ⅧPVC本体聚合（续）

本体聚合工艺可视为无水的悬浮聚合。本体聚合工艺具有的一些特点是简化了树脂生产流程,这可通过比较悬浮聚合方块流程图(图12a)与本体聚合方块流程图(图33a)来说明,本体聚合反应器内无水,因而反应器体积可以小些,相应地用于控制反应器温度的冷却和加热系统也可以小些。第二点,由于没有水要从树脂中脱出,所以离心机和干燥器就不需要了,工艺水的前后处理也不需要了。     

氯乙烯悬浮(本体)聚合用过氧化物引发剂

介绍了氯乙烯(VC)悬浮(本体)聚合常用过氧化引发剂的合成方法，着重阐述引发剂与聚合动力学的关系以及聚合动力学的检测方法。研究了单一和复合引发剂条件下的VC聚合动力学，为优化引发剂体系、缩短聚合时间、提高聚合釜的生产能力提供理论基础。     

茚聚合反应研究进展

主要介绍了茚的聚合反应,特别综述了某些聚合反应(如电化学聚合、自由基聚合、阳离子聚合和活性阳离子聚合等)的研究进展。最后对茚聚合反应的发展前景进行了展望,并指出茚聚合反应正在向寻求新型催化剂(如环保、高效及反应条件温和等)、开发功能性共聚物和拓宽活性阳离子共聚单体等方向发展。     

碳纤维用聚丙烯腈合成工艺研究进展

综述了近年来碳纤维用聚丙烯腈(PAN)合成工艺的研究进展,介绍了均相溶液聚合、水相悬浮聚合和水相沉淀聚合等传统聚合方式的特点和不足。详细阐述了可逆加成断裂链转移自由基聚合(RAFT)新型聚合工艺,展望了新型工艺在碳纤维用PAN合成中的应用和未来发展方向。     

苯乙烯热引发本体聚合动力学

研究了加少量乙苯的苯乙烯热引发本体聚合于120～170℃聚合速率在0～95%转化率内的变化规律,建立了如下聚合动力学模型:(dx)/(dt)=A[M]_0~(382)(1-x)~(5/2)/(1+∈x)~(3/2)其中 A=[]A_0+A_1x+A_2x~2+A_3x~3,x 表示转化率A_i(i=0,1,2,3)是温度和乙苯含量的函数。实验测定了不同聚合阶段的转化率,并进行了参数回归。     

活性自由基聚合法合成偶氮聚合物研究进展

偶氮聚合物具有光致顺反异构和光学各向异性,其在光电信息技术领域具有重要的潜在应用前景.利用活性自由基聚合的方法可以在温和的条件下合成得到特定结构与预定相对分子质量的偶氮聚合物.综述了该技术领域的最新研究进展,并对近年来出现的聚合体系与方法,包括氮氧稳定自由基聚合(NMP)、原子转移自由基聚合(ATRP)、可逆加成一断裂链转移(RAFT)聚合等,作了简要的评述.     

纳米CaCO3原位本体聚合制聚丙烯的研究

研究了纳米CaCO3原位聚合制聚丙烯的方法及其产品的性能。采用经表面处理的纳米CaCO3和加入聚合釜的方法，经过在12m^3聚合釜的本体聚合生产表明，聚合物产品中纳米CaCO3分散均匀，物理性能和热性能均有所改善，尤其是机械性能显著提高。其中，断裂伸长率可提高1～2倍，缺口冲击强度在常温(23℃)和低温(-20℃)下分别可提高100％和34％，拉伸强度基本保持不变。     

原子转移自由基聚合的研究进展

介绍活性聚合原子转移自由基聚合(ATRP)聚合机理，并综述ATRP聚合新型催化体系研究现状，最后对ATRP聚合新型催化体系的发展前景和挑战进行讨论。     

甲基丙烯酸甲酯-苯乙烯-马来酸酐三元共聚物的本体转移悬浮聚合法

本研究采用本体转移悬浮聚合法合成苯乙烯(ST)-甲基丙烯酸甲酯(MMA)-马来酸酐(MAH)三元共聚物。本聚合法结合了本体聚合和悬浮聚合的优点,通过本体预聚降低马来酸酐水解程度,制备了高酸酐含量的三元共聚产物,研究了引发剂、分散剂用量和预聚转化率对反应的影响,并比较不同单体比例与最终产物的性能关系。     

活性自由基乳液聚合的研究进展

活性自由基乳液聚合是一个非常新的研究领域。介绍了目前活性自由基乳液聚合领域的3种常用的方法及应用这些方法进行乳液聚合的研究进展,包括:原子转移自由基聚合(ATRP),氮氧调节自由基聚合(NMP)和可逆加成-断裂链转移自由基聚合(RAFT)。     

聚乳酸熔融缩聚的研究

综述了近年来国内外聚乳酸熔融聚合的研究情况,概述了直接熔融缩聚、熔融-固相和熔融-扩链合成聚乳酸的研究,并研究探讨了熔融聚合中影响聚乳酸相对分子质量的因素。     

Evaluating The Extent of Bio-Polyester Polymerization in Solid Wood by Thermogravimetric Analysis

In this study, the thermogravimetric analysis (TGA) technique has been applied to determine the extent of in situ polymerization achievable in solid wood on treating with bio-polyester oligomers. Low-molecular-weight oligomers of poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(butylene succinate) (PBS), and poly(butylene adipate) (PBA) were impregnated and then thermally polymerized within solid wood to enhance the physical properties of wood. TGA revealed a similar degree of oligomer polymerization was achieved either with pure oligomers or within the wood structure. The influence of relatively acidic treatments, such as low-molecular-weight PGA oligomers, was observed to lead to degradation of the hemicellulose wood component. Polymerization of PLA and PGA oligomer treatments which penetrate the wood cell wall gave relatively lower wood thermal stability. Treatment and polymerization of lumen filling PBS and PBA oligomers contributed to increased wood thermal stability.     

Grafting of poly(acrylic acid) onto poly(amidoamine)-functionalized graphene oxide via surface-mediated reversible addition-fragmentation chain transfer polymerization

Graphene oxide was modified with third-generation poly(amidoamine) (PAMAM) to obtain dendrimer-grafted GO (DGO) with high content of functional groups. DGO's amine groups were conjugated with S-(thiobenzoyl)thioglycolic acid as proved by XPS and poly(acrylic acid) was grafted onto surface via RAFT polymerization (DGO@PAA). FT-IR results approved the synthesis of samples whereas TGA revealed 40.3% grafting of PAA. XRD patterns showed that with further modification, d-spacing increased. According to Raman spectra, modification resulted in more disordered structure whereas DGO@PAA showed a high value of I_D/I_G. Morphological studies were performed by SEM and TEM that showed a polymeric layer covered the surface of nanosheets.     

Synthesis,Characterization of Fulvic Acid–Poly(Methylmethacrylate) Graft Copolymers Based on Surface-Initiated Atom Transfer Radical Polymerization and its Effect on Performance of Poly(Lactic Acid)

Fulvic acid–poly(methylmethacrylate) graft copolymers were synthesized by surface-initiated atom transfer radical polymerization with fulvic acid. The result demonstrated that the hydrophobicity of fulvic acid–poly(methylmethacrylate) was improved after modification by surface-initiated atom transfer radical polymerization. Furthermore, poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites were prepared to improve the performances of poly(lactic acid) by blend melting. Compared to poly(lactic acid) with X_c of 5.38%, the X_c of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was 19.94%. Moreover, the impact strength of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was increased by 5.19% compared to poly(lactic acid). In all, this study provided an effective and feasible method for optimizing interface performance and enhancing the thermal stability of poly(lactic acid).     

One-step preparation of electrorheological suspension containing poly(lithium acrylate) via inverse emulsion polymerization and study of its electrorheological effect

Electrorheological (ER) fluid or suspension containing lithium salt of poly(acrylic acid) were synthesized directly by inverse emulsion polymerization. Effects of the amounts of crosslinking agent and the stabilizer and neutralization degree used in the polymerization, as well as water content of the polymer particles on the ER activity were investigated. The ER suspension exhibited maximum yield stress at optimum amounts of stabilizer and crosslinking agent used in the inverse emulsion polymerization, as well as at optimum water content of the polymer particles. Glycerol was tried to be used as an activator instead of water and was shown to have a favorable effect on the thermal stability of the ER suspension. Core–shell-type polymer particles were synthesized through inverse emulsion polymerization with supplemental addition of a second monomer. The ER suspension containing particles with poly(lithium acrylate) as core and polyacrylamide as shell showed better ER behavior than those without the polyacrylamide shell. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 2169–2174, 1998     

Crystalline oligomeric stereocomplex as an intermediate compound in racemic poly(DL-lactic acid) degradation

Hydrolytic degradation of intrinsically amorphous poly(DL -lactic acid) was re-examined in pH 7.4 isoosmolar phosphate buffer at 37°C. Size-exclusion chromatogarphy, X-ray scattering and differential scanning calorimetry were used to monitor molecular weight and morphology changes up to the ultimate degradation stage. It was found that heterogeneous degradation of poly(DL -lactic acid) yielded a crystalline residual material of low molecular weight. Comparison with a stereocomplex made of equimolar poly(L -lactic acid) and poly(D -lactic acid) showed that the poly(DL -lactic acid) degradation residue was actually an oligomeric stereocomplex. The formation of stereoregular oligomeric enantiomers agreed well with the predominantly isotactic structure of poly(DL -lactic acid) obtained by ring-opening polymerization of DL -lactide and argued in favour of the stereodependence of main chain ester bond cleavage.     

Polyacrylic acid (poly-A) as a chelant and dispersant

Polyacrylic acid was synthesized in water by persulfate-initiated polymerization (solution polymerization) of glacial acrylic acid in the absence of a chain-transfer agent. The final product is odorless and colorless. Chelation for calcium ions using a calcium electrode show that our poly(acrylic acid) has a higher chelation capacity than that of existing commercial poly(acrylic acids). A design of experiments was performed to optimize the synthesis conditions to obtain poly(acrylic acid) with a high maximum chelation value. These studies also helped us to gain insight into its high chelation capacity. The chelation capacity for calcium reaches its highest values when polymerization near isothermal conditions is done ∼ 95°C with an acrylic acid concentration of ≤21 wt % and an addition time >1 h. These conditions favor higher molecular weight poly(acrylic acid) with a polydispersity ∼ 4. The dispersion properties of our poly(acrylic acid) are similar to those of the commercial ones. This dual capability of chelation and dispersion is absent in commercial chelants such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and their analogs. At pH > 7, chelation of calcium by our poly(acrylic acid) is much higher than that observed with EDTA. Characterization by NMR, Raman, FTIR, and molecular modeling are included in an attempt to understand structural features that can explain the higher chelation capacity of our atactic poly(acrylic acid).     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements Part 4. Radical polymerization of acrylic acid in the presence of poly(vinyl alcohol): characterization of resulting polymer blends

The radical polymerization of acrylic acid in the presence of poly(vinyl alcohol) as a template in aqueous solution has been studied using conductimetry, which shows template influences on the reaction rate. A comparison is made between data obtained by differential scanning calorimetry and infrared spectroscopy for poly(acrylic acid)–poly(vinyl alcohol) blends prepared either by template polymerization or by casting of the preformed polymers. Evidence for more significant interpolymer interactions in blends prepared by template polymerization than in those obtained by simple mixing is given. © 2001 Society of Chemical Industry     

开环聚合法制备聚D-乳酸的初步研究

以辛酸亚锡(SnOct2)为催化剂通过开环聚合反应由D-丙交酯(D-LA)制备聚D-乳酸(PDLA),并采用红外光谱(FTIR)、核磁共振(NMR)、差示扫描量热法(DSC)以及乌氏粘度计等对聚合产物进行表征。结果表明,聚合温度、聚合时间、催化剂用量以及真空度对PDLA的相对分子质量均有显著的影响,当聚合温度为160℃,聚合时间为20 h,催化剂用量为D-LA的0.03%以及真空度为60 Pa的条件下,可以得到粘均相对分子质量为26.5×104的PDLA产物。     

低分子量聚N-乙烯基甲酰胺-co-乙烯胺的合成

以N-乙烯基甲酰胺为单体,N,N-二甲基甲酰胺和乙酸乙酯为混合溶剂,偶氮二异丁腈为引发剂,十二硫醇为链转移剂,通过沉淀聚合法制备了低分子量的聚N-乙烯基甲酰胺。详细研究了单体质量分数、混合溶剂配比、引发剂用量、链转移剂用量、反应温度及反应时间对聚合反应的影响。在最佳聚合条件下,聚合物收率可达93.1%、聚合物的数均分子量(Mn)为2 975.2,PDI=2.64,且聚合残液可循环利用。然后将所得聚合物在酸性条件下水解,制备了不同胺化度的聚N-乙烯基甲酰胺-co-乙烯胺,产品的数均分子量为1 000~1 400,PDI为1.34~1.40。