Biosynthesis and characterization of poly(d-lactate-co-glycolate-co-4-hydroxybutyrate)

Poly(d -lactate-co-glycolate-co-4-hydroxybutyrate) [poly(d -LA-co-GA-co-4HB)] and poly(d -lactate-co-glycolate-co-4-hydroxybutyrate-co-d -2-hydroxybutyrate) [poly(d -LA-co-GA-co-4HB-co-d -2HB)] are of interest for their potential applications as new biomedical polymers. Here we report their enhanced production by metabolically engineered Escherichia coli. To examine the polymer properties, poly(d -LA-co-GA-co-4HB) polymers having various monomer compositions (3.4–41.0mol% of 4HB) were produced by culturing the engineered E. coli strain expressing xylBC from Caulobacter crescentus, evolved phaC1 from Pseudomonas sp. MBEL 6-19 (phaC1437), and evolved pct from Clostridium propionicum (pct540) in a medium supplemented with sodium 4HB at various concentrations. To produce these polymers without 4HB feeding, the 4HB biosynthetic pathway was additionally constructed by expressing Clostridium kluyveri sucD and 4hbD. The engineered E. coli expressing xylBC, phaC1437, pct540, sucD, and 4hbD successfully produced poly(d -LA-co-GA-co-4HB-co-d -2HB) and poly(d -LA-co-GA-co-4HB) from glucose and xylose. Through modulating the expression levels of the heterologous genes and performing fed-batch cultures, the polymer content and titer could be increased to 65.76wt% and 6.19g/L, respectively, while the monomer fractions in the polymers could be altered as desired. The polymers produced, in particular, the 4HB-rich polymers showed viscous and sticky properties suggesting that they might be used as medical adhesives.     

Synthesis of biodegradable polyesters by Gram negative bacterium isolated from Malaysian environment

A locally isolated Gram negative bacterium, Cupriavidus sp. USMAA9-39 was able to produce various types of biodegradable polyesters through a two-step cultivation process. These are copolymer poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)], copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] and terpolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-3HV-co-4HB)]. These polymers were synthesized by this bacterium when grown with a combination of some carbon sources. The biosynthesis of P(3HB-co-4HB) was achieved by using carbon sources such as γ-butyrolactone or 1,4-butanediol or by a combination of oleic acid with either γ-butyrolactone or 1,4-butanediol. Meanwhile, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was produced using 1-pentanol or valeric acid or by a combination of oleic acid with either 1-pentanol or valeric acid. When γ-butyrolactone or 1,4-butanediol with either valeric acid or 1-pentanol were used as mixed carbon sources, P(3HB-co-3HV-co-4HB) terpolymer were produced. The presence of 3HB, 3HV or/and 4HB monomers were confirmed by gas chromatography and nuclear magnetic resonance (NMR) spectroscopy.     

Formation of blends of various poly(3-hydroxyalkanoic acids) by a recombinant strain of Pseudomonas oleovorans

Summary Recombinant strains of Pseudomonas oleovorans, which harbour the poly(3-hydroxybutyrate)-biosynthetic genes of Alcaligenes eutrophus, accumulated poly(hydroxyalkanoates), composed of 3-hydroxybutyrate(3HB), 3-hydroxyhexanoate (3HHx) and 3-hydroxyactanoate (3HO), up to 70% of the cell dry weight if the cells were cultivated with sodium octanoate as the carbon source. Physiological and chemical analysis revealed multiple evidence that this polymer is a blend of the homopolyester poly(3HB) and of the copolyester poly(3HHx-co-3HO) rather than a random or a block copolyester of 3HB, 3HHx and 3HO. The molar ratio between poly(3HHx-co-3HO) and poly(3HB) varied drastically during the process of fermentation. Whereas synthesis of poly(3HHx-co-3HO) started immediately after ammonium was exhausted in the medium, synthesis of poly(3HB) occurred only after a lag-phase. From freeze-dried cells poly(3HHx-co-3HO) was much more readily extracted with chloroform than was poly(3HB). The blend was fractionated into petrol-ether-insoluble poly(3HB) and petrol-ether-soluble poly(3HHx-co-3HO). The molecular weight values of these polyesters measured by gel permeation chromatography were 2.96 × 10⁶ and 0.35 × 10⁶ and were similar of those polymers accumulated by A. eutrophus or by wild-type P. oleovorans, respectively. Offprint requests to: A. Steinbüchel     

Instant formation of molecularly imprinted poly(ethylene-co-vinyl alcohol)/quantum dot composite nanoparticles and their use in one-pot urinalysis

The high stability of quantum dots (QDots) with photoluminescence has led to their increased use as imaging approaches in biological systems to replace conventional fluorescence labels. The antibodies are generally coated on the surface of QDots to the targeting site, and molecular imprinting polymers are designed to mimic the antibodies. Hence, quantum dots can be incorporated into molecularly imprinted polymers, which provide shape and selectivity, and then respond to template rebinding by emitting quenched photoluminescence. In this study, poly(ethylene-co-ethylene alcohol) creatinine-, albumin- and lysozyme-imprinted polymers nanoparticles are synthesized via phase inversion of poly(ethylene-co-ethylene alcohol) with various ethylene mole ratios when target molecules and hydrophobic quantum dots are mixed within the polymer solution. Finally, those particles were prepared for the detection of creatinine, human serum albumin and lysozyme in real sample (urine) and compared with commercial ARCHITECT ci 8200 system.     

Studies on the biodegradability of polythioester copolymers and homopolymers by polyhydroxyalkanoate (PHA)-degrading bacteria and PHA depolymerases

The biodegradability of microbial polythioesters (PTEs), a novel class of biopolymers which were discovered recently and can be produced by polyhydroxyalkanoate (PHA)-accumulating bacteria, was studied. Using poly(3-hydroxybutyrate-co-3-mercaptopropionate) [poly(3HB-co-3MP)] as sole carbon source for screening, 22 new bacterial strains were isolated and characterized. Interestingly, none of the PHA-degrading bacteria was able to utilize the homopolymer poly(3MP) as a carbon source for growth or to form clear zones on poly(3MP)-containing agar plates. The extracellular PHA depolymerases from two strains ( Schlegelella thermodepolymerans, Pseudomonas indica K2) were purified to electrophoretic homogeneity and biochemically characterized. The PHA depolymerase of S. thermodepolymerans exhibited a temperate optimum of about 75°C to 80°C and was stable at 70°C for more than 24 h. Regarding the substrate specificities of the PHA depolymerase of S. thermodepolymerans, enzyme activities decreased significantly with increasing 3MP content of the copolymer substrates. Interestingly, no activity could be detected with homoPTEs consisting only of 3MP or of 3-mercaptobutyrate. Similar results were obtained with the PHA depolymerases PhaZ2, PhaZ5 and PhaZ7 of Paucimonas lemoignei which were also investigated. The PHA depolymerase of Ps. indica K2 did not cleave any of the investigated polymers containing 3MP. Gas chromatography, infrared and ¹H-NMR spectrometry and matrix-assisted laser desorption/ionization time-of-flight analysis revealed that 3MPs containing oligomers were enriched in the water-insoluble fraction remaining after partial digestion of poly(3HB-co-3MP) by purified poly(3HB) depolymerase of S. thermodepolymerans. In contrast, 3HB was enriched in the water-soluble fraction, which also contained 3HB-co-3MP dimer obtained by partial digestion of this copolymer by the enzyme. This study clearly indicates that PHA depolymerases are specific for oxoester linkages of PHAs and that the thioester bonds of PTEs cannot be cleaved by this type of enzyme.This publication is dedicated to Prof. Dr. Hans G. Schlegel in honor of his 80th birthday     

A novel reductive graphene oxide‐based magnetic molecularly imprinted poly(ethylene‐co‐vinyl alcohol) polymers for the enrichment and determination of polychlorinated biphenyls in fish samples

The novel reductive graphene oxide‐based magnetic molecularly imprinted poly(ethylene‐co‐vinyl alcohol) polymers (rGO@m‐MIPs) were successfully synthesized as adsorbents for six kinds of polychlorinated biphenyls (PCBs) in fish samples. rGO@m‐MIPs was prepared by surface molecular imprinting technique. Besides, Fe₃O₄ nanoparticles (NPs) were employed as magnetic supporters, and rGO@Fe₃O₄ was in situ synthesis. Different from functional monomer and cross‐linker in traditional molecularly imprinted polymer, here, 3,4‐dichlorobenzidine was employed as dummy molecular and poly(ethylene‐co‐vinyl alcohol) was adopted as the imprinted polymers. After morphology and inner structure of the magnetic adsorbent were characterized, the adsorbent was employed for disperse solid phase extraction toward PCBs and exhibited great selectivity and high adsorption efficiency. This material was verified by determination of PCBs in fish samples combined with gas chromatography‐mass spectrometry (GC‐MS) method. According to the detection, the low detection limits (LODs) of PCBs were 0.0035–0.0070 µg l⁻¹ and spiked recoveries ranged between 79.90 and 94.23%. The prepared adsorbent can be renewable for at least 16 times and expected to be a new material for the enrichment and determination of PCBs from contaminated fish samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Chirality induction in cyclocopolymerization of bis(p-vinylbenzoate)s of carbohydrates with styrene: Chiroptical study of resulting polymer by exciton chirality method

Three bis(p-vinylbenzoate) monomers, 2,3-O-isopropylidene-1,4-bis-O-(p-vinylbenzoyl)-L-threitol (BIT), methyl 4,6-O-isopropylidene-2,3-bis-O-(p-vinylbenzoyl)-α,D -glucopyranoside (BIG), and 1,2:5,6-di-O-isopropylidene-3,4-bis-O(p-vinylbenzoyl)-D-mannitol (BIM), were prepared and cyclocopolymerized with styrene. The resulting copolymers were hydrolyzed with KOH to remove the chiral template, and treated with diazomethane to give poly[(methyl p-vinylbenzoate)-co-styrene] [poly(MVB-co-St)]. All the poly(MVB-co-St) had a specific rotation and their CD spectra exhibit a split Cotton effect. Poly(MVB-co-St) derived from poly(BIT-co-St) showed a positive Cotton effect at 255 nm and a negative one at 235 nm. According to the exciton chirality method, poly(MVB-co-St) possessed negative chirality, and the stereochemistry of the carbon atom attached to the 4-benzoyl group had the S configuration. The absolute configuration of poly(MVB-co-St) was determined as R for the BIG/St system and S for the BIM/St system. © 1995 Wiley-Liss, Inc.     

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with high molar fractions of 3-hydroxyvalerate by a threonine-overproducing mutant of Alcaligenes sp. SH-69

A threonine overproducing mutant of Alcaligenes sp. SH-69 was isolated and its ability to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3HB-co-3HV), was investigated. The 3HV fraction in poly(3HB-co-3HV) produced from glucose as the sole carbon source exceeded 22 mol%, which is approximately six times higher than that achieved by the wild type under the same culture conditions. Furthermore, the addition of a relatively low concentration (10 mM) of propionic acid, valeric acid or levulinic acid to the glucose medium greatly increased the molar fraction of 3HV in the copolyester, to 38–77 mol%. The results suggest that metabolic engineering of the biosynthetic pathways supplying polyhydroxyalkanoate monomers, such as the threonine biosynthetic pathway, can lead to new poly(3HB-co-3HV)-producing strains.     

Production of short-side-chain polyhydroxyalkanoates by various bacteria from the rRNA superfamily III

 A group of 13 bacterial species from the rRNA superfamily III were tested for their ability to produce the biodegradable polyesters poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3-HB-co-4-HB)] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate [P(3HB-co-3-HV)]. Screening for polyhydroxyalkanoate production was performed on cultures obtained from solid media, rolling cultures and shaking flasks. All 13 species were able to store a poly(3-hydroxybutyrate) homopolymer, 12 species could produce P(3-HB-co-3-HV) copolymers, but only 9 species accumulated P(3-HB-co-4-HB) copolymers. Similarities in polyhydroxyalkanoate-accumulation behaviour between closely related strains were noted. Received: 18 December 1995/Received revision: 3 April 1996/Accepted: 28 May 1996     

Production of copolymer consisting of 3-hydroxybutyrate and 3-hydroxyvalerate by fed-batch culture of Alcaligenes SP. SH-69

Summary Production of copolymer consisting of 3-hydroxybutyrate and 3-hydroxyvalerate [poly(3HB-co-3HV)] by fed-batch culture of Alcaligenes sp. SH-69 was investigated using glucose as a sole carbon source. Synthesis of poly(3HB-co-3HV) during the polymer accumulation stage was favored under dissolved oxygen tension at 20% and C/N ratio (mol glucose/mol ammonium) of 23.1. When conditions were optimal, 36 g liter^-1 of poly(3HB-co-3HV) containing 3.0 mol% of 3HV was produced. Decreasing C/N ratio resulted in an increase of 3HV fraction in the copolymer to a maximum level of 6.3 mol%.     

Isolation and characterization of a bacterium that degrades various polyester-based biodegradable plastics

Microorganisms isolated from soil samples were screened for their ability to degrade various biodegradable polyester-based plastics. The most active strain, designated as strain TB-13, was selected as the best strain for degrading these plastics. From its phenotypic and genetic characteristics, strain TB-13 was closely related to Paenibacillus amylolyticus. It could degrade poly(lactic acid), poly(butylene succinate), poly(butylene succinate-co-adipate), poly(caprolactone) and poly(ethylene succinate) but not poly(hydroxybutylate-co-valerate). However, it could not utilize these plastics as sole carbon sources. Both protease and esterase activities, which may be involved in the degradation of plastic, were constitutively detected in the culture broth.     

Production of a copolyester of 3-hydroxybutyric acid and 3-hydroxyvaleric acid from single unrelated carbon sources by a mutant of Alcaligenes eutrophus

Summary Alcaligenes eutrophus mutant strain R3, which is a spontaneous revertant to prototrophy of an isoleucine-auxotrophic mutant of the wild-type strain H16, accumulated a copolyester consisting of 3-hydroxybutyric acid (3HB) as main constituent and of 3-hydroxyvaleric acid (3HV), i.e. poly(3HB-co-3HV), as the only other constituent from various single unrelated substrates, which were provided in excess, after a nutrient essential for growth was depleted in the medium. Poly(SHB-co-3HV) was produced from fructose, gluconate, succinate, acetate or lactate during cell starvation of the nitrogen, sulphur or magnesium source. Although 3HV amounted to only 8 mol% of the constituents of the polyester, this study provides a general rationale for construction and utilization of mutants of poly(3HB)-accumulating bacteria that are altered in the metabolism of branched-chain amino acids for the production of poly(3HB-co-3HV) from single unrelated substrates. Offprint requests to: A. Steinbüchel     

Thiol-functionalized copolymeric polyesters by lipase-catalyzed esterification and transesterification of 1,12-dodecanedioic acid and its diethyl ester,respectively, with 1-thioglycerol

Copolymeric polyoxoesters containing branched-chain methylenethiol functions, i.e., poly(1,12-dodecanedioic acid-co-1-thioglycerol) and poly(diethyl 1,12-dodecanedioate-co-1-thioglycerol), were formed by lipase-catalyzed polyesterification and polytransesterification of 1,12-dodecanedioic acid and diethyl 1,12-dodecanedioate, respectively, with 1-thioglycerol (3-mercaptopropane-1,2-diol) using immobilized lipase B from Candida antarctica (Novozym 435) in vacuo without drying agent in the reaction mixture. After 360–480 h, both polyoxoesters were purified by extraction from the reaction mixtures followed by solvent fractionation. The precipitate of poly(1,12-dodecanedioic acid-co-1-thioglycerol) demonstrated a M_W of ~170,000 Da, whereas a M_W of ~7,100 Da only was found for poly(diethyl 1,12-dodecanedioate-co-1-thioglycerol). Both polycondensates were analyzed by GPC/SEC, alkali-catalyzed transmethylation, NMR- and FTIR-spectrometry.     

A comparison between different fouling-release elastomer coatings containing surface-active polymers

Surface-active polymers derived from styrene monomers containing siloxane (S), fluoroalkyl (F) and/or ethoxylated (E) side chains were blended with an elastomer matrix, either poly(dimethyl siloxane) (PDMS) or poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS), and spray-coated on top of PDMS or SEBS preformed films. By contact angle and X-ray photoelectron spectroscopy measurements, it was found that the surface-active polymer preferentially populated the outermost layers of the coating, despite its low content in the blend. However, the self-segregation process and the response to the external environment strongly depended on both the chemistry of the polymer and the type of matrix used for the blend. Additionally, mechanical testing showed that the elastic modulus of SEBS-based coatings was one order of magnitude higher than that of the corresponding PDMS-based coatings. The coatings were subjected to laboratory bioassays with the marine alga Ulva linza. PDMS-based coatings had superior fouling-release properties compared to the SEBS-based coatings.     

Tailor-made type II <Emphasis Type="Italic">Pseudomonas</Emphasis> PHA synthases and their use for the biosynthesis of polylactic acid and its copolymer in recombinant <Emphasis Type="Italic">Escherichia coli</Emphasis>

Previously, we have developed metabolically engineered Escherichia coli strains capable of producing polylactic acid (PLA) and poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] by employing evolved Clostridium propionicum propionate CoA transferase (Pct _Cp ) and Pseudomonas sp. MBEL 6-19 polyhydroxyalkanoate (PHA) synthase 1 (PhaC1 _Ps6-19). Introduction of mutations four sites (E130, S325, S477, and Q481) of PhaC1 _Ps6-19 have been found to affect the polymer content, lactate mole fraction, and molecular weight of P(3HB-co-LA). In this study, we have further engineered type II Pseudomonas PHA synthases 1 (PhaC1s) from Pseudomonas chlororaphis, Pseudomonas sp. 61-3, Pseudomonas putida KT2440, Pseudomonas resinovorans, and Pseudomonas aeruginosa PAO1 to accept short-chain-length hydroxyacyl-CoAs including lactyl-CoA and 3-hydroxybutyryl-CoA as substrates by site-directed mutagenesis of four sites (E130, S325, S477, and Q481). All PhaC1s having mutations in these four sites were able to accept lactyl-CoA as a substrate and supported the synthesis of P(3HB-co-LA) in recombinant E. coli, whereas the wild-type PhaC1s could not accumulate polymers in detectable levels. The contents, lactate mole fractions, and the molecular weights of P(3HB-co-LA) synthesized by recombinant E. coli varied depending upon the source of the PHA synthase and the mutants used. PLA homopolymer could also be produced at ca. 7 wt.% by employing the several PhaC1 variants containing E130D/S325T/S477G/Q481K quadruple mutations in wild-type E. coli XL1-Blue.     

Application of acetyl-CoA acetyltransferase (AtoAD) in Escherichia coli to increase 3-hydroxyvalerate fraction in poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polyhydroxyalkanoate (PHA) is a family of biodegradable polymers, and incorporation of different monomers can alter its physical properties. To produce the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) containing a high level of 3-hydroxyvalerate (3HV) by altering acetyl-CoA pool levels, we overexpressed an acetyl-CoA acetyltransferase (atoAD) in an engineered E. coli strain, YH090, carrying PHA synthetic genes bktB, phaB, and phaC. It was found that, with introduction of atoAD and with propionate as a co-substrate, 3HV fraction in PHA was increased up to 7.3-fold higher than a strain without atoAD expressed in trans (67.9 mol%). By the analysis of CoA pool concentrations in vivo and in vitro using HPLC and LC-MS, overexpression of AtoAD was shown to decrease the amount of acetyl-CoA and increase the propionyl-CoA/acetyl-CoA ratio, ultimately resulting in an increased 3HV fraction in PHA. Finally, synthesis of P(3HB-co-3HV) containing 57.9 mol% of 3HV was achieved by fed-batch fermentation of YJ101 with propionate.

     

Exploiting metagenomic diversity for novel polyhydroxyalkanoate synthases: production of a terpolymer poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate) with a recombinant Pseudomonas putida strain

A metagenomic library of 2.1 × 10⁶ clones was constructed using oil-contaminated soil from Gujarat (India). One of the fosmid clones, 40N22, encodes a polyhydroxyalkanoate synthase showing 76% identity with an Alcaligenes sp. synthase. The corresponding gene was expressed in Pseudomonas putida KT2440 ΔphaC1 which is impaired in PHA production. The gene conferred the recombinant strain PpKT-40N22 with the ability to produce copolymers with up to 21% in medium-chain-length content. Thus, 37% and 45% of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate), respectively were obtained when using sodium heptanoate and oleic acid as carbon sources. These 3-hydroxybutyrate-(3HB)-based polymers are of interest since they incorporate the properties of medium chain length polymers and thus increase the range of applications of PHAs.     

Polymer coated liposomes for use in the oral cavity – a study of the in vitro toxicity,effect on cell permeability and interaction with mucin

In this study we investigated the in vitro toxicity, impact on cell permeability and mucoadhesive potential of polymer-coated liposomes intended for use in the oral cavity. A TR146 cell line was used as a model. The overall aim was to end up with a selection of safe polymer coated liposomes with promising mucoadhesive properties for drug delivery to the oral cavity. The following polymers were tested: chitosan, low-methoxylated pectin (LM-pectin), high-methoxylated pectin (HM-pectin), amidated pectin (AM-pectin), Eudragit, poly(N-isopropylacrylamide-co-methacrylic acid) (p(NIPAAM-co-MAA)), hydrophobically modified hydroxyethyl cellulose (HM-HEC), and hydrophobically modified ethyl hydroxyethyl cellulose (HM-EHEC). With chitosan as an exception, all the systems exhibited no significant effect on cell viability and permeability at the considered concentrations. Additionally, all the formulations showed to a varying degree an interaction with mucin (BSM type I-S); the positively charged formulations exhibited the strongest interaction, while the negatively and neutrally charged formulations displayed a moderate or low interaction. The ability to interact with mucin makes all the liposomal formulations promising for oromucosal administration. Although the chitosan-coated liposomes affected the cell viability, this formulation also influenced the cell permeability, which makes it an interesting candidate for systemic drug delivery from the oral cavity.     

Phosphorylcholine Group-immobilized Surface Prepared on Polydimethylsiloxane Membrane by In Situ Reaction for Its Reduced Biofouling

To reduce interactions between biological molecules and the surface of microchip devices including the microchip, which should be conducted to improve sensitivity, reactivity, and the typical phospholipid polar group, the phosphorylcholine group-immobilized surfaces were prepared. The surface modification of polydimethylsiloxane (PDMS) was performed by in situ reaction during curing by cross-linking the PDMS prepolymers. Since it is known that 2-methacryloyloxyethyl phosphorylcholine (MPC) facilitates the preparation of biomedical polymers with excellent biocompatibility and antithrombogenicity, it was used as the reactant for surface modification. The MPC was coated on the glass substrate, and two-liquid-type PDMS prepolymers were then applied. During the curing process of the vinyl groups of poly(dimetylsiloxane-co-methylsiloxane) and poly(dimethylsiloxane-co-methylvinylsiloxane), the methacrylate group in MPC was attached onto the PDMS surface via a hydrosilyl group. Analysis of the surface characteristics by X-ray photoelectron spectroscopy and measurement of the surface contact angle revealed that the introduction of the phosphorylcholine group in the MPC unit on the surface induced hydrophilicity at the surface. Further, protein adsorption on the surface decreased with an increase in the number of phosphorylcholine groups. Based on these results, we concluded that the construction of the phosphorylcholine group-enriched surface on the PDMS substrate could be achieved by immobilization of MPC, and it may facilitate fabrication of biomedical devices, particularly microfluidic devices.     

Preparation of polymers containing Fe(0)-coordinated 2,5-diethynylsilole units

UV irradiation of poly(organosilanylene-2,5-diethynylenesiloles) in benzene with an excess of Fe(CO)₅ led to the formation of Fe(CO)₃-coordinated silole units in the polymer backbone. The Fe(CO)₃-coordinated polymers exhibited suppressed π-conjugation, relative to the parent non-coordinated polymers. Hole-transporting properties of poly(organosilanylene-2,5-diethynylenesiloles) were examined by the performance of EL devices containing the polymer layer as the hole-transport and Alq3 layer as the electron-transporting emitter.