Reversible crosslinking during thermal degradation of PVC

Summary PVC undergoes rapid crosslinking during thermal degradation. Diels-Alder addition of conjugated polyenes was proposed as a possible crosslinking mechanism by earlier authors. By the use of conditions favoring retro Diels-Alder reaction of crosslinks (treatment with maleic anhydride at elevated temperature) it was proved that crosslinks are largely reversible. Evidently Diels-Alder addition of the conjugated polyenes plays an important role in crosslinking during thermal degradation of PVC.     

Lewis acid initiated melt reactions of polystyrene and EPDM rubber

Summary In order to obtain high impact polystyrene (PS), experiments have been performed on coupling of EPDM rubber and PS in the mixing chamber of a HAAKE plastograph. Lewis acids were added to the melt and the torque increase observed by their addition proved that chemical reactions take place in the system. During the reaction, the rubber proved to be more active, it became crosslinked and/or it was coupled with the PS molecules. Only a small fraction of the PS present coupled to the rubber molecules. No significant degradation process could be detected. Mechanical properties (tensile modulus and strength) improved during the reaction. This can be interpreted by the increased solubility of the coupled rubber molecules in the continuous PS phase.     

Mass Spectral Filtering by Mass-Remainder Analysis (MARA) at High Resolution and Its Application to Metabolite Profiling of Flavonoids

Flavonoids represent an important class of secondary metabolites because of their potential health benefits and functions in plants. We propose a novel method for the comprehensive flavonoid filtering and screening based on direct infusion mass spectrometry (DIMS) analysis. The recently invented data mining procedure, the multi-step mass-remainder analysis (M-MARA) technique is applied for the effective mass spectral filtering of the peak rich spectra of natural herb extracts. In addition, our flavonoid-filtering algorithm facilitates the determination of the elemental composition. M-MARA flavonoid-filtering uses simple mathematical and logical operations and thus, it can easily be implemented in a regular spreadsheet software. A huge benefit of our method is the high speed and the low demand for computing power and memory that enables the real time application even for tandem mass spectrometric analysis. Our novel method was applied for the electrospray ionization (ESI) DIMS spectra of various herb extract, and the filtered mass spectral data were subjected to chemometrics analysis using principal component analysis (PCA).     

Enzalutamide Enhances PSMA Expression of PSMA-Low Prostate Cancer

Prostate-specific membrane antigen (PSMA)-directed radioligand therapy (RLT) prolongs overall survival in men with metastatic castration-resistant prostate cancer (mCRPC). However, men with low PSMA expression are excluded from RLT. We explored the effect of androgen receptor blockade with enzalutamide on PSMA expression. Assessment of PSMA and androgen receptor (AR) expression on the human PC cell lines 22Rv1, C4-2, and LNCaP by immunohistochemistry and flow cytometry revealed low (22Rv1) and high (C4-2 and LNCaP) PSMA expression, and high, comparable AR positivity. Treatment with enzalutamide increased PSMA levels in 22Rv1, C4-2, and LNCaP (2.2/2.3/2.6-fold, p = 0.0005/0.03/0.046) after one week compared to DMSO-treated controls as assessed by flow cytometry. NOD/Scid mice bearing 22Rv1 tumors were treated with enzalutamide for two weeks. Positron emission tomography/computed tomography (PET/CT) demonstrated higher tumor uptake of ⁶⁸Ga-PSMA after enzalutamide treatment (p = 0.004). Similarly, a clinical case with low baseline PSMA avidity demonstrated increased uptake of ⁶⁸Ga-PSMA after enzalutamide on PET/CT and post-therapeutic ¹⁷⁷Lu-PSMA scintigraphy in a patient with mCRPC. Enzalutamide induced PSMA expression in the 22Rv1 xenograft model and in an mCRPC patient, both with low baseline tumoral PSMA levels. Therefore, enzalutamide pre-treatment might render patients with low PSMA expression eligible for ¹⁷⁷Lu-PSMA RLT.     

N-甲基甘氨酸及类乙二胺二乙酸型配体钴(Ⅲ)配合物的合成与表征

合成了N-甲基甘氨酸及相应四齿配体[乙二胺二乙酸(edda)、乙二胺二丙酸(eddp)、1,3-丙二胺二乙酸(pdda)]钴(Ⅲ)配合物的几种经式几何异构体,其中edda和eddp钴(Ⅲ)配合物的合成是通过相应的N-甲基甘氨酸与edda碳酸合钴(Ⅲ)酸钠及反对称-顺式-pdda碳酸合钴(Ⅲ)酸钠二水合物来制备的.而pdda-Co(Ⅲ)配合物采用一种新方法直接合成(CoCl2*H2O在有PbO2存在下直接与pdda反应).诸配合物通过层析色谱柱分离,并用元素分析、电子光谱、红外和1H核磁共振所表征.     

Biodegradable zinc-based materials with a polymer coating designed for biomedical applications

Over the last decades, biodegradable metals have gained popularity for biomedical applications due to their ability to assist in tissue healing. These materials degrade in vivo, while the corrosion products formed are either absorbed or excreted by the body, and no further surgical intervention is required for removal. Intensive research has been carried out mainly on degradable biomaterials based on Mg and Fe. In recent years, zinc-based degradable biomaterials have been explored by the biomedical community for their intrinsic physiological relevance, desirable biocompatibility, intermediate degradation rate, tuneable mechanical properties and pro-regeneration properties. Since pure Zn does not exhibit sufficient mechanical properties for orthopedic applications, various Zn alloys with better properties are being developed. In this work, the combined effect of minor Fe addition to Zn and a polyethyleneglycol (PEG) coating on the surface morphology, degradation, cytotoxicity and mechanical properties of Zn-based materials was studied. There are several studies regarding the influence of the production of Zn alloys, but the effect of polymer coating on the properties of Zn-based materials has not been reported yet. A positive effect of Fe addition and polymer coating on the degradation rate and mechanical properties was observed. However, a reduction in biocompatibility was also detected.     

Multidimensional high‐temperature liquid chromatography: A new technique to characterize the chemical heterogeneity of Ziegler‐Natta‐based bimodal HDPE

High temperature two‐dimensional liquid chromatography (HT 2D‐LC) was recently introduced as a new technique to analyze the heterogeneities with regard to composition and molar mass present in model blends of polyolefins and various olefin copolymers. The method uses graphite as stationary phase and solvent gradients of 1‐decanol → 1,2,4‐trichlorobenzene as mobile phase for the compositional separation. With the aim to maximize the chromatographic resolution, the influence of the separation's temperature in the first dimension was evaluated: approaching the θ‐temperature of polyethylene (PE) in 1‐decanol selectively enhances the retention of higher molar mass PE standards while that of the lower molar mass ones is hardly affected. A bimodal ethylene/1‐butene copolymer and its temperature rising elution fraction (TREF) fractions were separated by HT 2D‐LC. For the first time, both axes of the contour plot were calibrated with regard to chemical composition and molar mass, respectively. Prefractionation of the bulk sample by TREF enhances the detectability of separated components of the 2D separation. The influence of the separation temperature, that is, working around the θ‐temperature of PE in 1‐decanol, can be used to enhance the chromatographic resolution of the 2D chromatography. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Livig carbocationic polymerization

Summary Diblock copolymers of isobytylene (IB) — methyl vinyl ether (MeVE) have been prepared by sequential monomer addition by employing 2-chloro-2, 4, 4-trimethylpentane (TMPCl)/TiCl₄ initiating system in the presence of nBu₄NCl or dimethyl-acetamide (DMA) in CH₂Cl₂/hexanes at –80°C. In line with our earlier observations (1), living carbocationic polymerizations (LCPZn) were obtained in the presence of nBu₄NCl (i.e., the molecular weight of the poly(vinyl methyl ether) segment increased upon TiCl₄ addition), however, extensive chain transfer occurred in the presence of DMA. According to column chromatography analysis, the product prepared in the presence of nBu₄NCl is essentially pure PIB-b-PMeVE diblock (96w%) contaminated with a very small amount (4w%) of PIB. In contrast, the product obtained with DMA contains only 21w% PIB-b-PMeVe together with 72w% PIB and 5w% PMeVe homopolymers. This large difference in blocking efficiencies suggests that the structures of the growing species are different in the presence of the common anion salt,nBu₄NCl, and the electron donor, DMA.For paper LIII in this series see Polym. Bull., vol. 29/1