铈对锰钒钢过冷奥氏体转变的影响

研究了稀土元素铈对锰钒钢中先共析铁素体转变和贝氏体转变的影响。测定了先共析铁素体形核率和恒温转变动力学曲线。同时,观察了组织转变特征。结果表明,铈明显地推迟先共析铁素体转变,降低形核率。此外铈也推迟贝氏体转变。     

NEW INITIATION SYSTEMS FOR ATOM TRANSFER RADICAL POLYMERIZATION

This review summarizes our achievements in designing new initiation systems for atom transfer radical polymerization (ATRP). First-order kinetics and extension experiments revealed the living nature of these reactions. Tailormade vinyl polymers with functional end groups were characterized by ^1H-NMR and UV-vis spectroscopic analyses. Replacing traditional radical initiators AIBN and BPO, carbon-carbon bond compounds, 1,1,2,2-tetraphenyl-l,2-ethanediol, diethyl 2,3-dicyano-2,3-diphenylsuccinate and diethyl 2,3-dicyano-2,3-di(p-tolyl)succinate, were utilized in reverse ATRP to produce the initiating radical. Sulfur-sulfur bond iniferter, tetraethylthiuram disulfide (TD), in conjunction with CuBr/bpy or NiCI2/PPh3 complex could control the styrene polymerization via redox reaction. Pseudo-halogen transfer reaction was demonstrated to maintain the dormant-active species equilibrium in normal and reverse ATRP with Cu(S2CNEt2), Cu(S2CNEt2)CI and Fe(S2CNEt2)3 as catalysts. The organic halide initiator and reduced transition metal compound that started the living polymerization were produced in situ from the components of TD/FeCI3/PPh3, TD/CuBr2/bpy and Fe(S2CNEt2)3/FeCI3/PPh3 systems. Accurate control of UV irradiation time favored the radical generation process in photo ATRP with the 2,2-dimethoxy-2-phenylacetophenone/Fe(S2CNEt2)3 initiation system.     

一个新的液晶相转变动力学理论

本文以保留系统的宏观特性为基本原则,从用动力学方法处理非稳态相转变入手,在物理化学基础上,建立了描述液晶相转变的动力学方程,提出了动力学意义上的相转变级数参数,推导出相转变级数的理论公式及参数的变化范围,丹卉将其应用于一新的聚合物体系,获得了该体系各聚合物加热过程中所经历相态的动力学相转变级数。     

交联聚醚聚氨酯的表征及其聚集态转变和自由体积特性的正电子湮没研究

采用全反射红外光谱（ＡＴＲ－ＩＲ）对聚合物的结构进行了表征，证明其为交联聚醚聚氨酯（ＰＥＵ），且其碱金属盐络合物的导电性与其自由体积有关。在１１０～３５０Ｋ温度范围内测量了ＰＥＵ的正电子湮没寿命谱，结果表明正电子湮没寿命谱的温度关系可灵敏地反映聚合物的聚集态转变及其自由体积特性随温度的变化。得到了ＰＥＵ的次级转变、玻璃化转变及结晶相的熔融变化等方面的信息。并由实验测得的ｏ－Ｐｓ寿命计算出不同温度下ＰＥＵ中自由体积孔洞的尺寸。     

高分子链的去拥挤转变及低温流动

简述了拥挤理论的基本原理,运用拥挤理论来说明高分子链间弱相互作用对高分子链所处的状态的影响,特别是对高分子玻璃化转变的影响.在实验中,采用固体核磁共振方法探测高分子的链间邻近度,并比较了不同链间邻近度的高分子样品在玻璃化转变温度以下的压力诱导流行行为,发现即使测试温度比高分子玻璃化转变温度低132℃,高分子链在压力下依...     

关于Cu-Pd合金的固态转变

应用热分析,电阻和伦琴射线方法修正了Cu-Pd合金相图,在300 ℃经过2200 h热处理后,含Cu9%～32.5%(原子分数)范围内合金由α→α〃,含Pd35%～55%(原子分数)合金由α→β.这两个相区的最高有序-无序转变温度分别为510和655 ℃.     

衔稀土对高碳钢回火转变及动力学影响的研究

从非等温动力学理论出发，应用扫描量热法，研究了稀土对高碳钢回火过程及马氏体和残余奥氏体分解动力学的影响。结果表明：稀土使马氏体和残余奥氏体分解温度升高，热效应值降低，激活能升高，相变机制发生变化。     

两个不同分子量聚苯乙烯混合体系的玻璃化转变

用差示扫描热量法测定了两个分子量不同的聚苯乙烯混合体系的玻璃化转变温度随组成的变化，并与Ｆｏｘ方程，Ｇｏｒｄｏｎ－Ｔａｙｌｏｒ方程和Ｃｏｕｃｈｍａｎ方程的预测结果进行了比较，以验证这些经验方程的适用性。     

戊二醛交联前后明胶微球热转变研究

在空气和氮气气氛中,对未交联的明胶微球(GMs)和戊二醛交联明胶微球(CGMs)进行了受热转变研究,并利用250℃热处理的明胶球制备出具有多孔内核的明胶基结构.经过热重分析(TGA)、差示扫描量热法(DSC)、扫描电子显微镜(SEM)和付里叶变换红外光谱(FTIR)等分析测试表明:戊二醛交联明胶微球300℃后热失重略大于未交联明胶微球,两者的熔化温度Tm都为228℃;在空气中250℃热处理7 h的未交联明胶微球经过稀硫酸处理后可以得到多孔内核结构,多孔内核含碳、氧元素,外壳以碳元素为主;105℃和190℃热处理的明胶球化学成分基本相同,250℃热处理使明胶分子中的酰胺键减少、并发生三级结构的转变.     

青蒿乙素的化学转化

本文报道青蒿乙素(2)的若干化学转化,如:青蒿乙素的催化氢化得到三个化合物5,6,7.6与三氟化硼-乙醚配合物反应生成8和9.6用硷水解以及2,6,7分别与五羰基铁进行脱氧反应,得到相应的化合物18,3和4。     

The effect of copolymerization on transition temperatures of polymeric materials

The relationship between transition temperatures and copolymer composition was studied by DSC. Three types of copolymers were studied: styrene-acrylonitrile (SAN), vinyl chloride-vinyl acetate (VC-VA), and ethylene vinyl acetate (EVA). SAN's and VC-VA's are amorphous copolymers, whereas EVA's are semi-crystalline copolymers. The variation of the glass transitions and the crystalline melting are discussed in this study.     

VDF/TrFE共混物晶区相容性的热释电流研究

Ferroelectric blends of vinylidene fluoride（VDF）/ trifluoroethylene（TrFE）copolymer with different molar ratio of 56/44,60/40,63/37,67/33,70/30,73/27 and 77/23 were fabricated by casting from methyl ethyl ketone solution. Wide angle X-ray diffraction shows two peaks（17. 6o and 19. 5o）for all blends and copolymers,associating with amorphous region and（110）（200）reflections,respectively. It indicates that blending does not introduce any new crystal lattice. Analysis of differential scanning calorimetry（DSC）presents that the blends display the phase transition characters of both copolymers of 77/23 and 56/44. The blend components are immiscible in the crystalline phase. Thermally stimulated depolarization current of the blends exhibits the characters of both components at different polarization temperatures. In accordance with DSC results,it also proves that the crystalline phases of 56/44 and 77/23 are just independent. In addition,it is also proved that the space charge can stabilize the remnant polarization to some extent.     

Synthesis and properties of segmented block copolymers based on mixtures of poly(ethylene oxide) and poly(tetramethylene oxide) segments

The synthesis and characterisation of segmented block copolymers based on mixtures of hydrophilic poly(ethylene oxide) and hydrophobic poly(tetramethylene oxide) polyether segments and monodisperse crystallisable bisester tetra-amide segments are reported. The PEO length was varied from 600 to 8000 g/mol and the PTMO length was varied from 650 to 2900 g/mol. The influence of the polyether phase composition on the thermal mechanical and the elastic properties of the resulting copolymers was studied.The use of high melting monodisperse tetra-amide segments resulted in a fast and almost complete crystallisation of the rigid segment. The copolymers had only one polyether glass transition temperature, which suggests that the amorphous polyether segments were homogenously mixed. Thermal analysis of the copolymers showed one polyether melting temperature that was lower than in the case of ideal co-crystallisation between the two polyether segments. However, at PEO or PTMO lengths larger than 2000 g/mol two polyether melting temperatures were observed. The copolymer with the best low temperature properties was based on a mixture of PEO and PTMO segments, both having a molecular weight of 1000 g/mol, at a weight ratio of 30/70.     

Modifying an amorphous polymer to a fast crystallizing semi‐crystalline material by copolymerization with monodisperse amide segments

Segmented block copolymers of polysulphone with monodisperse amide segments were synthesized by a melt and a solution polymerization method. Both triblock and multiblock copolymers were prepared. The length of the difunctional polysulphone was varied from 2000 to 20,000 g/mol. The monodisperse amide segment was the tetra‐amide T6T6T based on terephthalic acid (T) and hexamethylene diamine (6) units. The main goal of this work was to study if the high T_g amorphous polysulphone could be modified to a high T_g semi‐crystalline PSU‐T6T6T copolymer. The copolymers were characterized by viscosity measurements, NMR, FTIR, MALDI‐TOF, DSC, and DMA. Depending on the amide concentration in the copolymers the T6T6T melting temperatures ranged between 220 and 270 °C and thus the crystallization window was small 50–100 °C. From the FTIR results, it was revealed that the crystallinity of the T6T6T segments in the copolymer could be very high, up to 92–97%. The T6T6T has crystallized out into nanoribbons with a high aspect ratio. These high T_g semi‐crystalline copolymers had a high dimensional and solvent resistance. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 63–73, 2010     

Synthesis and properties of hydrophilic segmented poly(urethanes) based on poly(ethylene glycols) and glycerol monostearate

Poly(urethanes) having the structure of comb-shaped copolymers were synthesized from glycerol monostearate, poly(ethylene glycols) with M _n = 300–6000, and 1,6-hexamethylene diisocyanate. Effects of the molecular mass of segments and of the contents of soft segments and side chains on both the glass transition temperature of the soft segment and on the melting point and the enthalpy of melting of crystalline phases involving soft segments and side chains were studied by DSC and IR spectroscopy. The resulting comb-shaped copolymers were shown to exhibit thermoplastic and hydrophilic behavior. It was demonstrated that the ultimate tensile strength, yield stress, and Young’s modulus of copolymer films increase with an increase in the molecular masses of soft and hard segments with their ratio maintained constant.     

Structure and property relationships in ethylene–vinyl acetate copolymers

The effects of vinyl acetate content on crystallinity of ethylene–vinyl acetate (E/VA) copolymers were investigated by x-ray diffraction and differential thermal analysis (DTA). The values of these parameters obtained from DTA were found to agree quantitatively with data calculated from x-ray, probability equations, and copolymer theory. The melting points of the crystalline copolymers, and the molar amounts of vinyl acetate to produce a completely amorphous rubber corresponds exactly to that predicted by the Flory theory. The random character expected in E/VA copolymers is thereby confirmed. The physical properties of E/VA copolymers of all ranges of compositions and crystallinity were determined. Depending directly upon vinyl acetate content, the copolymers changed progressively from highly crystalline polyethylene to semicrystalline polyethylene, a completely amorphous rubber, a soft plastic with a glass transition near room temperature. Properties which were correlated with copolymer composition include: crystallinity, melting point, density, modulus, tensile strength, glass transition, and solubility. Finally, the effect on crystallinity and physical properties of replacing the acetoxy group in E/VA with the smaller, highly polar hydroxyl group (ethylene—vinyl alcohol copolymer) was also investigated.     

Thermal fractionation of vinyl acetate-vinyl alcohol copolymers

Thermal fractionation via the method of successive self-nucleation and annealing was used for the first time to study the crystallinity of vinyl acetate-vinyl alcohol copolymers with different random distributions of chain units. The lamella-thickness distribution was calculated through the Gibbs-Thomson equation. It was shown that, for all samples, the minimum lamella thickness is the same and corresponds to a block of no less than 15 vinyl alcohol units. On the basis of these data and with the use of the computer simulation of the polymer-analogous reaction via the Monte Carlo method, the block-length distribution in the crystalline phase was found. It was shown through a comparison of the lamella-thickness and block-length distributions that the maximum lamella thickness increases with the block length and vinyl alcohol content in the copolymer. In crystallites, blocks with lengths exceeding the maximum lamella thickness comprise a significant fraction. Thus, it is probable that these blocks form folds. The dependences of melting temperatures of crystalline lamellas on their thicknesses, as well as the dependences of the melting temperatures of copolymers not subjected to thermal fractionation on the chain-structure parameters, are adequately described by the Flory crystallization theory.     

不同软段长度PBT-co-PBS-b-PEG嵌段共聚物的合成与表征

用熔融缩聚法合成了一系列具有不同软段长度的聚对苯二甲酸丁二酯 (PBT) co 聚丁二酸丁二酯(PBS) b 聚乙二醇 (PEG)嵌段共聚物 (PTSG) ,考察了PEG分子量 (Mn(PEG) )及PBS摩尔分数 (MPBS)对材料性能的影响 实验表明 ,随Mn(PEG)增加 ,缩聚反应时间延长 ,所得产物分子量均呈较为对称的单峰分布 ,多分散性指数小于 2 0 硬段序列结构分析显示 ,随MPBS 增加 ,PBT平均序列长度减小 ,而PBS平均序列长度增加 ,二者呈无规分布 .受组成及硬段平均序列长度变化影响 ,材料内部呈微观相分离状态 ,DSC曲线上可分别观察到软、硬段熔点及玻璃化转变温度 ;硬段熔点及结晶度随MPBS升高而降低 ,主要是受其平均序列长度变化及共晶作用所致 .材料断裂延伸率及降解速率均随Mn(PEG)及MPBS增加而增加 ,可见提高软段长度及降低硬段结晶度等均能有效改善共聚物高分子链的柔韧性及亲水性 ,赋予共聚物更好的降解性能 .     

Phase behavior of blends of linear low density polyethylene and poly(ethene-propene-1-butene)

The aim of this work was the study of blends of linear low density polyethylene (LLDPE) and an ethene-propene-1-butene terpolymer (t-PP). Two types of polyethylene were used to prepare the blends: an ethene-co-1-hexene (LLDPE(H)) copolymer and an ethene-co-1-octene (LLDPE(O)) copolymer. These copolymers present similar comonomer contents, molar mass, molar mass distribution and catalyst systems, but differ in their comonomer distribution. The blends were obtained through mechanical mixing using a single screw extruder at different compositions: 20, 40, 50, 60 and 80 wt.% of LLDPE. From DSC measurements two separated melting and crystallization peaks were observed and dynamic mechanical analysis showed two glass transitions indicating that LLDPE/t-PP blends are immiscible in amorphous and crystalline phases in the solid state. X-ray diffraction showed that the unit cell parameters of both polymers in the blends remain unchanged independent of the composition of the blend.     

苯乙烯-氧乙烯-苯乙烯三嵌段聚合物的受限结晶行为的反气相分析

 采用反气相法研究了苯乙烯 氧乙烯 苯乙烯三嵌段结晶聚合物 (PS PEO PS)的结晶熔融相变 ,测定了PS PEO PS的结晶度、熔点以及熔程 ,探讨了正构烷烃探针分子的碳链长度对测定结果的影响。研究结果表明 :PS PEO PS的微相分离对PEO链段的结晶行为有较大的影响 ,其晶体结构中存在由多种不完善PEO结晶和PS非结晶构成的中间层 ;正构烷烃探针分子的碳链长度对测定PS PEO PS的熔点和熔程无影响 ,但对结晶度测定和PEO结晶熔融相变的检测影响较大 ,所测得PS PEO PS的结晶度随正构烷烃探针分子碳链的增长而降低。