Ring‐opening polymerization of 1‐methyltrimethylene carbonate by rare earth initiators

Ring‐opening polymerization of 1‐methyltrimethylene carbonate (MTMC) initiated by highly active single‐component rare earth tris(2,6‐di‐tert‐butyl‐4‐methylphenolate)s [Ln(OAr)₃, Ln = La, Dy, Y] or yttrium isopropoxide [Y(OiPr)₃] is reported for the first time. PolyMTMC (M_w = 8.4 × 10⁴, molecular weight distributions = 1.5) initiated by La(OAr)₃ at [MTMC]/[initiator] = 1000 was obtained with the yield over 99% in toluene within 1 h at 30 °C. Random and block copolymers of MTMC with ε‐caprolactone (CL), 2,2‐dimethyltrimethylene carbonate (DTC) or polyethylene glycol (PEG) including poly(MTMC‐r‐CL), poly(MTMC‐b‐CL), poly(MTMC‐r‐DTC), poly(MTMC‐b‐DTC), and poly(MTMC‐b‐PEG‐b‐MTMC) were synthesized. The differential scanning calorimetry results show that thermal behaviors of the polymers sensitively depend on their compositions and chain structures. Furthermore, the measurements of ¹H‐¹H COSY and density functional theory calculation are applied to investigate the mechanism. The polymerization of MTMC takes place according to a coordination‐insertion mechanism, and the ring is opened via acyl‐oxygen bond cleavage resulting in a Ln? O active center. There exist two ring‐opening modes of MTMC in which mode b , breaking the CH₂O? CO bond, is the major pathway. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3807–3815, 2010     

Thermal degradation of poly(lactic acid) measured by thermogravimetry coupled to Fourier transform infrared spectroscopy

Thermogravimetric (TG), differential thermal analysis (DTA) and thermal degradation kinetics, FTIR and X-ray diffraction (XRD) analysis of synthesized glycine–montmorillonite (Gly–MMT) and montmorillonite bound dipeptide (Gly–Gly–MMT) along with pure Na–MMT samples have been performed. TG analysis at the temperature range 25–250 °C showed a mass loss for pure Na–MMT, Gly–MMT and Gly–Gly–MMT of about 8.0%, 4.0% and 2.0%, respectively. DTA curves show the endothermic reaction at 136, 211 and 678 °C in pure Na–MMT whereas Gly–MMT shows the exothermic reaction at 322 and 404 °C and that of Gly–Gly–MMT at 371 °C. The activation energies of the first order thermal degradation reaction were found to be 1.64 and 9.78 kJ mol⁻¹ for Gly–MMT and Gly–Gly–MMT, respectively. FTIR analyses indicate that the intercalated compounds decomposed at the temperature more than 250 °C in Gly–MMT and at 250 °C in Gly–Gly–MMT.     

Ultrasound assisted ionic liquid dispersive liquid phase extraction of lovastatin and simvastatin: A new pretreatment procedure

A fast and novel sample preparation procedure: ultrasound assisted ionic liquid (IL) dispersive liquid extraction for the concentration of lovastatin and simvastatin in aqueous samples was developed. An IL ([C₆MIM][PF₆]) was used as the extraction solvent, and the factors affecting the extraction efficiency such as initial temperature, the volume of IL, pH of water samples, cooling time, and salt concentration were optimized. In combination with HPLC‐UV, both lovastatin and simvastatin exhibited a good linear range of 1–100 ng/mL. The limits of detection (LODs) of lovastatin and simvastatin were 0.17 and 0.29 ng/mL, respectively. Precisions of the proposed method (RSDs, n = 9) were 4.12 and 4.52%, respectively. This method has been successfully applied for the analysis of target compounds in three real water samples and good spiking recoveries were obtained in the range of 90.0–102.2% for lovastatin and 80.5–112.0% for simvastatin. These results indicated that ultrasound assisted IL dispersive liquid phase extraction would have good application prospect in the pretreatment of environmental samples.     

征地移民管理中的分歧博弈及其决策模型

征地移民的协商管理中的分歧问题中主要是征地方与被征地方之间分歧．分歧主要体现在双方认知和利益诉求的差异．分析了征地移民双方的分歧特点,研究了征地移民的分歧管理模式.利用完善的博弈理论,探讨征地移民分歧管理的基本概念、方法和决策规律.借鉴线性支出系统的效用函数,研究分歧管理博弈矩阵的建立、博弈类型、博弈分析方法,为征地移民协商管理的科学体系提供科学分析方法.     

液相法制取Y_2(WO_4)_3的工艺探讨及其负热膨胀性能比较

采用液相共沉淀法成功合成Y2(WO4)3,利用高、低温X射线衍射方法研究Y2(WO4)3的结构及其负热膨胀性能,发现液相共沉淀法制得的Y2(WO4)3与固相反应法制得的Y2(WO4)3具有一致的Pnca空间群正交结构和相差不大的晶胞参数和体积(经TOPAS软件计算),二者的本征体热膨胀系数分别为-18.8×10-6℃-1(液相法)和-19.5×10-6℃-1(固相法)。液相共沉淀法相对传统固相化学反应法,具有减少合成循环次数和降低反应温度的优点。这证明该法制备稀土钨酸盐类负膨胀材料是可行的。     

Synthesis and anionic polymerization of optically active N-phenylmaleimides bearing bulky oxazoline substituents

Anionic polymerizations of chiral N-phenylmaleimide derivatives bearing an oxazoline pendant (OPMI) were carried out with n-BuLi initiator to obtain optically active polymers. The polymer yields and specific optical rotations () were found to be significantly influenced by the reaction solvent, temperature, and the molar ratio of initiator to monomer. Particularly, the specific optical rotations exhibited a linear dependence on the molecular weights for the formed polymers, and the inversion from levo- to dextro-specific rotation was also observed with an increase in the molecular weights. On the basis of the results from circular dichroism (CD) and ¹³C NMR spectral analyses, the optical activity of poly(OPMI)s was attributed not only to the chirality of oxazolinyl groups in monomeric units but also to the partial helical structure due to an excess of threo-diisotactic configuration in the main chain.     

Poly(ionic liquid)s: a new material with enhanced and fast CO2 absorption

Novel sorbent and membrane materials for CO2 separation, poly(ionic liquid)s made from ionic liquid monomers, poly[p-vinylbenzyltrimethyl ammonium tetrafluoroborate](P[VBTMA][BF4]) and poly[2-(methacryloyloxy)ethyltrimethylamnonium tetrafluoroborate](P[MATMA][BF4]) have absorption capacities 7.6 and 6.0 times of those of room-temperature ionic liquids, e.g.[bmim][BF4], respectively, with reversible and fast sorption and desorption.     

低温试验冷库传热系数的测量研究

简述了对于低温冷库传热系数测量所采用的一般方法,采用稳态法对一低温试验冷库进行了测量实验,然后通过非稳态积分法对试验数据进行验证。针对冷风机电机功率较大的特点,本实验采用变频器将电机功率调小,从而成功得出该低温试验冷库的传热系数。并与理论计算的数据进行对比,找出存在差别的原因。     

湾顶切向流动成因及其对海岸地貌的作用

本文讨论了海湾湾顶地区切向流动的成因及其作用。在湾顶地区,在入射和反射凯尔文波之间,在潮位方面存在着横向振动的“半波损失”,在潮流方面产生了平行于岸壁的切向流动。这种流动对湾顶岸壁起着切向冲刷作用,它的强弱,对海岸地貌形态具有一定的影响,山东省南岸属于冲刷型的沙砾质海岸,与切向流动强有关,浙江省中部和南部属于淤涨型的淤泥质海岸,与缺少这种性质的流动有关。本文还讨论了沿底坡上升的向岸流动的作用。     

1,4-双[4-(2-氨基-5-苯基)噻唑基]苯及其聚酰亚胺的合成及性能

以１ ,４ 双（ 苯乙酰基） 苯为原料,合成了新有机二胺化合物———１ ,４ 双［４ （２ 氨基 ５ 苯基） 噻唑基］ 苯,以此二胺或４ ,４’ 二氨基二苯醚和３ ,３’,４ ,４’ 二苯酮四酸二酐反应制备出新型的聚酰亚胺均聚物和共聚物,研究了它们的耐温性能,耐热氧化性能和共聚物经高温裂解后的导电性能等