采用反应挤出三次加料法合成苯乙烯/异戊二烯/苯乙烯

以同向啮合双螺杆挤出机为反应器,采用苯乙烯和异戊二烯为聚合单体,以正丁基锂为引发剂,采用三次加料法合成苯乙烯/异戊二烯/苯乙烯(SIS)三嵌段热塑性弹性体.氢核磁共振(1H NMR)谱分析结果表明,共聚物中聚异戊二烯嵌段以1,4-结构为主.采用四氧化锇催化双氧水氧化降解聚合物分子链,利用凝胶渗透色谱对氧化降解后的聚苯乙烯碎片进行分析,证明共聚物分子为(聚苯乙烯-聚异戊二烯-聚苯乙烯)(PS-PI-PS)三嵌段结构.动态力学分析(DMA)及透射电子显微镜(TEM)分析结果表明,SIS具有两相分离结构.拉伸试验结果表明,共聚物拉伸强度与苯乙烯含量有关.     

Formation of the Interphase of a Cured Epoxy Resin Near a Metal Surface: Reactive Coarse-Grained Molecular Dynamics Simulations

Mesoscale molecular dynamics simulations are performed to analyze the curing process of an epoxy resin with polyfunctional amines on a generic surface. The coarse grained potentials were derived from all-atomistic molecular dynamics simulations using iterative Boltzmann inversion. The reactive scheme incorporates cross-linking between an epoxy resin and an amine, as well as amine adsorption on the surface. The structure of the cured network is examined and compared with equilibrium properties of the uncured system. Special attention has been paid on the implications of the surface that is believed to play a crucial role in the performance of epoxy systems.     

Phenylethynyl-terminated Imide Oligomers Modified by Reactive Diluent for Resin Transfer Molding Application

To meet the processing requirements of resin transfer moulding(RTM)technology,reactive diluent containing m-phenylene moiety was synthesized to physically mixed with phenylethynyl terminated cooligoimides with well-designed molecular weights of 1500-2500 g/mol derived from 4,4’-(hexafluoroisopropylidene)diphthalic anhydride(6 FDA),3,4’-oxydianiline(3,4’-ODA)and m-phenylenediamine(m-PDA).This blend shows low minimum melting viscosity(<1 Pa·s)and enlarged processing temperature window(260–361℃).FPI-R-1 stays below 1 Pa·s for2 h at 270℃.The relationship between the molecular weight of the blend and its melting stability was first explored.Blending oligoimides with lower molecular weights exhibit better melting stability.Upon curing at 380℃for 2 h,the thermosetting polyimide resin demonstrates superior heat resistance(T_g=420-426℃).     

Electro catalytic generation of reactive species at diamond electrodes and applications in microbial inactivation

Use of robust and safe water disinfection technologies which are inexpensive and energy-efficient are need of the hour to combat the problem of inadequate access of safe and clean drinking water. Energy and chemically intensive water treatment technologies warrant the need for a safe and environmentally sound treatment technology. Electrochemical disinfection or electrodisinfection (ED) is experiencing a great resurgence among the scientific communities owing to its novel use of electrode materials and electric current in an inexpensive and energy-efficient way for achieving the inactivation of microorganisms. Among the various electrodes used in the ED, boron-doped diamonds emerge as a sustainable alternate for their ability to electro generate strong potent oxidants which result in effective pathogen control in drinking water. ED for disinfecting waters occurs via generation of the reactive species which act in the bacterial inactivation mechanisms. In this mini-review, a critical discussion on the fundamentals and applications of promising electrochemical methods using boron-doped diamond anodes (namely electrochemical oxidation), evidencing their advantages for the remediation of drinking water infected with waterborne agents, is given.     

Synthesis and characterization of amino-terminated phosphorous polyborosiloxane and its effect on flame retardancy of polymethacrylimide

In this study, a novel flame retardant, that is, amino-terminated phosphorous polyborosiloxane (N-PBSi), was synthesized via a two-step polymerization reaction. The product's chemical structure was characterized firstly by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. It was proved that the prepared N-PBSi was indeed amino terminated and contained multiple flame-retardant elements including P, B, and Si. Besides, based on the variation of its FTIR spectra from room temperature to 700 °C and the subsequent thermogravimetric results, there also showed that the resultant N-PBSi had desirable thermal stability. This is a prerequisite for preparing flame-retardant polymethacrylimide (PMI) as PMI synthesis requires a high temperature treatment process up to 160 °C. On this basis, the condition for N-PBSi synthesis was then optimized to obtain flame retardants with better quality and higher yield. According to the experiments, the reactant ratio and reaction time were recommended to be 1:1.33:3 and 6 h, respectively. To evaluate the effectiveness of N-PBSi further, the flame retardancy of PMI with N-PBSi grafted was then investigated. The UL-94 rating and limiting oxygen index value of the PMI with 15 wt.% of N-PBSi incorporated were tested to be V-0 and 27%, respectively, indicative of greatly enhanced flame-retardant properties. In addition, the flame-retardant mechanism of N-PBSi on PMI was also discussed. Given all of these, the prepared N-PBSi as a reactive and effective flame retardant was promising for PMI.     

Adding Value in Production of Multifunctional Polylactide (PLA)–ZnO Nanocomposite Films through Alternative Manufacturing Methods

Due to the added value conferred by zinc oxide (ZnO) nanofiller, e.g., UV protection, antibacterial action, gas-barrier properties, poly(lactic acid) (PLA)–ZnO nanocomposites show increased interest for utilization as films, textile fibers, and injection molding items. The study highlights the beneficial effects of premixing ZnO in PLA under given conditions and its use as masterbatch (MB), a very promising alternative manufacturing technique. This approach allows reducing the residence time at high processing temperature of the thermo-sensitive PLA matrix in contact of ZnO nanoparticles known for their aptitude to promote degradation effects onto the polyester chains. Various PLA–ZnO MBs containing high contents of silane-treated ZnO nanoparticles (up to 40 wt.% nanofiller specifically treated with triethoxycaprylylsilane) were produced by melt-compounding using twin-screw extruders. Subsequently, the selected MBs were melt blended with pristine PLA to produce nanocomposite films containing 1–3 wt.% ZnO. By comparison to the more traditional multi-step process, the MB approach allowed the production of nanocomposites (films) having improved processing and enhanced properties: PLA chains displaying higher molecular weights, improved thermal stability, fine nanofiller distribution, and thermo-mechanical characteristic features, while the UV protection was confirmed by UV-vis spectroscopy measurements. The MB alternative is viewed as a promising flexible technique able to open new perspectives to produce more competitive multifunctional PLA–ZnO nanocomposites.     

How to Obtain the Maximum Properties Flexibility of 3D Printed Ketoprofen Tablets Using Only One Drug-Loaded Filament?

The flexibility of dose and dosage forms makes 3D printing a very interesting tool for personalized medicine, with fused deposition modeling being the most promising and intensively developed method. In our research, we analyzed how various types of disintegrants and drug loading in poly(vinyl alcohol)-based filaments affect their mechanical properties and printability. We also assessed the effect of drug dosage and tablet spatial structure on the dissolution profiles. Given that the development of a method that allows the production of dosage forms with different properties from a single drug-loaded filament is desirable, we developed a method of printing ketoprofen tablets with different dose and dissolution profiles from a single feedstock filament. We optimized the filament preparation by hot-melt extrusion and characterized them. Then, we printed single, bi-, and tri-layer tablets varying with dose, infill density, internal structure, and composition. We analyzed the reproducibility of a spatial structure, phase, and degree of molecular order of ketoprofen in the tablets, and the dissolution profiles. We have printed tablets with immediate- and sustained-release characteristics using one drug-loaded filament, which demonstrates that a single filament can serve as a versatile source for the manufacturing of tablets exhibiting various release characteristics.     

低功率超声增强碘帕醇氯氧化的效果和路径

研究了低功率超声(US, <38 W)对NaClO氧化非离子型碘代X射线造影剂—碘帕醇(IPM)的增强作用及机理, 考察了NaClO添加浓度和超声功率的影响, 分析并计算了体系中的主要活性物种及其贡献. 采用高效液相色谱/串联质谱(HPLC/MS/MS)对降解产物进行分析, 推测IPM的降解路径. 结果表明, 低功率US显著增强了NaClO对IPM的氧化效果, 在25 ℃, pH=5.8, NaClO浓度为0.12 mmol/L条件下, 10 mg/L IPM在60 min的降解率达到85.8%. 其中NaClO氧化、 HO·和活性氯自由基(RCSs)是US/NaClO增强IPM降解的主要原因, 自由基分析计算它们的贡献率分别为15.82%, 4.65%和79.53%. NaClO浓度在0~0.24 mmol/L范围内, IPM的降解率随NaClO浓度升高而增加, 60 min后降解率由4.75%增加到91.12%; 超声功率为28.5 W, 降解率达到最高. 在 15~45 ℃温度范围内, IPM的降解过程符合表观一级反应动力学, 反应活化能(E_a)为59.03 kJ/mol. HPLC/MS/MS共检测出5种中间产物, 结合密度泛函理论(DFT)计算结果, 初步推测了IPM在US/NaClO体系中的降解途径和机理.     

Reactive TiO2 Nanoparticles Compatibilized PLLA/PBSU Blends:Fully Biodegradable Polymer Composites with Improved Physical,Antibacterial and Degradable Properties

The fully biodegradable polymer blends remain challenges for the application due to their undesirable comprehensive performance.Herein,remarkable combination of superior mechanical performance,bacterial resistance,and controllable degradability is realized in the biodegradable poly(L-lactide)/poly(butylene succinate) (PLLA/PBSU) blends by stabilizing the epoxide group modified titanium dioxide nanoparticles (m-TiO2) at the PLLA-PBSU interface through reactive blending.The m-TiO2 can not only act as interfacial compatibilizer but also play the role of photodegradation catalyst:on the one hand,binary grafted nanoparticles were in situ formed and stabilized at the interface to enhance the compatibility between polymer phases.As a consequence,the mechanical properties of the blend,such as the elongation at break,notched impact strength and tensile yield strength,were simultaneously improved.On the other hand,antibacterial and photocatalytic degradation performance of the composite films was synergistically improved,it was found that the m-TiO2 incorporated PLLA/PBSU films exhibit more effective antibacterial activity than the neat PLLA/PBSU films.Moreover,the analysis of photodegradable properties revealed that that m-TiO2 nanoparticles could act as a photocatalyst to accelerate the photodegradation rate of polymers.This study paves a new strategy to fabricate advanced PLLA/PBSU blend materials with excellent mechanical performance,antibacterial and photocatalytic degradation performance,which enables the potential utilization of fully degradable polymers.