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Oikopleura dioica is a planktonic tunicate (Appendicularia class) found extensively across the marine waters of the globe. The genome of a single male individual collected from Okinawa, Japan was sequenced using the single-molecule PacBio Hi-Fi method and assembled with NOVOLoci. The mitogenome is 39,268 bp long, featuring a large control region of around 22,000 bp. We annotated the proteins atp6, cob, cox1, cox2, cox3, nad1, nad4, and nad5, and found one more open reading frame that did not match any known gene. This study marks the first complete mitogenome assembly for an appendicularian, and reveals that A and T homopolymers cumulatively account for nearly half of its length. This reference sequence will be an asset for environmental DNA and phylogenetic studies. [ABSTRACT FROM AUTHOR]

Although protein‐polymer phosphors are an emerging photon‐management filter concept for hybrid light‐emitting diodes, deep‐red‐emitting devices based on archetypal fluorescent proteins (FPs; mCherry) are still poorly performing with lifetimes <50 h under high photon‐flux excitation and ambient conditions. Here, the challenge is two‐fold: i) understanding the deactivation mechanism of red‐emitting FP‐polymer coatings and, in turn, ii) identifying the best polymer design for highly stable devices. This study first provides comprehensive photophysical/thermal/structural studies and device degradation (ambient/inert) analysis, revealing the presence of photo‐induced cis–trans isomerization and the effect of oxygen and water on the deactivation of mCherry in reference polymer coatings. Based on these findings, a new bio‐phosphor configuration using polyvinyl alcohol derivatives, in which crystallinity and amount of trapped water (stiffness and oxygen/moisture barriers) are easily controlled by the hydroxylation degree, is successfully achieved. Compared to the prior art, these devices significantly outperform the reference stability (>50‐fold enhancement), showing a brightness loss of <5% over the first 2000 h and a final device lifetime of 2600 h. Hence, this study describes a unique rationale toward designing polymers to stabilize FPs for lighting, overpassing stability frontiers in deep‐red hybrid light‐emitting diodes (HLEDs) going from hours to months. [ABSTRACT FROM AUTHOR]

The polymerization of methacrylate compositions used in bone cement is often accompanied by a strong exothermic effect. The polymerizing mass heats up to very high temperatures at the cement application site, irritating the adjacent tissues and even cell death. On the other hand, a bone cement composition should have the optimal curing time, which should be long enough to allow for proper preparation of the cement and short enough to prevent leaking of the cement out of the restoration place. Therefore, new compositions are being sought to reduce the curing temperature of bone cement and maintain a sufficiently long curing time. Our proposal is based on using five homopolymers obtained by polymerizing urethane-dimethacrylates. These were composed of diisocyanate cores: toluene 2,4 diisocyanate (TDI), isophorone diisocyanate (IPDI), 4,4′-methylenebis(cyclohexyl isocyanate) (CHMDI), and di-, tri-, and tetraethylene glycol monomethacrylate wings (DEGMMA, TEGMMA, TTEGMMA, respectively). The following monomers were obtained: DEGMMA/CHMDI, TEGMMA/IPDI, TEGMMA/TDI, TEGMMA/CHMDI, and TTEGMMA/CHMDI. Neat homopolymers as well as their composites with barium sulfate and hydroxyapatite were tested for curing temperature and time. Almost all of the proposed systems were characterized by appropriate values of both parameters. The presence of fillers positively affected the studied parameters by lowering the polymerization temperature and time. [ABSTRACT FROM AUTHOR]

n‐Type semiconducting polymers with high thermoelectric performance remain challenging due to the scarcity of molecular design strategy, limiting their applications in organic thermoelectric (OTE) devices. Herein, we provide a new approach to enhance the OTE performance of n‐doped polymers by introducing acceptor‐acceptor (A‐A) type backbone bearing branched ethylene glycol (EG) side chains. When doped with 4‐(2,3‐dihydro‐1,3‐dimethyl‐1H‐benzimidazol‐2‐yl)‐N,N‐dimethylbenzenamine (N‐DMBI), the A‐A homopolymer PDTzTI‐TEG exhibits n‐type electrical conductivity (σ) up to 34 S cm−1 and power factor value of 15.7 μW m−1 K−2. The OTE performance of PDTzTI‐TEG is far greater than that of homopolymer PBTI‐TEG (σ=0.27 S cm−1), indicating that introducing electron‐deficient thiazole units in the backbone further improves the n‐doping efficiency. These results demonstrate that developing A‐A type polymers with EG side chains is an effective strategy to enhance n‐type OTE performance. [ABSTRACT FROM AUTHOR]

A series of new homo- and copolymers P1 – P6 with the main chains comprised exclusively of benzo [1,2- b :4,5- b ']dithiophene units were synthesized using Stille polycondensation reaction. The optical and electrochemical properties of P1 – P6 polymers were studied to estimate the frontier orbitals energies and the E g values. The obtained data demonstrate the possibility of controlling the electronic properties of polybenzo [1,2- b :4,5- b ']dithiophenes by varying only the structure and combinations of solubilizing alkyl side chains. The polymers P1 – P6 were evaluated as hole transport materials in n-i-p perovskite solar cells. The highest efficiency of 18.6 % was delivered by the cells with one of the designed polymers with an optimal combination of alternating mono- and dialkylthiophene substituents. The high photovoltaic performance and decent operational stability were achieved using polymer films without any doping, which paves a way to design of inexpensive and scalable dopant-free materials for perovskite solar cells. [Display omitted] • A series of new benzodithiophene-backbone polymers P1 – P6 have been synthesized and studied. • The polymers P1 – P6 have electronic properties which are suitable for optoelectronic applications. • The polymers demonstrated good efficiency in perovskite solar cells with maximum power conversion efficiency of 16.8 % in the case of P2 as hole-transporting layer, without any dopation. • The devices with hole-transporting layer made of P1 demonstrated the best operation stability under MPPT conditions. [ABSTRACT FROM AUTHOR]

By studying the collapse of a simple ring homopolymer devoid of solvent interactions and chemical heterogeneity, it is shown that segments with an odd number of low‐energy dihedral angles are unusually frequent. The prevalence of odd‐size segments is due to the greater decrease in end‐to‐end length as compared with crumpling to even‐size segments. These results suggest that the sizes of some conformational features of polymers may arise, not due to specific chemical interactions, but rather from generic characteristics of polymers. [ABSTRACT FROM AUTHOR]

The stimuli‐responsive transition of nanostructures from amorphous to crystalline state is of high interest in polymer science, but is still challenging. Herein, the transformation of amorphous nanobowls to crystalline ellipsoids triggered by UV induced trans‐cis isomerization is demonstrated, using an azobenzene‐containing amphiphilic homopolymer (PAzoAA) as a building block. The amide bond and azobenzene pendants are introduced to the side chain of PAzoAA to afford hydrogen bonding and π–π interactions, which promote the formation of nanobowls rather than spherical nanostructures. Upon exposure to UV irradiation, trans‐cis isomerization of azobenzene pendants occurs, leading to the increase of hydrophilicity and destruction of π–π interaction, further resulting in the disassembly of the nanobowls. Then the PAzoAA re‐assembles to form crystalline ellipsoids instead of amorphous nanostructures when recovered at 70 °C without UV light. Further, it is confirmed that the high incubation temperature after UV irradiation is critical for the cis‐trans transformation and the high mobility of the polymer chains to facilitate the regular rearrangement of azobenzene pendants. Overall, a facile method to achieve the transformation of amorphous nanobowls to crystalline ellipsoids is proposed, which may bring new insight into preparation of crystalline nanoparticles using amorphous precursors. [ABSTRACT FROM AUTHOR]

The Polish TU 154M plane, Polish Air Force Flight 101, had crashed near Smolensk on 10th of April 2010. The crash was investigated by The Interstate Aviation Committee, whose conclusions were questioned by a number of Polish scientists. The cause of the crash still appears to be incompletely documented and requires additional evidence. In this paper, investigations of a solid material eluted from a piece of cloth of one of the victims of the crash are described. High resolution mass spectrometry was applied to analyze the soot left after controlled ethylene oxide (EO) explosions, performed under different conditions. These included electric ignition of EO vapors in a large volume steel container, and explosions of glass tubes filled with liquid EO, stimulated by thermally initiated explosions of pentaerythritol tetranitrate (PETN). One of these explosions was conducted in the vessel used for the electric ignition of EO and the other in a hermetically locked, small volume container. It was shown that the soot comprises a set of C2H4O homopolymers and copolymers whose characteristic MS patterns are condition‐dependent. The MS spectrum of the postcrash sample referred to above reveals a number of polymers that are also present in the soot obtained in PETN‐initiated ethylene oxide explosions. It can be concluded that the piece of cloth was subjected to an EO explosion initiated by an explosion of energetic material, possibly PETN. Similar control experiments with ethylene glycol (EG) showed that the polymers identified in the investigated postcrash sample could not originate from exploding EG. [ABSTRACT FROM AUTHOR]

The coefficient of thermal expansion (CTE) is an industrially crucial macroscopic property of polymers. Yet, there is no structure-based model expressing it with sufficient accuracy. In this work, we present two data-driven predictive models for the linear CTE of amorphous homopolymers in the glassy state based solely on chemical structure, showing consistent predictions. The first model is built with the SMILES-X software and is based on the simplified molecular-input line-entry system (SMILES) of polymer’s repeating unit as input. The second model is built with a random forest trained on extended-connectivity fingerprints of repeating units. Both models are trained on 106 experimental data samples taken from the PoLyInfo database. The out-of-sample prediction shows a root-mean-square error of 2.65 ± 0.09 × 10–5 K–1 (2.58 ± 0.09 × 10–5 K–1), a mean absolute error of 1.71 ± 0.06 × 10–5 K–1 (1.61 ± 0.06 × 10–5 K–1) and a coefficient of determination of 0.62 ± 0.03 (0.64 ± 0.03) for SMILES-X (random forest). Additionally, the models are validated experimentally using a lab-prepared sample with good agreement (p-value$$ \gg $$for both models). The attention mechanism, incorporated into SMILES-X, points out salient SMILES substructures, and the resulting maps suggest that the model takes decisions on a chemically interpretable basis. Abbreviations: SMILES; CTE; CLTE; CVTE

The coefficient of thermal expansion (CTE) is an industrially crucial macroscopic property of polymers. Yet, there is no structure-based model expressing it with sufficient accuracy. In this work, we present two data-driven predictive models for the linear CTE of amorphous homopolymers in the glassy state based solely on chemical structure, showing consistent predictions. The first model is built with the SMILES-X software and is based on the simplified molecular-input line-entry system (SMILES) of polymer’s repeating unit as input. The second model is built with a random forest trained on extended-connectivity fingerprints of repeating units. Both models are trained on 106 experimental data samples taken from the PoLyInfo database. The out-of-sample prediction shows a root-mean-square error of 2.65 ± 0.09 × 10–5 K–1 (2.58 ± 0.09 × 10–5 K–1), a mean absolute error of 1.71 ± 0.06 × 10–5 K–1 (1.61 ± 0.06 × 10–5 K–1) and a coefficient of determination of 0.62 ± 0.03 (0.64 ± 0.03) for SMILES-X (random forest). Additionally, the models are validated experimentally using a lab-prepared sample with good agreement (p-value ≫ for both models). The attention mechanism, incorporated into SMILES-X, points out salient SMILES substructures, and the resulting maps suggest that the model takes decisions on a chemically interpretable basis. Abbreviations: SMILES; CTE; CLTE; CVTE [ABSTRACT FROM AUTHOR]

The polymerization of methacrylate compositions used in bone cement is often accompanied by a strong exothermic effect. The polymerizing mass heats up to very high temperatures at the cement application site, irritating the adjacent tissues and even cell death. On the other hand, a bone cement composition should have the optimal curing time, which should be long enough to allow for proper preparation of the cement and short enough to prevent leaking of the cement out of the restoration place. Therefore, new compositions are being sought to reduce the curing temperature of bone cement and maintain a sufficiently long curing time. Our proposal is based on using five homopolymers obtained by polymerizing urethane-dimethacrylates. These were composed of diisocyanate cores: toluene 2,4 diisocyanate (TDI), isophorone diisocyanate (IPDI), 4,4′-methylenebis(cyclohexyl isocyanate) (CHMDI), and di-, tri-, and tetraethylene glycol monomethacrylate wings (DEGMMA, TEGMMA, TTEGMMA, respectively). The following monomers were obtained: DEGMMA/CHMDI, TEGMMA/IPDI, TEGMMA/TDI, TEGMMA/CHMDI, and TTEGMMA/CHMDI. Neat homopolymers as well as their composites with barium sulfate and hydroxyapatite were tested for curing temperature and time. Almost all of the proposed systems were characterized by appropriate values of both parameters. The presence of fillers positively affected the studied parameters by lowering the polymerization temperature and time.

Room temperature phosphorescence (RTP) has attracted broad attention due to their long lifetimes, large Stokes shift, and widespread applications. Achieving RTP emission has long been a challenging task under common conditions, for the necessary requirements of promoting intersystem crossing processes and suppressing nonradiative transitions are always tough to meet. Over the past decade, RTP has been obtained through several specific strategies, among which an important method lies in immobilizing phosphors into polymer matrices. Via the effect of steric overcrowding exerted by the polymeric structures, the phosphorescence of the initial phosphors can be promoted significantly. Hence, polymer‐based pure organic materials have proved to be one newly emerging subject in the field of RTP materials. In this review article, the progresses of polymer‐based pure organic room temperature phosphorescent materials are elaborated from four main approaches, including doped polymer systems, copolymer systems, homopolymer systems, and host–guest complexation systems, whereby the design principles, synthesis methods, possible mechanisms, and applications are summarized and discussed in detail. [ABSTRACT FROM AUTHOR]

We consider the problem of designing a set of DNA sequences (DNA codes) for various DNA computing applications, such as DNA based data storage. A chemically active DNA sequence forms unlikely secondary structure by folding back onto itself by hybridization among base pairs. DNA sequences with secondary structures are less active chemically and are needed to unfold before reading. On the other side, during synthesis and sequencing of DNA sequences with homopolymers of large run-length, errors occur frequently. In this letter, we have presented families of DNA codes with several properties such as DNA sequences free from secondary structures of stem length more than two and also free from homopolymers of run-length more than four. All constructed DNA sequences of any DNA codes are sufficiently dissimilar to their reverse-complement DNA sequences. Further, DNA sequences obtained by concatenating all those DNA sequences also avoid secondary structures and homopolymers. [ABSTRACT FROM AUTHOR]

DNA storage has emerged as an important area of research. The reliability of a DNA storage system depends on designing those DNA strings (called DNA codes) that are sufficiently dissimilar. In this work, we introduce DNA codes that satisfy the newly introduced constraint, a generalization of the non-homopolymers constraint. In particular, each codeword of the DNA code has the specific property that any two consecutive sub-strings of the DNA codeword will not be the same. This is apart from the usual constraints such as Hamming, reverse, reverse-complement and GC-content. We believe that the new constraints proposed in this paper will provide significant achievements in reducing the errors, during reading and writing data into the synthetic DNA strings. We also present a construction (based on a variant of stochastic local search algorithm) to determine the size of the DNA codes with a constraint that each DNA codeword is free from secondary structures in addition to the usual constraint. This further improves the lower bounds from the existing literature, in some specific cases. A recursive isometric map between binary vectors and DNA strings is also proposed. By applying this map over the well known binary codes, we obtain classes of DNA codes with all of the above constraints, including the property that the constructed DNA codewords are free from the hairpin like secondary structures. [ABSTRACT FROM AUTHOR]

Noninvasive ultrasound is a more effective strategy for on-demand drug delivery of polymeric nanoparticles than many other stimuli. However, the preparation of ultrasound-responsive homopolymer nanoparticles is still very challenging. In this study, we disclose the regulating factors of ultrasound responsiveness of homopolymer nanoparticles and the disaggregation behavior of homopolymer nanoparticle aggregates. Homopolymer nanoparticles such as vesicles and large compound micelles (LCMs) are self-assembled from poly(methoxyethyl methacrylate) (PMEMA) and poly(amic acid) (PAA), respectively. The ultrasound responsiveness of PAA vesicles at metastable state could be regulated by tuning the self-assembly temperature (Ts), and was optimized when Ts is around the glass transition temperature (Tg) of PAA. However, the PMEMA LCMs did not respond to ultrasound as they are at stable state. On the other hand, poly(2-(2-ethoxyethoxy)ethyl acrylate) (PEEA) could self-assemble into vesicle aggregates or complex micelle aggregates, which were dissociated upon sonication. Overall, the above findings provide us with a fresh insight for designing ultrasound-responsive polymeric nanoparticles. [ABSTRACT FROM AUTHOR]

The glass transition temperature (Tg) is an important decision parameter when synthesizing polymeric compounds or when selecting their applicability domain. In this work, the glass transition temperature of more than 100 homopolymers with saturated backbones was predicted using a neuro-evolutive technique combining Artificial Neural Networks with a modified Bacterial Foraging Optimization Algorithm. In most cases, the selected polymers have a vinyl-type backbone substituted with various groups. A few samples with an oxygen atom in a linear non-vinyl hydrocarbon main chain were also considered. Eight structural, thermophysical, and entanglement properties estimated by the quantitative structure–property relationship (QSPR) method, along with other molecular descriptors reflecting polymer composition, were considered as input data for Artificial Neural Networks. The Tg’s neural model has a 7.30% average absolute error for the training data and 12.89% for the testing one. From the sensitivity analysis, it was found that cohesive energy, from all independent parameters, has the highest influence on the modeled output.

Our group has recently invented a novel series of thermoresponsive ABC triblock terpolymers based on oligo(ethylene glycol) methyl ether methacrylate with average Mn 300 g mol−1 (OEGMA300, A unit), n-butyl methacrylate (BuMA, B unit) and di(ethylene glycol) methyl ether methacrylate (DEGMA, C unit) with excellent thermogelling properties. In this study, we investigate how the addition of OEGMA300x homopolymers of varying molar mass (MM) affects the gelation characteristics of the best performing ABC triblock terpolymer. Interestingly, the gelation is not disrupted by the addition of the homopolymers, with the gelation temperature (Tgel) remaining stable at around 30 °C, depending on the MM and content in OEGMA300x homopolymer. Moreover, stronger gels are formed when higher MM OEGMA300x homopolymers are added, presumably due to the homopolymer chains acting as bridges between the micelles formed by the triblock terpolymer, thus, favouring gelation. In summary, novel formulations based on mixtures of triblock copolymer and homopolymers are presented, which can provide a cost-effective alternative for use in biomedical applications, compared to the use of the triblock copolymer only.

A series of thermally stable dicyanate monomers was prepared containing different thermally stable structural units, namely 2,2′‐bis(4‐cyanatophenyl)propane, bis‐4‐cyanato‐biphenyl, bis‐4‐cyanato naphthalene, 3,3′‐bis(4‐cyanatophenyl)sulfide and 3,3′‐bis(4‐cyanatophenyl)sulfone, was prepared and the identity of the products was confirmed by Fourier transform infrared and NMR spectral methods. The corresponding cyanate homopolymers were prepared and their properties were evaluated and compared. The composites were analysed for their thermal stability and thermal degradation kinetics. The series of homopolymers exhibit excellent thermal characteristics, e.g. relatively high glass transition temperatures of at least 215 °C, which were inversely proportional to the molecular weight between the crosslinks, high thermal decomposition temperature and high activation energies for the decomposition of cured resins. Determination of their limiting oxygen indices indicates that all the homopolymers are characterized as 'self‐extinguishing' materials. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The liquid-crystal assembly of semiflexible-coil diblock copolymers with coil or semiflexible homopolymers is studied by dissipative particle dynamics simulation. Phase diagrams of the blends and orientation ordering parameters among semiflexible blocks are constructed as a function of chain stiffness and homopolymer volume fraction. For semiflexible-coil/coil blends with varying stiffness of semiflexible blocks, we display the rich phase behaviors of the system transited from coil-coil/coil to rod-coil/coil blends. The disorder-lamellae or lamellae-liquid crystalline transition and “dry brush” phenomenon induced by coil homopolymers are observed. For semiflexible-coil/semiflexible blends, adding semiflexible homopolymers also leads to a disorder-order transition and even a transition between monolayer and bilayer smectic-A phase. The results demonstrate that blending homopolymers into semiflexible copolymers can induce liquid-crystal assembly and even improve the orientation ordering of semiflexible blocks effectively. [ABSTRACT FROM AUTHOR]

A series of compounds, in which exo -norbornene scaffold appended with amino acids, was synthesized. These compounds underwent ring opening metathesis polymerization (ROMP) catalyzed by Grubbs second generation ruthenium catalyst to form polymers with bottlebrush architecture. Four different polymers P1-P4 were synthesized, differing in number of lipid units and degree of branching. These polymers were well-characterized by 1 H NMR and gel permeation chromatographic (GPC) techniques. These peptide-based homopolymers showed an exceptional ability to self-assemble to form polymersomes. The self-assembled structures were characterized by various ultramicroscopic techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The entrapment capability of polymer vesicles was confirmed by dye-encapsulation studies. [ABSTRACT FROM AUTHOR]

A series of water-soluble dual light- and thermo-responsive homopolymers bearing azobenzene units and terminal oligo(ethylene glycol) units with well-defined molecular weight ( Mn = 0.69 × 104 to 4.60 × 104 g mol−1) were synthesized via reversible addition-fragmentation chain transfer polymerization. All the homopolymers exhibited reversible photoisomerization and their lower critical solution temperatures showed an unusual increase with increasing molecular weight. Interestingly, by increasing the molecular weight, the aggregate morphology of these polymers was found to evolve from a spherical to a cylindrical shape. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A series of novel thermo/pH/CO 2 -triple responsive homopolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. These homopolymers contain ethoxy groups, and the end substituents are pyrrolidine, piperidine, N -methylpiperazine, morpholine and thiomorpholine, respectively. The effects of different heterocyclic substituents on the responsiveness of temperature, pH and CO 2 were studied. For temperature-response, it was found that the lower critical solution temperature (LCST)-type cloud point (CP) temperature decreased as the number of carbon atoms increases, while the solubility of the polymers changed greatly with the introduction of oxygen, nitrogen and sulfur atoms. And the CP of the polymers can be adjusted by molecular weight, concentration and salt. Furthermore, some of these polymers present upper critical solution temperature (UCST) behavior in alcohols. For pH-response, the initial pH of the polymer solution is different, their critical pH changed accordingly, and is affected by temperature; in addition, changing the pH of solution can also affect the CP. For CO 2 -response, all of the polymers were completely soluble after pumping with CO 2 , and their LCST behavior recovered after N 2 was pumped in, but there was a gap with the initial CP. The study of these properties reveals the influence of different heterocyclic substituents on the responsiveness of polymers, which is of great significance for understanding the stimulation response properties of polymers and provides ideas for the design of new stimuli-responsive polymers. [Display omitted] • A series of novel thermo/pH/CO 2 -triple responsive homopolymers were synthesized. • These homopolymers contain ethoxy groupsand heterocyclic substituents. • The heterocyclic substituents have great influence on the temperature, pH and CO 2 responsiveness of the polymers. [ABSTRACT FROM AUTHOR]

Pathogenic microbes confront an evolutionary conflict between the pressure to maintain genome stability and the need to adapt to mounting external stresses. Bacteria often respond with elevated mutation rates, but little evidence exists of stable eukaryotic hypermutators in nature. Whole genome resequencing of the human fungal pathogen Cryptococcus deuterogattii identified an outbreak lineage characterized by a nonsense mutation in the mismatch repair component MSH2. This defect results in a moderate mutation rate increase in typical genes, and a larger increase in genes containing homopolymer runs. This allows facile inactivation of genes with coding homopolymer runs including FRR1, which encodes the target of the immunosuppresive antifungal drugs FK506 and rapamycin. Our study identifies a eukaryotic hypermutator lineage spread over two continents and suggests that pathogenic eukaryotic microbes may experience similar selection pressures on mutation rate as bacterial pathogens, particularly during long periods of clonal growth or while expanding into new environments.

ABSTRACT This contribution presents a strategy for preparing amphiphilic homopolymers as building blocks for self-assembly into supramolecular nanostructures. The synthesis begins with norbornene monomers containing oligoethylene glycols on the side chains. Ring-opening metathesis polymerization of the monomers and subsequent dihydroxylation afford water-soluble dihydroxylated poly(norbornene)s (PNBs). Amphiphilic modifications of the hydrophilic PNBs can be achieved by reacting 1,2-diols on the backbones with hydrophobic dodecanals to form acetal linkages. The self-assembly of the resulting amphiphilic PNB homopolymers affords polymeric micelles whose morphologies can be tuned by breaking the acetal linkages under acidic conditions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3804-3808 [ABSTRACT FROM AUTHOR]

Constraints imposed by nanometer scale confinement lead to the changes in bulk equilibrium behavior of block copolymers (BCPs). Cylindrical pores with diameter corresponding to the equivalent length of several copolymer chains have been employed to investigate the influence of two-dimensional (2D) confinement on the behavior of BCPs. Herein, we reported the microdomain transition behavior of block copolymer/homopolymer (AB/A) binary blends in cylindrical confinement. Lamellae forming poly(styrene- b-butadiene) (PS- b-PBD) and PS homopolymers (hPS) were drawn into the pores of anodized aluminum oxide (AAO) and isolated by selective etching of the AAO templates. Concentric ring morphologies of neat PS- b-PBD in the cylindrical confinement varied with on the addition of hPS. Given the volume fraction of homopolymers, the phase behavior of polymer blends was dependent on the molecular weight of homopolymers. When the ratio between the molecular weight of hPS and PS block was much lower than unity ( α«1) ( i.e., wet brush regime), the concentric ring structure was transformed into helical or spherical structure depending on the volume fraction of hPS. For α≈1 ( i.e., dry brush regime), additional hPS chains were localized at the center of concentric ring where the entropic penalty of copolymer chains induced by confinement is maximized. Over the capability of hPS in the BCP domains in radial axis, the phase transition into microemulsions occurred in the dry brush regime. In both wet and dry brush regimes, the effect of hPS on the phase transition of BCP was significantly enhanced in the nanoscale 2D confinement compared to the bulk state due to the loss of conformational entropy of polymer chains. [ABSTRACT FROM AUTHOR]

Robust nanostructures were obtained from polymers that otherwise do not assemble by using a novel approach based on electrostatic self-assembly. The essence of this strategy involves the use of divalent counterions to temporarily perturb the packing features of the ionic groups in a homopolymer, which results in a vesicle-like structure that is captured in situ through a simple crosslinking reaction. The fidelity of the assembly has been tested for molecular transport across the nanomembrane, both for the molecules encapsulated in the lumen and for those trapped in the membrane itself. The membranes are addressable for robust multifunctionalization of their surfaces and for tunable transmembrane molecular transport. [ABSTRACT FROM AUTHOR]

The high stability and strong self-assembly properties made ferritins the most used proteins for nanotechnological applications. Human ferritins are made of 24 subunits of the H- and L-type that coassemble in an almost spherical nanocage 12 nm across, delimiting a large cavity. The mechanism and kinetics of ferritin self-assembly and why H/L heteropolymers formation is favored over the homopolymers remain unclarified. In order to study this, we used the Fluorescence Resonance Energy Transfer (FRET) tool by binding multiple donor or acceptor Alexa Fluor fluorophores on the outer surface of human H and L ferritins and then denaturing and reassembling them in different proportions and conditions. The FRET efficiency increase from < 0.3 of the disassembled to > 0.7 in the assembled allowed to study the assembly kinetics. We found that their assembly was complete in about one hour, and that the initial rate of self-assembly of H/L heteropolymers was slightly faster than that of the H/H homopolymers. Then, by adding various proportions of unlabeled H or L-chains to the FRET system we found that the presence of the L-chains displaced the formation of H-H dimers more efficiently than that of the H-chains. This favored formation of H/L heterodimers, which is the initial step in ferritin self-assembly, contributes to explain the preferred formation of H/L heteropolymers over the H or L homopolymers. Moreover, we found that the H-chains arrange at distant positions on the heteropolymeric shell until they reach a number above eight, when they start to co-localize. [ABSTRACT FROM AUTHOR]

The progress in efficiency of organic photovoltaic devices is largely driven by the development of new donor–acceptor (D–A) copolymers. The number of possible D–A combinations escalates rapidly with the ever-increasing number of donor and acceptor units, and the design process often involves a trial-and-error approach. We here present a computationally efficient methodology for the prediction of optical and electronic properties of D–A copolymers based on density functional theory calculations of donor- and acceptor-only homopolymers. Ten donors and eight acceptors are studied, as well as all of their 80 D–A copolymer combinations, showing absorption energies of 1.3–2.3 eV, and absorption strengths varying by up to a factor of 2.5. Focus lies on exhibited trends in frontier orbital energies, optical band gaps, and absorption intensities, as well as their relation to the molecular structure. Based on the results, we define the concept of donor and acceptor strength, and calculate this quantity for all investigated units. The light-harvesting capabilities of the 80 D–A copolymers were also assessed. This gives a valuable theoretical guideline to the design of D–A copolymers with the potential to reduce the synthesis efforts in the development of new polymers. [ABSTRACT FROM PUBLISHER]

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Background: Low complexity regions (LCRs) are a ubiquitous feature in genomes and yet their evolutionary history and functional roles are unclear. Previous studies have shown contrasting evidence in favor of both neutral and selective mechanisms of evolution for different sets of LCRs suggesting that modes of identification of these regions may play a role in our ability to discern their evolutionary history. To further investigate this issue, we used a multiple threshold approach to identify species-specific profiles of proteome complexity and, by comparing properties of these sets, determine the influence that starting parameters have on evolutionary inferences. Results: We find that, although qualitatively similar, quantitatively each species has a unique LCR profile which represents the frequency of these regions within each genome. Inferences based on these profiles are more accurate in comparative analyses of genome complexity as they allow to determine the relative complexity of multiple genomes as well as the type of repetitiveness that is most common in each. Based on the multiple threshold LCR sets obtained, we identified predominant evolutionary mechanisms at different complexity levels, which show neutral mechanisms acting on highly repetitive LCRs (e.g., homopolymers) and selective forces becoming more important as heterogeneity of the LCRs increases. Conclusions: Our results show how inferences based on LCRs are influenced by the parameters used to identify these regions. Sets of LCRs are heterogeneous aggregates of regions that include homo- and heteropolymers and, as such, evolve according to different mechanisms. LCR profiles provide a new way to investigate genome complexity across species and to determine the driving mechanism of their evolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Extension of molecular thermodynamic and neural network models to surface tension correlation. • Application to 7 homopolymers. • Simultaneous calculation of bulk properties and surface tension. A combined molecular thermodynamic model with an equation of state was successfully extended for correlating the surface tension of 7 molten polymers. The model was coming from the combination of a statistical mechanical expression according to Fowler-Kirkwood-Buff approximation with the perturbed hard-sphere-chain equation of statistical association fluid theory by an attractive term of Yukawa tail. The systems under study were of homopolymers type including Poly(ethylene oxide), High-Density Poly(ethylene), Poly(dimethyl siloxane), Poly(vinyl methyl ether), Poly(ethylene glycol), Atactic-Poly(propylene glycol), and Isotactic-Poly(propylene glycol). The model also used the dipole moment of the monomer molecule of those systems as an adjustable coefficient. The model was able to correlate 65 surface tension data points of the above-mentioned polymers in 297–532.2 K range with the average absolute relative deviation (AARD) of 2.00%. In addition, a single layer neural network comprising two input parameters (temperature and soft-core diameter of Lennard-Jones fluid) and 11 neurons was applied to complete the research, achieving more than satisfactory results with the AARD of 0.88%. [ABSTRACT FROM AUTHOR]

Background: Nucleoside and nucleobase antimetabolites are an important class of chemotherapeutic agents for the treatment of cancer as well as other diseases., Introduction: In order to avoid undesirable side effects, several prodrug strategies have been developed. In the present review, we describe a relatively unknown strategy that consists of using oligonucleotides modified with nucleoside antimetabolites as prodrugs., Methods: The active nucleotides are generated by enzymatic degradation once incorporated into cells. This strategy has attracted large interest and is widely utilized at present due to the continuous developments made in therapeutic oligonucleotides and the recent advances in nanomaterials and nanomedicine., Results: A large research effort was made mainly in the improvement of the antiproliferative properties of nucleoside homopolymers, but recently, chemically modified aptamers, antisense oligonucleotides and/or siRNA carrying antiproliferative nucleotides have demonstrated a great potential due to the synergetic effect of both therapeutic entities. In addition, DNA nanostructures with interesting properties have been built to combine antimetabolites and enhancers of cellular uptake in the same scaffold. Finally, protein nanoparticles functionalized with receptor-binders and antiproliferative oligomers represent a new avenue for a more effective treatment in cancer therapy., Conclusion: It is expected that oligonucleotides carrying nucleoside antimetabolites will be considered as potential drugs in the near future for biomedical applications., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

ABSTRACT Blends of self-assembling polystyrene- block-poly(4-vinyl pyridine) (PS- b-P4VP) diblock-copolymers and poly(4-vinyl pyridine) (P4VP) homopolymers were used to fabricate isoporous and nanoporous films. Block copolymers (BCP) self-assembled into a structure where the minority component forms very uniform cylinders, while homopolymers, resided in the core of the cylinders. Selective removal of the homopolymers by ethanol immersion led to the formation of well-ordered pores. In films without added homopolymer, just immersion in ethanol and subsequent swelling of the P4VP blocks was found to be sufficient to create pores. Pore sizes were tuned between 10 and 50 nm by simply varying the homopolymer content and the molecular weight of the block-copolymer. Uniformity was lost when the average pore size exceeded 30 nm because of macrophase separation. However, preparation of films from low MW diblock copolymers showed that it is possible to have excellent pore size control and a high porosity, while retaining a low pore size distribution. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1568-1579 [ABSTRACT FROM AUTHOR]

We present the results of a multicanonical Monte Carlo study of flexible and wormlike polymer chains, where we investigate how the polymer structures observed during the simulations, mainly coil, liquid, and crystalline structures, can help to construct a hyperphase diagram that covers different polymer classes according to their thermodynamic behavior. [ABSTRACT FROM AUTHOR]

Anti-reflection (AR) coatings designed for glass and other rigid, inorganic substrates are commercially available; however, these inorganic AR coatings tend to crack or delaminate on flexible substrates. A polymeric film with a gradient refractive index (GRIN) profile would make an ideal AR coating for flexible substrates, but such coatings are challenging to fabricate using traditional, solution-based techniques. Emulsion-based resonant infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) offers a straightforward approach to enabling the desired GRIN profile in polymeric materials. Two homopolymers (polystyrene (PS) and poly(methyl methacrylate) (PMMA)) are deposited as a blend and one component (PMMA) is dissolved, leaving behind a porous PS film. The porosity and refractive index (RI) are controlled by the volume ratio of the two homopolymers in the film. Structural and optical characterizations, as well as comparison to modeled optical properties, confirm that porous films fabricated from polymer blends deposited by RIR-MAPLE behave as effective media over most of the visible spectrum. While evidence for the partial collapse of the porous polymer networks is observed, the RI of the porous films is reduced from that of the bulk material. Importantly, these studies demonstrate that RIR-MAPLE should enable broadband, omnidirectional, polymeric AR coatings appropriate for flexible substrates. [ABSTRACT FROM AUTHOR]