电荷转移聚合——酚噻嗪及其衍生物引发丙烯腈光聚合

电荷转移引发的聚合近年来受到人们的广泛注意,许多电子给体,如芳香族的胺、醚、硫醚以及含氮芳杂环化合物,都可引发丙烯腈、甲基丙烯酸甲酯等负性单体光聚合,研究表明,其聚合都是通过电荷转移机制引发的^[1-3]。     

8-丙烯酰氧喹啉及其聚合物与四溴化碳双组分体系敏化的丙烯腈光聚合

我们曾报道过8-丙烯酰氧喹啉本身在光照下可以聚合;8-丙烯酰氧喹啉(AQ)及其聚合物(PAQ)的喹啉环上的氮原子可以和双键缺电子单体如丙烯腈(AN)在紫外光下能形成激基复合物引发AN的光聚合,并且通过荧光分析证明AQ或PAQ还参与AN聚合物链中,含有氮杂环的烯类单体如N-乙烯基咔唑等不仅和缺电子化合物,和一些卤代烷如CCl_4、CBr_4等在激发下也可以形成激基复合物,进而可以引发烯类单体聚     

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。     

哌嗪-二氧化硫电荷转移复合物引发的甲基丙烯酸甲酯光聚合

本文研究了哌嗪 (PPZ)与二氧化硫 (SO2 )电荷转移复合物 (CTC)的制备及其作为光引发剂引发甲基丙烯酸甲酯 (MMA)的聚合 ,发现PPZ/SO2 摩尔比对聚合速率影响甚大 .当PPZ/SO2 为 1∶2时 ,形成了具有潜在引发能力的复合物 (Ⅰ ) .Ⅰ引发MMA光聚合的动力学关系式为Rp =Kp [Ⅰ ] 0 .34[MMA] 1.0 6 ,表观活化能为 2 3 7kJ/mol.并对引发机理进行了探讨     

电荷转移聚合

链引发或链增长过程包含有电荷转移的聚合称电荷转移聚合。通常可分两类:一是电子受体(或给体)直接引发烯类单体聚合。典型例子是电子受体四腈基乙烯(TCNE)引发乙烯基咔唑(给电子单体)聚合,或苯胺(电子给体)引     

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。     

电荷转移聚合研究——三苯基磷引发丙烯腈光聚合

研究了三苯基磷(TPP)引发丙烯腈(AN)光聚合。测定了光聚合速率 R_p与单体浓度、引发剂浓度的关系为:R_p=K[AN]~(1.49)[TPP]~(0.47)以及光聚合反应活化能E_α=6.16千卡/摩尔,从激发态电荷转移机制,讨论了引发聚合机理。     

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:     

N-乙烯基咔唑引发丙烯腈光聚合研究

N-乙烯基咔唑(VCz)是一个正性单体,双键上电荷密度较大,容易在顺丁烯二酸酐、反丁烯二酸二乙酯、丙烯腈(AN)等负性单体诱发下进行正离子聚合,以及与这些单体进行自发的交替共聚合。从结构上看,它又是一个三级胺,氮原子连两个苯基和一个乙烯基,所以电荷密度较大,是一个强电子给体。从芳     

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。     

1H and13C NMR spectral study of the structural effects of substituents in N-vinyl-2-arylpyrroles

Conclusions Alterations of the dihedral angles between the planes of the three unsaturated fragments are interrelated in N-vinyl-2-arylpyrroles. Upon the introduction of a substituent at C³ in the pyrrole ring, the dihedral angle between the planes of the aryl and pyrrole ring increases, while the corresponding angle between the planes of the vinyl group and pyrrole ring decreases.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2765–2769, December, 1988.The authors express their gratitude to V. K. Turchanin for a useful discussion of these results.     

The Effective Conjugation Length Is Responsible for the Red/Green Spectral Tuning in the Cyanobacteriochrome Slr1393g3

The origin of the spectral shift from a red‐ to a green‐absorbing form in a cyanobacteriochrome, Slr1393g3, was identified by combined quantum mechanics/molecular mechanics simulations. This protein, related to classical phytochromes, carries the open‐chain tetrapyrrole chromophore phycocyanobilin. Our calculations reveal that the effective conjugation length in the chromophore becomes shorter upon conversion from the red to the green form. This is related to the planarity of the entire chromophore. A large distortion was found for the terminal pyrrole rings A and D; however, the D ring contributes more strongly to the photoproduct tuning, despite a larger change in the twist of the A ring. Our findings implicate that the D ring twist can be exploited to regulate the absorption of the photoproduct. Hence, mutations that affect the D ring twist can lead to rational tuning of the photoproduct absorption, allowing the tailoring of cyanobacteriochromes for biotechnological applications such as optogenetics and bioimaging.     

芳香叔胺引发丙烯腈光聚合的引发机理

芳香叔胺引发丙烯腈(AN)光聚合是通过形成激基复合物(exciPlex)进行的。紫外光谱和荧光光谱表明,芳香叔胺在基态可以和AN形成电荷转移复合物(CTC),而在激发态可和AN形成exciplc(称定域激发)。CTC经光照亦可激发(称CTC激发)。 定域激发引起光聚合速率为CH_3C_6H_4N(CH_3)_2>C_6H_5N(CH_3)_2>HOCH_2·C_6H_4N(CH_3)_2>CH_3C_6H_4N(CH_2CH_2OH)_2,与芳胺荧光被AN淬灭的Stern-Vo-lmer常数顺序一致。CTC激发引起的光聚合顺序为:CH_3C_6H_4N(CH_3)_2>CH_3C_6H_4N(CH_2CH_2OH)_2>HOCH_2C_6H_4N(CH_3)_2>C_6H_5N(CH_3)_2,与芳胺上取代基推电子能力一致。端基分析表明聚合物有芳胺端基。     

Indachlorins: Nonplanar Indanone‐Annulated Chlorin Analogues with Panchromatic Absorption Spectra between 300 and 900 nm

Indaphyrins, pyrrole‐modified porphyrins containing a cleaved pyrrole β,β′‐bond and two annulated indanone moieties, possess unusually broadened and redshifted UV/Vis spectra because of their π‐expanded chromophores. The parent free base indaphyrin has been crystallographically characterized, highlighting its strongly ruffled conformation incorporating a helimeric twist. It was shown to be susceptible to regiospecific derivatizations at the opposite side of the ring‐cleaved pyrrole (dihydroxylation, followed by functional group transformations of the resulting diol functionality), generating indaphyrin‐based chlorin analogues, indachlorins, that incorporate a dihydroxypyrroline, pyrrolindione, oxazolone, or a morpholine moiety. Structural modifications resulted in further broadening and hyper‐ and bathochromic shifts of the optical spectra, some of which possess a nearly panchromatic absorption between 300 to well above 900 nm. The extents to which these modifications affect their solid‐state conformations were analyzed.     

N‐(o‐Chloro­phenyl)‐2,5‐di­methyl­pyrrole‐3‐carb­aldehyde

Crystal structure analysis of the title compound, C₁₃H₁₂ClNO, reveals three crystallographically independent mol­ecules in the asymmetric unit. The main conformational difference between these mol­ecules is the orientation of the phenyl rings with respect to the pyrrole rings. The coplanar arrangement of the aldehyde groups attached to the pyrrole rings influences the pyrrole‐ring geometry. The C2—C3 and N1—C5 bonds are noticeably longer than the C4—C5 and N1—C2 bonds. Two independent mol­ecules of the title compound form dimers via intermolecular C—H⃛O hydrogen bonds [D⃛A = 3.400 (3) Å and D—H⃛A = 157°]. The perpendicular orientation of the phenyl and pyrrole rings of one independent mol­ecule and its symmetry‐related mol­ecule allows C—H⃛π interactions, with an H⃛centroid distance of 2.85 Å and a C—H⃛π angle of 155°. The distances between the H atom and the pyrrole‐ring atoms indicate that the C—H bond points towards one of the bonds in the pyrrole ring.     

THE EFFECT OF MOLECULAR SHAPE ON THE FLUORESCENT PROPERTIES OF 9, 10-DIPHENYLANTHRACENE

Abstract. ESR measurements on 9, 10-diphenylanthrace in solution show that the molecule is non-planar, the two phenyl rings being twisted by about 66° relative to the anthracene nucleus. This agrees with previous predictions made on the basis of scale models.
Evidence from absorption and fluorescence spectra for a change of angle between ground and excited state is examined, and a decrease of about 6° is found for the excited state. On the basis of the large angle of twist possible reasons are suggested for the difference between anthracene and 9, 10-diphenylanthracne with regard to dimer formation and quantum yield of fluorescence in solution.     

MODELS FOR THE CHROMOPHORE STRUCTURE OF THE PHOTOTRANSFORMATION INTERMEDIATES OF PEA PHYTOCHROME IN VITRO

Abstract— The changes in the chromophore structure of pea phytochrome during phototransformation in vitro from the red-light-absorbing form (P_r) to the far-red-light-absorbing form (P_fr), and from P_fr to P_r, were analysed in terms of wavelength and oscillator strength of absorption, using the zero-differential overlap approximation of the molecular orbital theory for electrons. The effect of a point-charge and a point-dipole on the optical absorption of phytochromobilin intermediates were examined using the stationary perturbation theory for degenerate states. The results indicate that the cis-trans photoisomerization of the pyrrole ring D, if any, occurred within 10 μs after a laser-flash excitation of the phytochrome, and that the conformations of phytochromobilin and the protein moiety of phytochrome were not significantly changed during the period of examination of phototransformation in either direction.     

Conformational study of N-vinyl-2-isopropyl- and N-vinyl-2-cyclopropylpyrroles by1H and13C NMR

In N-vinyl-2-isopropylpyrrole the isopropyl group is in a conformation with the CH₃ group in an anti position to the vinyl group. On introducing a substituent at the 3 position of the ring the isopropyl group passes into a gauche and (or) a syn conformation, leading to an increase in the dihedral angle between the plane of the vinyl group and the pyrrole ring. In N-vinyl-2-cyclo-propylpyrrole the cyclopropyl group is 80% in the gauche form, which is attributed to the repulsion between the electrons of the -shells of the cyclopropyl and pyrrole fragments.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1031–1038, May, 1991.     

聚苯乙烯的暗氧化及其反应机理研究

聚苯乙烯的暗氧化及其反应机理研究朱军民曹维孝冯新德（北京大学高分子科学与工程系北京１００８７１）关键词聚苯乙烯，异丙苯，接触电荷转移复合物（ＣＣＴ），暗氧化反应高分子材料在加工、贮存和使用的过程中，当受到大气中氧、光、热等作用时，会发生降解和交...     

AB initio calculations on the equilibruim geometry and rotation barriers in biphenyl

The geometry of the biphenyl molecule has been studied with the MO LCAO method using a gausian basis set of “double zeta” quality. For various values of the twist angle between the phenyl ring planes the positions of the hydrogen atoms in the 2-position and the distance between the two rings have been simultaneously optimized. The lowest energy has been obtained for a non-planar conformation having a twist angle of 32°. The rotation barriers are 1.2 and 4.5 kcal/mol for the planar perpendicular cases, respectively.