Stimuli‐Responsive Polymers Based on N‐Isopropylacrylamide and N‐Methacryloyl‐L‐Leucine

Linear and cross‐linked polymers capable of responding to both temperature and pH changes were synthesized by radical copolymerization of N‐isopropylacrylamide (NIPAAm) and N‐methacryloyl‐L ‐leucine (MALEU) in different NIPAAm/MALEU molar ratios. The solution behavior of linear polymers was investigated in 0.1 M NaCl and in citrate buffers pH 4.0, 4.5, 5.0 and 6.0. A sharp increase in the cloud point temperature (T_CP) was observed to occur around pH 4–5. Hydrogels were synthesized employing N,N ′‐methylenebisacrylamide as cross‐linking agent. The influence of composition and degree of cross‐linking on water absorption was investigated in 0.1 M NaCl and in citrate buffers pH 4.0 and 5.0. A reversible phase transition within a wide range of temperatures, depending on the composition and the pH, in accordance with the behavior of linear polymers, was observed.     

Effect of Fullerene on Photocurrent Performance of 6‐O‐Porphyrin‐2,3‐di‐O‐stearoylcellulose Langmuir‐Blodgett Films

Thin films consisting of 6‐O‐porphyrin‐2,3‐di‐O‐stearoylcellulose (H₂PCS) and fullerene (C₆₀) were fabricated for anodic photocurrent generation systems by the Langmuir‐Blodgett (LB) technique. The π‐complexation between the porphyrin moiety and C₆₀ in the LB films was investigated by means of the surface pressure (π)‐area (A) isotherms, UV‐vis, and fluorescence spectroscopy. The photocurrent density generated from the H₂PCS–C₆₀ LB monolayer films exhibited an increase with increasing the C₆₀ proportion and reached a maximum at a mixing ratio of 1:2, yielding a quantum yield of 12.5% and an IPCE (incident photon‐to‐current efficiency) of 0.50% at a bias potential of +100 mV vs. SCE. Furthermore, the LB five‐layer films could give rise to the IPCE value of 1.5% at +100 mV without significant decline of the quantum yields, which was due to the function of C₆₀ as an electron carrier to improve the interlayer electron transfer through each layer. These results have demonstrated a promising method for preparing the donor–acceptor systems using cellulose as a scaffold in the LB films.

     

pH‐Sensitive Drug‐Conjugates on Water‐Soluble Polymer Frameworks

A potent synthetic methodology is introduced to generate a useful intermediate for the preparation of ‘smart’ polymeric pro‐drugs. Herein, living anionic block polymerization of ethylene oxide (EO) and N‐phenylmaleimide (N‐PMI), as well as the Gabriel process, are introduced. Hydrazinolysis of the resulting poly(ethylene oxide)‐block‐poly(N‐PMI) (PEO‐b‐PN‐PMI) using hydrazine under acidic conditions leads to the production of PEO‐based frameworks with hydrazide (HZ) groups. The HZ groups are found to effect the formation of an acid‐sensitive bond in reactions with medicines or drugs under neutral conditions (pH 7.2). The PEO‐HZ intermediate, which shows a strong triplet splitting patterned chemical shift in the range δ = 6.5–8.5 ppm, represents the most powerful material employed for mass production of smart polymeric pro‐drugs while controlling the drug‐loading yield. Water‐soluble “smart” polymeric pro‐drugs, such as poly(ethylene oxide)‐doxorubicin (PEO‐HZ‐Dox), poly(ethylene oxide)‐methotrexate (PEO‐HZ‐MTX), and poly(ethylene oxide)‐folate (PEO‐HZ‐FA) conjugates, show excellent acid‐sensitive release profiles in water or alcohol at pH 4.5.

     

Encapsulating Hydrophilic Solution by PU‐PMF Double‐Component Capsule Based on Water‐In‐Oil‐In‐Oil Emulsion Template

This study demonstrates an effective method to encapsulate a hydrophilic payload through the use of polyurethane‐poly(melamine‐formaldehyde) (PU‐PMF) dual‐component capsules based upon the water‐in‐oil‐in‐oil (W/O/O) emulsion template. This emulsion has a middle oil layer that hosts the PU (outer shell) forming reaction while the internal PMF skeleton, fabricated concurrently by polymer precipitation in the aqueous dispersive phase, provides additional mechanical support. The resultant capsules exhibit dense and spherical shape, low permeability, and diameter of ≈50 µm. Remarkably, interfacial tension is the driving factor in the formation of the W/O/O template. This microencapsulation system and the methods used for its fabrication have a great technical potential for use in industrial applications.     

Extremely Color‐Stable Blue Light‐Emitting Polymers Based on Alternating 2,7‐Fluorene‐co‐3,9‐carbazole Copolymer

Novel alternating 2,7‐fluorene‐co‐3,9‐carbazole copolymer(3,9‐PFCz) was synthesized by Suzuki polycondensation between 3‐bromo‐9‐(2‐iodo‐9,9‐dioctyl‐9H‐fluoren‐7‐yl)‐9H‐carbazole and 2,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9‐dioctylfluorene. Cyclic voltammetry studies showed a higher HOMO level (?5.23 eV) than the polyfluorene homopolymer(PFO). The glass transition temperature of the copolymer (110 °C) was much higher than that of the PFO (67 °C). After the copolymer had been annealed at 200 °C for 2 h, the PL spectra showed almost no change and no aggregation‐ or oxidation‐related undesirable long‐wavelength emission has been observed. The light‐emitting diode in configuration of ITO/PEDOT/EML/CsF/Al showed a maximum external quantum efficiency of 1.54% with a luminance of 435 cd · m^?2 and the maximum brightness of 2 630 cd · m^?2 with CIE coordinate (0.17, 0.14) was achieved at 8.4 V. The device prepared in configuration of ITO/PEDOT/PVK/polymer/Ba/Al exhibits an efficient, stable blue emission; it has a turn‐on voltage of 6 V and maximum external quantum efficiency of 1.1%. The EL emission remains stable at high current density and after thermal treatment at 150 °C for 30 min. Extremely color‐stable blue emission from alternating poly[(2,7‐fluorene)‐co‐(3,9‐carbazole)] copolymer makes it a promising candidate for flat‐panel display applications.

     

Synthesis of High‐Molecular Weight Polymers Based on N,N‐Diallyl‐N‐Methylamine

High‐molecular weight polymers, namely poly(N,N‐diallyl‐N‐methylammonium trifluoroacetate) and poly(N,N‐diallyl‐N‐methylamine), were prepared by radical polymerization of N,N‐diallyl‐N‐methylamine in aqueous solution in the presence of an equimolar amount of trifluoroacetic acid and by polymerization of the newly synthesized equimolecular salt N,N‐diallyl‐N‐methylammonium trifluoroacetate in gentle conditions. We have established that chain termination is controlled by the bimolecular mechanism and that degradative chain transfer to monomer transforms into effective chain transfer (see Scheme). The possibility of controlling the polymerization rate and molecular weight of polymers is demonstrated. The mechanisms of the observed phenomena are discussed.

     

Bandgap and Molecular‐Energy‐Level Control of Conjugated‐Polymer Photovoltaic Materials Based on 6,12‐Dihydro‐diindeno[1,2‐b;10,20‐e]pyrazine

Six conjugated polymers based on the indenopyrazine ( IPY) unit are designed and synthesized by copolymerization with different electron‐deficient and electron‐rich building blocks. All of the polymers show good solubility, excellent film‐forming ability, and low‐lying highest occupied molecular orbit (HOMO) energy levels. The effects of the different copolymerized units on the optical, electrochemical, and photovoltaic properties are investigated. Results indicate that their bandgaps and molecular energy levels are readily tuned by copolymerizing with electron‐deficient and electron‐rich units. Polymer solar‐cell devices are fabricated utilizing the polymers as electron donors and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) as an electron acceptor. The best power conversion efficiency of the cell based on PIPY‐DTBTA , one of the IPY‐ based polymers, reaches 0.77%, with a relatively high V_oc up to 0.78 V.

     

High‐Performance Photorefractive Composite Based on Non‐conjugated Main‐Chain,Hole‐Transporting Polymer

The photorefractivity of a non‐conjugated main‐chain polymeric composite, composed of electron‐rich N,N‐di‐toly‐N,N′‐diphenylbiphenyldiamine doped with 2‐{3‐[(E)‐2‐(piperidino)‐1‐ethenyl]‐5,5‐dimethyl‐2‐cyclohexenylidene}‐malononitrile (P‐IP‐DC) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM), is studied using two‐beam coupling and degenerate four‐wave mixing at 633 nm. The N,N′‐di‐toly‐N,N′‐diphenylbiphenyldiamine‐based composite shows a gain coefficient of 215 cm^?1 at 80 V μm^?1 with s‐polarized beams and a diffraction efficiency of 67% at 30 V μm^?1, with a response time of the diffraction efficiency of 344 ms at T_g + 4.6 °C. Comparing the photorefractive grating response time of the 3,3′‐dicarbazole‐containing polymer composite with that of the N,N′‐di‐toly‐N,N′‐diphenylbiphenyldiamine‐based composite shows that the former is more than three times faster.     

Toll‐like Receptor‐2 and Toll‐like Receptor‐4 Expression on Maternal Neutrophils During Pregnancy

Nitsche JF, Jiang S‐W, Brost BC. Toll‐like receptor‐2 and toll‐like receptor‐4 expression on maternal neutrophils during pregnancy. Am J Reprod Immunol 2010; 64: 427–434 Problem Toll‐like receptors (TLR) are an important part of the innate immune system and are present in a variety of human tissues. Work investigating the role of the TLR in pregnancy has thus far focused on placental tissue; however, minimal data is currently available concerning TLR expression in other tissues. Unlike placental tissue, neutrophils are easily retrievable during pregnancy and thus allow assessment of TLR’s prior to delivery. Method of study Using real time quantitative PCR this study investigated whether TLR‐2 and TLR‐4 expression on maternal neutrophils is altered throughout gestation or at the time of labor. A group of 12 non‐pregnant women and two groups of ten pregnant patients were enrolled and followed longitudinally, one group throughout gestation and one group throughout the third trimester. Results Although increased in the placenta, TLR2 and TLR4 expression on maternal neutrophils changes minimally throughout gestation. Conclusion There appears to be very little regulation of TLR2 and TLR4 at the mRNA level during normal pregnancy and labor. However, now that the normal values of TLR expression on maternal neutrophils have been determined it will be possible to compare them to those from pregnancies complicated by such conditions as preeclampsia, preterm labor, or preterm premature rupture of membranes.     

Full‐Color Processible Electrochromic Polymers Based on 4,4‐Dioctyl‐Cyclopentadithiophene

Three soluble electrochromic copolymers based on 4,4‐di‐octyl‐cyclopentadithiophene (DOCPDT): PDOCPDT‐OT, PDOCPDT‐PT, and PDOCPDT‐Cz were synthesized and the electrochromic properties were investigated. Colorimetric analysis revealed that red‐colored PDOCPDT‐OT, green‐colored PDOCPDT‐PT and their blue mother polymer PDOCTDT are cathodic coloration polymers. PDOCPDT‐Cz is yellow in its neutral state and shows an anodic electrochromism. The structural flexibility, color diversity, processibility and good electrochromic performance make octyl‐cyclopentadithiophene‐containing polymers prominent candidates for electrochromic applications.

     

Protective effect of γ‐tocopherol‐enriched diet on N‐methyl‐N‐nitrosourea‐induced epithelial dysplasia in rat ventral prostate

Despite recent advances in understanding the biological basis of prostate cancer (PCa), the management of this disease remains a challenge. Chemoprotective agents have been used to protect against or eradicate prostate malignancies. Here, we investigated the protective effect of γ‐tocopherol on N‐methyl‐N‐nitrosourea (MNU)‐induced epithelial dysplasia in the rat ventral prostate (VP). Thirty‐two male Wistar rats were divided into four groups (n = 8): control (CT): healthy control animals fed a standard diet; control+γ‐tocopherol (CT+γT): healthy control animals without intervention fed a γ‐tocopherol‐enriched diet (20 mg/kg); N‐methyl‐N‐nitrosourea (MNU): rats that received a single dose of MNU (30 mg/kg) plus testosterone propionate (100 mg/kg) and were fed a standard diet; and MNU+γ‐tocopherol (MNU+γT): rats that received the same treatment of MNU plus testosterone and were fed with a γ‐tocopherol‐enriched diet (20 mg/kg). After 4 months, the VPs were excised to evaluate morphology, cell proliferation and apoptosis, as well as cyclooxygenase‐2 (Cox‐2), glutathione‐S‐transferase‐pi (GST‐pi) and androgen receptor (AR) protein expression, and matrix metalloproteinase‐9 (MMP‐9) activity. An increase in the incidence of epithelial dysplasias, such as stratified epithelial hyperplasia and squamous metaplasia, in the MNU group was accompanied by augmented cell proliferation, GST‐pi and Cox‐2 immunoexpression and pro‐MMP‐9 activity. Stromal thickening and inflammatory foci were also observed. The administration of a γ‐tocopherol‐enriched diet significantly attenuated the adverse effects of MNU in the VP. The incidence of epithelial dysplasia decreased, along with the cell proliferation index, GST‐pi and Cox‐2 immunoexpression. The gelatinolytic activity of pro‐MMP‐9 returned to the levels observed for the CT group. These results suggest that γ‐tocopherol acts as a protective agent against MNU‐induced prostatic disorders in the rat ventral prostate.     

An Injectable ROS‐Responsive Self‐Healing Hydrogel Based on tetra‐poly(ethylene glycol)‐b‐oligo(l‐methionine)

Abnormal physiological conditions provide an ideal stimulus for the design of responsive hydrogels which function as controlled and site‐specific release of drugs. Here, an injectable reactive oxygen species (ROS) responsive self‐healing hydrogel based on tetra‐poly(ethylene glycol)‐b‐oligo (l ‐methionine) (t‐PEG₅₆‐b‐OMeth_n) synthesized by a novel and facile method is reported. The hydrophobic interactions between the side chains of l ‐methionine make the polymer chains crosslinked and lead to the formation of hydrogels which can be injected and self‐healed, meanwhile, the cross‐linker also provides a hydrophobic domain to encapsulate Dox. In presence of ROS, the side chain of l ‐methionine can be oxidized to methionine sulfoxide. The side chain of l ‐methionine is changed accordingly from hydrophobic to hydrophilic. As a result, both the hydrophobic domain and the hydrogel itself are destroyed. The controlled release of Dox by ROS at site‐specific is realized. The excellent biocompatibility of hydrogel based on t‐PEG₅₆‐b‐OMeth_n indicates the door of the potential application in controlled release of drug in a truly physiological environment.     

Congenital heart disease in low‐and‐middle‐income countries: Focus on sub‐Saharan Africa

The etiology of congenital heart disease (CHD) is multifactorial. The birth prevalence of CHD is shaped by a wide variety of maternal, fetal, and neonatal risk factors, along with the rates of prenatal diagnosis and terminations of pregnancy, all of which have geographic variability Epidemiology data availability from low‐and‐middle‐income countries (LMIC) on CHD prevalence, morbidity, and mortality are far more limited than from high income countries. Data on specific genetic, environmental, and prenatal risk associated with CHD are almost nonexistent. In this article, we will focus on defining what data are available, genetic risk factors, birth and overall prevalence, morbidity, and the impact of limited access to interventions, both surgery and cardiac catheterizations. We will highlight CHD in sub‐Saharan Africa to detail epidemiology studies in the poorest regions of the world. Existing literature as well as estimates from the Global Burden of Disease Study ( http://ghdx.healthdata.org ) form the basis for this review. The intersection of poverty, high fertility rates, and limited access to care results in a unique profile of CHD in LMIC. CHD is not a preventable disease (by most standards), so early detection and access are our key interventions to improve the dire outcomes for children in low‐resources settings of the world.     

Differential Age‐Related Effects on Visual‐ and Associative‐Based Semantic Encoding

This study investigated how aging modulates semantic encoding. We used a task where participants were required to determine the semantic relatedness between the cue and target stimuli. Single‐character Chinese words were the cues, whereas two‐character words describing the cues were the targets. The targets can be visual‐based (appearance) or associative‐based (meaning). Experiment One compared the reaction times on the two types of targets between older (n  = 29) and younger participants (n  = 31). Older participants performed significantly slower on the visual‐ than associative‐based trials, while the younger participants showed no difference. The results suggest that aging would hinder semantic encoding of visual‐ rather than associative‐based processes. The slowness in processing is likely attributable to age‐related decline in attentional control. Experiment Two tested the aging effect on top‐down attentional control by presenting pre‐cue before each trial on older (n  = 26) and younger participants (n  = 49). The results indicated that valid pre‐cue reduced the latency differences between the visual‐ and associative‐based trials among the older participants. The valid pre‐cues were found to effectively shorten the reaction time of the visual‐based trials suggesting possible facilitation of attentional control among the older adults. Our findings substantiate age‐related attentional control decline only in visual‐ but not associative‐based processing. Future studies should explore the mechanisms underlying such differential age‐related effect.     

Ring‐Opening Homo‐ and Copolymerization of Cis/Trans‐3‐oxa‐4‐oxobicyclo‐ and Cis/Trans‐4‐oxa‐3‐oxobicyclo[5.4.0]undecane

Ring‐opening polymerization of the bicyclic lactone mixture 2 , cis/trans‐3‐oxa‐4‐oxo‐ and cis/trans‐4‐oxa‐3‐oxobicyclo[5.4.0]undecane with Sn(Oct)₂ as a catalyst was investigated for the first time (Scheme 1 ). The lactones were obtained by Baeyer–Villiger oxidation of cis/trans‐2‐decalone 1 (Scheme 2 ). Additionally, copolymerization of 2 with ε‐caprolactone in different ratios was performed. GPC measurements and ¹H NMR spectroscopy proved that 2 was quantitatively incorporated into the polymer, leading to polycaprolactone with cyclohexane moieties in its backbone. values were up to 25 000 with ≤ 2.4. DSC measurements revealed a linear dependence of the melting points and the glass transition temperatures of the polymers on the feed of the bicyclic lactone 2 . Additionally, the time dependence of the cis/trans ratio of the residual monomers was followed during the course of polymerization reaction by gas chromatography. The crystallinity of the resulting copolymers was investigated via polarization microscopy. Finally, it was shown that the mixture of 2 with ε‐caprolactone could be selectively polymerized with lipase. Only ε‐caprolactone was converted, while 2 remained unreacted in the residue.

     

Biodegradable Polyesters Based on cis‐1,4‐Butenediol

Summary: Homopolyesters based on cis‐1,4‐butenediol (cBeD) and aliphatic dicarboxylic acids (ADAs) were prepared by three different methods. First, cBeD was polycondensed with the dimethyl esters of ADAs in bulk. Regardless of the catalyst, only low‐molar‐mass polyesters were obtained. Second, polycondensations of cBeD with ADA dichlorides catalyzed by pyridine yielded polyesters with in the range of 8 000–13 500 Da. around 20 000 Da were achieved when the ADA dichlorides were polycondensed with DSDEN. These ring‐opening polycondensations were optimized by a broad variation of the reaction conditions. Under optimized conditions a high molar fraction of cyclic polyesters was formed. All polyesters proved to be crystalline with melting temperatures (T_m) in the range of 55–120 °C.

Polycondensations of cBeD.     

End‐Group Selectivity of Low‐Molecular‐Weight Polystyrenes on a Carbon‐Clad Zirconia Stationary Phase in Reversed‐Phase HPLC

The separation of isomers of polystyrene oligomers was demonstrated on a carbon‐clad zirconia stationary phase in an acetonitrile mobile phase. The carbon‐clad zirconia surface gave considerably better resolution of isomers than a C18 surface, and the separation was sensitive to the end group of the oligomer. Oligomers with sec‐butyl end groups displayed almost twice as many isomers as the corresponding n‐butyl oligomer on the carbon‐clad zirconia surface. These additional bands could be explained by the stereochemistry of the sec‐butyl end group. In addition, the migration rate of the polystyrene isomers was dependent upon the end group, with n‐butyl polystyrenes displaying significantly greater retention on the carbon‐clad zirconia stationary phase. In comparison, the selectivity of conventional C18 columns could not discriminate between the n‐butyl and sec‐butyl end groups.     

Polyelectrolyte‐in‐Ionic‐Liquid Electrolytes

Novel polymer electrolyte materials based on a polyelectrolyte‐in‐ionic‐liquid principle are described. A combination of a lithium 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSLi) and N,N′‐dimethylacrylamide (DMMA) are miscible with the ionic liquid, 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIDCA). EMIDCA has remarkably high conductivity (≥ 2 · 10^?2 S · cm^?1) at room temperature and acts as a good solvating medium for the polyelectrolyte. At compositions of AMPSLi less than or equal to 75 mol‐% in the copolymer (P(AMPSLi‐co‐DMAA)), the polyelectrolytes in EMIDCA are homogeneous, flexible elastomeric gel materials at 10 ? 15 wt.‐% of total polyelectrolyte. Conductivities higher than 8 · 10^?3 S · cm^?1 at 30 °C have been achieved. The effects of the monomer composition, polyelectrolyte concentration, temperature and lithium concentration on the ionic conductivity have been studied using thermal and conductivity analysis, and pulsed field gradient nuclear magnetic resonance techniques.

Comparison of the measured and calculated lithium conductivity at 30 °C.