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Synthetic surfaces engineered to regulate phase transitions of matter and exercise control over its undesired accrual (liquid or solid) play a pivotal role in diverse industrial applications. Over the years, the design of repellant surfaces has transitioned from solely modifying the surface texture and chemistry to identifying novel material systems. In this study, selection criteria are established to identify bio-friendly phase change materials (PCMs) from an extensive library of vegetable-based/organic/essential oils that can thermally respond by harnessing the latent heat released during condensation and thereby delaying ice/frost formation in the very frigid ambient that is detrimental to its functionality. Concurrently, a comprehensive investigation is conducted to elucidate the relation between microscale heat transport phenomena during condensation and the resulting macroscopic effects (e.g., delayed droplet freezing) on various solidified PCMs as a function of their inherent thermo-mechanical properties. In addition, to freeze protection, many properties that are responsive to the thermal reflex of the surface, such as the ability to dynamically tune optical transparency, moisture harvesting, ice shedding, and quick in-field repairability, are achievable, resulting in the development of protective coatings capable of spanning a wide range of functionalities and thereby having a distinctive edge over conventional solutions.

Author(s): Fan, Y; Gomez, A; Muliana, A; La Saponara, V | Abstract: This study presents a multiscale analysis for describing the fluid diffusion in polymeric sandwich composites, comprising of glass-epoxy fiber reinforced polymer (FRP) skins and polyurethane foam core. The multiscale framework includes the unit-cell micromechanics model for determining the overall diffusion behavior in the FRP skins by incorporating different diffusivities of the fiber and matrix and the diffusion model for foam core. In addition, multiscale diffusion tests have been conducted for the sandwich composites, FRP skins, foam core, and epoxy resin. The specimens were immersed in deionized water at 50°C. The capability in predicting the overall diffusion behavior of sandwich composites while recognizing the different diffusion processes of the constituents is not only beneficial for designing polymeric sandwich composites with desired performance but also enhances understanding on the durability of polymeric sandwich composites. POLYM. COMPOS., 40:3520–3532, 2019. © 2019 Society of Plastics Engineers.

Rechargeable batteries are necessary for the decarbonization of the energy systems, but life-cycle environmental impact assessments have not achieved consensus on the environmental impacts of producing these batteries. Nonetheless, life cycle assessment (LCA) is a powerful tool to inform the development of better-performing batteries with reduced environmental burden. This review explores common practices in lithium-ion battery LCAs and makes recommendations for how future studies can be more interpretable, representative, and impactful. First, LCAs should focus analyses of resource depletion on long-term trends toward more energy and resource-intensive material extraction and processing rather than treating known reserves as a fixed quantity being depleted. Second, future studies should account for extraction and processing operations that deviate from industry best-practices and may be responsible for an outsized share of sector-wide impacts, such as artisanal cobalt mining. Third, LCAs should explore at least 2–3 battery manufacturing facility scales to capture size- and throughput-dependent impacts such as dry room conditioning and solvent recovery. Finally, future LCAs must transition away from kg of battery mass as a functional unit and instead make use of kWh of storage capacity and kWh of lifetime energy throughput.

Author(s): Higa, Chad Masaharu | Advisor(s): Braslau, Rebecca | Abstract: Poly(vinyl chloride) (PVC) is one of the most utilized thermoplastics on Earth. However, PVC by itself is brittle and not readily processable. This material reached the success of its worldwide demand because of phthalates, a cost-effective additive (emollient) that imparts flexibility and resistivity towards weathering, temperature extremes and electrical conductivity. The use of phthalates as plastic emollients is widespread, representing approximately three quarters of all plasticizers globally, with applications ranging from industrial to consumer products. The pervasive utilization of low molecular weight blended phthalates as emollients inevitably leads to leaching, contamination and exposure. Phthalates and their metabolites have displayed negative effects on various organs and act as potent endocrine disrupting chemicals that cause deleterious pre- and postnatal developmental effects, notably in males. Bans of phthalates by the European Union and the United States in children’s articles have spurred the development of less toxic PVC plasticizer alternatives.Branched and linear non-migratory internal plasticizers attached to PVC by a pendant triazole linkage were synthesized. Copper-free azide-alkyne thermal cycloaddition was employed to covalently bind triazole-based phthalate mimics to poly(vinyl chloride) (PVC). To systematically investigate the effect of plasticizer structure on glass transition temperature, several architectural motifs were explored. Free volume theory was considered when designing many of these internal plasticizers: hexyl-tethers were utilized to generate additional space between the triazole-phthalate mimic and the polymer backbone. Miscibility of these triazole-plasticizers in PVC is important: variation of the ester moieties on the triazole possessing alkyl and/or poly(ethylene oxide) (PEO) chains produced a wide range of glass transition temperatures (Tg): from anti-plasticizing 96 °C, to highly efficient plasticized materials exhibiting Tg values as low as -42 °C.Triazole methyl esters directly appended to PVC displays an inherent anti-plasticization effect originating from the aromatic ring, which diminishes with increasing molecular weight and branching of the alkyl ester chains. Introduction of a flexible hexyl tether to the secondary triazole group acts as additional molecular weight and branching, further lowering Tg values. Attachment of two hexyl tethered secondary triazoles follows this trend by enforcing another branch point and increasing molecular weight. Utilization of PEO esters in all architectural types significantly enhances Tg depressions, with longer PEO chains exhibiting remarkable results. Single PEO triazole esters readily prepared from propiolic esters using low-cost, commercially available materials combine excellent plasticization with straightforward synthesis, making these non-migratory internal plasticizers extremely attractive for industrial applications.An alternative strategy to post-polymerization direct modification of PVC to obtain internally plasticized materials involves the copolymerization of vinyl chloride monomer (VCM) with a monomer functionalized with a triazole-phthalate mimic. Electron-rich vinyl acetate monomers with an appended triazole-plasticizer were synthesized for this purpose. Copolymerizations with the vinyl acetate triazole monomers and VCM were largely unsuccessful. It was envisaged that an acrylate derivative should remedy the low reactivity of these vinyl acetate monomers. An acrylate incorporating a hexyl-tethered triazole-phthalate mimic served two purposes: 1) generate space between the triazole and polymerizing vinyl group to prevent monomer deactivation and, 2) enhance the plasticization efficiency of the triazole.

Author(s): Khedekar, K; Rezaei Talarposhti, M; Besli, MM; Kuppan, S; Perego, A; Chen, Y; Metzger, M; Stewart, S; Atanassov, P; Tamura, N; Craig, N; Cheng, L; Johnston, CM; Zenyuk, IV | Abstract: The heterogeneity of polymer electrolyte fuel cell catalyst degradation is studied under varied relative humidity and types of feed gas. Accelerated stress tests (ASTs) are performed on four membrane electrode assemblies (MEAs) under wet and dry conditions in an air or nitrogen environment for 30n000 square voltage cycles. The largest electrochemically active area loss is observed for MEA under wet conditions in a nitrogen gas environment AST due to constant upper potential limit of 0.95nV and significant water content. The mean Pt particle size is larger for the ASTs under wet conditions compared to dry conditions, and the Pt particle size under land is generally larger than under the channel. Observations from ASTs in both conditions and gas environments indicate that water content promotes Pt particle size growth. ASTs under wet conditions and an air environment show the largest difference in Pt particle size growth for inlet versus outlet and channel versus land, which can be attributed to larger water content at outlet and under land compared to inlet and under channel. From X-ray fluorescence experiments Pt particle size increase is a local phenomenon as Pt loading remains relatively uniform across the MEA.

All-polymer solar cells (all-PSCs) are a highly attractive class of photovoltaics for wearable and portable electronics due to their excellent morphological and mechanical stabilities. Recently, new types of polymer acceptors (PAs) consisting of non-fullerene small molecule acceptors (NFSMAs) with strong light absorption have been proposed to enhance the power conversion efficiency (PCE) of all-PSCs. However, polymerization of NFSMAs often reduces entropy of mixing in PSC blends and prevents the formation of intermixed blend domains required for efficient charge generation and morphological stability. One approach to increase compatibility in these systems is to design PAs that contain the same building blocks as their polymer donor (PD) counterparts. Here, a series of NFSMA-based PAs [P(BDT2BOY5-X), (X = H, F, Cl)] are reported, by copolymerizing NFSMA (Y5-2BO) with benzodithiophene (BDT), a common donating unit in high-performance PDs such as PBDB-T. All-PSC blends composed of PBDB-T PD and P(BDT2BOY5-X) PA show enhanced molecular compatibility, resulting in excellent morphological and electronic properties. Specifically, PBDB-T:P(BDT2BOY5-Cl) all-PSC has a PCE of 11.12%, which is significantly higher than previous PBDB-T:Y5-2BO (7.02%) and PBDB-T:P(NDI2OD-T2) (6.00%) PSCs. Additionally, the increased compatibility of these all-PSCs greatly improves their thermal stability and mechanical robustness. For example, the crack onset strain (COS) and toughness of the PBDB-T:P(BDT2BOY5-Cl) blend are 15.9% and 3.24MJ m–3, respectively, in comparison to the PBDB-T:Y5-2BO blends at 2.21% and 0.32MJ m–3.

Methionine sulfoxide and phosphonate containing double hydrophilic block copolypeptides and their mineralization of calcium carbonate Ilya Captain † and Timothy J. Deming †‡ * †Department of Chemistry and Biochemistry, ‡Department of Bioengineering, University of California, Los Angeles, CA 90095. demingt@seas.ucla.edu Correspondence to: Timothy J. Deming (E-mail: demingt@seas.ucla.edu) ((Additional Supporting Information may be found in the online version of this article.)) ABSTRACT: In effort to address challenges in the efficient synthesis of highly functional block copolypeptides, we report use of a combination of functional monomer polymerization and post- polymerization modification to obtain new double hydrophilic block copolypeptides with desirable properties. We prepared copolymers that contain discrete hydrophilic, non-ionic poly(L-methionine sulfoxide) and Ca 2+ ion binding poly(L-phosphonohomoalanine) segments. The facile and selective post- polymerization conversion of inexpensive, readily prepared poly(L-methionine) segments into non-ionic, hydrophilic poly(L-methionine sulfoxide) segments reduces the need for use of combinations of protecting groups. The complex copolypeptides prepared using this strategy were able to promote formation of CaCO 3 microspheres with tunable polymorphism. KEYWORDS: block copolypeptides, hydrophilic polypeptides, stimuli-sensitive polymer, calcium carbonate, microspheres. INTRODUCTION The ability to readily prepare complex copolymers that contain a diverse array of side- chain functional groups is an ongoing goal in the field of polymer synthesis. 1-3 Desirable functionalities include those that impart stimuli responsiveness, 4 ability to bind to select molecules, 5 as well as undergo efficient reactions with specific partners. 2,6 As the desire for increasingly complex functional polymers continues, obtaining compatibility between functional groups and polymerization chemistries has become a challenging problem. This is especially true for the polypeptide field, where high monomer reactivity limits the types of functional side-chain groups that can be used, and often requires use of cumbersome protecting group strategies. 1-3 Here, we report the use of a combination of functional monomer polymerization and post- polymerization modification to obtain new, highly functional, double hydrophilic block copolypeptides with desirable properties. This strategy provides an efficient method to prepare complex copolypeptides that were used to promote formation of CaCO 3 microspheres with tunable polymorphism. Inorganic materials of specific shape, size, and polymorph are valuable in the fields of nano- materials, 7 ceramics, 8 electronics, 9 and medicine. Biological systems have been expertly forming minerals for millennia, mainly through use of organic molecules as control agents. 7 Much effort has gone into mimicking these natural processes using synthetic polymers, which have successfully been used to control many aspects of mineralization processes. 11,12 CaCO 3 , in particular, has received considerable attention in these studies due to its importance as a biomineral in many organisms, its use in paper and paint industries, and since it is a major component in scale

Transition metal dichalcogenides (TMDs, such as MoS2, WS2 and MoSe2) with lamellar structures have attracted tremendous attention owing to their similar structure to graphite. However, two-dimensional (2D) TMD nanomaterials display a strong tendency to restack and condense, which leads to a marked decrease of performance in their applications. In this study, we report the synthesis of TMDs by using polyoxometalates (POMs) as tungsten or molybdenum precursors. Hierarchical TMDs with novel structures can be formed below 200 °C, including WS2 rods, MoS2 rods and MoSe2 hollow spheres. All of these structures assembled from the corresponding nanosheets. Meanwhile the epitaxial growth of noble metal nanoparticles (NPs) on TMDs could be achieved very easily. The obtained Pt/WS2 and Pt/MoS2 hybrids were highly active and durable HER catalysts. In addition, the Pt NPs on the surface of TMDs could improve the HER activity sharply, which was likely due to the synergistic effect between Pt NPs and MoS2 rods.

Author(s): Kim, Min-cheol; Ham, So-Yeon; Cheng, Diyi; Wynn, Thomas A; Jung, Hyun Suk; Meng, Ying Shirley

Author(s): Hirsh, Hayley S; Li, Yixuan; Tan, Darren HS; Zhang, Minghao; Zhao, Enyue; Meng, Y Shirley

Author(s): Babbe, F; Sutter-Fella, CM | Abstract: Halide perovskites have emerged as materials for high-performance optoelectronic devices. Often, progress made to date in terms of higher efficiency and stability is based on increasing material complexity, i.e., formation of multicomponent halide perovskites with multiple cations and anions. In this review article, the use of in situ optical methods, namely, photoluminescence (PL) and UV-vis, that provide access to the relevant time and length scales to ascertain chemistry–property relationships by monitoring evolving properties is discussed. Additionally, because halide perovskites are electron/ion conductors and prone to solid-state ion transport under various external stimuli, application of these optical methods in the context of ionic movement is described to reveal mechanistic insights. Finally, examples of using in situ PL and UV-vis to study degradation and phase transitions are reviewed to demonstrate the wealth of information that can be obtained regarding many different aspects of ongoing research activities in the field of halide perovskites.

High molecular weight polyacrylonitrile (PAN) with low dispersity has been successfully synthesized utilizing reversible addition-fragmentation chain transfer (RAFT) polymerization. A comprehensive study was performed to understand the influence of reaction temperature, RAFT agent structure, and [M]0:[CTA]0[I]0 on the polymerization kinetics, molecular weight, and dispersity. Enhanced control is attributed to reduction of side reactions by conducting the polymerization at lower temperature, and optimizing the radical exchange between active and dormant states via appropriate selection of RAFT agent and initiator. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015

In this work, we investigated the effects of metal stearate salts on the structure, morphology, and properties of poly(ethylene-acrylic acid) neutralized by zinc salts (PI). The samples were characterized in detail with spectroscopic [Fourier transform infrared (FTIR) spectroscopy], microscopic (hot-stage optical microscopy), thermal [thermogravimetric analysis, modulated differential scanning calorimetry, and dynamic mechanical analysis], mechanical, and scattering (small-angle neutron scattering and small-angle X-ray scattering) techniques. The melt rheological properties of the samples were also investigated. The structure of the ionic domains was determined by the type of cations and the salt proportion (FTIR). The predominant interaction was found to exist between the metal stearate and the ionic group. Na+cation exhibited a unique behavior, whereas Zn2+showed a coordinated structure and, hence, properties. The ionic groups in the Na and Zn stearate systems existed as multiplets and clusters, but multiplets were the main structure in the Al salt system. The salts acted as plasticizers above their melting points (mp's) but as fillers below their mp's. The melt flow properties of PI were significantly affected by the metal cation and salt proportion and were improved greatly by the introduction of the salts. © 2012 Wiley Periodicals, Inc.

Author(s): Gregory, SA; Menon, AK; Ye, S; Seferos, DS; Reynolds, JR; Yee, SK | Abstract: This study reports on the thermoelectric properties of poly(3-alkylchalcogenophene) thin films (500 nm) as a function of heteroatom (sulfur, selenium, tellurium), and how these properties change with dopant (ferric chloride) concentration. UV–vis–NIR spectroscopy shows that polaronic charge carriers are formed upon doping. Poly(3-alkyltellurophene) (P3RTe) is most easily doped followed by poly(3-alkylselenophene) (P3RSe) and poly(3-alkylthiophene) (P3RT), where R = 3,7-dimethyloctyl chain is the pendant alkyl group. Thermoelectric properties vary as functions of the heteroatom and doping level. At low dopant concentrations (≈1 × 10−3 m), P3RTe shows the highest power factor of 10 µW m−1 K−2, while, at higher dopant concentrations (≈5 × 10−3 m), P3RSe shows the highest power factor of 13 µW m−1 K−2. Most notably, it is found that the measured properties are consistent with Mott's polaron hopping model and not consistent with other transport models. Additionally, temperature-dependent conductivity measurements show that for a given dopant concentration, the activation energies for electronic transport decrease as the heteroatom is changed from sulfur to selenium to tellurium. Overall, this work presents a systematic study of poly(chalcogenophenes) and indicates the potential of polymers beyond P3HT by tuning the heteroatom and doping level for optimized thermoelectric performance.

Author(s): Wood, Sean M; Fang, Chengcheng; Dufek, Eric J; Nagpure, Shrikant C; Sazhin, Sergiy V; Liaw, Boryann; Meng, Y Shirley

Summary: A simple method for the fabrication of a chemical composition gradient from organic to inorganic by the pyrolysis of a polymethylsilsesquioxane (PMSQ) thin film in a gradient temperature field is reported. The resultant chemical gradient surface demonstrates gradual changes in wettability, and slight microstructural changes are observed along the substrate. FT-IR spectra of gradient PMSQ surface along the length from the unheated side to the heated side.

This review surveys methods for the fabrication, by plasma surface treatments or plasma polymerization, of polymeric surfaces and thin plasma polymer coatings that contain reactive chemical groups useful for the subsequent covalent immobilization, by solution chemical reactions or vapor phase grafting, of molecules or polymers that can exert bio-specific interfacial responses. Surfaces containing amine, carboxy, hydroxy, and aldehyde groups are the subject of this review. Aminated surfaces have been fabricated using various plasma vapors or mixtures and have found wide use for bio-interface applications. However, in many cases the amine surfaces have a rather limited shelf life, with post-plasma oxidation reactions and surface adaptation leading to the disappearance of amine groups from the surface. Aging is a widespread phenomenon that often has not been recognized, particularly in some of the earlier studies on the use of plasma-fabricated surfaces for bio-interfacial applications, and can markedly alter the surface chemistry. Plasma-fabricated surfaces that contain carboxy groups have also been well documented. Fewer reports exist on hydroxy and aldehyde surfaces prepared by plasma methods. Hydroxy surfaces can be prepared by water plasma treatment or the plasma polymerization of alkyl alcohol vapors. Water plasma treatment on many polymer substrates suffers from aging, with surface adaptation leading to the movement of surface modification effects into the polymer. Both hydroxy and aldehyde surfaces have been used for the covalent immobilization of biologically active molecules. Aging effects are less well documented than for amine surfaces. This review also surveys studies using such surfaces for cell colonization assays. Generally, these surface chemistries show good ability to support cell colonization, though the effectiveness seems to depend on the process vapor and the plasma conditions. Carboxylate co-polymer surfaces have shown excellent ability to support the colonization of some human cell lines of clinical interest. Immobilization of proteins onto plasma-carboxylated surfaces is also well established.

Significant reinforcement of styrene-butadiene-rubber was achieved by the novel modification of starch through the use of a resorcinol-formaldehyde and a silane surfactant. The mechanical property improvement by the modified starch is comparable with that reinforced by carbon black. SEM micrograph shows fine morphologies caused by the modification. Dynamic mechanical test shows the advantages of the modified SBR/starch composite: the lowered glass transition temperature means improved low temperature properties; the decreased Tan delta value predicts a smaller internal temperature rise produced by dynamic stress; the increased storage modulus indicates this material is of higher hardness; the improved loss modulus demonstrates higher resistance to tearing.

A novel method was developed to prepare an exfoliated styrene butadiene rubber (SBR)/clay nanocomposite with a strong interface between the clay layers and the rubber. An exfoliation mechanism was proposed and verified based on X-ray diffraction (XRD)/transmission electron microscopy (TEM) analyses of the intercalation/exfoliation phenomena after each step of the process. The significant improvements of mechanical properties may give the first evidence that both exfoliation and a strong interface play critical roles in nanoreinforcement.

Polysilsesquioxane nanosheets with a thickness of four nanometers and lateral dimensions of several hundreds of nanometers were synthesized by polymerization of a trifunctional monomer in the layer space of montmorillonite as the confined environment.

Editorial Peptide-based Materials for Nanomedicine There has been an abundance of research in recent years on the development of polymers for medi- cal uses. These materials, formulated in a variety of different forms, such as fibers, micelles, vesicles, hydro- gels, emulsion droplets, and thin films, are being developed to incor- porate useful functionality for inter- acting with biological systems. While much has been accomplished with traditional synthetic polymers, improved biomimetic materials are desirable, that can be highly func- tional as well as degradable, and where individual components are capable of performing multiple functions as often seen in biological materials. Incorporation of such complex functionality can be chal- lenging since many synthetic poly- mer based systems have limited capability for modification, and when functionalized, finely bal- anced properties may be signifi- cantly altered or impaired. For these reasons, there is a need for biomi- metic polymers that can be prepared using versatile methods allowing for fine tuning of chemical compo- sition and structure, and using building blocks that are biocompat- ible, biodegradable, and easily functionalized. Incorporation of peptide and poly- peptide domains has been widely used as powerful means to introduce functionality, structural stability, degradability, and stimuli respon- siveness in polymeric materials. In other systems, control over polymer assembly and prediction of structure and properties remains challenging when functional groups are added, preventing the predictable formation of highly multifunctional materials with controllable properties. Recent advances in synthesis and structural and functional characterization have enabled peptide and polypeptide materials as legitimate candidates for medical uses. This themed issue of Macromolec- ular Bioscience highlights exciting recent developments in the applica- tion of peptide and polypeptide based materials in medicine. The importance of this topic was reflected in a 3-day symposium entitled ‘‘Peptide-based Materials in Nanomedicine’’ held at the 247th ACS National Meeting in Dallas on March 16–20, 2014. Selected contributions from this symposium together with articles from other leading researchers in the field are assembled in this special issue. Peptide and polypeptide mate- rials have many advantages over conventional synthetic polymers since they are able to hierarchically assemble into stable ordered con- formations. Depending on the amino acid side chain substituents, pepti- des and polypeptides are able to adopt a multitude of conformation- ally stable regular secondary struc- tures (helices, sheets, turns), and also assemble into ordered aggregates. These structures may be robust and can present functional molecules in ways similar to biological materials. Consequently, there have been many recent breakthroughs in crea- tion of designed peptide and poly- peptide sequences to make candi- date materials for applications in medicine as scaffolds (artificial tis- sues, implants), therapeutic carriers (micelles, vesicles, emulsions), and for analysis (biosensors, medical diagnostics). The issue contains both in-depth reviews of contemporary topics as well as papers describing the latest developments in the field. Smits & van Hest review the preparation of nanoparticles obtained from stimuli- Macromol. Biosci. 2015, 15, 7–8 s 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com responsive elastin-like peptides and peptide hybrids, while Danial and Klok provide an overview of poly- meric anti-HIV therapeutics. Several of the primary research articles showcase the preparation of diverse polypeptides by ring-opening poly- merization of N-carboxyanhydrides (NCAs). Micelle-forming PEO-peptide hybrids that encapsulate doxorubicin are described by Lecommandoux et al. In this work, the NCA-derived polypeptide is clicked to PEO-azide to generate hybrid block copolymers. Deming and coworkers show how blending together diblock copolypep- tides leads to the production of cell penetrating polymersomes, while Cameron et al. describe the produc- tion of polypeptide nanoparticles from diblock copolypeptides, and their loading with the ocular drug dexamethasone. Heise et al. have prepared glycosylated star polypep- tides by NCA ring-opening polymer- ization then functionalization of the polypeptide side chain with sugars. Other papers describe work that employs solid phase synthesis meth- ods to prepare sequence-defined pep- tides. Kiick, Theato and co-workers present the preparation of hybrid materials involving collagen-like peptide sequences coupled to ther- moresponsive polymers. Caged colla- gen-mimetic peptides that, upon exposure to UV, pattern gelatin films and hydrogels to encourage spatially- defined cell attachment are described by Yu et al. Boerner and coworkers present their work on polymer-pep- tide hybrids as solubilisers for poorly water-soluble drugs. Finally, Cor- nellisen and coworkers demonstrate how virus-like particles (VLPs) can be prepared from plant viruses, thus harnessing Nature’s ability to pro- duce exquisitely defined peptides. The VLPs are clustered by different DOI: 10.1002/mabi.201400499

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Charge transport materials (CTMs) are traditionally inorganic semiconductors or metals. However, over the past few decades, new classes of solution-processable CTMs have evolved alongside new concepts for fabricating electronic devices at low cost and with exceptional properties. The vast majority of these novel materials are organic compounds and the use of transition metal complexes in electronic applications remains largely unexplored. Here, a solution-processable solid-state charge transport material composed of a blend of [Co(bpyPY4)](OTf)2and Co(bpyPY4)](OTf)3where bpyPY4 is the hexadentate ligand 6,6′-bis(1,1-di(pyridin-2-yl)ethyl)-2,2′-bipyridine and OTf−is the trifluoromethanesulfonate anion is reported. Surprisingly, these films exhibit a negative temperature coefficient of conductivity (dσ/dT) and non-Arrhenius behavior, with respectable solid-state conductivities of 3.0 S m−1at room temperature and 7.4 S m−1at 4.5 K. When employed as a CTM in a solid-state dye-sensitized solar cell, these largely amorphous, transparent films afford impressive solar energy conversion efficiencies of up to 5.7%. Organic–inorganic hybrid materials with negative temperature coefficients of conductivity generally feature extended flat π-systems with strong π–π interactions or high crystallinity. The lack of these features promotes [Co(bpyPY4)](OTf)2+xfilms as a new class of CTMs with a unique charge transport mechanism that remains to be explored.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Design rules are presented for significantly expanding sequential processing (SqP) into previously inaccessible polymer:fullerene systems by tailoring binary solvent blends for fullerene deposition. Starting with a base solvent that has high fullerene solubility, 2-chlorophenol (2-CP), ellipsometry-based swelling experiments are used to investigate different co-solvents for the fullerene-casting solution. By tuning the Flory-Huggins χ parameter of the 2-CP/co-solvent blend, it is possible to optimally swell the polymer of interest for fullerene interdiffusion without dissolution of the polymer underlayer. In this way solar cell power conversion efficiencies are obtained for the PTB7 (poly[(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)(3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl)]) and PC61BM (phenyl-C61-butyric acid methyl ester) materials combination that match those of blend-cast films. Both semicrystalline (e.g., P3HT (poly(3-hexylthiophene-2,5-diyl)) and entirely amorphous (e.g., PSDTTT (poly[(4,8-di(2-butyloxy)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)-alt-(2,5-bis(4,4'-bis(2-octyl)dithieno[3,2-b:2'3'-d]silole-2,6-diyl)thiazolo[5,4-d]thiazole)]) conjugated polymers can be processed into highly efficient photovoltaic devices using the solvent-blend SqP design rules. Grazing-incidence wide-angle x-ray diffraction experiments confirm that proper choice of the fullerene casting co-solvent yields well-ordered interdispersed bulk heterojunction (BHJ) morphologies without the need for subsequent thermal annealing or the use of trace solvent additives (e.g., diiodooctane). The results open SqP to polymer/fullerene systems that are currently incompatible with traditional methods of device fabrication, and make BHJ morphology control a more tractable problem.

By controlling the crystallinity and average grain size of thermoelectric NaxCoO2 thin films, a doubling of the thermoelectric power factor is achieved in combination with a strong suppression of the thermal conductivity. These structurally engineered NaxCoO2 thin films outperform single crystalline and polycrystalline samples at room temperature and demonstrate the potential of thermoelectric oxide thin films. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.