芳香叔胺引发丙烯腈光聚合研究

我们发现芳香叔胺是丙烯腈聚合极有效的光引发剂。芳香叔胺苯环上氢被正性基取代时,引发能力增加,被负性基取代时,引发能力下降。下列胺的活性次序是:N,N-二甲基对甲苯胺(DMT)>N,N-二羟乙基对甲苯胺(DHET)>N,N-二甲基苯胺(DMA)>N,N-二甲胺基苯甲醛(DMB)>N,N-二甲基对硝基苯胺(DNA)。芳香叔胺引发丙烯腈光聚合属自由基机构,聚合速度与叔胺浓度的0.66次方成正比。在叔胺浓度为10~(-2)—10~(-4)M范围内,聚合物平均聚合度的倒数与叔胺浓度的0.5次方成正比。初步认为在紫外光激发下,芳香叔胺与丙烯腈分子生成激发态电子转移络合物,再分解产生自由基,引发丙烯腈聚合。     

丙烯酸酯在胺存在下的氧化和聚合研究

胺促进丙烯酸酯氧化和聚合与胺及丙烯酸酯结构有关。芳香胺氮原子或苯环上有正性取代基时,促进作用大。带醚键的丙烯酸酯氧化和聚合快。 胺引发丙烯酸酯聚合认为先是胺促进丙烯酸酯氧化,生成单体过氧化物,与胺再形成复合物,分解产生自由基,促进更多丙烯酸酯氧化,继而引起聚合。     

含胺基功能性单体的聚合研究——Ⅲ.甲基丙烯酸4-(N,N-二甲氨基)苄酯在过氧化月桂酰引发下的聚合动力学

<正> 由芳香叔胺如N,N-二甲基对甲苯胺(DMT),N,N-二甲基苯胺(DMA)与过氧化苯甲酰(BPO)所组成的氧化还原体系以引发烯类单体的聚合已有较多报道,这种引发体系在医用高分子的硬组织材料如齿科材料,骨水泥的甲基丙烯酸甲酯(BMA)的低温快速固化上广被应用,构成这种氧化还原体系的低分子胺具有一定的毒性,其用量虽少,     

甲基丙烯酸甲酯辐射引发聚合

约于1940年开始研究的甲基丙烯酸甲酯的辐射聚合,是辐射聚合中研究得最早和最多的单体之一。其研究路线,早期为场内辐射聚合,即整个聚合过程在辐射场内完成;后期则对场外辐射聚合(聚合过程在辐射场外完成)进行了一些研究工作。按自由基机构聚合的乙烯基单体,在辐射场内有氧存在下辐照时,由于最初生成的自由基与氧作用形成不稳定的过氧化物,单体不被聚合。当辐照体系离开辐射场,并去氧(抽真空或氮置换),或加还原剂后,形成的过氧化物立即分解,聚合以高速率进行。基于     

芳香叔胺与卤代烷光化学反应的研究——产物结构与反应机理

胺类化合物与分子氧形成接触电荷转移复合物(CCT,Contact Charge Transfer Complex),本文研究了卤代烷存在下芳香叔胺与O_2 CCT的光化学反应,分析结果表明反应产物为胺正离子自由基盐,以N,N-二甲基对甲苯胺为例,产物为胺正离子自由基盐具有一定的氧化性,可将肾上腺素氧化成肾上腺素红,本文对卤代烷存在下胺与O_2 CCT光化学反应机理作了初步阐述,并讨论了肾上腺素氧化反应的机理。     

含胺基功能性单体的聚合研究——Ⅵ.4-N′,N′-二甲氨基苯基N-取代丙烯酰胺的合成及其聚合

<正> 前文报道了含芳香叔胺基丙烯酸酯-甲基丙烯酸4-N,N-二甲氨基苄酯(DMABMA)的合成和聚合。这种在分子中既含有二甲氨基苯基,又含有双键的单体为“可聚合芳香叔胺”,在过氧化二酰如过氧化苯甲酰(BPO),过氧化月桂酰(LPO)引发下,芳香叔胺残基参与氧化还原引发体系,进而双键发生聚合反应。本文报道了二甲氨基苯基取代丙烯酰胺,即N-(4-N,N‘-二甲氨基苯基)丙烯酰胺(DMAPAA)和N-(4-N,N-二甲氨基苯基)甲基丙烯酰胺(DMAPMA)的合成及聚合。     

电荷转移聚合研究——苯肼及其衍生物引发丙烯腈聚合

研究了苯肼(PHZ)及其衍生物引发丙烯腈(AN)聚合以及苯肼作为电子给体与醌作为电子受体形成的电荷转移复合物(CTC)对丙烯腈的引发聚合作用。测定了光聚合时的引发剂、单体指数和聚合活化能分别为0.66、2.1和33.4千焦耳/摩尔。光聚合机理认为是PHZ与AN在光照下形成激基复合物(exciplex),它分解产生自由基引发单体聚合。而暗聚合的机理认为是PHZ与醌形成CTC,CTC再分解引发单体聚合。exciplex与CTC分别已由荧光光谱和紫外吸收光谱检出。     

电荷转移引起的光聚合反应

通过电荷转移引发的光聚合反应中涉及电子给体和电子受体形成的激基复合物,这激基复合物进一步产生活性中心,引发聚合。本文重点介绍两类聚合:1、电子给体引发剂引发电子受体单体光聚合,以芳香胺引发丙烯腈、甲基丙烯酸甲酯等烯类单体聚合为代表;2、双组分引发体系经光的电荷转移产生自由基引发聚合,以二苯酮一芳香胺、稠芳烃—芳香胺体系为代表。     

电荷转移复合物和光诱导电荷转移聚合

讨论了电子受体和给体的强弱与形成基态、激发态电荷转移复合物的性质、类型等的关系。着重讨论了氧与有机化合物分子形成的接触电荷转移复合物及烯类单体与电子给体或受体形成的光诱导电荷转移复合物。讨论了使烯类单体发生光诱导电荷转移聚合和电子给体的分子结构对它的影响;并从形成激基复合物的观点对自由基阻聚剂酚噻嗪在光照下失去阻聚能力作了解释。     

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。     

STRUCTURAL EFFECT ON VINYL POLYMERIZATION INITIATED WITH AROMATIC TERTIARY AMINE

The polymerization mechanism of various vinyl monomers in the presence of aromatic tertiary amines has been studied. It was found that the mechanisms of different monomers are varied with the structures of monomers. Those monomers, such as methacrylic esters containing α-CH_3 group on the double bond could be polymerized with aromatic tertiary amine in the absence of light, while the monomers without α-CH_3 group, such as methyl acrylate, acrylonitrile etc. would polymerize only under light.The structural effects, both of the monomer and the amine, on the rate of photopolymerization were studied. The activities of monomers and amines may be arranged in the following orderMonomer: AN>MA>VA>St Amine: DMT>DMA>DMB>DNAIt is revealed that both the electro-negative group on the double bond of monomer which acts as an acceptor and the electro-positive group on the nitrogen atom of amine which acts as a donor would effectively increase the rate of photopolymerization.     

用电子吸收光谱和荧光光谱研究芳胺引发的光聚合机理

用紫外吸收光谱和荧光光谱分析了苯胺等芳胺引发光聚合的聚丙烯腈和聚甲基丙烯酸甲酯的端基,认为一级胺引发的聚合物端基为二级胺,二级胺引发的聚合物端基为三级胺,从而表明,一级芳胺和二级芳胺在光照下与烯类单体相互作用产生氮自由基引发聚合。     

甲基丙烯酸(N,N-二甲氨基)乙酯的自引发催化氧化聚合

作为一种自身还原性单体,甲基丙烯酸(N,N-二甲氨基)乙酯(DMAEMA)可与部分氧化剂构成氧化还原引发剂体系,并引发自身的聚合.为验证该假设,进行了以CuCl2络合物催化DMAEMA的本体氧化聚合.动力学研究表明,所得聚合物的分子量随着聚合时间的延长而逐渐增加.核磁波谱分析表明,低转化率下所得低聚物同时含有甲基丙烯酸酯末端和C-Cl端基,显示DMAEMA的二甲氨基(N-CH3)被CuCl2氧化成单体自由基(N-CH2·),并通过原子转移自由基聚合(ATRP)机理形成聚合物.由于叔胺广泛地用作ATRP的络合物,由此可见,在传统ATRP体系中,来自CuCl2/叔胺的氧化还原引发不可忽略.     

Vinyl polymerization. 422. Initiation mechanism of uncatalyzed polymerization by polyethyleneglycol

The initiation mechanism on the radical polymerization of vinyl monomers by polyethyleneglycol (PEG-300) in aqueous solution was studied. The initiating radical species were determined by means of the spin trapping technique. They were concluded to be generated by the hydrogen atom transfer from the monomer adsorbed at the ether group of PEG-300 to the free monomer.     

Graft polymerization of vinyl monomers onto cellulose in presence of soda lime glass. I

Sodium bisulfite–soda lime glass has proved to be a good initiator for polymerization and graft polymerization onto cellulose of some vinyl monomers. A scheme dealing with the mechanism of initiation has been proposed assuming trapping of the bisulfite radical inside the glass frame-work to form a so-called sulfur-impregnated solid. Such a solid has paramagnetic properties and acts on the vinyl monomers and cellulose as any free-radical-producing source thus leading to polymerization and graft polymerization onto cellulose. Other radicals containing sulfur, such as sulfite, sulfate, and persulfate failed to give such property with soda lime glass. With the sodium bisulfite–soda lime glass system the reactivity decreases in the order methyl methacrylate > ethyl acrylate > acrylonitrile which is inconsistent with the arrangement of acceptor monomers with decreasing electron-donating ability. This may reflect interference of the addition reaction which may take place between the monomer and bisulfite and the rate of which may depend on the activation energy of the monomer.     

甲基丙烯酸2-(N-吖啶酮基)乙酯的合成及其敏化的烯类单体光聚合

我们曾报道过4-甲基丙烯酰氧基二苯甲酮(MABP)与甲基丙烯酸N,N-二甲氨基乙酯(DMAEMA)构成的氧化还原引发体系敏化丙烯腈的光聚合。由于MABP及DMAEMA是可聚合的二芳基酮和脂肪叔胺,因而既能参与引发又能参与聚合而进入聚合物链中。一般二苯甲酮要同三级胺,如三乙胺等一起在紫外光照条件下形成光氧化还原引发体系才能有较好的引发效果。同一分子中既含二苯甲酮基又含三级胺基的光敏剂,     

甲基丙烯酸2-(N-吖啶酮基)乙酯的合成及其敏化的烯类单体光聚合

A novel acrylic monomer having acridonechromophore, 2-(N-acridonono)ethyl methacry-late (AEMA) was prepared from methacryloyl chloride and N-hydroxyethyl acridone (HEA), which was obtained by reaction of acridone with ethylene carbonate. Both the monomer and its polymer can initiate the photopolymerization of vinyl monomers, such as AN, MMA etc, but P(AEMA) has higher initiation ability than monomeric AEMA does. The effects of oxygen and aliphatic tertiary amine on the polymerization rate were also revealed. The UV-analysis indicates that AEMA not only initiates photopolymerization of vinyl monomers,but also enters into the polymer chains.     

Synthesis and polymerization of 4-o-vinylbenzyl-2,2,6,6-tetramethylpiperidine

Some hindered amine polymers containing 2,2,6,6-tetramethylpiperidine structure were synthesized. A new monomer, 4-O-vinylbenzyl-2,2,6,6-tetramethylpiperidine, was homopolymerized and copolymerized with some vinyl monomers in the presence of AIBN as an initiator. The obtained amine polymers were oxidized with hydrogen peroxide to obtain the polymers having nitroxyl radical moiety.     

Complexed copolymerization of vinyl compounds with alkylaluminum halides

The monomer reactivity in the complexed copolymerization of vinyl compounds with alkylaluminum halides has been extensively surveyed. Equimolar copolymers were obtained in various combinations of monomers which are classified into two monomer groups, A and B. The group B monomers are conjugated vinyl compounds having nitrile or carbonyl groups in the conjugated position and form complexes with alkylaluminum halides. The group A monomers are donor monomers having low values, such as olefins, haloolefins, dienes, and unsaturated esters. These A monomers belong to the same group of monomers which give alternating copolymers in conventional radical copolymerization with maleic anhydride, SO₂, and so on. In addition the complexed copolymerization has the same specific characteristics as the conventional alternating copolymerization, i.e., high reactivities of allyl-resonance monomers and inner olefins and no transfer of halogen atom to the copolymers in CCl₄. These features suggest little or no participation of the A monomer radical. The Q-e scheme is also discussed in terms of the monomer reactivity. More than two monomers selected from groups A and B give multicomponent copolymers in which alternating sequential structures hold with respect to A and B. Anomalous mutual reactivities between two B monomers in the terpolymerization were observed and indicate that the nature of radical in the complexed copolymerization may be different from that expected by the Lewis-Mayo equation. The complexed radical mechanism previously proposed is discussed in connection with the specific behavior mentioned above.