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We use all-atom molecular dynamics simulations to study the effect of polymer polarity, as quantified by the dielectric constant, on the transport properties of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) doped polyethers. Our results indicate that increasing the host dielectric constant leads to a decrease in ionic cluster sizes and reduction in correlated motion of oppositely charged ions. This causes the ionic conductivity to more closely approach the Nernst-Einstein limit in which ionic conductivity is only limited by the diffusivities of Li+ and TFSI–. We compare our results to recent experimental observations which demonstrate similar qualitative trends in host polarity.

Expanding the range of strong and self-healable polymer networks is of fundamental interest and practical importance. In this work, we report a network of poly(3-azido-1-propyne)-block-poly(ethylen...

We apply a machine learning (ML) technique to the multiobjective design of polymer blend electrolytes. In particular, we are interested in maximizing electrolyte performance measured by a combinati...

Lower critical solution behavior in binary blends of hydrophobic polyethers with 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]) exhibited a difference in lower critica...

Under the right conditions, some biological systems can maintain high viability after being frozen and thawed, but many others (e.g., organs and many mammalian cells) cannot. To increase the rates of post-thaw viability and widen the library of living cells and tissues that can be stored frozen, an improved understanding of the mode of action of polymeric cryoprotectants is required. Here, we present a polymeric cryoprotectant, poly(methyl glycidyl sulfoxide) (PMGS), that achieved higher post-thaw viability for fibroblast cells than its small-molecule analogue dimethyl sulfoxide. By limiting the amount of water that freezes and facilitating cellular dehydration after ice nucleation, PMGS mitigates the mechanical and osmotic stresses that the freezing of water imparts on cells and facilitates higher-temperature vitrification of the remaining unfrozen volume. The development of PMGS advances a fundamental physical understanding of polymer-mediated cryopreservation, which enables new material design for long-term preservation of complex cellular networks and tissue.

During the course of studying silicon-containing diblock copolymers, it was discovered that poly(3,5-di(trimethylsilyl)styrene)-block-poly(3,4-methylenedioxystyrene) (PDTMSS-b-PMDOS) showed very un...

Copolymerization of ethylene oxide and a series of glycidyl ethers with precise linear/cyclic oligo(ethylene oxide) side-chains allows access to a library of well-defined poly(ethylene oxide) (PEO)...

Polarity-switching photopatternable guidelines can be directly used to both orient and direct the self-assembly of block copolymers. We report the orientation and alignment of poly(styrene-block-4-...

We use coarse-grained molecular dynamics simulations to study the effect of salt concentration and host polymer molecular weight on ion transport in polymer electrolytes. We find that increasing salt concentration or molecular weight similarly slows polymer dynamics across a wide range of host polarities, and that the resulting relaxation times display a correlation to the product of the salt concentration and polymer molecular weight. However, we find that molar conductivity only decreases with polymer dynamics at high polarities but is uncorrelated with the latter at low polarities. We attribute such differences to the variation in ionic aggregation between high and low polarity electrolytes. At low polarity, ionic dissociation significantly increases with molecular weight and salt concentration, offsetting the slowdown in polymer dynamics and yielding the observed insensitivity of molar conductivity. However, at high polarity, ions are mostly dissociated, independent of either molecular weight or salt concentration, thereby strongly coupling molar conductivity to polymer dynamics.

The fabrication of sub-100 nm features with bioactive molecules is a laborious and expensive process. To overcome these limitations, we present a modular strategy to create nanostructured substrates (ca. 25 nm features) using functional block copolymers (BCPs) based on poly(styrene-b-ethylene oxide) to controllably promote or inhibit cell adhesion. A single type of BCP was functionalized with a peptide, a perfluorinated moiety, and both compounds, to tune nanoscale phase separation and interactions with NIH3T3 fibroblast cells. The focal adhesion formation and morphology of the cells were observed to vary dramatically according to the functionality presented on the surface of the synthetic substrate. It is envisioned that these materials will be useful as substrates that mimic the extracellular matrix (ECM) given that the adhesion receptors of cells can recognize clustered motifs as small as 10 nm, and their spatial orientation can influence cellular responses.

Graft polymers are useful in a versatile range of material applications. Understanding how changes to the grafted architecture, such as the grafting density (

We report a partial elucidation of the relationship between polymer polarity and ionic conductivity in polymer electrolyte mixtures comprising a homologous series of nine poly(vinyl ether)s (PVEs) and lithium bis(trifluoromethylsulfonyl)imide. Recent simulation studies have suggested that low dielectric polymer hosts with glass transition temperatures far below ambient conditions are expected to have ionic conductivity limited by salt solubility and dissociation. In contrast, high dielectric hosts are expected to have the potential for high ion solubility but slow segmental dynamics due to strong polymer-polymer and polymer-ion interactions. We report results for PVEs in the low polarity regime with dielectric constants of about 1.3 to 9.0. Ionic conductivity measured for the PVE and salt mixtures ranged from about 10

Plastic waste poses an ecological challenge1. While current plastic waste management largely relies on unsustainable, energy-intensive, or even hazardous physicochemical and mechanical processes, enzymatic degradation offers a green and sustainable route for plastic waste recycling2. Poly(ethylene terephthalate) (PET) has been extensively used in packaging and for the manufacture of fabrics and single-used containers, accounting for 12% of global solid waste3. The practical application of PET hydrolases has been hampered by their lack of robustness and the requirement for high processing temperatures. Here, we use a structure-based, deep learning algorithm to engineer an extremely robust and highly active PET hydrolase. Our best resulting mutant (FAST-PETase: Functional, Active, Stable, and Tolerant PETase) exhibits superior PET-hydrolytic activity relative to both wild-type and engineered alternatives, (including a leaf-branch compost cutinase and its mutant4) and possesses enhanced thermostability and pH tolerance. We demonstrate that whole, untreated, post-consumer PET from 51 different plastic products can all be completely degraded by FAST-PETase within one week, and in as little as 24 hours at 50 °C. Finally, we demonstrate two paths for closed-loop PET recycling and valorization. First, we re-synthesize virgin PET from the monomers recovered after enzymatic depolymerization. Second, we enable in situ microbially-enabled valorization using a Pseudomonas strain together with FAST-PETase to degrade PET and utilize the evolved monomers as a carbon source for growth and polyhydroxyalkanoate production. Collectively, our results demonstrate the substantial improvements enabled by deep learning and a viable route for enzymatic plastic recycling at the industrial scale.

Plastic waste poses an ecological challenge

We study ternary polymer-polymer-salt blend electrolytes using coarse-grained molecular dynamics. We specifically examine the influence of the polymer hosts’ incompatibility and polarity contrast o...

In the present scenario, the invention of bacteria-selective antimicrobial agent comprising negligible toxicity and hemolytic effect is a great challenge. To surmount this challenge, here, a series of polypeptide nanogels (PNGs) have been fabricated by a coordination-assisted self-assembly of a mannose-conjugated antimicrobial polypeptide, poly(arginine-r-valine)-mannose (poly(Arg-r-Val)-M2), with Zn2+ ions. The fabricated PNGs are spherical in shape with a unique structural appearance similar to that of Taxus baccata fruits. PNGs, with a unique structural arrangement and threshold surface charge density, selectively interact with the bacterial membrane and exhibit potent antimicrobial activity, as reflected in their lower minimum inhibitory concentration values (varies from 2 to 16 μg/mL). PNGs show a remarkably high binding constant, 6.02 × 105 M-1 (from isothermal titration calorimetry, ITC), with the bacterial membrane which manifests its potent bactericidal effect. PNGs are nontoxic against mammalian and red blood cells as reflected from their higher cell viability and insignificant hemolytic effect. PNGs are taken up by the bacterial membrane and selectively undergo structural deformation (scrutinized by ITC) followed by an exposure of free poly(Arg-r-Val)-M2 molecules. The free poly(Arg-r-Val)-M2 molecules are enforced to lyse the bacterial membrane (visualized by cryo-transmission electron microscopy) followed by the diffusion of the cytoplasmic component out of the membrane which culminates in the final death of the bacterium.

A set of copolymerization data at prescribed reactivity ratios was numerically generated and then fit using common methods of data analysis including the copolymer equation, Fineman–Ross, Kelen–Tud...

Typically, Suzuki couplings used in polymerizations are performed at raised temperatures in inert atmospheres. As a result, the synthesis of aromatic materials that utilize this chemistry often demands expensive and specialized equipment on an industrial scale. Herein, we describe a bimetallic methodology that exploits the distinct reactivities of palladium and copper to perform high yielding aryl–aryl dimerizations and polymerizations that can be performed on a benchtop under ambient conditions. These couplings are facile and can be performed by simple mixing in the open vessel. To demonstrate the utility of this method in the context of polymer synthesis: polyfluorene, polycarbazole, polysilafluorene, and poly(6,12-dihydro-dithienoindacenodithiophene) were created at ambient temperature and open to air.

Multiple computational and experimental techniques are used to understand the nanoscale morphology and water/proton transport properties in a series of sulfonated Diels–Alder poly(phenylene) (SDAPP...

This study aims to expand structure-property relationships of diaminophenylindane (DAPI)-containing polyimides and the influence of thermal cross-linking on gas transport properties of such materials. A polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride (6FDA), DAPI, and diaminobenzoic acid (DABA) in a molar ratio of 0.5/0.33/0.17, 6FDA0.5-DAPI0.33/DABA0.17, was crosslinked by thermal decarboxylation. After cross-linking, pure gas permeability of 6FDA0.5-DAPI0.33/DABA0.17 increased with increased cross-linking time; gas permeability increased by about 30% after cross-linking at 353 °C for 40 min. This increase in permeability correlated with an increase in d-spacing measured by wide angle x-ray scattering, suggesting an increase in inter-chain spacing upon cross-linking. Minimal changes in O2/N2 and N2/CH4 selectivities occurred with increased thermal cross-linking time for 6FDA0.5-DAPI0.33/DABA0.17. However, CO2/CH4 and C2H4/C2H6 pure gas selectivities increased with thermal treatment, suggesting a potential narrowing of free volume distribution.

In this work, we use computer simulations to demonstrate that there may be limits to which polymer polarity alone can be used to influence the ionic conductivity of salt-doped polymer electrolytes. Specifically, we use coarse-grained molecular dynamics simulations to probe the effect of the polarity of the polymer electrolyte upon ion mobilities and conductivities of dissolved salts. At low polymer polarities, increasing the polymer dielectric constant reduces ionic aggregation and the resultant correlated ionic motion, and increases the ionic conductivity. At higher polymer polarities, polymer-polymer and polymer-ion interactions slows polymer segmental dynamics, leading to a reduction in the conductivity of the electrolyte. As a consequence, ionic conductivity achieves an optimum at an intermediate polymer polarity.

A mono(μ-oxo)bis(alkylaluminum) (MOB) catalyst and initiator for epoxide polymerization, [(H3C)2NCH2CH2(μ2-O)Al(iBu)2·Al(iBu)3] (1), produced a ca. 170-fold enhancement in epoxide polymerization rate over previously reported MOB initiators demonstrated with allyl glycidyl ether (AGE). This discovery reduces polymerization times to minutes. 1 exhibited an exponential dependence of polymerization rate on concentration, rather than an expected low integer order relationship. A proposed polymerization intermediate was identified via direct synthesis, isolation, kinetic comparison, and corroborating in situ spectroscopic evidence to be a symmetric bis((μ-alkoxo)dialkylaluminum) (BOD) with a characteristic R3N·AlR′3 (N–Al) adduct. The N–Al adduct on the BOD intermediate is proposed to act as a catalyst, whereas the aluminoxane ring is proposed to be the site of monomer enchainment on the basis of mass spectrometry and spectroscopic analysis of resultant polymer structure. The distinct catalytic and initiation/p...

Polysulfide-shuttle has been a critical concern for the advancement of lithium-sulfur (Li-S) batteries. Celgard membranes that are generally used in Li-S batteries exhibit a porous structure with a pore dimension generally on the micrometer scale. During cell operation, soluble lithium polysulfide species can easily migrate from the cathode through the porous separator and react with the lithium-metal anode. Such an unexpected chemical reaction induces a cascade of negative effects on the overall performance of Li-S batteries. Use of ion-selective membranes with reduced pore size provides a promising approach to suppress the migration of polysulfide species. In this study, a membrane based on a polymer with intrinsic nanoporosity (PIN) with a pore size of

Membranes are a critical component of many energy generation and storage technologies, including artificial photosynthesis systems that reduce atmospheric CO2 to high-value products. In this study, we used in situ ATR FTIR spectroscopy to monitor the crossover of three commonly-reported CO2 reduction products—methanol, sodium formate, and sodium acetate—through Nafion® 117, a common cation exchange membrane. Measurement errors for the permeation of mixtures of solutes are discussed. Permeabilities from one-, two-, and three-solute mixed aqueous solutions were measured using a standard diffusion cell, and ATR FTIR spectra were used to obtain time-resolved concentration data that were fit to a model describing transport of ions and small molecules through hydrated polymer films. The permeability of Nafion® 117 to methanol measured using this methodology was in agreement with literature reports. The sorption of methanol, sodium formate, and sodium acetate, and mixtures thereof, were measured using a desorption technique. From the measured permeabilities and solubilities, diffusivities of each solute were calculated. Differences in permeability among the solutes were found to be primarily due to differences in their solubility in Nafion® 117.

A combined theoretical and experimental investigation into the structure and mechanism of the classical Vandenberg catalyst for the isoselective polymerization of epoxides has led to a consistent mechanistic proposal. The most likely reaction pathway was based on a bis(μ-oxo)di(aluminum) (BOD) resting state that proceeded through a mono(μ-oxo)di(aluminum) (MOD) transition state. The isoselectivity of the Vandenberg catalyst was derived from the rigidity of the BOD structure and its bonding to the ultimate and penultimate oxygen heteroatoms along the polyether backbone. The energetic driving force for isoselectivity was the loss of an energetically favorable secondary Al–O interaction during enchainment of oppositely configured epoxides, providing a ca. 2 kcal/mol driving force for the emergent isoselectivity. Experimental spectroscopic and kinetic evidence based on model BOD and MOD complexes support the new mechanistic framework developed using density functional theory calculations. A purposefully synth...

Polyketides represent an extremely diverse class of secondary metabolites often explored for their bioactive traits. These molecules are also attractive building blocks for chemical catalysis and polymerization. However, the use of polyketides in larger scale chemistry applications is stymied by limited titers and yields from both microbial and chemical production. Here, we demonstrate that an oleaginous organism (specifically, Yarrowia lipolytica) can overcome such production limitations owing to a natural propensity for high flux through acetyl–CoA. By exploring three distinct metabolic engineering strategies for acetyl–CoA precursor formation, we demonstrate that a previously uncharacterized pyruvate bypass pathway supports increased production of the polyketide triacetic acid lactone (TAL). Ultimately, we establish a strain capable of producing over 35% of the theoretical conversion yield to TAL in an unoptimized tube culture. This strain also obtained an averaged maximum titer of 35.9 ± 3.9 g/L with an achieved maximum specific productivity of 0.21 ± 0.03 g/L/h in bioreactor fermentation. Additionally, we illustrate that a β-oxidation-related overexpression (PEX10) can support high TAL production and is capable of achieving over 43% of the theoretical conversion yield under nitrogen starvation in a test tube. Next, through use of this bioproduct, we demonstrate the utility of polyketides like TAL to modify commodity materials such as poly(epichlorohydrin), resulting in an increased molecular weight and shift in glass transition temperature. Collectively, these findings establish an engineering strategy enabling unprecedented production from a type III polyketide synthase as well as establish a route through O-functionalization for converting polyketides into new materials.

Poor selectivity of conventional desalination membranes for boron often necessitates multi-stage treatment trains to achieve desired boron removal for end uses such as irrigation. One approach to membrane design for improved single-pass boric acid removal is via incorporation of chelating ligands that selectively sorb boron. In this study, membranes based on epoxy-amine cross-linked poly(glycidyl glycidyl ether) (PGGE) were synthesized and functionalized with N-methyl- d -glucamine (NMDG), a polyol known to interact selectively with boron. PGGE and PGGE-NMDG membranes exhibited boron sorption isotherms that were well-described by dual mode isotherms. PGGE-NMDG sorbed 2.5 mmol B/g dry polymer from a neutral aqueous solution containing 100 mmol B/L, which was almost three times the adsorption density of a commercial boron selective resin, Amberlite IRA743. The membranes were regenerated in acid without a significant loss of boron sorption capacity over four cycles. Interactions between boron and NMDG and PGGE sites (e.g., epoxides) impacted boron diffusion in both membranes. The use of ligand functionalized membranes to capture target solutes such as boron requires high loading of interacting sites to maximize uptake capacity. Establishing fundamental structure/property rules for boron selectivity could lead to new material designs with improved boron separation properties for water purification.

We report a new class of organoaluminum-based initiator for anionic ring-opening polymerization of epoxides that is simple to synthesize from readily available precursors. The resultant organometallic initiator was the triethylaluminum adduct of (2-dibenzylamino)ethoxydiethylaluminum (TAxEDA) [(AlEt3)·(O(AlEt2)CH2CH2N(Bn)2)], which was isolated by direct crystallization from the reaction medium and then compositionally and structurally characterized by NMR spectroscopy and XRD. We studied the reactivity and versatility of the new initiator through the polymerization of propylene oxide, butylene oxide, epichlorohydrin, and allyl glycidyl ether into homopolymer, statistical copolymer, and block copolymer architectures with heterobifunctional end-groups consisting of dibenzylamine and hydroxyl functionalities. The TAxEDA-initiated polymerizations were consistent with a controlled, living, anionic mechanism that was tolerant of chemical functionality and exhibited no chain transfer to monomer that limits the ...

Copolymerization provides a modular strategy for compositional control of structure–property relationships in polymeric materials. However, this versatility is typically limited to structurally homologous comonomers. To further expand the scope of copolymerization in heterocyclic systems, we explored the copolymerization of structurally distinct lactones and epoxides utilizing the classical Vandenberg catalyst. Copolymerizations were conducted between monomer pairs selected from among two common lactones (dl-lactide, e-caprolactone) and four epoxides (epichlorohydrin, butylene oxide, propylene oxide, ethylene oxide). The resultant materials had molecular weights of up to 16 Mg/mol. Reactivity ratios were determined for the copolymerization of dl-lactide and propylene oxide, which were consistent with a gradient copolymer with propylene oxide (PO) being the preferred monomer: rPO = 2.81 ± 0.27 and rLA = 0.36 ± 0.02. The copolymerization between e-caprolactone and propylene oxide was also monitored by 1H NM...

Polymer topology dictates dynamic and mechanical properties of materials. For most polymers, topology is a static characteristic. In this article, we present a strategy to chemically trigger dynamic topology changes in polymers in response to a specific chemical stimulus. Starting with a dimerized PEG and hydrophobic linear materials, a lightly cross-linked polymer, and a cross-linked hydrogel, transformations into an amphiphilic linear polymer, lightly cross-linked and linear random copolymers, a cross-linked polymer, and three different hydrogel matrices were achieved via two controllable cross-linking reactions: reversible conjugate additions and thiol-disulfide exchange. Significantly, all the polymers, before or after topological changes, can be triggered to degrade into thiol- or amine-terminated small molecules. The controllable transformations of polymeric morphologies and their degradation herald a new generation of smart materials.

Performing radical polymerizations under ambient conditions is a major challenge because molecular oxygen is an effective radical quencher. Here we show that the facultative electrogen Shewanella oneidensis can control metal-catalysed living radical polymerizations under apparent aerobic conditions by first consuming dissolved oxygen via aerobic respiration, and then directing extracellular electron flux to a metal catalyst. In both open and closed containers, S. oneidensis enabled living radical polymerizations without requiring the preremoval of oxygen. Polymerization activity was closely tied to S. oneidensis anaerobic metabolism through specific extracellular electron transfer proteins and was effective for a variety of monomers using low (parts per million) concentrations of metal catalysts. Finally, polymerizations survived repeated challenges of oxygen exposure and could be initiated using lyophilized or spent (recycled) cells. Overall, our results demonstrate how the unique ability of S. oneidensis to use both oxygen and metals as respiratory electron acceptors can be leveraged to address salient challenges in polymer synthesis.

Directed self-assembly (DSA) of block copolymers (BCPs) is one approach to the pattern density multiplication required to achieve high-volume manufacturing of the next-generation memory and storage devices. One important application for DSA is in manufacturing of nanoimprint templates for the next-generation bit patterned media. A hybrid chemo-/grapho-epitaxy DSA process has been developed that produced 5 nm line-and-space DSA patterns on a chromium hard mask surface. The guide lines for this process were produced by imprint lithography. The process requires a polar guide stripe, which is the trim-etched imprint resist, and a near neutral substrate, which is the etched chromium. This requires selective grafting of near neutral polymer brushes to the etched chromium and not to the etched imprint guidelines. This selectivity is one critical requirement for the process [1]. Orientation and alignment of line-and-space patterns that traverse through the entire BCP film were successfully employed to pattern the chromium hard mask. We have investigated the reactivity of etched chromium surfaces with various polymer brush chemistries and found that the choice of the end-functional groups, monomer structures, and grafting temperature all play significant roles in selective functionalization. The etched chromium surface was found to be more reactive with various polymer brushes than etched silicon under mild brush grafting conditions. Hence, lower grafting temperatures could be exploited for achieving selectivity of polymer brush to the etched chromium while not reacting with the etched imprint guidelines. Thus, several polymer brushes that form a thin layer of brush on etched chromium were found to modify the surface energy of the etched chromium without significant interaction with the etched imprint resist. Successful pattern transfer of 5 nm line-and-space patterns was achieved. 1. Lane, A. P., et al. ACS Nano (2017), 11 (8), 7656–7665.

This project, “Pitch Division Photolithography at I-line,” seeks to accomplish pitch multiplication by using a traditional 248 nm photoresist polymer in conjunction with a photo-acid generator (PAG) and a photo-base generator (PBG). This formulation can achieve a two-fold improvement in resolution without the need for new equipment or significant changes in processing conditions. The photoresist matrix used in this work is poly[4-[(tert-butoxycarbonyl)oxy] styrene] (PTBOC), which is employed in combination with a PAG in 248 nm resists. When exposed to light, the PAG decomposes to form acid which, upon post-exposure baking, deprotects multiple pendant groups on the PTBOC to produce hydroxyl groups, thereby changing its solubility. This polymer exhibits another key feature: the dissolution rate with respect to dose has a threshold-like response, meaning that below a threshold dose, the polymer will not appreciably dissolve in a developer containing tetramethyl ammonium hydroxide (TMAH), but above this dose, the dissolution rate increases several orders of magnitude. This behavior becomes vital at feature sizes that approach theoretical resolution limits where the aerial image near the photoresist becomes more sinusoidal. Because the dissolution rate is controlled by the acid content within the polymer matrix, it is possible to cross this dissolution threshold twice with increasing dose if the acid is somehow quenched at higher doses. A PBG is an easy way to achieve this goal. If a PBG is chosen such that it is decomposes more slowly than the PAG and is incorporated with a stochiometric excess, then this dissolution threshold may be crossed twice. The addition of a PBG generates three different regimes with respect to dose: At low doses, neither the PAG nor PBG will have appreciably decomposed and the resist remains insoluble in aqueous base. At medium doses, enough acid will be generated by the PAG to cross the threshold, with too little PBG decomposition to effectively quench said acid. At high doses, both the PAG and PBG have mostly decomposed and the net acid concentration will be below the dissolution threshold. If the relative rates of the PAG and PBG can be tuned such that these two dissolution thresholds properly match the sinusoid intensity profile, the resolution of patterns can be improved by a factor of two. Dr. Xinyu Gu previously demonstrated the feasibility of such a system for 193 nm tools [1]. In this work, we report several combinations of PAGs and PBGs that meet the above criteria and show promise for exhibiting pitch-division. In some cases, a photosensitizer was needed to enable the decomposition of the PAG. These combinations were tested by exposing a film to a given dose and then developing in an aqueous solution of TMAH. It was found that the relative dissolution rates closely match the ideals as described above. These combinations are ready for testing with an exposure tool to verify and optimize their function as a pitch division photoresist. Reference: [1] Gu, X. et al. “Photobase generator enabled pitch division: a progress report,” Proc. SPIE 7972, 79720F (2011).

Although the small-molecule lithium salt solutions currently employed in lithium-ion batteries display high ionic conductivity, σ, most of the initial current is carried by the electrochemically inactive anion, resulting in concentration polarization of the salt during cycling. Liquid electrolytes with high Li+ transference number, t+, and high σ could improve battery performance by limiting these concentration gradients. We propose lithium-neutralized polyanions in solution as an intriguing strategy to attain both high t+ and high σ at room temperature and validate the approach using a model system. Pulsed field gradient nuclear magnetic resonance spectroscopy (PFG-NMR) is used to attain self-diffusion coefficients of the ions and hence t+. Conductivity calculated from PFG-NMR showed good agreement with conductivity measured using a conductivity meter. Although the polyelectrolyte solutions exhibit maxima in conductivity at around 0.5 M Li+ (1.5 mS/cm), t+ continuously increases with concentration, achie...

We present an improvement in the rate, utility, and mechanistic understanding of mono-μ-oxo-dialuminum initiators for epoxide ring-opening polymerization based on investigation of a homologous series of trialkylaluminum adducts of (2-dibenzylamino)ethoxy-dialkylaluminum (TAxEDA) [(AlR3)·(O(AlR2)CH2CH2N(Bn)2), with R = Me, Et, iBu]. Using in situ FTIR spectroscopy of neat AGE polymerizations, we determined that the isobutyl-substituted TAxEDA (iBu-TAxEDA) exhibited a propagation rate constant (kp) of 1.100 ± 0.022 × 10−3 M−1 s−1, which was twice that of the methyl-functional TAxEDA (Me-TAxEDA) (kp = 0.500 ± 0.011 × 10−3 M−1 s−1) and four times that of ethyl-functional TAxEDA (Et-TAxEDA) (kp = 0.270 ± 0.003 × 10−3 M−1 s−1). The dative R3Al–O bond length in the mono-μ-oxo-dialuminum was longest for the iBu-TAxEDA (1.93 A) and shortest for the Et-TAxEDA (1.88 A). Consistent with a previously proposed mechanism for TAxEDA-initiated polymerization, the increased Al–O bond length may accommodate more-facile coordination and enchainment of the monomer by separation of the Al–O interaction leading to an increased polymerization rate. The generality of the improved iBu-TAxEDA was supported by polymerization of a range of monomer substrates such as propylene oxide (PO), butylene oxide (BO), epichlorohydrin (ECH), allyl glycidyl ether (AGE), propargyl glycidyl ether (PGE), and adamantylmethyl glycidyl ether (AMGE). In all cases investigated, the triisobutyl-functional TAxEDA (iBu-TAxEDA) represented an improved initiator for epoxide polymerization.

Elucidating the relationship between chemical structure, morphology, and ionic conductivity is essential for designing novel high-performance materials for electrochemical applications. In this work, the effect of lamellar domain spacing (d) on ionic conductivity (σ) is investigated for a model system of hydrated diblock copolymer based on a protic polymerized ionic liquid. We present a strategy that allows for the synthesis of a well-defined series of narrowly dispersed PS-b-PIL with constant volume fraction of ionic liquid moieties (fIL ≈ 0.39) and with two types of mobile charge carriers: trifluoroacetate anions and protons. These materials self-assemble into ordered lamellar morphologies with variable domain spacing (ca. 20–70 nm) as demonstrated by small-angle X-ray scattering. PS-b-PIL membranes exhibit ionic conductivities above 10–4 S/cm at room temperature, which are independent of domain spacing consistent with their nearly identical water content. The conductivity scaling relationship demonstra...