of when the conjugated backbone's redox potential is less than that of the organic radical group. Cyclic voltammetry on the as-prepared CRP exhibits two wellresolved redox peaks at E pa1 = 3.15 V and E pa2 = 3.61 V vs Li/Li + , corresponding to the redox activities of the (dithieno[3,2b:2′,3′-d]pyrrole) (DTP) backbone and nitroxide radical, respectively. Galvanostatic charge/discharge studies also reveal a twostep charge/discharge process. The lower oxidation potential of DTP contributes to a conductive pathway during the charge/ discharge process. An internal electron transfer process occurs during the decay of the open circuit potential, as the final potential stabilizes around 3 V. This strategy emphasizes the effects on energy storage when the redox active polymer contains two moieties that are redox active at different potentials, thus impacting future CRP design.

Cationic aryl triazole oligomers have been synthesized through "click chemistry". The results show that cationic aryl triazole oligomers adopt a helical conformation in water or in a mixture of water and methanol, but prevail as a random-coiled conformation in methanol. Importantly, circular dichroism spectroscopy and dynamic light scattering experiments revealed that cationic oligomers aggregated intermolecularly to form higher order architectures with a helical sense opposite to that of the individual helix, which eventually led to the formation of aggregates with sizes in the range 100-500 nm. The aggregation of cationic oligomers was governed by the concentration and polarity of the environment. More interestingly, cationic foldamers were able to recognize chloride and fluoride anions in aqueous solution. The recognition consequently destabilized intermolecular aggregation.