Synthesis and characterization of biodegradable block copolymers of poly(propylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) and poly(ethylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol)

The synthesis of two low molecular weight linear unsaturated oligoester precursors, poly(propylene fumarate‐co‐sebacate) (PPFS) and poly(ethylene fumarate‐co‐sebacate) (PEFS), are described. PPFS, PEFS, and poly(ethylene glycol) are then used to prepare poly(propylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) (PPFS‐co‐PEG) and poly(ethylene fumarate‐co‐sebacate)‐co‐poly(ethylene glycol) (PEFS‐co‐PEG) block copolymers. The products thus obtained are investigated in terms of the molecular weight, composition, structure, thermal properties, and solubility behavior. A number of design parameters including the molecular weights of PPFS, PEFS, and PEG, the reaction time in the polymer synthesis, and the weight ratio of PEG to PPFS or to PEFS are varied to assess their effects on the product yield and properties. The hydrolytic degradation of PPFS‐co‐PEG and PEFS‐co‐PEG in an isotonic buffer (pH 7.4, 37°C) is investigated, and it is found that the fumarate ester bond cleaves faster than does the sebacate ester bond. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 295–300, 2004     

Preparation of bimodal polypropylene in two‐step polymerization

Polymerization of propylene was carried out by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system in n‐heptane, where MgCl₂, EtOH, TiCl₄, DIBP (diisobutyl phthalate), TEA (triethyl aluminum), and cHMDMS (cyclohexyl methyl dimethoxy silane) were support, ethanol for alcoholation, catalyst, external donor, cocatalyst (activator), and internal donor, respectively. The catalyst activity and polymer isotacticity were studied by measuring the produced polymer and its solubility in boiling n‐heptane, respectively. The molecular weight and molecular weight distribution of the polymers were evaluated by gel permeation chromatography. Hydrogen was used for controlling the molecular weight. For producing the bimodal polypropylene, the polymerization was carried out in two steps (i.e., in the presence and absence of hydrogen). It was found that the catalyst showed high activity and stereoselectivity, on the other hand, bimodal polymer could simply be produced in two‐step polymerization by using MgCl₂.EtOH.TiCl₄.DIBP.TEA.cHMDMS catalyst system. Meanwhile, the effect of the step of the hydrogen adding on propylene polymerization was investigated. It was shown that the addition of hydrogen in the second step was more suitable. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1456–1462, 2006     

高压下无规聚甲基丙烯酸甲酯的玻璃化转变

采用PVT～100分析仪测试了无规聚甲基丙烯酸甲酯(a-PMMA)在30～180℃，20～180MPa下的压力-体积-温度(PVT)曲线。与常压下玻璃化转变是某一点不同，高压下a-PMMA的玻璃化出现一个反常的转变区，并且随着压力增加，该转变区逐渐加宽。PVT实验后，a-PMMA的数均和重均摩尔质量均明显下降；由DSC测试的Tg和TGA测定的Td也明显降低，说明这一测试的复杂温度和压力历史对样品的结构有显著影响。     

等温挤压的实现方式与控制算法

提出了一种使挤压液压机实行等温挤压的双闭环串级控制方案和控制算法，讨论了串级策略的设计要点，给出了仿真实例     

甲基化处理气相色谱-质谱法同时检测大米中12种酸性除草剂

实验采用丙酮酸性水溶液(150∶20,体积比)提取试样中农药残留物,提取液用乙酸乙酯液液分配、凝胶渗透色谱仪(GPC)净化后,用重氮甲烷乙醚溶液衍生化,用气相色谱-质谱(GC/MS)选择离子监测模式(SIM)内标法(IS)测定,分离色谱柱为DB-5MS。10种农药的回收率≥80%;相对标准偏差≤10%;最低检测限0.01~0.05 mg/kg。     

Molecular mass characteristics of polyethylene produced with supported vanadium‐magnesium catalysts

Highly active supported vanadium‐magnesium catalysts (VMC) produce polyethylene (PE) with broad and bimodal molecular mass distribution (MMD) in comparison with the famous titanium‐magnesium catalysts (TMC). The effect of hydrogen as an efficient chain‐transfer agent on the MMD of PE has been studied. Increasing hydrogen concentration causes a considerable broadening of MMD of PE due to the shift of the low molecular weight peak on the MMD curve. At the same time, the high molecular weight shoulder stays at the same position even at high hydrogen concentration. This means that VMC contain two types of active centre. One type is very reactive in the chain‐transfer reaction with hydrogen. These centres produce low molecular weight PE in polymerization in the presence of hydrogen. The other type of active centre is not active in chain transfer with hydrogen. These centres produce high molecular weight PE ((1–3) × 10⁶) and hydrogen does not affect the position of the high molecular weight shoulder. MMD data were used to analyze the kinetics of the chain‐transfer reaction with hydrogen and to calculate the rate constants of this reaction. Copyright © 2005 Society of Chemical Industry     

Synthesis,Characterization, and Antimicrobial Properties of p-Chloroacetophenone Oxime-Based Furan Resins

A copolymer resin, p-chloroacetophenone oxime-furfuraldehyde (CAOFU), and a terpolymer resin, p-chloroacetophenone oxime-formaldehyde-benzoic acid (CAOFUBA), were synthesized in the presence of hydrochloric acid as catalyst. The structures of copolymer and terpolymer were established by FT-IR and ¹H NMR techniques. Molecular weight and polydispersity index were determined by gel permeation chromatography. The thermal stability was evaluated by thermogravimetric analyses (TGA). Softening temperatures (T_s) of these polymers were obtained from differential scanning calorimetry (DSC). All the synthesized polymers have shown reasonably good antimicrobial activities.     

Cyclic poly(dimethylsiloxane) from kinetically controlled cyclodepolymerization of linear precursors in dilute solution

Cyclic poly(dimethylsiloxane) (PDMS), [(CH₃)₂SiO]_x or D_x, was prepared in high yield (>70% for x > 12) from commercially available linear α,ω-dihydroxy-PDMS by base-catalyzed unimolecular ring closure in dilute solution. Cyclization, which occurs with formation of charged linear byproducts, was confirmed by GPC, FTIR, MALDI-ToF and NMR spectroscopy. Product mixtures were analyzed with a newly developed dual-detector GPC method in which the linear byproducts were end-labeled with a UV-absorbing group and separately detectable with a UV detector. Alternatively, charged linear byproducts were removed with anion-exchange resin. Yields and molecular weight distributions of the cyclic products are consistent with Monte Carlo simulations of kinetically controlled cyclodepolymerization. Large cycles from this cyclodepolymerization route are obtained in much higher yields (>70% for x > 12) than those reported for the traditional base-catalyzed ring-chain equilibration of D₄ and D₅ (∼13% for x > 6) [1].     

光固化涂料稳定性考察

用凝胶渗透色谱（ＧＰＣ法）和粘度法跟踪测定光固化涂料贮存期间的分子量参数和粘度，探讨了影响光固化涂料贮存稳定性的各种因素，对２种光固化树脂在加入不同光引发剂、不同活性稀释剂后的贮存稳定性作了评价。     

Bio-oil fractionation by temperature-swing extraction: Principle and application

Bio-oils produced by direct thermal liquefaction often contain heavy components that hinder their utilization as a liquefaction medium. This paper reports a new approach to fractionate the liquefaction bio-oil into a light and a heavy fraction based on solvent extraction and temperature-swing regeneration. This approach is based on hot extraction (T ∼ 70 °C) of the light fraction of the oil with a suitable extraction solvent followed by cold (T ∼ 25 °C) de-mixing of the light fraction and the extraction solvent. In this paper, we (i) illustrate the selection of the extraction solvent and define the solvent properties required, (ii) demonstrate the potential of multistage extraction/regeneration for the bio-oil produced by direct thermal liquefaction, (iii) extend the concept to fractionate a petroleum crude oil, (iv) discuss the theoretical basis of the fractionation using polymer solution theory and, finally, (v) show a low energy requirement of the extraction process by means of process simulation, i.e., an equivalent of ∼1% of the biomass intake.