乙烯系单体自由基聚合的阻聚效应——Ⅸ.受阻胺-醌类电荷转移络合物对甲基丙烯酸甲酯自由基聚合的阻聚及历程

 用膨胀计法研究了西氯苯醌(CA)、苯醌(BQ)与受阻胺二异丙胺(DIPA)、2,2,6,6-四甲基-4-羟基哌啶(TMP)形成的电荷转移络合物(CTC)对偶氮二异丁腈(AIBN)引发的甲基丙烯酸甲酯(MMA)自由基聚合阻聚效应。结果表明,CA-DIPA、CA-TMP、BQ-DIPA和BQ-TMP对MMA的自由基聚合均产生较单独的醌或胺更显著的阻聚能力。其中以CA-DIPA阻聚效果更佳。比较了MMA在苯或乙腈中的溶液聚合,得类似结果。初步讨论了受阻胺-醌电荷转移络合物对MMA自由基聚合的阻聚反应机理。     

乙烯系单体聚合阻聚反应(Ⅵ)——4-位取代2,2,6,6-四甲基哌啶-1氧自由基衍生物同醌类混合对MMA自由基聚合的阻聚效应

本文研究了几种4位取代2,2,6,6-四甲基哌啶-1-氧自由基及1-位取代的2,2,6,6-四甲基哌啶类化合物同醌类混合对甲基丙烯酸甲酯(MMA)自由基聚合的阻聚效应。     

乙烯类单体自由基聚合的阻聚效应——Ⅻ.酰氨基硫脲及某些杂环衍生物对醋酸乙烯酯聚合的影响

众所周知,酚类、胺类、醌类、硝基以及亚硝基化合物对烯类单体的自由基聚合有阻聚作用。一些杂原子化合物如RNHNHR′,RSR(RNHCSS)₂M等对烯类单体的自由基聚合也能产生阻聚^[1-5]。     

乙烯系单体自由基聚合的阻聚效应 ⅩⅢ.1,3,5-三苯甲(月替)与取代硝基苯混合物对甲基丙烯酸甲酯聚合的影响

研究1,3,5-三苯甲(月替)(TFH)与一些4-取代硝基苯(4SNB)和4-取代-1,3-二硝基苯(4SDNB)的混合物对偶氮二异丁腈引发的甲基丙烯酸甲酯(MMA)自由基聚合的影响。结果表明,TFH-4SNB配方对MMA聚合的阻聚功效与4SNB中取代基的电子效应有关。吸电子取代基能延长诱导期,提高阻聚能力。推电子基则降低聚合诱导期。对于TFH-4SDNB配方,聚合诱导期依赖于取代基的空间位阻:取代基的原子半径增大,聚合诱导期降低。     

乙烯系单体自由基聚合的阻聚效应——Ⅷ.1,3,5-三苯甲(月替)对甲基丙烯酸甲酯的自由基阻聚及历程

用膨胀计法研究了1,3,5-三苯甲(月替)(TFH)及其与苯醌(BQ)、四氯苯醌(CA)和1,4-萘醌(NQ)的混合物对偶氮二异丁腈引发的甲基丙烯酸甲酯的阻聚效应。结果表明,TFH与BQ或NQ按一定比例混合阻聚效果显著。但TFH与CA混合则阻聚效果反倒比TFH单独用作阻聚时差。文中研究TFH的变色反应以及聚合系统中(TF·)的存在。初步讨论了TFH及TFH-Q混合对MMA的阻聚反应机理。     

胺存在下自由基聚合与活性自由基聚合

综述了胺存在下自由基聚合,包括含胺的过氧化二酰与芳叔胺氧化还原体系、有机过氧化氢物与芳叔胺或脂肪叔胺氧化还原体系、过硫酸盐与脂肪胺氧化还啄体系和极性单体的胺光诱导电荷转移引发自由基聚合,以及活性／控制自由基聚合,主要为原子转移自由基研究的成果。     

乙烯系自由基聚合阻聚效应(XⅧ)──哌啶氮氧自由基氨基硫脲化合物与通用阻聚剂混合对MMA阻聚效应研究

本文研究了3种1-(芳酰基)-4[4'-(2,2,6,6-四甲基哌啶)-1-氧自由基]氨基硫脲化合物(ATSCPO)分别同通用阻聚剂(CIH),如对苯二酚(HQ)、苯醌(BQ)、吩噻嗪(PT)及二乙羟胺(DEHA)组成的混合阻聚剂对AIBN引发的MMA自由基聚合的影响。研究结果表明:当[ATSCPO]/CIH=5:1时,除ATSCPO-BQ外,其余阻聚效果均较ATSCPO和CIH单独用作阻聚剂时高,如聚合反应诱导期延长、聚合速率下降、聚合物粘均分子量变小等,表明ATSCPO和CHI间有协同效应。通过对阻聚因素的考察,得出阻聚剂的活性次序为ATSCPOHQ>ATSCPO-PT>ATSCPO-DEHA≈ATSCPO-BQ.     

氧气分子参与的乙烯基单体自由基聚合

尽管被公认在自由基聚合中往往起着缓聚、阻聚或链转移的作用,越来越多的结果表明,在某些情况下,如高温、高压,或当某些催化剂存在时,氧气分子(O2)可以参与甚至加速乙烯基单体的自由基聚合。本文综述了上世纪90年代以来,O2参与的乙烯基单体的热/光诱导自由基聚合、化学引发自由基聚合、氧载体催化自由基聚合以及可逆加成-断裂链转移自由基聚合。以上结果表明,在上述情况下,O2,作为一个普通不饱和单体,可以与苯乙烯、甲基丙烯酸甲酯等乙烯基单体形成交替共聚物(聚过氧化物),而此类聚过氧化物均可裂解为自由基。     

甲基丙烯酸甲酯自由基聚合歧化终止机理

首先用过氧化二苯甲酰(BPO)引发甲基丙烯酸甲酯(MMA)自由基聚合合成聚甲基丙烯酸甲酯(PMMA),然后用偶氮二异丁腈(AIBN)为引发剂,研究PMMA中由歧化终止生成的末端双键与苯乙烯(St)的共聚合反应行为。采用体积排除色谱(SEC)、核磁共振波谱(NMR)对聚合物进行了分析表征。结果表明：与单体MMA相似,PMMA在化学位移δ=6.20和5.47处有对应于聚合物末端双键氢的NMR信号。远程异核和近程异核相关NMR,¹³C-NMR和DEPT-135 NMR分析和自由基共聚合实验确证：MMA自由基聚合的双基歧化终止为单一的链自由基末端β位甲基氢自由基转移机理,生成1,1-二取代甲基丙烯酸酯型双键。除双基歧化终止反应外,体系还明显地存在苯甲酰初级自由基和苯初级自由基与链自由基间的初级终止反应。     

N-乙烯基咔唑与卤代烃引发甲基丙烯酸甲酯聚合的研究

<正> N-乙烯基咔唑(NVC)具有大的共轭结构和中间有一个杂原子氮,而容易与其它试剂反应,形成自由基、阳离子和电荷转移络合物,故是一种活性较高的单体,1970年有人发现NVC与N-C_4H_9NCl_2一起可以引发甲基丙烯酸甲酯(MMA)聚合,此外,文献报道了电子给体如胺与CCl_4体系在二甲亚砜(DMSO)中引发MMA聚合,本文研究了NVC与几种卤代烃所组成的双组分体系对MMA的引发聚合反应;该体系的引发活性和组成与分子量及分子量分布的关系;并探讨了反应机理。     

Inhibition of polymerization of methyl methacrylate by an ortho-benzoquinone-amine system

The kinetic features of the bulk polymerization of MMA in the presence of sterically hindered ortho-benzoquinones and the tertiary amines N,N-dimethylaniline and N,N-dimethylisopropanolamine have been studied. The irradiation of solutions of quinones and amines in MMA with visible light causes inhibition of the thermal polymerization of MMA, with the effects of quinones and amines being synergistic. The effect of inhibition is enhanced as the steric shielding of carbonyl groups of ortho-benzoquinone by substituents becomes weaker. The dependence of the induction period on the redox potentials of quinones passes through a maximum. It is shown that inhibition involves oxyphenoxyl radicals arising from the interaction of the original quinone with the product of its photoreduction in the presence of amines, pyrocatechol. The inhibiting effect depends on the concentration ratio of quinone and pyrocatechol and the nature of amine. When quinone is in excess with respect to pyrocatechol, additional inhibition of polymerization is observed and the rate of quinone consumption during the induction period is increased.     

EFFECTS OF VINYL ETHERS UPON RADICAL POLYMERIZATIONS

Various vinyl ethers have been examined as additives during radical polymerizations initiated by azobisisobutyronitrile at 60°C; the monomers were methyl methacrylate (MMA), styrene (STY) and acrylonitrile (AN). For MMA and STY, the vinyl ethers were incorporated to only small extents but they caused reductions in rate of polymerization and chain length of the resulting polymer; the effects can be attributed to the low reactivities in growth reactions of radicals to which a vinyl ether unit was last added. Copolymerization of the vinyl ethers with AN was more evident but, in many cases, it was accompanied by increased rate of consumption of AN and increased chain length of the polymer. These changes can be explained in terms of a physical effect which can be likened to that believed to be responsible for the gel effect. It is considered that polymer radicals are rather tightly coiled in an indifferent solvent so that the normal bimolecular termination is impeded.     

胺对有机过氧化物引发聚合的影响

<正> 有机过氧化物引发烯类单体的聚合,可以加入芳叔胺促进过氧化物的分解,提高聚合速度。其中最常用的芳叔胺有N,N-二甲苯胺(DMA)、N,N-二甲基对甲苯胺(DMT),本文采用过氧化二苯甲酰(BPO)、过氧化二月桂酰(LPO)、叔丁基过氧化氢(TBH)和过氧化苯甲酸叔丁酯(TBPB)四种过氧化物为引发剂进行甲基丙烯酸甲酯(MMA)的本体聚合,测得其聚合速度R_p的顺序为LPO>BPO>TBH>TBPB,但在添加芳叔胺DMT或脂环叔胺N-乙基哌啶(NEP)时,则聚合速度的顺序变为BPO-胺>LPO-胺>TBH-胺>TBPB-胺。添加这两种叔胺虽然都能促进聚合,但只对BPO引发剂有显著的影响,研究结果如下:     

CuX2络合物催化甲基丙烯酸甲酯的氧化聚合

研究了高氧化态过渡金属卤化物络合物催化甲基丙烯酸甲酯(MMA)的氧化聚合.首先在叔胺类聚合物存在条件下以CuBr2/2,2′-联吡啶(bPy)络合物催化MMA在不同溶剂中的氧化聚合,结果在环己酮中得到PMMA均聚物,CuBr2/bPy同叔胺的氧化还原引发可以忽略.随后在环己酮中分别以不同络合物催化MMA的氧化聚合.结果...     

N-甲基-N-(2-羟乙基)-对-甲苯胺存在下甲基丙烯酸甲酯的自由基聚合

测定了在N-甲基-N-(2-羟乙基)-对-甲苯胺(HMT)存在下,MMA以过氧化物引发的聚合速率和聚合表观活化能.发现HMT对BPO、LPO引发的MMA聚合有促进作用,提高聚合速率.由聚合物端基分析证实了含有HMT的碎片,表明由芳叔胺HMT与BPO反应产生的自由基能引发单体聚合,BPO-HMT引发聚合为一氧化还原引发聚合.     

THE EFFECTS OF ALLYL ETHERS UPON RADICAL POLYMERIZATIONS

Three allyl ethers, viz. the ethyl, 2-hydroxyethyl and phenyl compounds, have been examined as additives in radical polymerizations of styrene (STY), methyl methacrylate (MMA) and acrylonitrile (ACN) at 60°C using azobisisobutyronitrile as initiator. As retarders and transfer agents, the ethers are considerably more effective with ACN than with the other monomers. Allyl phenyl ether engages in significant copolymerization with ACN and slight copolymerization with MMA; there is negligible incorporation in polySTY.     

受阻胺对甲基丙烯酸甲酯聚合的影响

本文研究了受阻胺TMP、TMPM、TUV-770对MMA、St本体聚合的影响。无论用BPO或AlBN引发MMA聚合时,TMPM或TUV-770都能延长诱导期,但对R_p的影响较小,而TMP能使R_p略增。测定了聚合反应的表观活化能和动力学方程。     

Catalytic Effect of Dimethylsulfoxide Complexes of Rh(III) and Ru(II) on the Polymerization of Vinyl Monomers Initiated by 2,2′-Azobisisobutyronitrile

Transition metal salts and complexes catalyze the polymerization of vinyl monomers in the presence or absence of 2,2′-azobisisobutyronitrile (AIBN). In this article the effect of some dimethyl sulfoxide complexes of Rh(III) and Ru(II) on the polymerization of vinyl monomers such as methyl methacrylate (MMA) and methyl acrylate (MA) initiated by AIBN is reported. The percentage conversion and the rate of polymerization of MMA and MA are found to increase rapidly with time. At the critical concentrations of the complexes, the percentage conversion and the rates of reaction are found to be higher than those with AIBN alone, which significantly proves their accelerating effect. At concentrations above and below that of the critical value, the percentage conversion and the rates of polymerization of MMA and MA are found to decrease from those with AIBN alone. The trend of the increase and decrease of the percentage conversion and the rate of reaction with both types of complexes are similar. The solvent used in the polymerization of MMA and MA is dimethylsulfoxide (DMSO) and the temperature of the reaction is 60°C. A precise mechanism for the catalytic reaction is suggested.     

FURTHER STUDY OF ALLYL ETHERS AND RELATED COMPOUNDS AS TRANSFER AGENTS IN RADICAL POLYMERIZATIONS

Allyl glycidyl ether (AGE), allyl 1,1,2,3,3,3-hexafluoropropyl ether (AFE), allyl 2-naphthyl ether (ANE), 2-vinyl-1,3-dioxolane (2VD) and allyl alcohol (AA) have been examined as transfer agents in the radical polymerization of methyl methacrylate (MMA) at 60°C; the transfer constants are 1.1 × 10^?3, 0.1 × 10^?3, 0.2 × 10^?3, 1.1 × 10^?3 and 0.6 × 10^?3, respectively. AFE and AA barely affect the rate of polymerization: AGE, ANE, and 2VD act as weak retarders. There is no direct correlation between effectiveness as a transfer agent and the extent of retardation for these additives. For copolymerization with MMA (monomer-1), the monomer reactivity ratios r₁ are 42 ± 5 and 32 ± 5 for AGE and ANE, respectively; for both cases, r₂ is very close to zero; 2VD engages in copolymerization with MMA to a negligible extent. Experiments involving styrene or acrylonitrile gave results consistent with those obtained using MMA.     

Charge-transfer complexes as polymerization inhibitors. I. Amine–chloranil complexes as inhibitors for the radical polymerization of methyl methacrylate

Charge-transfer complexes of N,N-dimethylaniline (DMA) and triethylamine (TEA) with chloranil have been investigated as inhibitors for the sensitized polymerization of methyl methacrylate (MMA) in bulk and in solution. Complete inhibition is achieved by the complexes of both amines followed by retardation only in case of DMA. The higher inhibiting efficiency of the TEA complexes is attributed to their greater stability. The polymers formed in the presence of chloranil alone or its complexes with both amines are quinonoid and contain no combined nitrogen. The results support the idea that inhibition reaction involve electron transfer from the growing chains to the quinone, with formation of molecular complexes of polymeric cations and semiquinone anions. The latter are the actual inhibiting species, so that the efficiency of inhibiting depends on their concentration, which is determined by the stability of the molecular complexes formed. The inhibition reactions should accordingly be considered as oxidation–reduction processes in which the growing chains are the electron donors. The suggested mechanism affords an explanation for the great differences in the inhibiting power of a particular quinone for the polymerization of different monomers.