Polar Segments Research Articles

Amphiphilic olefin block copolymers synthesized by successive coordinative chain transfer and ring-opening polymerizations

Introducing polarity is a necessity for widening the application scope of polyolefins specifically for developing biocompatible products. To this end, we exploit a two-step polymerization process to synthesize poly(ethylene‑b‑caprolactone) PE‑PCL block copolymers, which contain both polar and non-polar segments. First ethylene is polymerized by a generic metallocene catalyst in the presence of ZnEt2 as the chain transfer agent according to the coordinative chain transfer polymerization (CCTP) technique. Terminal zinc atoms are subsequently replaced by hydroxyl groups (PE‑OH) by exposing dormant polymer chains to oxygen. Afterward, ring-opening polymerization (ROP) of ε‑caprolactone is initiated by PE‑OH to form PE‑PCL block copolymers. Successful formation of both blocks is verified by FTIR and NMR spectroscopy. The presence of PCL blocks greatly lowers the crystallinity of ethylene sequences according to XRD and DSC results. Moreover, a second type of PE crystals with more chain folds and lower lamella thickness is found in block copolymers, which is absent in the equivalent physical blend. The diverse crystal structure of block copolymers suggest that phase separation exists between PE and PCL segments. The SEM image of the equivalent physical blend confirms the tendency of PCL and PE chains to phase separate, and infers a compatibilization in the presence of PE‑PCL block copolymers. This phase separation is detected by rheological measurements, as well, where block copolymers show deviations from Maxwell behavior in the terminal relaxation zone at low frequencies. Rheology results also show that the order-disorder transition temperature (TODT) of these block copolymers is higher than 180 °C. These results provide a clear picture from the morphology and utility of such block copolymers specifically for compatibilizing blends of polar polymers and non-polar polyolefins, which significantly broaden the utility of polyolefins.

New Topical Drug Delivery System Pharmaceutical Organogel: A Review

A simple working definition of this term'Gel' is a soft, durable or solid material,containing both solids and liquid parts, where the solid part(gelator) exists as amesh / network of aggregates, viz immobilize part of the liquid,a strong network prevents the liquid from leaking flow, especially by local pressure. The gel is called a hydrogel or Organogel depending on the type liquid component: water in hydrogel and a living solvent in organogels .Organogels have been discovered as a multipurpose tool in pharmaceuticals for topical as well as transdermal delivery of various drugs. They are semisolid classifications consists of apolar phase and a solid phase. Gels are form through the mechanism of entrapment of a polar segment into the three-dimensional networked assembly of solid phase. Apolar phase is inculded as a solvent such as isopropyl palmitate, isopropyl myristate etc.an organogelator such as sorbiatanmonostearte, lecithin etc. are consist by solid phase Organogel, non-crystalline, nonglassythermoreversible (thermoplastic)solid materials and viscoelastic system,can be considered semi-solid an immobilized preparation external apholar phase. Apholar the section closes between spaces of a three-dimensional network a structure built due to physical condition negotiation between collectors compound properties considered as gelators. Generally, these programs are supported in structurant integration molecules .These systems are good transporter for both hydrophilic and lipophilic therapeutic agents. The present review describes a number of important properties of organogel, different types of organogel based on organogelator, method of preparation and various applications in pharmaceuticals.

Visualization of fibroblast activation after myocardial infarction using 68Ga-FAPI-PET

Abstract Introduction Fibroblast activation protein (FAP) alpha specifically expressed by activated fibroblasts has been shown to be significantly involved in processes of tissue healing after injury, including fibrotic remodeling after myocardial infarction (MI). Positron-emission tomography (PET) with the tracer FAP-inhibitor (FAPI) is a novel diagnostic tool primarily described in oncologic patients for tumor stroma detection. We present data from a pilot study investigating patients after MI who underwent subsequent 68Ga-FAPI-PET for assessment of potential FAP-related myocardial remodeling. Methods In this retrospective study we analyzed a cohort of 10 post-MI patients who underwent 68Ga-FAPI-PET imaging with respect to cardiac tracer pattern. Standardized maximum and mean uptake values and total volume of tracer enrichment (fibroblast activation volume, FAV) of the infarcted area were calculated. A visual grading scale was established to assess the level of agreement between maximum localized tracer uptake and segments belonging to the supply area of the culprit vessel. Tracer uptake was correlated to clinical variables, with readers blinded to the clinical characteristics. Results Focal 68Ga-FAPI uptake was detected in all 10/10 patients after MI. According to our grading system for visual agreement of polar map segments and culprit lesion, we observed a very good (in 37.5% of patients) and a moderate (62.5% of patients) match between tracer uptake and the culprit lesion, respectively. We demonstrated a negative correlation of FAV uptake and left ventricular systolic function (R2=−0.69, p<0.05) and a very strong positive correlation of FAV and peak creatinine kinase level (R2=0.90, p<0.01). Conclusion Increased myocardial 68Ga-FAPI uptake, serving as a surrogate for FAP expression after MI, corresponds well to the supply area of the culprit coronary vessel as well as to biomarker levels of myocardial injury. This imaging technique represents a highly promising, novel bio-signal in the assessment of myocardial injury and consecutive remodeling. Large controlled studies are warranted to further evaluate the prognostic impact of this novel imaging technique. Funding Acknowledgement Type of funding sources: None.

Synergistic effects of porphyrin-ring catalytic center and metal catalytic site from crosslinked porphyrin-based porous polyimides cathode host for lithium polysulfides conversion in lithium-sulfur batteries

The construction of three-dimensional (3D) microporous structure cathode host material used in lithium sulfur battery perfectly provides the combination advantages of good physical confinement and chemical immobilization to suppress polysulfide shuttling. Hence, the construction of advanced POPs-based sulfur cathode hosts with hierarchical pore channel, high pore volume, strong polar segments, and catalytic sites is significant and necessary. Herein, a series of crosslinked porphyrin-based porous polyimides (CR-Por-PPIs) with hierarchical structures were fabricated from porphyrin-based tetramine (TAPP), alkynyl dianhydride (PEPHQDA) and metal inorganic salt (Cu, Co, Ni, Pb, Zn) via polymerization and 360℃ treatment. Owing to the well-constructed porous skeleton architectures, CR-Por-PPIs provide hierarchical pore channels and sufficient pore cavities for trapping polysulfides and relieving volume expansion, afford considerable heteroatom N species for buffering shuttle behaviors via strong chemisorption interaction, endow porphyrin ring catalytic center and metal catalytic sites for enhancing redox kinetics. Profiting from the synergistic efforts, S/CR-Por-PPIs composites cathodes show improved long-term cycle capabilities and rate properties. Chelated metal (Cu, Co, Zn) S/CR-Por-PPIs have superior cycling stabilities due to the promoted catalytic property by virtue of the co-existence of porphyrin-ring catalytic center and metal catalytic sites. These findings can help to facilitate scalable acquisition of high-performance cathode materials for lihium-sulfur batteries, and promote their commercialization.

Utilization of copper sulphide nanoparticles for the development of cashew tree gum/ chitin biopolymer blend nanocomposites

This work focused on the preparation of biopolymer blend nanocomposites from chitin (CT) and cashew tree gum (CTG) with different contents of copper sulphide nanoparticles (CuS) by solution casting method. The formation of nanocomposites have been characterized by FT infrared (FTIR), UV spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), thermogravimetry (TGA), differential scanning calorimetry (DSC) and impedance analysis. The characteristic absorption of nanoparticles in the FTIR spectra and shift in UV spectra of blend composites revealed the strong interaction between CuS nanoparticles and the polar segments of CT/CTG blend. With the increase in dosage of nanoparticles, a decrease in amorphous domains has been noted in the XRD scans. The uniform distribution of nanoparticles in CT/CTG network has been confirmed by the SEM analysis. HRTEM of the blend composites reveals the formation of hemispherical nanoparticles with a diameter of 15–30 nm. The glass transition temperature of blend composites increased with the addition of nano-CuS in the polymer matrix. Compared to the pure CT/CTG blend, the prepared nanocomposite showed higher thermal stability. Mechanical properties such as tensile strength and hardness of the blend nanocomposites were greatly enhanced by the reinforcement of CuS into the CT/CTG matrix. The AC conductivity and dielectric properties of the nanocomposites increased with the concentration of fillers and the magnitude of these properties was higher than the pure polymer blend.

DeepStrain: A Deep Learning Workflow for the Automated Characterization of Cardiac Mechanics.

Myocardial strain analysis from cinematic magnetic resonance imaging (cine-MRI) data provides a more thorough characterization of cardiac mechanics than volumetric parameters such as left-ventricular ejection fraction, but sources of variation including segmentation and motion estimation have limited its wider clinical use. We designed and validated a fast, fully-automatic deep learning (DL) workflow to generate both volumetric parameters and strain measures from cine-MRI data consisting of segmentation and motion estimation convolutional neural networks. The final motion network design, loss function, and associated hyperparameters are the result of a thorough ad hoc implementation that we carefully planned specific for strain quantification, tested, and compared to other potential alternatives. The optimal configuration was trained using healthy and cardiovascular disease (CVD) subjects (n = 150). DL-based volumetric parameters were correlated (>0.98) and without significant bias relative to parameters derived from manual segmentations in 50 healthy and CVD test subjects. Compared to landmarks manually-tracked on tagging-MRI images from 15 healthy subjects, landmark deformation using DL-based motion estimates from paired cine-MRI data resulted in an end-point-error of 2.9 ± 1.5 mm. Measures of end-systolic global strain from these cine-MRI data showed no significant biases relative to a tagging-MRI reference method. On 10 healthy subjects, intraclass correlation coefficient for intra-scanner repeatability was good to excellent (>0.75) for all global measures and most polar map segments. In conclusion, we developed and evaluated the first end-to-end learning-based workflow for automated strain analysis from cine-MRI data to quantitatively characterize cardiac mechanics of healthy and CVD subjects.

ABOUT THE REASONS FOR THE CHANGE IN THE MECHANICAL PROPERTIES OF PAPER ASHLESS FILTERS DURING THEIR PROCESSING IN A UNIPOLAR CORONA DISCHARGE

The article presents the study results of the structure and properties of paper ashless filters "Blue tape". It is shown that the "Blue tape" filter paper has a fairly high density with a relatively small number and size of voids (pores) between the fibers. When processing filters in the corona discharge field, an increase in their mechanical properties by 3.5–6% is observed, this is mainly due to the strengthening of the interfiber bond forces. The implementation of increased electrostatic bonding forces in the sheet structure leads to an increase in the resistance to the external tensile force necessary to break the paper filter. The observed dependences are associated with the orientation and ordering of the pulp and paper material structural elements, with an increase in the potential of the double electric layer on the fibers surface under the charge action carriers injected into the paper volume from the corona discharge and with the formation of a hetero charge due to the orientation of the polar cellulose groups and macromolecule segments during electreting. This is confirmed by the increase in the ζ – potential of the fibers of filters during processing in a negative corona discharge - it was found that the zeta – potential value of electret ashless filters is 18% higher than for the initial ones. The achieved results of increasing the ashless filters physico- mechanical properties will increase the efficiency of their use.

In-situ block copolymerization of 1,3-butadiene with cyclohexene oxide and trimethylene carbonate via combination of coordinative chain transfer polymerization and ring opening polymerization by neodymium-based catalyst system

Incorporating polar segment or polar block to non-polar polybutadiene is eye-catching as they can modify the interfacial energy and adhesion between polybutadiene matrix and polar materials. Herein, we report the in-situ preparation of well-defined polybutadiene-based block copolymers (poly(1,3-butadiene)-b-poly(cyclohexene oxide) and poly(1,3-butadiene)-b-poly(trimethylene carbonate)) using a commercially available neodymium-based catalytic system Nd(vers)3/AliBu2H/Me2SiCl2. First, the polybutadiene block was conveniently and highly efficiently synthesized via Coordinative Chain Transfer Polymerization (CCTP), yielding 5–11 polymer chains per catalyst molecule. This system revealed a high catalytic efficiency and well-controlled fashion, narrowly distributed together with well-regulated molecular weights were also resulted. Then, taking advantage of the living metal-capped polybutadienyl chain that were produced during the CCTP reaction in the first step, in-situ Ring Opening Polymerization of cyclohexene oxide, trimethylene carbonate were assessed. All the products were carefully characterized by combination of GPC, FTIR, 1H NMR, 2D DOSY NMR and DSC analysis, providing advantages and limitations for this method to prepare nonpolar-polar block copolymers.

Nanocrystallization-locked Network of Poly(styrene-b-isobutylene-b-styrene)-g-Polytetrahydrofuran Block Graft Copolymer

Poly(styrene-b-isobutylene-b-styrene) triblock copolymer (SIBS), a kind of thermoplastic elastomer with biocompatibility and biostability containing fully saturated soft segments, could be synthesized via living cationic copolymerization. A novel poly[(styrene-co-methylstyrene)-b-isobutylene-b-(styrene-co-methylstyrene)]-g-polytetrahydrofuran (M-SIBS-g-PTHF) block graft copolymer was prepared to increase the polarity and service temperature of SIBS by grafting polar PTHF segments onto SIBS. A series of the above block graft copolymers with average grafting numbers from 2 to 6 and molecular weights of PTHF branches ranging from 200 g·mol−1 to 4200 g·mol−1 were successfully synthesized via living cationic ring-opening polymerization of tetrahydrofuran (THF) coinitiated by AgClO4. The introduction of PTHF branches led to an obvious microphase separation due to thermodynamic incompatibility among the three kinds of segments of polyisobutylene (PIB), polystyrene (PS) and PTHF. Moreover, the microphase separation promotes the rearrangement of PTHF branches to form the nanocrystallization-locked physically cross-linked network after storage at room temperature for 2 months, leading to insolubility of the copolymers even in good solvents. The melting temperature and enthalpy of PTHF nanocrystallization locked in hard domains of M-SIBS-g5-PTHF-1.1k block graft copolymer increased remarkably up to 153 °C and 117.0 J·g−1 by 23 °C and 11.6 J·g−1 respectively after storage for long time. Storage modulus (G′) is higher than loss modulus (G″) of M-SIBS-g-PTHF block graft copolymer at temperatures ranging from 100 °C to 180 °C, which is much higher than those of the SIBS triblock copolymer. To the best of our knowledge, this is the first example of high performance M-SIBS-g-PTHF block graft copolymers containing segments of PIB, PS and PTHF with nanocrystallization-locked architecture.

Plasticization behavior of crown-ether containing polyimide membranes for the separation of CO2

This paper describes the influence of crown-ether ring size and rigidity on the gas separation performance of CO2/N2 and plasticization behavior of crown-ether containing Matrimid® 5218 polyimide membranes. The crown-ethers provide the membrane material with good affinity for CO2 due to the polar ether segments. Three different crown-ethers were used that differ in ring size and in rigidity (DB21C7, DB18C6 and 18C6). The gas separation performance of the crown-ether containing membranes was evaluated using pure gas and mixed gas conditions at pressures up to 40 bar. Thermal analysis (TGA and DSC) shows that the incorporation of the crown-ethers in the polyimide matrix was successful and that the crown-ethers have good compatibility with the polymer matrix. Gas sorption in the crown-ether containing membranes shows an enhanced solubility selectivity due to the enhanced interaction with CO2 compared to the pristine Matrimid®. However, both solubility and permeability of CO2 and N2 are decreased in these crown-ether containing membranes over the whole pressure range. When the molecular size of the crown-ether decreases (DB21C7 > DB18C6 > 18C6) the permeability increases. In addition, the incorporation of the more rigid crown-ethers (DB18C6 and DB21C7) causes rigidification of the polymer matrix contributing to the lower permeability of DB18C6 and DB21C7-based membranes. Pure gas CO2 permeation measurements show a typical plasticization behavior for pristine Matrimid®, while for the crown-ether containing membranes the extent of plasticization is significantly reduced. Next to that the plasticization pressure is shifted to higher CO2 feed pressures. No plasticization was observed for the crown-ether containing membranes in the mixed gas conditions, as a result of the lower solubility of the crown-ether containing membranes and competition effects of CO2 and N2. The differences in size and rigidity of the different crown-ethers showed no significant influence on the plasticization resistance of crown-ether containing membranes. Altogether, the operating window of these crown-ether containing membranes is increased with respect to Matrimid® showing their potential to operate at higher CO2 partial pressure without compromising selectivity.

Environmental Stability of Polymer Tantalum Capacitors

Stability of Polymer Tantalum capacitors with pre-polymerized PEDOT (slurry PEDOT) cathodes were investigated under different environmental conditions. Capacitance dependence on temperature, frequency, and dc bias voltage were investigated in humid and dry capacitors with different dielectric thicknesses. Electrical measurements and scanning electron microscopy (SEM) were used to characterize the capacitors. Humid capacitors were observed to have higher capacitance than dry capacitors for all dielectric thicknesses. The capacitance for all dielectric thicknesses was observed to increase with temperature in both humid and dry capacitors. Humid capacitors showed a strong temperature dependence at lower temperatures while dry capacitors showed a strong temperature dependence at higher temperatures. These temperature effects were more pronounced in thinner dielectric capacitors, and the results were explained by the integrity of the dielectric-polymer interface. The capacitance for all dielectric thicknesses was also observed to decrease with an increase in frequency, both in humid and dry capacitors. The frequency effect was more pronounced in humid capacitors with thinner dielectrics. These results were explained by a distributed capacitance model, secondary transitions of the polar segments of the polymer cathode, and lower reactance and lower self-resonance frequency of the thinner dielectric capacitors. The technological principles of improving environmental stability of Polymer Tantalum capacitors are also discussed.

Multiwavelength Polarimetry of the Filamentary Cloud IC 5146. II. Magnetic Field Structures

Abstract The IC 5146 cloud is a nearby star-forming region in Cygnus, consisting of molecular gas filaments in a variety of evolutionary stages. We used optical and near-infrared polarization data toward the IC 5146 cloud, reported in the first paper of this series, to reveal the magnetic fields in this cloud. Using the newly released Gaia data, we found that the IC 5146 cloud may contain two separate clouds: a first cloud, including the densest main filament at a distance of ∼600 pc, and a second cloud, associated with the Cocoon Nebula at a distance of ∼800 pc. The spatially averaged H-band polarization map revealed a well-ordered magnetic field morphology, with the polarization segments perpendicular to the main filament but parallel to the nearby subfilaments, consistent with models assuming that the magnetic field is regulating cloud evolution. We estimated the magnetic field strength using the Davis–Chandrasekhar–Fermi method and found that the magnetic field strength scales with volume density with a power-law index of ∼0.5 in the density range from to 3000 cm−3, which indicates an anisotropic cloud contraction with a preferred direction along the magnetic field. In addition, the mass-to-flux ratio of the cloud gradually changes from subcritical to supercritical from the cloud envelope to the deep regions. These features are consistent with strong magnetic field star formation models and suggest that the magnetic field is important in regulating the evolution of the IC 5146 cloud.

Polyurethane nanocomposites containing the chemically active inorganic Sn-POSS cages

Nanocomposite polyurethane (PUR) elastomers were synthesized, which contained the heavier, tin-based homologues of POSS (“Sn-POSS”). Most remarkable was the tremendous effect of extremely small Sn-POSS concentrations (around 0.05 wt%) on the glass transition (up-shift by 30–60 °C) of the oxidized Sn-POSS/PUR hybrids, which offers the possibility of improving the properties of an important engineering material class (PUR). Important in this context is the hydrogen bonding between the polar segments of Sn-POSS and the carbamate groups of PUR, which was elucidated by NMR. The rigid Sn-POSS cages are of interest due to their specific aggregation behaviour (observed above 5 wt%), and particularly due to their chemical reactivity, which counteracts oxidative degradation of the nanocomposites. This chemical effect of Sn-POSS is strong already at 0.01 wt%. At 0.5 wt%, the properties of the oxidized samples stay close to their initial state before the oxidation. On the other hand, at ‘high’ Sn-POSS loadings (5–25 wt%), oxidative crosslinking of Sn-POSS with matrix becomes excessive and the oxidized samples are brittle, while also specific heat-induced carbamate–Sn-POSS reactions deteriorate the properties of such oxidized nanocomposites.

On the influence of morphology and chemical defects on charge transport dynamics in polyethylene: thermal ageing and concentration gradient

A blend composed of a high-density polyethylene and a low-density polyethylene was subjected to thermo-oxidative ageing at 160 °C, under conditions where oxygen diffusion effects lead to a non-uniform distribution of chemical defects throughout the specimens. The existence of highly and lightly oxidised regions was demonstrated by Fourier transform infrared spectroscopy and confocal Raman microprobe spectroscopy and the effect of these on the dielectric behaviour of the system was investigated. Dielectric spectroscopy revealed a broad loss peak at frequencies above 1 Hz that increases in strength with increasing ageing time, which we associate with the motion of polar chain segments within the polymer. For ageing times below 3 h, samples exhibited reduced conductivity under a constant electric field compared with the initial unaged system; above 3 h, the conductivity was found to increase monotonically with ageing time and corresponded to the appearance of an additional low frequency (<1 Hz) dielectric loss process and marked migration of space charge into the bulk away from the relevant physical electrode. This change in behaviour was found to occur abruptly and the final distribution of space charge was found to correlate well with the distribution of ageing inducing chemical defects within the system. From these observations, the effects of chemical defects on charge transport dynamics are discussed.

Probing the dielectric relaxation processes and their correlation with ions transportation in the complexes of plasticized nanocomposite solid polymer electrolyte

Plasticized nanocomposite solid polymer electrolyte (PNSPE) film consisted of poly(ethylene oxide) and poly(methyl methacrylate) blend as host matrix, lithium perchlorate salt as ions dopant, ethylene carbonate as plasticizer, and montmorillonite clay nanoplatelets as inorganic nanofiller has been prepared by solution cast followed by the melt pressing. X-ray diffraction study of the PNSPE film confirms its amorphous structure with the existence of exfoliated nanoplatelets of the nanofiller. Dielectric and electrical dispersion of the film has been characterized systematically by employing the dielectric relaxation spectroscopy in the frequency range 2 × 101 to 1 × 106 Hz, at different temperatures. The relaxation times attributed to the various processes of structural dynamics of the PNSPE film have been probed by considering the individual spectrum of all the dielectric and electrical functions which are further validated by their master plot representation. The relaxation times corresponding to the dynamics of the electric double layers, electrode polarization, and interfacial polarization-affected polymer chain segments, cations coordinated polymers chain segments, and also the ionic conductivity in the ion–dipolar–nanofiller coordinated structures of the film have been determined. A generalized behaviour of these relaxation processes for probing the dynamical structures in all the solid polymer electrolytes has been demonstrated. It is further explored that these relaxation times of the PNSPE film exhibit a correlation with the dc ionic conductivity, and their temperature-dependent variation obeys the Arrhenius behaviour of nearly the same relaxation activation energies which are also found in good agreement with the conductivity activation energy.

Amine-Containing Block Copolymers for the Bottom-Up Preparation of Functional Porous Membranes

The remarkable ability of biological systems to specifically recognize, sort, and process molecules encourages the development of novel bio-inspired membranes and interfaces. Herein, we focus on the functionalization of amphiphilic polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) with the amino acid glycine yielding polar block segments with primary amine functionalities. Excellent control over the tailored block copolymer (BCP) synthesis and functionalization is proven by size exclusion chromatography (SEC), 1H solution NMR, and 15N solid state NMR spectroscopy. For the first time, BCPs containing primary amines were used for the self-assembly and non-solvent induced phase separation (SNIPS) process for the preparation of isoporous and integral asymmetric membranes. Hexagonally arranged open pores with diameters of 19 nm were obtained as shown by scanning electron microscopy (SEM), atomic force microscopy (AFM), and pH-dependent water flux measurements. Additionally, the primary amine was...

Diverse Role of Solvents in Controlling Supramolecular Chirality.

Supramolecular self-assembly stands for the spontaneous aggregation of small organic compounds or polymers into ordered structures at any scale. When being induced by inherent molecular chiral centers or ambient asymmetric factors, asymmetric spatial arrangement between building units shall occur, which is defined as supramolecular chirality. Except for molecular design, utilizing external stimulus factors to tune supramolecular chirality is a promising approach. In this Concept article, we particularly discuss the important role of solvents in manipulating the chirality of self-assembled systems. The impact of solvents on the chirality is generally based on three properties of solvents, i.e., chirality, polarity, and active coassembly with building blocks. Molecular self-assembly in chiral solvents could undergo the chirality transfer, exhibiting a chiral induction effect. Solvent polarity often determines intermolecular orientation. As a consequence, those building blocks with both polar and apolar segments might change their chirality depending on the solvent polarity. We elaborate the active participation of solvent molecules into ordered structures together with building blocks, where solvents and building blocks exhibit a coassembly manner. By specific treatments such as heating and cooling, solvents could be released or re-entrapped, allowing a smart control over supramolecular chirality. The solvent effect in manipulating two-dimensional chiral self-assemblies is then discussed. The perspective and future development in this research field are presented at last.

A submillimeter polarization analysis of Frosty Leo

We present a polarimetric investigation of the protoplanetary nebula Frosty Leo performed with the Submillimeter Array. We were able to detect, in the low continuum level (peak at 14.4 mJy beam$^{-1}$), a marginal polarization at $\sim2.6\sigma$. The molecular line investigation based on the CO $J=3\rightarrow2$ emission shows a peak emission of 68.1 Jy beam$^{-1}$ km s$^{-1}$ and the polarization detection in this CO line is also marginal, with a peak at $\sim3.8\sigma$. In both cases, it was therefore not possible to use the electric vector maps (B-field) to accurately trace the magnetic field (B-field) within the PPN. The spatio-kinematic modelling realised with the different velocity channel maps indicates three main structures: a distorted torus accompanied by a bipolar outflow or jet aligned with its axis and a flattened spherical "cap". The comparison of the CO polarization segments with our model suggests that the polarized emission probably arises in the first two components.

End-functional polyolefins for block copolymer synthesis.

Polyolefins that contain polar functionalities are highly desired because they could extend the range of applications of these low production cost materials by modifying surface and other interfacial properties. Block copolymers containing polyolefin and polar segments are among the most sought-after architectures because of their ability to span the phase boundaries. This review focusses on the end-functionalisation of polyolefins by catalytic olefin polymerisation processes, almost invariably by metal-catalysed routes, followed by the growth polar blocks by various polymerisation techniques.

High energy density and high efficiency all-organic polymers with enhanced dipolar polarization

The dielectric constant of polymers was increased by combining flexible segments and rigid polar segments in the polymer backbone.