较高等规度丙烯腈成纤聚合物的合成

以无水氯化镁为添加剂,考察了不同条件下的丙烯腈聚合反应,研究了溶剂种类、聚合温度和氯化镁与丙烯腈的摩尔配比对聚合反应及聚合物等规度的影响,并确定了最佳反应条件,正己烷为溶剂,偶氮二异丁腈(AIBN)为引发剂,聚合温度为60℃,氯化镁与丙烯腈的摩尔比为2∶1.在此条件下,研究了单体浓度和引发剂浓度对丙烯腈(AN)均聚合、丙烯腈/衣康酸(AN/IA)二元共聚合和丙烯腈/衣康酸/丙烯酸甲酯(AN/IA/MA)三元共聚合反应的影响,并获得了较高等规度(三单元组全同分数30.2%～55.9%)的丙烯腈均聚物和共聚物.不同等规度的丙烯腈聚合物的热分析(DSC及TGA)表明,随着聚合物等规度的提高,聚合物的环化放热峰值温度向高温区移动,而且随着聚合物等规度的提高,环化放热峰变宽.随着聚合物等规度的提高,聚合物的热稳定性变差,热失重增加,碳收率降低.     

丙烯腈与衣康酸在DMSO/H_2O中的聚合及聚合物性能表征

采用丙烯腈 (AN)与衣康酸 (IA)为共聚单体 ,以偶氮二异丁腈为引发剂在混合介质二甲基亚砜 水(DMSO H2 O)中自由基沉淀共聚合 ,合成了高分子量的聚丙烯腈 .通过正交设计方法研究了聚合反应条件 ,如反应温度、单体浓度、混合介质DMSO H2 O配比等对聚合反应的转化率的影响 ,还重点探讨了混合介质DMSO H2 O配比对转化率和粘均分子量的影响 .采用DSC ,TG ,IR等手段研究了PAN均聚物及 (PAN co IA)的结构与性能 .研究结果表明 ,增加反应温度 ,降低单体浓度 ,降低喂料AN IA配比中IA的含量 ,均有利于提高聚合反应的转化率 .AN与IA共聚反应的转化率随着反应介质中DMSO含量的增加而降低 ,同时聚合物的粘均分子量也降低 .对于喂料AN IA配比中IA含量相同的P(AN co IA)共聚物 ,高分子量P(AN co IA)共聚物比常规低分子量的放热峰起始温度低 ,放热峰宽     

云点法研究丙烯腈共聚体系反应活性及其与热稳定性能的关联

采用滴定实验法分别测试了衣康酸(IA)、丙烯酰胺(AM)、丙烯酸甲酯(MA)与丙烯腈(AN)一系列单体组成比时的云点;采用红外光谱、示差扫描量热分析和热失重分析研究了共聚单体的选择对共聚物热稳定化反应的影响和机理及其与共聚体系反应活性的关联.结果显示,IA、AM或MA的引入有利于提高AN聚合体系的云点,不同共单体用量构成的云点迹线斜率可以比较共聚体系反应活性,并对AN共聚体系组成的优化选择具有普适性;而AN与IA较高的共聚反应活性使得P(AN/IA)聚合物热稳定性能好,氰基未环化指数、环化反应起始温度及表观活化能低,环化反应速率快,这可能由于IA分子结构含有2个羧基,引发活性点较多,可以在低温条件下引发氰基环化形成更多的梯形结构.     

乙烯基单体/N-苯基马来酰亚胺共聚物组成预测、控制和优化

采用递推方法成功地预测了乙烯基单体/N-苯基马来酰亚胺(PMI)共聚物组成随转化率的变化.选择共聚单体种类和用量,控制和优化共聚物组成.针对氯乙烯(VC)/PMI/丙烯腈(AN)三元悬浮共聚合特殊体系的聚合特点和工艺,得到该三元体系的单体选择范围.     

聚合反应介质对丙烯腈/衣康酸共聚物结构与性能的影响

利用混合溶剂沉淀聚合法研究了水/环丁砜(H_2O/TMS)等4种不同聚合反应介质对丙烯腈/衣康酸(AN/IA)共聚物的转化率、重均分子量(Mw)及分布(D)、表面微观形貌、竞聚率及链结构、聚合物热性能和纺丝性能的影响.结果表明,P(AN/IA)聚合物转化率随着混合溶剂中H_2O含量的增加,呈先升高后降低的趋势.P(AN/IA)的Mw与水/溶剂比例成线性增加的关系,其中,以H_2O/TMS作为混合反应介质所制备P(AN/IA)的Mw最大,D最小(小于2).AN与IA以H_2O/TMS为聚合介质时倾向于理想共聚,2IA链段分布几率仅为2.87%.以H_2O/TMS为聚合体系所制备P(AN/IA)结构疏松、颗粒粒径较小且易溶解,预氧化时环化反应放热速率低、放热区间宽,热稳定化阶段形成耐热梯形结构反应所需能垒小.P(AN/IA)/TMS纺丝溶液的表观黏度低,TMS为PAN的良溶剂.     

St/AN乳液共聚合的表观竞聚率和恒比组成

<正> 共聚合中竞聚率的正确测算对于研究共聚物组成与单体配料比及转化率的关系、共聚物组成分布及链段分布和共聚合机理都有重要意义。对于大多数二元自由基共聚体系,聚合方法不同对竞聚率无影响,但对某些聚合体系,如苯乙烯/丙烯腈,不同的聚合方法测得的“竞聚率”会有所不同。一般文献报道,苯乙烯/丙烯腈自由基共聚合,60℃下的竞聚率分别为r_st=0.41±0.08,r_(AN)=0.04±0.04,均系本体聚合的实验结果。为此,     

乙醇/水介质中丙烯酰胺的分散聚合动力学

以聚乙烯吡咯烷酮(PVP)为稳定剂,亚硫酸氢钠和过硫酸铵为引发剂(I),丙烯酰胺(AM)为单体,在体积分数为90%的乙醇水溶液中,采用分散聚合方法合成了聚丙烯酰胺(PAM)双水相乳液。 考察了聚合反应温度、引发剂质量分数、单体质量分数、PVP质量分数对分散聚合转化率、聚合速率、聚合物分子量和乳液稳定性等性质的影响。 结果表明,AM质量分数从10%提高至25%时,初始聚合速率、最终转化率及聚合物相对分子质量增大,其中初始聚合速率增大约20倍。 但单体质量分数不可过高,否则会因体系粘度过大而形成凝胶。 PVP质量分数增大,初始聚合速率及最终转化率变小,但PVP质量分数过大和过小均不利于双水相乳液的稳定。 随着温度的升高,聚合速率显著增加,而聚合物相对分子质量从20 ℃时的5.08×105降至70 ℃时的0.39×105。 引发剂的质量分数从0.05%增加至0.15%时,单体AM转化率增大,而聚合物PAM的相对分子质量则从4.31×105降至3.73×105。 当引发剂质量分数为0.05%时,反应存在20～25 min的诱导期,导致最大聚合速率推后60 min左右出现。 AM、引发剂和稳定剂的质量分数分别为15%、0.05%和6%时,在30 ℃下反应6 h所得乳液的粒径范围为10～75 μm,平均粒径为21.94 μm。 粒径较大且分布较宽,乳液稳定性较差。 转化率50%时分散聚合速率与各组分质量浓度的关系为：rp=kρ0.33Iρ0.84AMρ-2.56PVP,聚合反应表观活化能为40.95 kJ/mol。     

衣康酸对聚丙烯腈原丝结构和性能的影响

控制单体配比 ,采用丙烯腈 (AN)与衣康酸 (IA)自由基溶液共聚 ,以偶氮二异丁腈为引发剂在溶剂二甲基亚砜中合成了聚丙烯腈原丝纺丝溶液 ,并纺制了碳纤维前驱体聚丙烯腈原丝 .通过元素分析、IR、DSC、13 C NMR等手段 ,讨论了共聚单体IA对共聚反应及聚丙烯腈原丝结构和性能的影响 .共聚反应时 ,共聚单体IA的加入量控制在AN/IA =98/2 (W/W )较合适 .利用IR谱 ,可定量分析IA在共聚中的摩尔分数 .经13 C NMR分析 ,随着共聚单体IR在共聚物中的摩尔分数的增加 ,共聚物的全同规整度增加 ,达到一定值后又呈下降趋势 .共聚单体IA能在较低温度时引发聚丙烯腈原丝的氧化、环化放热反应 ,且能减缓放热效应 .     

用双硫酯链转移法合成嵌段聚合物

研究了以双硫酯为链转移剂进行的均聚和嵌段共聚物的合成。首先合成大分子链转移剂,得到分子量可控、多分散性系数（PDI）较小（＜1.30）的均聚物。用末端带有双硫酯基因的PSt,PBMA和PBA为链转移剂,加入第二单体聚合得到分子量可控、且PDI较小的两嵌段聚合物。嵌段聚合时必须加入微量的自由基引发剂以形成大分子自由基,达到较好的控制聚合效果。     

丙烯酰胺多面体低聚倍半硅氧烷在超临界CO2中的RAFT聚合

以超临界CO₂为聚合介质, 硫代苯甲酰基特丁基硫酯(TTBT)为链转移剂, 通过可逆加成-断裂链转移(RAFT)聚合制备了聚丙烯酰胺多面体低聚倍半硅氧烷(PAMPOSS)均聚物及其与甲基丙烯酸甲酯(PMMA)的嵌段共聚物(PAMPOSS-b-PMMA). 对产物结构组成和分子量及其分布进行表征. 结果表明, 在TTBT的控制下, POSS的均聚物和嵌段共聚物具有高分子量及窄分子量分布. 含POSS单体在超临界CO₂中为均相聚合, POSS聚合物的结晶性在一定程度上影响其在超临界CO₂中溶解性.     

辐射引发丙烯腈－丙烯酸甲酯－衣康酸三元沉淀共聚合

辐射引发丙烯腈－丙烯酸甲酯－衣康酸三元沉淀共聚合张志成,葛学武,葛敏,张健（中国科学技术大学应用化学系,合肥,２３００２６）关键词聚丙烯腈,超高分子量,辐射引发,沉淀共聚合制备高性能的碳纤维,首先要制备优良的丙烯腈基原丝（ＳＡＦ）．ＳＡＦ聚合物具有超...     

Copolymerization of 2,3-Dihydropyran and Ethyl Vinyl Ether with Maleic Anhydride

2,3-Dihydropyran (DHP) and ethyl vinyl ether (EVE) were co-polymerized with maleic anhydride (MA) with benzoyl peroxide at 60°C, and 1:1 alternating copolymers were obtained. The rates were maximum at 1:1 monomer composition. Spontaneous copolymerization and solvent effect on the rate were observed in the copolymerization of DHP with MA, in which initial rates were slower in more polar solvents. Participation of charge transfer complex was considered. EVE copolymerized rapidly with MA, reaching the theoretical limiting conversion of 1:1 alternating copolymerization. Although DHP-MA comonomer pair and EVE-MA comonomer pair formed similar 1:1 charge transfer complexes, DHP copolymerized slowly with MA to produce a low molecular weight copolymer, and the limiting conversion was much lower than the theoretical one. To explain these, degradative chain transfer to DHP monomer is proposed as the initial rate of DHP-MA copolymerization is proportional to the initiator concentration to the power 1.1. Q and e values of DHP were calculated to be 0.013 and -0.93, respectively, from the monomer reactivity ratios of copolymerization of DHP with acrylonitrile [r₁ (DHP)=0.003 ± 0.006 and r₂ (AN)=3.6 ± 0.3].     

Determination of chain transfer constant to dodecanethiol in styrene/methyl methacrylate and butyl acrylate/methyl methacrylate copolymerization and effect of chain length on composition and stereochemical configuration of copolymers

Free radical copolymerization of styrene/methyl methacrylate (S/MMA) and butyl acrylate/methyl methacrylate (BA/MMA) in the presence of n-dodecanthiol (DDT) has been studied at 60°C in a 3 mol/L benzene solution using 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. Overall chain transfer constant to DDT has been determined for both copolymerization systems, as a function of monomer feed composition using complete molecular weight distribution and the Mayo method. Overall transfer coefficients have values which are dependent on both monomer feed composition and individual comonomer transfer values. Composition, sequence distribution, and stereoregularity of copolymers obtained are, in our experimental conditions, independent of copolymer molecular weight. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2913–2925, 1998     

以双硫酯为链转移剂的活性自由基聚合

合成并研究了两种双硫酯链转移剂的纯化方法 ,进行了多种单体以双硫酯为链转移剂的活性自由基聚合及嵌段共聚 .发现以PhC(S)SC(CH3) 2 Ph为链转移剂的效果比PhC(S)SCH(CH3)Ph好 ,聚合产物的多分散性系数较小 .引发剂与链转移剂的摩尔数比为 1∶3 5～ 1∶4 2时 ,得到多分散性系数小 ,实测分子量与理论分子量相近的聚合产物 .聚合物的分子量随时间和转化率的增加而增加 ,加入第二单体形成嵌段共聚物 ,具有活性聚合特征 .聚甲基丙烯酸酯大分子引发剂引发丙烯酸酯单体聚合时 ,聚合速度最快 .     

Controlled synthesis of styrene and methyl methacrylate copolymers in the presence of reversible addition-fragmentation chain-transfer agents

Molecular-mass characteristics of styrene-methyl methacrylate copolymers formed via the reversible addition-fragmentation chain transfer copolymerization mediated by dithiobenzoates have been studied. Low-molecular-mass reversible-addition fragmentation chain-transfer agents active in the homopolymerization of both monomers and in the homopolymerization of only one of the monomers (styrene) can be used for the controlled synthesis of narrow dispersed copolymers. Conditions for the synthesis of narrow dispersed block copolymers with the desired structure and molecular mass of the blocks have been found. The polymer reversible addition fragmentation chain-transfer agent determines the composition and molecular mass of the first block. The structure of the second block is defined by the composition of the monomer mixture, and the molecular-mass characteristics are set by the concentration of the agent and the conversion of monomers.     

Property changes of powdery polyacrylonitrile synthesized by aqueous suspension polymerization during heat-treatment process under air atmosphere

High molecular weight powdery polyacrylonitrile (PAN) polymers were prepared by aqueous suspension polymerization employing itaconic acid (IA) as comonomer and alpha,alpha(')-azobisisobutyronitrile (AIBN) as initiator at 60 degrees C. PAN polymers obtained with different monomer ratios were characterized by EA, DSC, FTIR and XRD. It is investigated that the oxygen element content in PAN polymers increased with the increase of required IA amounts in the feed and heat-treatment temperatures. DSC curves of PAN copolymers exhibited the triplet character, owing to the exothermic cyclization and oxidative reactions during heat-treatment process. Introduction of IA in the feed relaxed exothermic reactions of PAN polymers under air atmosphere. Structure and crystallinity changes were affected by required IA amounts in the feed and enhancement of heat-treatment temperatures. The characteristic functional groups (including C[triple bond]N, C=O, CH(2)) presented in FTIR spectra of PAN polymers indicated copolymerization reaction of AN and IA. Existence of some organic groups (C-O, C=C and/or C=N) indicated formation of ladderlike structure during heat-treatment process. PAN homopolymer had the better crystallinity (mainly peak intensity and peak area around 2theta = 17 degrees) than most RT-PAN copolymers. When heat-treatment temperature is around 210 degrees C, peak intensity, peak area, L(c) and CI of HT-PAN polymers corresponding to samples 1# and 2# got maxima, while crystallinity became weak at higher heat-treatment temperatures.     

甲基丙烯酸丁酯和苯乙烯的原子转移自由基嵌段共聚

活性聚合以其无链转移、无链终止和引发速度远大于增长速率的特点,应用于合成单分散聚合物、预定序列结构的嵌段共聚物等．常用的活性聚合方法如阴离子聚合、阳离子聚合及基团转移聚合对反应条件要求苛刻,不能用于丙烯酸酯类极性单体和苯乙烯类非极性单体的嵌段共聚．与...     

4-乙酰氨基-4’-甲基丙烯酰氨基-二苯基甲烷的合成及其聚合

N-芳基丙烯酰胺是-类功能性单体,它能与丙烯酸酯类单体进行自由基共聚合。本文以4,4'-二氨基二苯基甲烷为起始原料,合成了新的带有较长侧基的甲基丙烯酰胺类单体,即4-乙酰氨基-4'-甲基丙烯酰氨基-二苯基甲烷(AMDPM)。它能进行自由基聚合或与丙烯酸甲酯(MA)共聚合。