Enhanced thermal conductivity and mechanical properties of polymeric composites through formation of covalent bonds between boron nitride and rubber chains

Hexagonal boron nitride (BN) platelets, also known as white graphite, are often used to improve the thermal conductivities of polymeric matrices. Due to the poor interfacial compatibility between BN platelets and polymeric matrices, in this study, polyrhodanine (PRd) was used to modify BN platelets and prepared functionalized BN-PRd platelets, thereby enhancing the interfacial interaction between the thermal conductive filler and polymeric matrix. Then, BN-PRd platelets were dispersed into the nitrile butadiene rubber (NBR) matrix to yield high thermally conductive composites. The presence of N? C═S groups in PRd allowed the combination of PRd and NBR chains containing stable covalent bonds via vulcanization reaction. The thermal conductivity of the as-prepared 30 vol% BN-PRd/NBR composite reached 0.40 W/mK, representing an increment of 135% over pure NBR (0.17 W/mK). In addition, the largest tensile strength of NBR composite containing 30 vol% BN-PRd platelets was 880% times of pure NBR. The 30 vol% BN-PRd/NBR composite also displayed a relatively high dielectric constant (9.35 at 100 Hz) and a low dielectric loss tangent value (0.07 at 100 Hz), indicating their usefulness as dielectric flexible materials of microelectronics. In sum, the simplicity and good efficiency of formation of covalent bonds between boron nitride and rubber chains look very promising for large-scale industrial production of high thermally conductive composites.     

Electrochemical sensor based on super-magnetic metal–organic framework@molecularly imprinted polymer for Sarcosine detection in urine

Accurate determination of Sarcosine (SAR) in urine with high sensitivity and selectivity is important, because it was recently recommended as a prospective biomarker for prostate cancer (PCa) and significant for the early identification of PCa. In this study, an electrochemical sensor based on Fe₃O₄ incorporated metal–organic frameworks (MOFs) @molecularly imprinted polymer (MIP) was constructed for SAR detection. Magnetic Fe₃O₄ nanoparticles embedded zeolitic imidazolate framework-8 (ZIF-8) was used as the support of MIP. MIP provides specific recognition sites for template molecules SAR and MOFs increase the rate of mass transfer and adsorption capacity due to the porous structure. The synthesized super-magnetic Fe₃O₄@ZIF-8@MIP was self-assembled onto an Au electrode in magnetic field and used as the sensing unit of electrochemical sensor. Cyclic voltammetry was used to monitor the electrochemical behavior, and the binding of SAR resulted in a reduction in the measured current. The results revealed a wide linear range from 1 to 100 pM towards trace SAR determination, with extremely low limit of detection down to 0.4 pM. In conclusion, the Fe₃O₄@ZIF-8@MIP based sensor provides a selective, sensitive, and convenient method for SAR diagnosis and other cancer marker detection.     

Selective extraction of catecholamines by packed fiber solid‐phase using composite nanofibers composing of polymeric crown ether with polystyrene

For the first time, electrospun composite nanofibers comprising polymeric crown ether with polystyrene (PCE‐PS) have been used for the selective extraction of catecholamines – dopamine (DA), norepinephrine (NE) and epinephrine (E) – prior to their analysis by high‐performance liquid chromatography–electrochemical detection. Using a minicartridge packed with PCE‐PS composite nanofibers, the target compounds were extracted effectively from urine samples to which diphenylborinic acid 2‐aminoethyl ester was added as a complexing reagent. The extracted catecholamines could be liberated from the fiber by the addition of acetic acid. A good linearity was observed for catecholamines in the range of 2.0–200 ng mL^?1 (NE, E and DA). The detection limits of catecholamines (signal‐to‐noise ratio = 3) were 0.5 ng mL^?1 (NE), 0.2 ng mL^?1 (E) and 0.2 ng mL^?1 (DA), respectively. Under the optimized conditions, the absolute recoveries of the above three catecholamines were 90.6% (NE), 88.5% (E) and 94.5% (DA). The repeatability of extraction performance was from 5.4 to 9.2% (expressed as relative standard deviation). Our results indicate that the proposed method could be used for the determination of NE, E and DA in urine. Copyright © 2014 John Wiley & Sons, Ltd.     

An Update on Molecularly Imprinted Polymer Design through a Computational Approach to Produce Molecular Recognition Material with Enhanced Analytical Performance

Molecularly imprinted polymer (MIP) computational design is expected to become a routine technique prior to synthesis to produce polymers with high affinity and selectivity towards target molecules. Furthermore, using these simulations reduces the cost of optimizing polymerization composition. There are several computational methods used in MIP fabrication and each requires a comprehensive study in order to select a process with results that are most similar to properties exhibited by polymers synthesized through laboratory experiments. Until now, no review has linked computational strategies with experimental results, which are needed to determine the method that is most appropriate for use in designing MIP with high molecular recognition. This review will present an update of the computational approaches started from 2016 until now on quantum mechanics, molecular mechanics and molecular dynamics that have been widely used. It will also discuss the linear correlation between computational results and the polymer performance tests through laboratory experiments to examine to what extent these methods can be relied upon to obtain polymers with high molecular recognition. Based on the literature search, density functional theory (DFT) with various hybrid functions and basis sets is most often used as a theoretical method to provide a shorter MIP manufacturing process as well as good analytical performance as recognition material.     

Surface Polymers on Multiwalled Carbon Nanotubes for Selective Extraction and Electrochemical Determination of Rhodamine B in Food Samples

In this study, we combine magnetic solid phase extraction (MSPE), with the screen-printed carbon electrode (SPCE) modified by a molecular imprinted polymer (MIP) for sensitive and selective extraction and electrochemical determination of Rhodamine B in food samples. A magnetic solid phase extraction (MSPE) was carried out using magnetic poly(styrene-co-divinylbenzene) (PS-DVB) and magnetic nanoparticles (MNPs) synthetized on the surface of multiwalled carbon nanotubes (MWCNTs). An MIP was prepared on the surface of MWCNTs in the presence of titanium oxide nanoparticles (TiO₂NPs) modifying the SPCE for the rapid electrochemical detection of Rhodamine B. The MIPs synthesis was optimized by varying the activated titanium oxide (TiO₂) and multiwalled carbon nanotubes (MWCNTs) amounts. The MSPE and electrochemical detection conditions were optimized as well. The present method exhibited good selectivity, high sensitivity, and good reproducibility towards the determination of Rhodamine B, making it a suitable method for the determination of Rhodamine B in food samples.     

Molecularly engineering polymeric membranes for H2/CO2 separation at 100–300 °C

Over the last two decades, polymers with superior H₂/CO₂ separation properties at 100–300 °C have gathered significant interest for H₂ purification and CO₂ capture. This timely review presents various strategies adopted to molecularly engineer polymers for this application. We first elucidate the Robeson's upper bound at elevated temperatures for H₂/CO₂ separation and the advantages of high-temperature operation (such as improved solubility selectivity and absence of CO₂ plasticization), compared with conventional membrane gas separations at ~35 °C. Second, we describe commercially relevant membranes for the separation and highlight materials with free volumes tuned to discriminate H₂ and CO₂, including functional polymers (such as polybenzimidazole) and engineered polymers by cross-linking, blending, thermal treatment, thermal rearrangement, and carbonization. Third, we succinctly discuss mixed matrix materials containing size-sieving or H₂-sorptive nanofillers with attractive H₂/CO₂ separation properties.     

Tailoring a Dress to Single Protein Molecules: Proteins Can Do It Themselves through Localized Photo-Polymerization and Molecular Imprinting

Molecularly imprinted polymer nanoparticles (MIP NPs) are antibody-like recognition materials prepared by a template-assisted synthesis. MIP NPs able to target biomolecules, like proteins, are under the spotlight for their great potential in medicine, but efficiently imprinting biological templates is still very challenging. Here we propose generating a molecular imprint in single NPs, by photochemically initiating the polymerization from individual protein templates. In this way, each protein molecule tailors itself its own “polymeric dress”. For this, the template protein is covalently coupled with a photoinitiator, Eosin Y. Irradiated with light at 533 nm, the Eosin moiety acts as an antenna and transfers energy to a co-initiator (an amine), which generates a radical and initiates polymerization. As a result, a polymer network is forming only around the very template molecule, producing cross-linked NPs of 50 nm, with single binding sites showing high affinity (K_D 10⁻⁹ m ) for their biological target, and selectivity over other proteins.     

Polymer Scaffolds for Biomedical Applications in Peripheral Nerve Reconstruction

The nervous system is a significant part of the human body, and peripheral nerve injury caused by trauma can cause various functional disorders. When the broken end defect is large and cannot be repaired by direct suture, small gap sutures of nerve conduits can effectively replace nerve transplantation and avoid the side effect of donor area disorders. There are many choices for nerve conduits, and natural materials and synthetic polymers have their advantages. Among them, the nerve scaffold should meet the requirements of good degradability, biocompatibility, promoting axon growth, supporting axon expansion and regeneration, and higher cell adhesion. Polymer biological scaffolds can change some shortcomings of raw materials by using electrospinning filling technology and surface modification technology to make them more suitable for nerve regeneration. Therefore, polymer scaffolds have a substantial prospect in the field of biomedicine in future. This paper reviews the application of nerve conduits in the field of repairing peripheral nerve injury, and we discuss the latest progress of materials and fabrication techniques of these polymer scaffolds.     

Temperature and pH dual‐sensitive polyaspartamide derivatives for antitumor drug delivery

The pH‐sensitive tertiary amino groups were introduced to synthesize temperature and pH dual‐sensitive degradable polyaspartamide derivatives (phe/DEAE‐g‐PHPA) containing pendant aromatic structures and ionizable tertiary amino groups. The thermo/pH‐responsive behavior of phe/DEAE‐g‐PHPA polymer can be tuned by adjusting the graft copolymer composition. Due to the pH sensitivity of the phe/DEAE‐g‐PHPA‐g‐mPEG polymer with hydrophilic long PEG chain, the micelles and the anticancer drug‐loaded micelles were prepared by a quick pH‐changing method without using toxic organic solvent. The obtained polymeric micelles, paclitaxel‐loaded micelles and doxorubicin‐loaded micelles were stable under physiological conditions. Both the drug‐loaded micelles showed much faster release at pH 5 than at pH 7.4. The doxorubicin‐loaded micelles showed obvious and better anticancer activity against both HepG2 and HeLa cells than free doxorubicin. Thus these nontoxic, dual thermo‐ and pH‐sensitive phe/DEAE‐g‐PHPA‐g‐mPEG micelles may be a promising anticancer drug delivery system. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 879–888