Oligomer Chain Length Research Articles

Dispersity determination of poly(ethylene glycol)s using supercritical fluid chromatography-mass spectrometry and different mass analysers.

Dispersity values are considered critical quality attributes for the quality control of poly(ethylene glycol) formulations due to the direct impact on drug performance. However, when these polymers are analysed using mass spectrometry, the design of the mass analyser can impact the oligomer response and affect the obtained dispersity values, so further understanding is needed. The deconvoluted electrospray ionisation mass spectra of poly(ethylene glycol)s obtained using supercritical fluid chromatography (SFC) hyphenated to different mass analysers were compared, and visualisation diagrams were used to understand the differences in the dispersity value calculations. Five calibration approaches based on a surrogate single oligomer that represents the whole distribution, or the whole distribution itself, for response selection, were used to evaluate ionisation efficiency prior to quantitation. The impact of using an internal standard (ISTD) on the expanded uncertainty was also assessed. Although there were challenges related to the resolution of multiply charged species when low-resolution instruments were used, similar quantitation capabilities were obtained to those when high-resolution mass analysers were used. Evaluation of approaches using a surrogate oligomer or the whole distribution suggested the independence of both approaches and a constant ionisation efficiency across the oligomer chain length. The higher degree of chromatographic resolution of SFC allowed incorporating a monodispersed ISTD to improve the accuracy and precision of the method. The use of low resolution mass analysers was sufficient to provide accurate and precise dispersity values; however, higher resolution instruments were recommended for characterisation due to the improved mass resolution of ions. The introduction of a monodispersed ISTD improved precision without compromising the calculated dispersity value due to the lack of analyte suppression.

Effect of polymer concentration and cross-linking density on the microstructure and properties of polyimide aerogels

Polyimide aerogels display excellent mechanical strength, high thermal stability, low thermal conductivity, and outstanding dielectric properties. Typically, the synthesis of polyimide aerogels involves the polycondensation of dianhydride and diamine into poly(amic acid) (PAA) oligomers, which are then cross-linked and chemically imidized into polyimide. The stoichiometry of dianhydride and diamine determines the number of repeat units and length of the PAA oligomers, which in turn determines the cross-linking density. Despite the critical role of polymer concentration and number of repeating units in determining the microstructure and properties of polyimide aerogels, few detailed studies exist on these two parameters. Here, we synthesized and characterized 16 polyimide aerogel formulations from the common monomers biphenyl-3,3′,4,4′-tetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA), with different repeat units (n = 5, 15, 30, 45) and total polymer concentrations (4, 7, 10, 13 wt%). An increased polymer concentration accelerated gelation and enhanced the mechanical performance of aerogels, but surprisingly, it also led to higher volumetric shrinkage during aging, solvent exchange, and supercritical drying (SCD). Specific surface areas (SSAs) reached a maximum at intermediate polymer concentrations. A shorter oligomer chain length, i.e., a higher cross-linking density, led to moderately higher SSAs (between 320 and 400 m2/g) and reduced shrinkage, resulting in lower densities for a given polymer concentration. The density dependence of the thermal conductivity exhibits a pronounced U-shaped curve with a minimum in thermal conductivity of 21–23 mW/(m·K) between 0.080 and 0.120 g/cm3, with somewhat lower values for more highly cross-linked aerogels. This systematic study of polyimide aerogels forms the basis for designing polyimide aerogels with tailored properties for targeted applications.Graphical

Pre-Polymer Chain Length: Influence on Permanent Memory Effect of PDLC Devices

This study delved into the correlation between the chain length of PEG polymerizable oligomers and the electro-optical properties exhibited by the resultant PDLC films. A range of di(meth)acrylate oligomers derived from polyethylene glycol with varying molecular weights (Mn = 1000, 2000, 4000, and 6000 g mol−1) was synthesized for incorporation as the polymer matrix in PDLC devices. Comprehensive analyses employing 1H-NMR, 13C-NMR, and MALDI-TOF mass spectroscopy were conducted to validate the structure and purity of the synthesized products. The investigation revealed a significant influence of pre-polymer molecular chain length on the thermal properties of the polymer, including amorphousness and crystallinity, which in turn impact the permanent memory effect. Specifically, it was observed that amorphous PEG polymers serve as an ideal matrix for fostering the permanent memory effect in PDLCs. Among the polymerizable PEG oligomers examined, those with a molecular weight of 1000 g/mol yielded polymer chains existing in an amorphous state, exhibiting a glass transition temperature lower than room temperature (−50 °C). This characteristic imparts flexibility and mobility to the polymer matrix chains, facilitating a 37% permanent memory effect. Conversely, longer polymer chains lead to the formation of crystal aggregates, resulting in semi-crystalline polymer matrices. This reduces the malleability of the polymer chains, thereby nullifying the permanent memory effect in the corresponding PDLC devices.

On the Fabrication of Hydrophobic Coatings by Polycondensation of Fluoroalkylalkoxysilanes

It has been shown that for obtaining hydrophobic coatings, it is reasonable to use fluoroalkylalkoxysilanes (FASs) with a longer fluoroalkyl chain than FAS-19, so that the F/Si molar ratio exceeds 5–6. It is proposed to purposefully change not only the chain length of oligomers, but also the structure of solutions from dilute colloidal solutions to structured gels, with the F/Si ratio being controlled. In the case of polycondensation of investigated fluoroalkylalkoxysilanes on a hydroxylated surface, a strong silicone framework is formed, which is chemically bonded to the surface and to fluoroalkyl chains oriented perpendicular to it

Ultraviolet-curable optically clear resins using novel fluorinated imide-modified urethane acrylates

Homologs of novel fluorinated aromatic imide-modified urethane acrylate oligomers (FI-UAs) with different flexible methylene chain lengths were successfully synthesized using 4,4-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA)-based diimide diols (FI-OHs), isophorone diisocyanate (IPDI), and 2-hydroxyethyl methacrylate (HEMA). Ultraviolet (UV)-curable resins (FI-UARs) were prepared using these oligomers, and the UV-curing behavior of these resins was studied by monitoring the C=C bond conversion and gel fraction while varying the UV dose. The thermal (glass transition temperature and thermal stability), optical (transmittance, yellowness, and haze), and adhesion properties of the cured films were investigated. The cured films of the resins exhibited improved thermal and optical properties, except for haze, which could be primarily due to the presence of fluorinated aromatic imide moieties in the oligomer. Furthermore, higher adhesion and improved haze were observed with increasing methylene chain length of FI-UA oligomers. • A series of new fluorinated imide-modified urethane acrylates (FI-UAs) were synthesized by reacting 6FDA-based diimide-diol and diisocyanate, followed by capping with a hydroxyl functional acrylate. • Ultraviolet-curable fluorinated imide-modified urethane acrylates resins (FI-UARs) were prepared by combining novel FI-UAs, isobonyl acrylate (IBOA), and Irgacure 1173, which were used as oligomers, the monomer, and photoinitiator, respectively. • The cured FI-UAR films exhibited enhanced glass transition temperature, thermal stability, transmittance, and yellowness, which could be primarily due to the presence of fluorinated aromatic imide moieties in the oligomer. • In addition, the adhesion and haze of cured films were improved as the methylene chain length of the FI-UA oligomers increased.

Investigation of the effects of solvent-mismatch and immiscibility in normal-phase × aqueous reversed-phase liquid chromatography

Comprehensive two-dimensional liquid chromatography (LC × LC) is an attractive separation technique that allows achieving high peak capacities and information on chemical correlations. Unfortunately, its application in industrial practice is still not widespread due to limiting factors such as complex method development, tedious method optimization and solvent-incompatibility (such as solvent-strength mismatch or immiscibility experienced during fraction transfer).A severe case of solvent-incompatibility is encountered in the comprehensive coupling of normal-phase LC and reversed-phase LC (NPLC × RPLC). NPLC × RPLC is considered a desirable LC × LC system, especially for the characterization of synthetic polymers, due to the high orthogonality of the two retention mechanisms. However, its experimental realization often suffers from solvent-injection effects in the RPLC dimension, such as peak-deformation, peak-splitting, or even unretained elution (“breakthrough”) of sample components. Such a decrease in performance or loss of retention is highly dependent on the types of solvents used.To explore the boundaries of solvent compatibility, we applied large-volume injections (LVI) of reference analytes (e.g. alkyl benzenes; ethoxylate and propoxylate polymers) dissolved in water-immiscible sample solvents, such as dichloromethane, n-hexane, and isooctane in fast water-based gradient RPLC separations (using methanol or acetonitrile as eluent). It was found that, when using highly aqueous initial gradient conditions, hydrophobic sample diluents were retained and eluted during the applied gradient. Depending on the relative retention of the retained diluent and the sample analytes, good chromatograms for LVI of immiscible solvents were obtained, comparable with injections under ideal conditions. The conclusions from injection experiments in aqueous RPLC were verified by coupling an NPLC system with a gradient from isooctane to tetrahydrofuran and an RPLC system with a gradient from water to acetonitrile in an online comprehensive NPLC × RPLC separation of a mixture of propoxylate polymers. The separation provided separation of the polymers based on their number of hydroxyl end-groups (NPLC) and oligomer chain-length (RPLC), without suffering from significant band-broadening effects due to solvent-mismatch upon injection in the second-dimension RPLC system.

How Long are Polymer Chains in Poly(3,4-ethylenedioxythiophene):Tosylate Films? An Insight from Molecular Dynamics Simulations.

Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most important conductive polymers utilized in a variety of applications in organic electronics and bioelectronics and energy storage. PEDOT chains are believed to be rather short, but detailed knowledge of their length is missing because of the challenges in its experimental determination due to insolubility of PEDOT films. Here, we report a molecular dynamics (MD) study of in situ oxidative chemical polymerization and simultaneous crystallization of molecularly doped PEDOT focusing on the determination of its chain lengths at different polymerization temperatures. We find the average chain length to be 6, 7, and 11 monomers for 298, 323 and 373 K, respectively. At the same time, the length distribution is rather broad, for example, between 2 and 16 monomer units for T = 323 K. We demonstrate that the limiting factor determining the chain length is the diffusivity of the reactants (PEDOT monomers and oligomers). We also study the polymer film formation during solvent evaporation, and we find that although crystallization starts and proceeds already during the polymerization and doping phases, it mostly occurs during the evaporation phase. Finally, we believe that our results providing the oligomer chain length and polymerization and crystallization mechanisms obtained by means of MD "computational microscopy" provide an important insight into the morphology of PEDOT that cannot be obtained by other means.

Structure–activity relationships in well-defined conjugated oligomer photocatalysts for hydrogen production from water

Oligomer chain length and backbone twisting were found to have a strong effect on optoelectronic properties but a trimer of dibenzo[b,d]thiophene sulfone was found to have high photocatalytic activity approaching that of its polymer analogue.

Molecular heterogeneity drives reconfigurable nematic liquid crystal drops.

With few exceptions, polydispersity or molecular heterogeneity in matter tends to impede self-assembly and state transformation1–3. Here we report shape transition studies of nematic liquid crystal oligomer (NLCO) drops, which reveal, surprisingly, that molecular heterogeneity in the drops promotes reversible transitions to a rich variety of non-spherical morphologies with unique internal structure. Previously, shape transitions of homogeneous liquid drops with monodisperse ingredients have been reported in equilibrium4–7 and non-equilibrium studies8, 9, with the latter producing filaments at active interfaces, albeit randomly without control. Our experiments employ equilibrium suspensions of drops composed of polydisperse NLCOs. Variation of oligomer chain length distribution, temperature, and surfactant concentration alters the balance between NLCO elastic energy and interfacial energy and drives formation of visually striking nematic structures ranging from roughened spheres to flowers to branched filamentous networks with controllable diameters. The branched structures with confined LC director fields can be produced reversibly over centimeter areas and converted into LC elastomers by UV curing. Remarkably, observations and modeling reveal that chain length polydispersity plays a crucial role in driving these morphogenic phenomena, via spatial segregation. This insight suggests new routes for encoding network structure and function in soft materials.

Mechanochemical Effects of Adsorbates at Nanoelectromechanical Switch Contacts.

Herein, classical molecular dynamics simulations are used to examine nanoscale adsorbate reactions during the cyclic opening and closing of nanoelectromechanical system (NEMS) switches. We focus upon how reactions change metal/metal conductive contact area, asperity morphology, and plastic deformation. We specifically consider Pt, which is often used as an electrode material for NEMS switches. The structural evolution of asperity contacts in gaseous environments with molecules which can potentially form tribopolymers is determined by various factors, for example, contact forces, partial pressure and molecular weight of gas, and the fundamental reaction rates of surface adsorption and adsorbate linkages. The modeled systems exhibit significant changes during the first few cycles, but as the number of contact cycles increases, the system finds a steady-state where the morphologies, Pt/Pt contact area, oligomer chain lengths, amount of Pt transfer between opposing surfaces, and deformation rate stabilize. The stress generated during asperity contact increases the rate of reactions among the adsorbates in the contact region. This makes the size of the adsorbate molecules increase and thus more exposed metal, which implies higher electrical conductance in the closed contact, but more plastic deformation, metal-metal transfer, and mechanical work expended in each contact cycle.

Templated Ring-Opening Metathesis (TROM) of Cyclic Olefins Tethered to Unimolecular Oligo(thiophene)s

We developed a fully abiotic approach to template the synthesis of discrete unimolecular polyolefins. Discrete, unimolecular oligo(thiophene)s with alternating sequence were obtained by iterative convergent/divergent couplings and then functionalized with pendant cyclic olefin monomers in the side chains. Upon treatment with the Grubbs third-generation catalyst in dilute solution (0.15 mM in DCM at 0 °C), the pendant monomers undergo templated ring-opening metathesis (TROM). Then, the daughter olefin is liberated from the parent thiophene by hydrolysis. Cyclooctenes undergo TROM to afford macrocyclic products that exactly replicate the chain length of the parent oligomer, as evidenced by MALDI MS/MS and NMR. Norbornene derivatives also undergo TROM and replicate unimolecular chain lengths, but in contrast, they exclusively form the linear oligomeric products with styrenic end groups. A template that was functionalized with one norbornene unit at the α chain end, followed by five cyclooctene units along th...

Effect of chain length of polyisobutylene oligomers on the molecular motion modes of butyl rubber: Damping property

It is a promising method to obtain desirable damping materials by introducing dangling chains used as additional relaxation components. Regrettably, the strict condition of introducing dangling chains limits its application to saturated polymer or low unsaturated degree polymer, for example butyl rubber (IIR). Hence, we propose a simple yet effective method to obtain desirable IIR based damping composites by blending with miscible polyisobutylene (PIB) oligomers as additional relaxation components in this study. As expected, the damping property of IIR is easily controlled by tuning the chain length of PIB oligomers. The effects of PIB oligomers with different chain length on the molecular motions and damping mechanism of IIR were characterized by dynamical mechanical analysis and 2D correlation dynamic mechanical spectroscopy (2DC-DMS). The damping improvement of IIR was ascribed to the additional relaxation generated by introducing PIB oligomers and the movement of sub-Rouse modes and Rouse modes. It seems a universal method to enhance damping property by using miscible polymer oligomers as additional relaxation component. Furthermore, this method may give some inspirations for preparing polymer matrix specially used for damping composites.

High sensitivity of polypyrrole sensor for uric acid over urea, acetamide and sulfonamide: A density functional theory study

Polypyrrole is experimentally reported as an excellent sensor for biological molecules including urea and uric acid. DFT calculations at M05-2X/6–31++G(d,p) are performed to gain theoretical insight into the sensing mechanism of polypyrrole for urea, uric acid, acetamide and sulfonamide. Geometry optimization and electronic property calculations have been performed on a series of oligopyrrole (1, 3, 5, 7 and 9) complexes, and the properties are extrapolated to infinite polymer through 2nd degree polynomial fit. Energy decomposition analyses (SAPT0) have been performed to demonstrate the contribution of electrostatic, induction, exchange and dispersion. The trend of SAPT0 interaction energies is very much comparable to that of binding energies. The noncovalent components of SAPT0 regularly increase with oligomer chain length; however, these components become almost constant after trimer for urea, acetamide, and sulfonamide. The increase in interaction and SAPT0 energies illustrate an increase in sensitivity of polypyrrole. Charge transfer and electronic properties also illustrate the high sensitivity of polypyrrole for uric acid. Energy difference between HOMO and LUMO orbitals of polypyrrole decreases upon doping with analytes. The decrease in the HOMO-LUMO gap shows an increase in the conductivity of polypyrrole. Our results indicate that polypyrrole has the highest sensing ability for uric acid, consistent with the experimental observations.

Soluble Oligomeric Nucleants: Simulations of Chain Length, Binding Strength, and Volume Fraction Effects.

Recent theories and simulations suggest that molecular additives can bind to the surfaces of nuclei, lower the surface energy, and accelerate nucleation. Experiments have shown that oligomeric and polymeric additives can also modify nucleation rates of proteins, ice, and minerals; however, general design principles for oligomeric or polymeric promoters do not yet exist. Here we investigate oligomeric additives for which each segment of the oligomer can bind to surfaces of nuclei. We use semigrand canonical Monte Carlo simulations in a Potts lattice gas model to study the effects of oligomer chain length, volume fraction, and binding strength. We find that increasing each of those parameters lowers the nucleation barrier. At extremely low oligomer concentrations, the nucleation kinetics can be modeled as though each oligomer is a heterogeneous nucleation site in solution.

Olefin conversion on nitrogen-doped carbon-supported cobalt catalyst: Effect of feedstock

A nitrogen-doped carbon-supported cobalt oxide catalyst is able to oligomerize ethylene, propylene, 1-butene and 1-hexene into mixtures of oligomers with above 94.1% dimers. Higher than 72.5% of the dimers produced from 1-butene and 1-hexene are internal linear olefins, while the dimer products from propylene oligomerization are 47.0% linear including 5.9% 1-hexene. Ethylene had the highest oligomerization activity with 56.1–87.0% 1-butene selectivity. The selectivity to linear alpha olefins decreases with an increasing oligomer chain length during ethylene oligomerization. The oligomers formed from ethylene conversion follow a Schulz-Flory distribution. Cossee type mechanism rationalizes the product selectivity from the four olefin feeds, suggesting that a 1,2-2,1 insertion sequence is critical to obtaining linear olefin products. The catalyst was inactive in oligomerizing internal olefins.

Enzymatic Synthesis of a Bio-Based Copolyester from Poly(butylene succinate) and Poly((R)-3-hydroxybutyrate): Study of Reaction Parameters on the Transesterification Rate.

The enzyme-catalyzed synthesis of fully biobased poly(3-hydroxybutyrate-co-butylene succinate) (poly(HB-co-BS)) copolyesters is reported for the first time. Different Candida antarctica lipase B (CALB)-catalyzed copolyesters were produced in solution, via a one-step or a two-step process from 1,4-butanediol, diethyl succinate, and synthesized telechelic hydroxylated poly(3-hydroxybutyrate) oligomers (PHB-diol). The influence of the ester/hydroxyl functionality ratio, catalyst amount, PHB-diol oligomer chain length, hydroxybutyrate (HB) and butylene succinate (BS) contents, and the nature of the solvent were investigated. The two-step process allowed the synthesis of copolyesters of high molar masses (Mn up to 18 000 g/mol), compared to the one-step process (Mn ∼ 8000 g/mol), without thermal degradation. The highest molar masses were obtained with diphenyl ether as solvent, compared with dibenzyl ether or anisole. During the two-step process, the transesterification rate between the HB and BS segments (i) increased with increasing amount of catalyst and decreasing molar mass of the PHB-diol oligomer, (ii) decreased when anisole was used as the solvent, and (iii) was not influenced by the HB/BS ratio. Tendencies toward block or random macromolecular architectures were observed as a function of the reaction time, the PHB-diol oligomer chain length, and the chosen solvent. Immobilized CALB-catalyzed copolyesters were thermally stable up to 200 °C. The crystalline structure of the poly(HB-co-BS) copolyesters depended on the HB/BS ratio and the average sequence length of the segments. The crystalline content, Tm and Tc decreased with increasing HB content and the randomness of the copolymer structure.

Step‐growth thiol–thiol photopolymerization as radiation curing technology

ABSTRACTThis report introduces a novel UV‐curing technology based on thiol–thiol coupling for polydisulfide network formation. Beginning with a model tris(3‐mercaptopropionate) trithiol monomer and xanthone propionic acid‐protected guanidine as photobase generator, a comprehensive characterization based on spectroscopic techniques supports the reaction of thiols into disulfides without side reactions. The best experimental conditions are described as regards to film thickness, irradiance, emission wavelength, and atmosphere composition. The results shed light on a step‐growth photopolymerization mechanism involving two steps: first, the formation of thiyl radicals by thiolate air oxidation or/and thiol photolysis, and second, their recombination into disulfide. By varying thiol functionality and structure, oligomer chain length and monomer/oligomer ratio, the network architecture can be finely tuned. The molecular mobility of the polydisulfide network is crucial to high thiol conversion rates and yields as revealed by 1H T2 NMR relaxation measurements. Ultimately, spatial control enables the formation of a photopatterned poly(disulfide) film, used as next‐generation high refractive index photoresist. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 117–128.

DFT study of conjugational electronic structures of aminoalkyl end-capped oligothiophenes up to octamers

The molecular geometries and electronic properties of a series of bis(aminoalkyl) end-capped oligothiophenes (BRnTs) were investigated by means of the density functional theory (DFT). The calculations were performed on dimers up to octamers in the neutral and ionic species using the B3LYP/6-31G(d,p) level of theory. The results obtained show that the conjugated systems in the p- and n-doped oligomers had more aromaticity, with expanded and planar chains. The calculated energy gap values between the frontier molecular orbitals for the end-capped oligomers were larger than those for the unsubstituted oligomers, in which with increase in the oligomer chain length, the conduction band gap decreased. The calculated first excitation energies of BRnTs at the TD-B3LYP/6-31G(d,p) level indicated that both doped oligomers (p- and n-type) had lower excitation energies than the neutral states, and that they displayed red shifts in their absorption spectra. Moreover, the results obtained for the natural bond orbital (NBO) analysis showed that closing the end-side oligothiophene chains with the aminoalkyl groups eased the hole or electron transfer, owning to better charge delocalization through the backbone structures of BRnTs.

Menthols as Chiral Auxiliaries for Asymmetric Cycloadditive Oligomerization: Syntheses and Studies of β-Proline Hexamers

To produce a novel class of structurally ordered poly-β-prolines, an emergent method for synthesizing chiral β-peptide molecular frameworks was developed based on 1,3-dipolar cycloaddition chemistry of azomethine ylides. Functionalized short β-peptides with up to six monomeric residues were efficiently synthesized in homochiral forms using a cycloadditive oligomerization approach. X-ray, NMR, and CD structural analyses of the novel β-peptides revealed secondary structure features that were generated primarily by Z/E-β-peptide bond isomerism. Anticancer in cellulo activity of the new β-peptides toward hormone-refractory prostate cancer cells was observed and was dependent on the absolute configuration of the stereogenic centers and the chain length of the β-proline oligomers.

Fundamental Charge Transfer Processes in Stable Free-Radical Organic Polymer Systems

Polymers with stable pendant radical groups are a unique class of redox-active materials emerging as potentially the next generation energy storage breakthrough. These polymers facilitate apparently remarkably rapid, efficient and reversible multi-step charge-transfer processes. The focus of this project is to advance the fundamental understanding of the structure-property relationships associated with the mechanism(s) of electron transfer and ion transport, along with associated interfacial mass-transfer processes that impact the charge-transfer processes of a unique class of organic free-radical polymeric redox active materials. The project involves an integrated approach of chemical synthesis, electrochemistry, spectroscopy and theoretical modeling of a series of stable organic radical materials. Initially, we have focused on the 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) organic radical moiety incorporated into a complex materials set of poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (PTMA). We focused our work to probe, and establish, the charge-transfer mechanisms of a series of the TEMPO-containing macromolecules with varying chain lengths and side-chain compositions. We have investigated the model compound, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl (4-oxo-TEMPO), and compared the results to those for non-cross-linked and cross-linked PTMA oligomers and polymers with: (i) various oligomer chain-lengths; and (ii) controlled densities of the TEMPO radical moieties along the chain (i.e. with some TEMPO-methacrylate units replaced by methyl methacrylate). Our presentation will discuss a complete electrochemical analysis of the TEMPO polymeric materials. The discussion will include the correlation of electron-transfer rates and ionic mobility in various electrochemical solvents, and the role that radical content has on both the heterogeneous electron-transfer rate and the self-exchange charge transfer mechanism of the various materials.