Effect of Branched Side Chains on the Physicochemical and Photovoltaic Properties of Poly(3‐hexylthiophene) Isomers

Two P3HT isomers with branched alkyl side chains, P3EBT and P3MPT, are synthesized. The HOMO energy levels of P3EBT and P3MPT are ?5.35 and ?5.24 eV, respectively, which are significantly lower than that of P3HT with a linear side chain. The absorption edges of the two P3HT isomer films, especially those of P3EBT, are blue‐shifted in comparison with that of P3HT. A PSC based on P3EBT:IC₆₀BA (2:1 w/w) shows a high open‐circuit voltage of 0.98 V, which is the highest V_oc reported so far for polythiophene‐based PSCs. A PSC based on P3MPT:IC₇₀BA (2:1 w/w) exhibits a power conversion efficiency of 3.62% with a V_oc of 0.91 V. P3MPT is suitable for the application in tandem PSCs.     

Coplanar Donor–Acceptor Semiconducting Copolymers to Achieve Better Conjugated Structures: Side‐Chain Engineering

It is reported on the allocation effects of branched alkyl chains, when used as solubility and ordering enhancers of the conjugated donor–accepter (D –A ) copolymer backbones, on the ordering and π–π overlapping of the copolymers, that drastically affect the electrical properties of organic field‐effect transistors (OFETs). Triisopropylsilylethynyl‐benzo[1,2‐b :4,5‐b ′]dithiophene (TIPSBDT) and diketopyrrolopyrrole (DPP)‐based copolymers, which have two linear alkyl spacers (methylene (C 1) or butylene (C 4)) between the DPP and side‐substituent (C₁₀H₂₁)CH(C₈H₁₇) , are synthesized by Suzuki cross‐coupling. These copolymer films are spun cast onto a polymer‐treated SiO₂ dielectric surface, and some are further thermally annealed. The longer spacer, C 4, is found to efficiently enhance the coplanarity and conjugation of the D –A backbone, while the C 1 does not. The resulting C 4‐bridged TIPSBDT‐DPP‐based copolymer readily develops a superior π‐extended layer on the dielectric surface; the edge‐on chains with randomly oriented side chains can be closely packed with a short π‐planar distance (d ₍₀₁₀₎) of 3.57 Å. Its properties are superior to those of the short spacer C 1 system with d ₍₀₁₀₎ ≈3.93 Å. The C 4‐bridged TIPSBDT‐DPP copolymer films yield a field‐effect mobility up to 1.2 cm² V⁻¹ s⁻¹ in OFETs, 12 times as higher than that of the C 1 spacer system.

     

Tandem catalysis for the production of alkyl lactates from ketohexoses at moderate temperatures

Retro-aldol reactions have been implicated as the limiting steps in catalytic routes to convert biomass-derived hexoses and pentoses into valuable C₂, C₃, and C₄ products such as glycolic acid, lactic acid, 2-hydroxy-3-butenoic acid, 2,4-dihydroxybutanoic acid, and alkyl esters thereof. Due to a lack of efficient retro-aldol catalysts, most previous investigations of catalytic pathways involving these reactions were conducted at high temperatures (≥160 °C). Here, we report moderate-temperature (around 100 °C) retro-aldol reactions of various hexoses in aqueous and alcoholic media with catalysts traditionally known for their capacity to catalyze 1,2-intramolecular carbon shift (1,2-CS) reactions of aldoses, i.e., various molybdenum oxide and molybdate species, nickel(II) diamine complexes, alkali-exchanged stannosilicate molecular sieves, and amorphous TiO₂–SiO₂ coprecipitates. Solid Lewis acid cocatalysts that are known to catalyze 1,2-intramolecular hydride shift (1,2-HS) reactions that enable the formation of α-hydroxy carboxylic acids from tetroses, trioses, and glycolaldehyde, but cannot readily catalyze retro-aldol reactions of hexoses and pentoses at these moderate temperatures, are shown to be compatible with the aforementioned retro-aldol catalysts. The combination of a distinct retro-aldol catalyst with a 1,2-HS catalyst enables lactic acid and alkyl lactate formation from ketohexoses at moderate temperatures (around 100 °C), with yields comparable to best-reported chemocatalytic examples at high temperature conditions (≥160 °C). The use of moderate temperatures enables numerous desirable features such as lower pressure and significantly less catalyst deactivation.Chemocatalytic routes for the production of α-hydroxy carboxylic acids, e.g., glycolic acid, lactic acid, 2-hydroxy-3-butenoic acid, and 2,4-dihydroxybutanoic acid, from biomass-derived sugars have been extensively investigated in the recent years, as these acids, as well as their esters and lactones, have been recognized to have a large potential to function as renewable, platform chemicals for a number of applications such as polymers, solvents, and fine chemicals (1–7). Considerable progress has been achieved with the production of lactic acid and alkyl lactates from trioses [glyceraldehyde (GLA) and dihydroxyacetone (DHA)], with nearly quantitative yields obtained with state-of-the-art catalysts, e.g., tin-containing zeotypes Sn-Beta and Sn-MFI, which are known for their capacity to catalyze 1,2-intramolecular hydride shift (1,2-HS) reactions, at moderate temperatures (around 100 °C) (8). Similarly, the C₂ and C₄ products (glycolic acid, 2-hydroxy-3-butenoic acid, 2,4-dihydroxybutanoic acid, and esters thereof) can be produced in good yields when glycolaldehyde, glyoxal, or tetroses (erythrose, threose, and erythrulose) are used as substrates (4, 6). However, the substrates required for these reactions are not easily obtained or isolated from biomass, as the majority of terrestrial biomass comprises cellulose and hemicellulose (polymers of hexoses and pentoses) (5).To enable the formation of these C₂–C₄ α-hydroxy carboxylic acids from cellulosic and hemicellulosic biomass, retro-aldol reactions are required to fragment the hexose and pentose carbon backbones (r₂ and r₃ in Fig. 1). For the common aldoses and ketoses, these C–C bond-splitting reactions have large activation energies and unfavorable thermodynamics at low-to-moderate temperatures. As a result, most attempts at the catalytic production of C₂–C₄ α-hydroxy carboxylic acids from hexoses and pentoses have involved high temperatures (≥160 °C) (3, 9). Carbon basis yields of ∼64–68% of methyl lactate at full conversion were reported for reactions of sucrose catalyzed by Sn-Beta at 160 °C for 20 h (3). Lower yields of ∼40–44% were reported for monosaccharide substrates in the same study (3). Recently, methyl lactate yields upwards of 75% from sucrose were achieved with Sn-Beta at 170 °C, when specific amounts of alkali carbonates were added to the reaction system (9). Furthermore, the authors suggested that, in the initial study involving Sn-Beta, materials were possibly contaminated by alkali during synthesis, and that alkali-free Sn-Beta recently led to lower yields (30%) (9).Open in a separate windowFig. 1.Schematic representation of reaction network in which ketohexoses can isomerize to aldohexoses via 1,2-HS (r₁) and to 2-C-(hydroxymethyl)-aldopentoses via 1,2-CS (r₁₁) reactions. Retro-aldol reactions of hexose species (r₂, r₃, and r₁₂) lead to the formation of C₂, C₃, and C₄ carbohydrate fragments. Lewis acids can then catalyze the formation of α-hydroxy carboxylic acids from these smaller fragments (e.g., r₇, r₈, and r₉ in the formation of alkyl lactate from trioses). Side reactions, involving dehydration reactions of fructose to 5-HMF (r₅), redox and fragmentation reactions of unstable intermediates, and various humin-forming condensation reactions, lead to loss of yield of desired products.Low thermal stability of sugars at high temperatures and lack of substrate and reaction specificity of the catalytic sites investigated in the aforementioned systems likely lead to dehydration reactions of ketohexoses to 5-hydroxymethyl furfural (5-HMF) (r₅ in Fig. 1). The subsequent fragmentation and coupling reactions of 5-HMF can lead to the formation of insoluble humins that deposit on the catalyst, thereby leading to deactivation and loss of yield of useful products. Large-pore catalysts like Sn-Beta can promote aldose–ketose isomerization reactions (r₁ in Fig. 1) of substrates as large as disaccharides (10) because the Lewis acid sites that are active for 1,2-HS reactions are accessible to such species. The same Lewis acid sites have been previously proposed as the active sites in retro-aldol reactions (8). This inability of Sn-Beta (and other 12-MR materials) to perform size-dependent reaction discrimination results in aldose–ketose interconversion and parallel retro-aldol reactions of aldohexoses and ketohexoses. Thus, even when ketohexose substrates are used, C₂ and C₄ products derived from aldoses concomitantly form with the more desired C₃ products derived from ketoses (r₄ and r₇–r₁₀ in Fig. 1, respectively) (3). Because of these features, catalytic strategies that allow for retro-aldol reactions of hexoses to proceed in the absence of aldose–ketose isomerization would be highly useful, as they would have the potential to significantly affect the distribution of C₂, C₃, and C₄ products.Here, we report moderate-temperature (around 100 °C) retro-aldol reactions of various hexoses in aqueous and alcoholic media with catalysts traditionally known for their capacity to catalyze 1,2-intramolecular carbon shift (1,2-CS) reactions of aldoses, i.e., various molybdenum oxide and molybdate species, nickel(II) diamine complexes, alkali-exchanged stannosilicate molecular sieves, and amorphous TiO₂–SiO₂ coprecipitates. Because these catalysts do not readily catalyze aldose–ketose interconversion through 1,2-HS, they are candidate cocatalysts for reaction pathways that benefit from aldose- or ketose-specific, retro-aldol fragmentation. Here, these retro-aldol catalysts are combined with solid Lewis acid catalysts to enable the moderate-temperature conversion of hexoses into α-hydroxy carboxylic acids.     

Biodegradation of L-Valine Alkyl Ester Ibuprofenates by Bacterial Cultures

Nowadays, we consume very large amounts of medicinal substances. Medicines are used to cure, halt, or prevent disease, ease symptoms, or help in the diagnosis of illnesses. Some medications are used to treat pain. Ibuprofen is one of the most popular drugs in the world (it ranks third). This drug enters our water system through human pharmaceutical use. In this article, we describe and compare the biodegradation of ibuprofen and ibuprofen derivatives—salts of L-valine alkyl esters. Biodegradation studies of ibuprofen and its derivatives have been carried out with activated sludge. The structure modifications we received were aimed at increasing the biodegradation of the drug used. The influence of the alkyl chain length of the ester used in the biodegradation of the compound was also verified. The biodegradation results correlated with the lipophilic properties (log P).     

Comparative study of the ocular irritation potential of various alkyl polyglucoside surfactants

In the present work, we assessed the relationship between alkyl carbon chain length and ocular irritation potentials using the hen’s egg test–chorioallantoic membrane (HET-CAM) and bovine corneal opacity and permeability (BCOP) assays using 5 commercial alkyl polyglucoside surfactants with different compositions of alkyl chain lengths (C₆–C₁₆). With HET-CAM, there was a good correlation between the proportion of C₁₀ alkyl polyglucoside and the eye irritation potential Q score (r²?=?0.912, p?=?.011). There were no significant differences between the proportion of C₁₀ alkyl polyglucoside and corneal opacity in BCOP assays; however, there was a relatively high positive correlation between the proportion of C₁₀ alkyl carbon chain lengths and corneal permeability (r²?=?0.736, p?=?.063).