Conducting organic polymers have found two main kinds of application in electronics so far: as materials for construction of various devices and as selective layers in chemical sensors. In either case, interaction with ambient gases is critical. It may compromise the performance of a device based on conducting polymers, whereas it is beneficial in a sensor. Conductivity has been the primary property of interest. Work function--related to conductivity, but in principle a different property--has received only scant attention. Our aim here is to discuss the usability of conducting polymers in both types of electronic applications in light of these two parameters.

Conducting polymers in electronic chemical sensors.

The synthesis and use of cyclic alkylene carbonates as reactive intermediates first appeared in the literature more than 50 years ago. However, the range of their usefulness in industrial applications has only been fully realized in the past decade. In this article, numerous reactive applications of the cyclic alkylene carbonates, specifically the five-membered cyclics, are discussed. In addition, utilization of the chemistry presented in this review for the preparation of industrially useful monomers, polymers, surfactants, plasticizers, cross-linking agents, curing agents, and solvents, to name a few, is also discussed.

Reactive Applications of Cyclic Alkylene Carbonates

Introduction to Surface Chemistry and Catalysis

Higher alcohols are important compounds with widespread applications in the chemical, pharmaceutical and energy sectors. Currently, they are mainly produced by sugar fermentation (ethanol and isobutanol) or hydration of petroleum-derived alkenes (heavier alcohols), but their direct synthesis from syngas (CO + H2) would comprise a more environmentally-friendly, versatile and economical alternative. Research efforts in this reaction, initiated in the 1930s, have fluctuated along with the oil price and have considerably increased in the last decade due to the interest to exploit shale gas and renewable resources to obtain the gaseous feedstock. Nevertheless, no catalytic system reported to date has performed sufficiently well to justify an industrial implementation. Since the design of an efficient catalyst would strongly benefit from the establishment of synthesis–structure–function relationships and a deeper understanding of the reaction mechanism, this review comprehensively overviews syngas-based higher alcohols synthesis in three main sections, highlighting the advances recently made and the challenges that remain open and stimulate upcoming research activities. The first part critically summarises the formulations and methods applied in the preparation of the four main classes of materials, i.e., Rh-based, Mo-based, modified Fischer–Tropsch and modified methanol synthesis catalysts. The second overviews the molecular-level insights derived from microkinetic and theoretical studies, drawing links to the mechanisms of Fischer–Tropsch and methanol syntheses. Finally, concepts proposed to improve the efficiency of reactors and separation units as well as to utilise CO2 and recycle side-products in the process are described in the third section.

Status and prospects in higher alcohols synthesis from syngas

One promising approach to reduce the cost of fuel cell systems is to develop hydroxide exchange membrane fuel cells (HEMFCs), which open up the possibility of platinum-group-metal-free catalysts and low-cost bipolar plates. However, scalable alkaline polyelectrolytes (hydroxide exchange membranes and hydroxide exchange ionomers), a key component of HEMFCs, with desired properties are currently unavailable, which presents a major barrier to the development of HEMFCs. Here we show hydroxide exchange membranes and hydroxide exchange ionomers based on poly(aryl piperidinium) (PAP) that simultaneously possess adequate ionic conductivity, chemical stability, mechanical robustness, gas separation and selective solubility. These properties originate from the combination of the piperidinium cation and the rigid ether-bond-free aryl backbone. A low-Pt membrane electrode assembly with a Ag-based cathode using PAP materials showed an excellent peak power density of 920 mW cm−2 and operated stably at a constant current density of 500 mA cm−2 for 300 h with H2/CO2-free air at 95 °C. A key challenge for hydroxide exchange membrane fuel cells is the development of membranes with both high ionic conductivity and mechanical strength. Here the authors report a high-performance family of poly(aryl piperidinium) membranes enabling promising durability and power density.

Poly(aryl piperidinium) membranes and ionomers for hydroxide exchange membrane fuel cells

A reliable and practical approach is offered for the two critical fundamental challenges that remain in step-growth polymerization: synthesis of narrow polydispersity and ultrahigh molecular weight polymers. The polymers are obtained by superacid catalyzed polyhydroxyalkylation involving two consecutive steps – slow and fast. Polymer syntheses with decrease in reactivity of intermediates lead to narrow polydispersity polymers, while nonstoichiometric reactions result in polymers of high and ultrahigh molecular weight. Linear aromatic polymers with ultra high molecular weight Mn > 1 000 000 and narrow polydispersity (Mw/Mn = 1.15–1.16) have been obtained. An unusual step-selective mechanism is suggested for the formation of these polymers.

Precision Synthesis of Narrow Polydispersity, Ultrahigh Molecular Weight Linear Aromatic Polymers by A2 + B2 Nonstoichiometric Step-Selective Polymerization

A novel series of linear, high-molecular-weight polymers was synthesized by one-pot, metal-free superacid-catalyzed reaction of isatins (1a−d) with linear, nonactivated, multiring aromatic hydrocarbons: biphenyl (A), p-terphenyl (B), p-quaterphenyl (C), 2-(4-biphenylyl)-6-phenylbenzoxazole (D), 9H-fluorene (E), 9,9-dimethyl-9H-fluorene (F), 2,2′-[2,5-bis(trifluoromethyl)-1,4-phenylene]bis(9,9-dimethyl-9H-fluorene) (G), oligo-9,9-bis(2,6-ethylhexyl)-9H-fluorene (H), biphenol (I), and bi-2-napththol (J). The reactions were performed at room temperature in the Bronsted superacid trifluoromethanesulfonic acid (CF3SO3H, TFSA) and in a mixture of TFSA with methylene chloride or TFA tolerant of hydroxyl, carboxy, and cyano groups. The polymers obtained were soluble in most common organic solvents, and flexible transparent films could be cast from the solutions. 1H and 13C NMR analyses of the polymers synthesized revealed their linear structure with para-substitution in the phenylene fragments of the main chain. ...

Novel, Metal-Free, Superacid-Catalyzed “Click” Reactions of Isatins with Linear, Nonactivated, Multiring Aromatic Hydrocarbons

Chiral Polypyrroles from Optically Active Pyrrole Monomers

The surface morphology of polypyrrole (ppy) films prepared by potentiostatic and voltammetric methods at the platinum electrode was studied by ex situ atomic force microscopy (AFM). The study was mainly focused on the early stages of polymer film growth up to a film thickness of 30 to 50 nm. AFM analysis revealed that polymer film morphology depends on the electrosynthesis method used. Electrosynthesized films produced by the voltammetric method consisted of nano-size ppy nodules, which during the polymer oxidation process become associated forming larger surface aggregates. However, in thicker films and those prepared using a large anion, this association was not observed. The ppy films formed by the potential step method (potentiostatic) allowed a better control of the early stages of the electropolymerization process. Thus, the AFM study showed that the first ppy nodules grow three-dimensionally during the application of the potential pulse steps, and simultaneously their number increase on the electrode surface according to the progressive nucleation and growth model. Negligible association of ppy nodules was noticed for the film prepared by the potentiostatic method, which suggests that this synthesis method is a better alternative for controlling ppy film growth.

Manuel Salmón

Papers

Precision Synthesis of Narrow Polydispersity, Ultrahigh Molecular Weight Linear Aromatic Polymers by A2 + B2 Nonstoichiometric Step-Selective Polymerization

Novel, Metal-Free, Superacid-Catalyzed “Click” Reactions of Isatins with Linear, Nonactivated, Multiring Aromatic Hydrocarbons

Chiral Polypyrroles from Optically Active Pyrrole Monomers

Effect of the Electrosynthesis Method on the Surface Morphology of the Polypyrrole Film An Atomic Force Microscopy Study

Effect of the Electrosynthesis Method on the Surface Morphology of the Polypyrrole Film