The influence of partial emulsification on coalescence suppression and interfacial tension reduction in PP/PET blends

This study examines how the relative role of coalescence suppression and interfacial tension reduction influence the particle size at various levels of in situ compatibilization. The polymers studied are polyethylene terephthalate (PET) as matrix and a polypropylene (PP) as dispersed phase compatibilized by a triblock copolymer of poly(styrene–hydrogenated butadiene–styrene) (SEBS) grafted with maleic anhydride. The interfacial tension was studied by the breaking‐thread method, and it was used along with the morphology to characterize the emulsification efficacy of the copolymers. By modifying the concentration of MA grafted on the SEBS, different levels of emulsification of the blends were obtained. A comparison of 1/99 and 10/90 PP/PET blends compatibilized by SEBS‐g‐MA allows one to distinguish the relative role of interfacial tension and coalescence suppression in diminishing particle size. It is shown that varying degrees of residual coalescence remain, depending on the level of %MA in the copolymer. A detailed study of the 2%MA system below interfacial saturation was carried out to shed further light on the dependence of coalescence suppression on emulsification level and interfacial coverage. After separating out the contribution of interfacial tension on particle size reduction, it is shown that coalescence suppression for this system increases gradually with areal density of modifier at the interface right up to the region of interfacial saturation. Finally, the interfacial and morphological data were used to test the ability of the Lee and Park model to describe coalescence in polymer blends. Reasonable agreement was found between the parameter c₁, describing the coalescence in that model, and the trends related to residual coalescence from this study. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 939–951, 1999     

Making Solid‐Phase Peptide Synthesis Greener: A Review of the Literature

To date, the synthesis of peptides is concurrent with the production of enormous amounts of toxic waste. DMF, CH₂Cl₂, and NMP are three of the most toxic organic solvents used in chemical synthesis and are the most common solvents used for peptide synthesis. Additionally, concerns about the hepatotoxicity caused by exposure to DMF and from the toxic and allergenic nature of additives used in peptide synthesis necessitates the need for a green, environmentally friendly, and safer protocol for peptide synthesis. This review summarizes the current literature on green solid‐phase peptide synthesis successes and challenges encountered. The review concludes with suggestions for future research towards a simple and efficient green peptide synthesis protocol.     

In-vitro degradation behavior and biological properties of a novel maleated poly (D,L-lactide-co-glycolide) for biomedical applications

Synthesized biodegradable polymers with controlled degradability and good biological safety would be useful in biomedical applications. In this work a novel maleated poly(D,L-lactide-co-glycolide) (MPLGA) was melt copolymerized from maleic anhydride, D,L-lactide and glycolide monomers. The degradation behavior in phosphate-buffered solution (PBS) was investigated and the biological properties were studied by using fibroblastic cells cultured in an extract of MPLGA and by an in-vitro cell cytotoxicity test. The results indicated that the MPLGA was successfully obtained using the melt-copolymerization method. The maleic anhydride groups in the MPLGA led to a faster degradation in PBS than PLGA. Fibroblastic cells showed normal morphologies in MPLGA extracts, and the MPLGA materials showed no cell cytotoxicity. The in-vitro biological properties indicated that the obtained MPLGA had good biocompatibility and would be useful for medical applications.     

Fe(acac)3-Al(i-Bu)3-CCl4催化马来酸酐与降冰片烯共聚

 研究了Fe(acac)3-Al(i-Bu)3-CCl4(acac=乙酰丙酮)催化体系对马来酸酐(MA)与降冰片烯(NBE)交替聚合反应的催化性能. 用元素分析、核磁共振和红外光谱研究了共聚物的结构,在单体比为1∶1时,共聚物中MA和NBE的含量分别为52.2%和47.8%. 凝胶渗透色谱结果表明共聚物分子量分布窄. 动力学研究结果表明, MA与NBE共聚对单体浓度呈一级反应,其表观活化能为74.3 kJ/mol.     

苯乙烯/马来酸酐和苯乙烯/甲基丙烯酸二甲氨基乙酯二元体系在聚四氟乙烯多孔膜上的γ辐射接枝

在氮气的氛围下用γ辐照的方法在聚四氟乙烯多孔膜上接枝苯乙烯 马来酸酐、苯乙烯 甲基丙烯酸二甲氨基乙酯二元单体 .并且研究了剂量、剂量率、溶液中单体的浓度和二元单体的摩尔比等条件对接枝率的影响 .探讨了两种单体的竞聚率对接枝率、接枝膜的组成及性能的影响 .结果表明 ,苯乙烯 马来酸酐二元体系对接枝率有协同效应 ,苯乙烯 甲基丙烯酸二甲氨基乙脂二元体系对接枝率表现为加合效应 .制备的二元接枝的聚四氟乙烯多孔膜可以进一步磺化来制备用于质子交换膜燃料电池的质子交换膜 .     

Propylphosphonic anhydride (T3P): an efficient reagent for the one-pot synthesis of 1,2,4-oxadiazoles, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles

Propylphosphonic anhydride (T3P^®) has been demonstrated to be an efficient and mild reagent for the one-pot synthesis of 1,2,4-oxadiazoles, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles from carboxylic acids.     

Evaluation of the Efficiency of the Macrolactonization Using MNBA in the Synthesis of Erythromycin A Aglycon

Various intermediates for the synthesis of erythronolide A, an aglycon of erythromycin A, are prepared from the corresponding seco‐acids using 2‐methyl‐6‐nitrobenzoic anhydride (MNBA) in the presence of 4‐(dimethylamino)pyridine (DMAP) with or without triethylamine. The efficiency of the MNBA lactonization is assessed by studying this method and comparing the results with those of the other established macrocyclization protocols. It has been finally concluded that (i) the conformationally appropriate substrate for the monomeric cyclization gave the desired lactone in excellent yield under mild reaction conditions in the presence of MNBA and DMAP, (ii) the highly‐strained substrate for the cyclization also afforded the monomeric lactone in relatively good yield at 100°C in toluene, and (iii) the seco‐acid having stable linear conformation, which preferred dimerizing more than forming the monomeric lactone, provided the corresponding diolide in high yield with the constant ratio of the monomer to dimeric lactone (approximately 1/5). © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 305–320; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.200900017     

氟喹酮的合成工艺改进

以靛红酸酐为起始原料,经硝化、还原上保护、氨解开环、环合、卤素交换和脱保护共七步反应合成了氟喹酮（7）,其结构经 ¹H NMR,¹³C NMR和ESI-MS确证。研究了硝化试剂、溶剂、催化剂等对7收率的影响,结果表明：在使用浓硝酸作为硝化试剂,甲苯,乙腈等为溶剂,Raney-Ni, TBAB等为催化剂时,总收率可达58%,纯度达99%以上。     

(5-氨基-[1,3,4]噻二唑-2-基)-丙酸乙酯的合成工艺改进

以丁二酸酐为起始原料,经醇解和酰化反应制得丁二酸单乙酯酰氯(3);3经甲烷磺酸催化与氨基硫脲环合合成了重要药物中间体——(5-氨基-[1,3,4]噻二唑-2-基)-丙酸乙酯,其结构经~1H NMR,IR和MS确证。运用正交试验对环合反应条件进行优化。最优反应条件为:3 132 mmol,n(氨基硫脲)∶n(3)∶n(甲烷磺酸)=1∶3∶3,于110℃反应3 h,总收率51.3%。     

Synthesis of Novel Isoindolo[2,1‐a]quinazolinedione Derivatives Containing a 1,2,3‐Triazole Ring System

A synthesis of isoindolo[2,1‐a]quinazolinedione derivatives, coupled with a 1,2,3‐triazole ring system, via the reaction of isatoic anhydride, HC?CCH₂NH₂, and 2‐formylbenzoic acid is described, which led to the formation of the isoindolo[2,1‐a]quinazoline‐5,11‐dione scaffold having a C?C bond that participated in a click reaction with various organic azides.