Solvent and kinetic penultimate unit effects in the copolymerization of acrylonitrile with itaconic acid

Copolymerization of acrylonitrile (AN) with itaconic acid (IA) in dimethylformamide (DMF) and DMF/water mixture was investigated at enhanced concentrations of the latter. Analysis of the copolymer composition revealed the existence of a marked penultimate unit effect with respect to radicals terminated in AN. The reactivity of IA was considerably less than that of AN, manifested as a negative reactivity ratio for the former. The r_IA values ranging from −0.28 to −0.50 and r_AN values ranging from 0.53 to 0.70, were obtained by Kelen-Tudo's (KT) and extended KT methods. The penultimate reactivity ratios were determined by both linear and non-linear methods. The values ranged from r₁=0.009 to 0.01, r₁^′=0.0015 to 0.0043, r₂=0.54 to 0.69 and r₂^′=0.9 to 1.03. The reactivity of AN radical towards IA decreased about twofold when the latter formed the penultimate group. The penultimate model explained an acceptable rational feed-copolymer composition profile for the whole composition range. Addition of water decreased the reactivity of IA slightly. IA caused a decrease in the apparent copolymerization rate in agreement with the observed trends in the reactivity ratios; presence of water caused a further decrease in the rate of polymerization. A statistical prediction of monomer sequences based on reactivity ratios implied that IA existed as a lone monomer unit between the long sequences of AN units.     

POLYACRYLONITRILE PRECURSORS FOR CARBON FIBER WITH IMIDOCARBOX YLIC ACID UNITS: COPOLYMERIZATION OF ACRYLONITRILE WITH MALEIMIDOBENZOIC ACID

ABSTRACT

4-Maleimidobenzoic acid (MBA) was explored as a comonomer in polyacrylonitrile (PAN) precursors for carbon fiber. The copolymerization of acrylonitrile (AN) with MBA was carried out in DMF. The reactivity of MBA was considerably less than that of AN, which was manifested as a negative reactivity ratio for the former. The r _MBA- values from ?0.24 to ?0.33 and r _AN values of 1.07 were obtained by Kelen-Tudos and extended Kelen-Tudos methods. The penultimate reactivity ratios were determined by both linear and non-linear methods. The values were r ₁=0.0093, r ₁′=0.0132, r ₂=1.063 and r ₂′=1.625. The relative MBA concentration in the copolymer decreased drastically on enhancing its content in the monomer mixture. The penultimate model could satisfactorily explain the feed-copolymer composition profile for the whole composition range. MBA caused a decrease in the apparent copolymerization rate and molecular weight in agreement with the observed trends in the reactivity ratios. A statistical prediction of monomer sequences based on reactivity ratios implied that MBA existed as a lone monomer unit between the long sequences of AN units. This sequence distribution is suited for the efficiency of MBA in cyclisation reaction, which stabilizes PAN during its pyrolysis. Optimum thermal stabilization effect and char yield were observed for copolymers with around 3 mol% MBA in the chain.     

基于Maple软件辅助绘制自由基二元共聚曲线的研究

运用数据处理软件(maple)对经典的自由基二元聚合公式进行图形绘制,得到了二元单体之间共聚关系的三组图.一是二元单体的自由基共聚曲线图F1-f1,二是聚合物中单体平均组成(Fp)与投料单体浓度(f1)的关系曲线图,三是聚合物转化率(C)与投料单体(f1)的关系曲线图.通过二组具有代表性的共聚实例,分别是有恒比点的非理...     

2-亚甲基丁二酸酐和甲基丙烯酸甲酯的共聚反应研究

2—亚甲基—丁二酸酐(M_1,ITANH)和甲基丙烯酸甲酯(M_2,MMA)在四氢呋喃(THF)中以过氧化二苯甲酰(BPO)作引发剂进行自由基共聚合。由作图法衣得这两种单体在66℃的共聚竞聚率:表明它们趋于嵌均共聚。用粘度法和GPC测量了共聚物的分子量和分子量分布。共聚物在温和的条件下进行部分水解,得到一带有短的羧基侧链的聚电解质[11]。将[11]与无机盐LiClO_4混合后测得电导率δ-2.8272×10~(-4)S·cm~(-1),表明它具有较好的离子导电性。     

甲基丙烯酸酯和丙烯酸酯基团转移共聚的竞聚率

甲基丙烯酸酯和丙烯酸酯基团转移共聚的竞聚率邹友思郭金全戴李宗潘容华（厦门大学化工系，厦门，３６１００５）基团转移聚合是制备极性单体的嵌段或无规共聚物的有效方法。如用甲基丙烯酸甲酯（ＭＭＡ）和丙烯酸丁酯（ＢＡ）进行嵌段共聚，可制得热塑性弹性体［１...     

丙烯酸甲酯和甲基丙烯酸酯基团转移无规共聚的竞聚率

丙烯酸甲酯和甲基丙烯酸酯基团转移无规共聚的竞聚率⒇邹友思林东海张景辉潘容华（厦门大学化工系，厦门大学核磁共振实验室，厦门，３６１００５）单体竞聚率作为一个定量数据，对于不同投料比下共聚物组成的预计和控制，共聚反应动力学和机理研究均有重要作用。丙烯酸...     

C60-苯乙烯-顺丁烯二酸酐的三元自由基共聚

自从研制出克量的Ｃ6 0 [1],其在超导光、电、磁、生物等领域的研究迅速发展 .由于Ｃ6 0 只溶于几种非极性溶剂中 ,其使用受到限制 ,从而制备Ｃ6 0 的高分子衍生物一直被认为是Ｃ6 0 材料化的重要途径[2 6 ].文献 [39]报道 ,富勒烯与含双键的单体如苯乙烯、甲基丙烯酸甲酯等可很方便地进行自由基共聚 ,得到富勒烯与烯类单体的共聚物 ,产物可溶于四氢呋喃等有机溶剂 .但迄今为止 ,可溶于水或其它强极性溶剂中的Ｃ6 0 聚合物研究的很少[10 ,11],而Ｃ6 0 的三元共聚物的制备几乎未见报道 ,为此 ,我们采用自由基共聚制备了Ｃ6 0 苯乙烯 顺丁烯…     

An MO-theoretical calculation of solvent effect upon the NH3 + HF = NH4F reaction

An ab initia molecular orbital calculation was done as to a reacting system, NH₃+HF=NH₄F, with the inclusion of the solvent effect as the origin of dipolar field. The reactants were assumed to stay in dimers, (NH₃)₂ and (HF)₂, in advance to the reaction, and the respective partners of two reactants were regarded as point dipoles. The system was stabilized to some extent by two dipoles adopted. A study of configuration analysis on this system was made with and without the dipoles. Their effect was found to be favorable for proceeding of the reaction.     

Acrylamide Hydrogels Preparation via Free Radical Crosslinking Copolymerization: Kinetic Study and Morphological Investigation

The simultaneous gravimetric and dilatometric techniques have been used to study the kinetics of aqueous free radical crosslinking copolymerization of acrylamide (AAm) and N,N^'-methylenebisacrylamide (MBA) at different crosslinker ratios, and reaction temperatures. In this study, the gel properties were investigated using swelling measurements and microscopic techniques. Based on the data, it was proposed that the deviation point of the results of dilatometric technique from those of the gravimetric one can be a new criterion for gel point. The monomer conversion and the equilibrium swelling ratio of the hydrogels were measured as a function of the reaction time. Experimental data showed an inverse dependence of the critical gel point on crosslinker concentration. As the MBA/AAm ratio was decreased to 0.1?wt%, the product appearance changed. In addition, the effects of temperature on the reaction rate and critical gel point were studied. At higher temperatures, the equilibrium swelling ratio reached to its minimum value earlier. Besides, the hydrogel surface became smoother.     

丙烯腈和丙烯酸酯基团转移共聚的竞聚率

丙烯腈和丙烯酸酯基团转移共聚的竞聚率邹友思，林国良，戴李宗，兰涛，潘容华（厦门大学化工系，厦门，３６１００５）共聚合中最重要的参数是竞聚率，二元共聚竞聚率对反应机理的研究及生产上的控制均有重要作用。丙烯腈是重要的共聚单体，但它参与的基团转移无规共聚至...     

不饱和环缩醛与苯乙烯的原子转移自由基共聚合反应

不饱和环状单体与烯类单体共聚所得的共聚物 ,已经或正在开发成一系列新的产品 .例如 ,水解后得到末端带有—OH,— SH,—COOH等官能团的聚苯乙烯、聚乙烯、聚甲基丙烯酸甲酯等的低聚物[1] ,用于制备新型聚酯和聚氨酯 ;与乙烯的共聚物可在细菌作用下彻底分解成脂肪酸或醇 ,可赋予聚合物生物降解活性 ;与双甲基丙烯酸酯等的共混物 ,可用于制作高强度补牙材料[2 ] 等 .以前报道的不饱和环状单体与烯类单体的共聚反应 ,均为无规共聚 ,而且是普通自由基引发聚合 ,不能控制分子量 ,分子量分布很宽 .原子转移自由基聚合是近几年发展起来的实现…     

富勒烯(C60/70)-丙烯酸的自由基共聚

富勒烯及其衍生物在超导、光电、磁学等领域展现出奇特性能[1],富勒烯的化学修饰成为化学工作者们关注的热点之一,而其中合成含富勒烯的新型聚合物是一个非常重要的方面.     

自由基交联共聚合理论模型进展

从模型所使用的数学方法，对自由基交联共聚合理论的模型：概率统计模型、动力学模型和基于逾渗的计算机仿真模型的进展进行了综述。     

Copolymerization of vinylidene fluoride and acrylic acid in supercritical carbon dioxide

The free‐radical copolymerization of vinylidene fluoride (VDF) and acrylic acid (AA) was carried out in supercritical carbon dioxide using both precipitation and dispersion techniques in the presence of an ammonium carboxylate perfluoropolyether compound. Formation of a copolymer was confirmed by variable contact time CP MAS NMR spectroscopy. Macromolecular matrices were significantly enriched in AA with respect to the initial feed composition and we found that the nonfluorinated monomer has a much higher reactivity ratio with respect to VDF. The cumulative concentration, crystallinity, and water affinity of the synthesized copolymers could be modified changing the initial feed composition, the density of the polymerization mixture, the specific interfacial area of the polymer phase, and the polymerization time. The solubility of the macromolecular product in water was greatly affected by its composition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 109–121, 2010     

有电荷转移络合物参与的共聚体系竞聚率

从有电荷转移络合物参与的共聚体系增长基元反应出,提出一种有ＣＴＣ参与的共聚体系竞聚率的求法,从中得到４个竞聚率,自由单体和ＣＴＣ的相对活性等信息。     

壳聚糖接枝共聚改性最新研究进展

壳聚糖是一种天然高分子,也是迄今为止唯一发现的阳离子碱性多糖。壳聚糖分子链中富含羟基和氨基等反应性官能团,具有生物相容性、生物可降解性、抗菌性、无细胞毒性等优良性能,在生化、医药、环保、农业等领域有广泛的应用前景。然而,由于其大分子具有较好的立构规整性和较强的氢键作用,除稀盐酸、稀醋酸外,壳聚糖不溶于水和其它有机溶剂,因而限制了它的应用范围。为了扩大其应用领域,常通过接枝共聚反应来改善壳聚糖的性能。本文介绍了壳聚糖接枝共聚改性的最新研究进展,包括自由基引发接枝法、偶联接枝法以及催化接枝法。     

异丁烯与对氯甲基苯乙烯正离子共聚合研究

以四氯化钛(TiCl4)、二氯乙基铝(AlEtCl2)、倍半铝(AlEt1.5Cl1.5)、三氯化铝(AlCl3)等路易斯酸为共引发剂,水或枯基醇(CumOH)为引发剂,在-80℃下的正己烷/二氯甲烷(V/V=6/4)的混合溶剂内,研究了异丁烯(IB)与对氯甲基苯乙烯(p-CMS)的正离子共聚合.利用示差凝胶渗透色谱仪(GPCRI)以及核磁氢谱(1H-NMR)对共聚物的表观分子量及分子量分布、共聚组成等进行分析,采用KelenTüd?s与Yezreielv-Brokhina-Roskin法计算了单体竞聚率,初步探讨了p-CMS与IB正离子共聚合的反应机理.结果表明,AlEtCl2、AlEt1.5Cl1.5、AlCl3均可催化大分子间的烷基化反应,产生凝胶;TiCl4作为共引发剂,可以得到无凝胶单峰分布共聚物;邻位氯甲基苯乙烯(o-CMS)不能参与共聚,p-CMS的共聚活性较低,IB与p-CMS的单体竞聚率为rIB=4.67,rp-CMS=0.70;随反应时间延长,共聚物中p-CMS的含量及共聚物分子量均逐渐增加;p-CMS单体自身几乎不参与引发,共聚到大分子链后,苄基氯缓慢参与引发,形成支化.提高共聚合温度至-60和-40℃,聚合速率降低,p-CMS的引发活性未发生明显变化.     

稀土配位催化环硫氯丙烷与环氧氯丙烷共聚合研究

研究了稀土配位催化剂对难以开环均聚和共聚的环硫氯丙烷（ＣＭＴ）与环氧氯丙烷（ＥＣＨ）的共聚合。发现稀土乙酰丙酮盐、环烷酸盐等与异丁基铝、水组成的络合催化剂有良好的催化活性，能制备得到类交替共聚物，产率高达６０％以上，分子量频高（［η］＝０．１５ｄＬ／ｇ）。应用ＩＲ、＾１３Ｃ ＮＭＲ、ＧＰＣ、ＶＰＯ等测试手段对共聚物的结构和分子量进行了表征。测定ＣＭＴ（１）与ＥＣＨ（２）共聚合的竞聚率分别为ｒ１＝０     

稀土配位催化环硫氯丙烷与环氧丙烷开环共聚合研究

报道了稀土配位催化剂对环硫氯丙烷（ＣＭＴ）与环氧丙烷（ＰＯ）的共聚合，许多稀土化合物与三异丁基铝组成的催化体系都能使两者共聚；尤为突出的是Ｙ（Ｐ２０４）３－Ａｌ（ｉ－Ｂｕ）３－Ｈ２Ｏ催化体系对此共聚反应具有优良的优良的催化活性，最大催化效率达６０００ｇ／ｍｏｌＹ，分子量较（η达１．０ｄｌ／ｇ）产率在５０％以上，应用ＩＲ、ＮＭＲ、ＧＰＣ等手段对共聚物进行一表征，测理ＣＭＴ（１）与ＰＯ（２）的共聚率分     

新型双苯并环己酮芳亚胺镍(Ⅱ)催化降冰片烯与甲基丙烯酸丁酯共聚合

采用自制的新型双苯并环己酮芳亚胺镍催化剂双苯并环己酮-2,6-二甲基苯亚胺镍(Ⅱ)(Ni{C₁₀H₈(O)C[2,6-C₆H₃(CH₃)₂N]CH₃}₂, C1)和双苯并环己酮-2,6-二氯苯亚胺镍(Ⅱ)(Ni{C₁₀H₈(O)C[2,6-C₆H₃Cl₂N]CH₃}₂, C2)与三五氟苯硼[B(C₆F₅)₃]结合, 在一定的反应条件下可高效催化降冰片烯(NB)与甲基丙烯酸正丁酯(n-BMA)的乙烯基加成共聚合. 提出了催化聚合时存在的可能失活机理; 研究了不同单体投料比对催化活性、 产率及产物性能的影响. 根据Kelen-Tüdõs方法分别估算出2种单体在不同催化体系下的竞聚率, 即当催化体系为C1/B(C₆F₅)₃时, 竞聚率r_n-BMA=0.02, r_NB=16.28, r_NB·r_n-BMA=0.32; 当催化体系为C2/B(C₆F₅)₃时, r_n-BMA=0.01, r_NB=64.83, r_NB·r_n-BMA=0.65. 结果表明, 2种单体在2种体系催化下均为无规共聚合.