Alternating copolymers consisting of arylalkyl methacrylates. I. Fluorescence properties of poly(arylalkyl methacrylate-alt-styrene) in organic solution

Alternating and random copolymers of 9-phenanthrylmethyl methacrylate or 2-(9-carbazolyl)ethyl methacrylate with styrene were synthesized and their fluorescence properties were examined. There was no noticeable difference in the spectral features of the alternating and random copolymers in tetrahydrofuran (THF), demonstrating that this type of polymers have no quenching sites in the polymer chains. The fluorescence quenching studies indicated that the alternating copolymers permitted singlet-state energy migration as efficiently as the corresponding random copolymers but less efficiently than the random copolymers with higher chromophore contents. These results strongly suggest that to be chromophores close to each other is most important for facilitation of an intramolecular energy migration. © 1995 John Wiley & Sons, Inc.     

交替共聚物的嵌段聚合物的合成与表征

以Mn_2(CO)_(10)—CBr_4为引发剂,在AlEt_(1.5) Cl_(1.5)存在下,合成了交替共聚物的嵌段聚合物,Poly[(St-a-MA)-b-(IP-a-MMA)-b-(St-a-MA)]。NMR研究表明该嵌段聚合物各段都具有交替结构。扭辫法测定动态力学性能显示有两个T_g,分别为38℃和75℃。透射电镜研究表明,该聚合物具有两相结构。微区随硬段分子量增大而增大。     

Alternating copolymers consisting of arylalkyl methacrylates. II. Effect of coil collapse on fluorescence spectra of alternating copolymers of 2-(9-carbazolyl)ethyl methacrylate and aromatic vinyl monomers

Alternating and random copolymers of 2-(9-carbazolyl)ethyl methacrylate with aromatic vinyl monomers were synthesized and their fluorescence properties were compared in good and poor solvents. Contraction of the polymer coils induced the hypochromic effect, i.e., the mutual interaction of the ground-state chromophores, but caused little quenching of their excited state. This is sharp in contrast with the vinyl-type of polymers, exhibiting large interactions in both the ground and excited states. Introduction of bulky groups on the comonomers in the alternating copolymers further suppressed these interactions. © 1996 John Wiley & Sons, Inc.     

THE PHOTOREACTIVITY OF PYRIMIDINE-PURINE SEQUENCES IN SOME DEOXYDINUCLEOSIDE MONOPHOSPHATES AND ALTERNATING DNA COPOLYMERS

Abstract— A reversed-phase HPLC system has been developed which separates the common nucleo-bases from the 6-methylimidazo[4,5- b ]pyridin-5-one (6-MIP) produced on acid hydrolysis of a thymine-adenine photoadduct (TA*) that is formed between adjacent thymine and adenine bases in UV-irradiated polydeoxyribonucleotides. By measuring the relative amounts of adenine and 6-MIP in acid hydrolysates, this system has been used to investigate how polynucleotide conformation affects the yield of TA* in poly(dA-dT) irradiated at 254 nm. The photoreactivity of other pyrimidine-purine sequences has been examined with the deoxydinucleoside monophosphates d(TpI) and d(m⁵CpA) and with the alternating DNA copolymers poly(dA-dU), poly(dI-dC), poly(dG-dC) and poly(dA-dC).poly(dG-dT). Samples were irradiated at 254 nm in aqueous solution and in ice, and at wavelengths >290 nm with acetone as photosensitizer. A photoproduct resembling TA*, and giving 6-MIP on acid hydrolysis, was isolated from d(TpI) irradiated at 254 nm in solution or in ice; d(m⁵CpA) was comparatively unreactive. Acid hydrolysates of the irradiated DNA copolymers were screened by HPLC and by TLC and paper electrophoresis, for the presence of imidazo[4,5- b ]pyridin-5-one, 6-MIP, or other species attributable to specific photoproduct formation. By this criterion, however, none of the copolymers showed evidence of significant photoreactivity in either their single- or double-stranded conformational states. The formation of mixed pyrimidine-purine photoadducts in DNA is therefore probably restricted to T-A doublets.     

酸性条件下两种马来酸-烯烃交替共聚物诱导细胞色素c的结构转换

在pH=2·9时,细胞色素c保持类天然的结构;和马来酸-烯烃交替共聚物作用后,细胞色素c的α-螺旋结构基本保持不变,但是三级结构被破坏.另一方面,在pH=2·1时,细胞色素c去折叠形成伸展的无规卷曲构象;马来酸-烯烃交替共聚物可以诱导酸变性的细胞色素c从无规卷曲构象转变为α-螺旋结构.在酸性溶液中,由于马来酸-异丁烯交替共聚物和细胞色素c之间更强的相互作用,其对蛋白质结构的影响大于马来酸-1-十四烯交替共聚物.相对于小分子,聚合物可以在低浓度条件下提供有利于蛋白质结构转换的微环境.     

SYNTHESIS AND CHARACTERIZATION OF BLOCK POLYMER OF ALTERNATING COPOLYMERS

Block polymer of alternating copolymers, poly[(ST-a-MA)-b(IP-a-MMA)-b-(ST-a-MA)](I), has been synthesized in the presence of AlEt_(1.5)Cl_(1.5),by using Mn_2(CO)_(10)/CBr_4. initiation system.The GPC results indicate that there is no unreacted prepolymer in I purified by precipitation andfractionation. The study of NMR shows that every block of polymer I has alternating structure. The dynamicmechanical properties of I measured by torsional braid method indicate that the polymer has two T_g s,being 38 and 75℃, respectively. The transmission electron micrographs of I show they have two phasestructure and the domain size increases with increasing molecular weight of hard block.     

NON-LINEAR LEAST SQUARE CURVE FITTING OF COPOLYMERIZATION MODELS TO THE ALTERNATING TRIAD FRACTION OF COPOLYMERS OF STYRENE AND CITRACONIC ANHYDRIDE,AND COPOLYMERS OF STYRENE AND MALEIC ANHYDRIDE PREPARED IN N,N-DIMETHYLFORMAMIDE

Copolymers of styrene (ST) and citraconic anhydride (α-methylmaleic anhydride) (CA) were prepared in a very polar solvent, N,N-dimethylformamide (DMF), at 50.0°C with AIBN. The monomer unit triad fractions were determined by ¹³C NMR in acetone-d ₆ solution. Non linear least square (NLLS) curve fitting was performed for the copolymerization models of the terminal model, the penultimate unit effect model, the complex participation model, the complex dissociation model, and the so-called comppen model. The theoretical equations for the ST-centered alternating triad mole fraction were fitted by NLLS minimization routine to the triad fraction data of the ST-CA copolymers and that of the ST-maleic anhydride (MA) copolymers prepared in identical polymerization conditions. It was found that for rigidly alternating copolymers of ST-MA, the difference among the copolymerization models disappeared and all models merged together. The difference among the copolymerization models were somewhat more apparent for less alternating copolymers of ST-CA copolymers. The sum of squares values indicated that the copolymerization models, which involved some complex participation, fit the data better with the comppen model. This was a combination of a complex participation and penultimate unit effects, which performed best.     

不同低聚乙二醇链长的聚对亚苯基亚乙烯基类交替型发光共聚物

合成了3种分子主链由1,4二苯乙烯基苯(DSB,聚对亚苯基亚乙烯基PPV三单元的低聚物)与不同长度的离子传导型隔离链段低聚乙二醇(OEO,或聚氧乙烯)组成的交替型蓝色发光共聚物DSB二缩三乙二醇(TEO)、DSB五缩六乙二醇(SEO)和DSBPEG1500.研究了3种聚合物在其氯仿溶液中的电荷传输机理.通过多种手段考察了不同长度的OEO链段对聚合物的结晶能力、相结构以及其对锂盐溶解能力的影响,并讨论了此类材料的合理结构设计原则.以DSBTEO为发光层材料,装配了电致发光器件.     

具有温度敏感和荧光特性的侧链查尔酮共聚物的研究

采用2,2′-偶氮二异丁腈作为引发剂,将N-异丙基丙烯酰胺和4-甲基丙烯酰氧基-4′-二甲氨基查尔酮单体,在四氢呋喃溶剂中通过自由基共聚制备了一系列具有溶剂和温度双重敏感荧光特性的侧链查尔酮共聚物,并通过红外光谱、核磁共振氢谱和紫外-可见光谱对其结构进行表征,通过吸光度法测定了共聚物中查尔酮单元的含量.研究了侧链查尔酮共聚物的温敏性以及溶剂极性和温度双重敏感的荧光特性.结果表明,侧链查尔酮共聚物是一类具有最低临界溶解温度(LCST)的温敏性聚合物,其LCST温度随着共聚物中查尔酮含量的增加而降低;随着溶剂极性的增加,侧链查尔酮共聚物的紫外-可见最大吸收波长红移,其荧光发光波长红移并且发光强度先增强后降低,具有溶剂极性敏感的荧光特性;同时对比侧链查尔酮共聚物水溶液低温和高温下的荧光,发现低温下几乎无荧光,高温下其荧光得到明显增强,其荧光具有可逆的温度"开/关"特性。     

N-丙烯酰-2-氯吩噻嗪、N-丙烯酰-2-乙酰基吩噻嗪单体和聚合物的合成以及荧光行为的研究

含芳杂环的丙烯酰类功能性单体及其聚合物的合成一直吸引人们的兴趣,原因之一是由于这类单体可用一般的自由基引发剂引发聚合,这类聚合物所表现出的光化学、电化学性质甚被瞩目。如含吩噻嗪的丙烯酰类衍生物可以和缺电子的化合物形成电荷转移     

N-丙烯酰-2-氯吩噻嗪、N-丙烯酰-2-乙酰基吩噻嗪单体和聚合物的合成以及荧光行为的研究

Two N-acrylic monomers having phenothiazine moieties , N-acrylyl-2-chlorophe-nothiazine ( I ) , N-acrylyl-2-acetylphenothiazine ( I ) were synthesized and their polymers were obtained by free radical polymerization . The fluorescence study showed that at the same molar concentration of the chromophores, the fluorescence intensities of the polymers were much stronger than that of the monomers. This would be explained by what we called "Structural Self-quenching Effect. " The Stern-Volmer constants of the polmers quenched by several electron defecient vinyl monomers were obtained. The results indicated that their quenching efficiencies were relevant to the degree of the electron deficiency of the double bond.     

Amphiphilic copolymers with pendant ­carbazolylalkyl groups. ­Effect of polymer structure on ­retardation of self‐quenching

A series of amphiphilic polyanions containing (9‐carbazolyl)alkyl methacrylamide or acrylamide were prepared and their fluorescence properties were compared in organic and aqueous solution. In organic solution, all copolymers exhibited a monomer emission which decayed exponentially, indicating no self‐quenching. Decreasing the length of the methylene spacer in the side chain induced the spectral broadening and sharpening, depending on the carbazolyl content in the copolymer. This may be related to the interchromophore interactions and the mobility of chromophores. In H ₂O, by contrast, quenched fluorescence was observed for the copolymers. It should be however noted that acrylamide‐type of amphiphilic copolymers, poly(9‐carbazolylmethyl‐acrylamide‐co‐sodium 2‐acrylamido‐2‐methylpropanesulfonate), are the least quenched polymers among those reported so far. Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis, light-harvesting and energy-transfer properties of regioregular silylene-spaced alternating [(donor-SiMe2-)(n=1-3)-(acceptor-SiMe2)] copolymers

A series of silylene-spaced alternating [(donor-SiMe2)(n=1-3)-(acceptor-SiMe2)] copolymers 4-6 was synthesized by rhodium-catalyzed hydrosilylation of bisalkynes with bissilyl hydrides. Monomeric reference compounds 7-10 with similar chromophore components were prepared for comparison. The ratio of donor to acceptor groups is well-controlled by the precise regiochemistry and nature of the repeat units. The silylene moieties serve as insulating spacers between chromophores. The polymers exhibit light-harvesting abilities, for which the intensity of the emission enhanced with larger donor-to-acceptor ratios. No emission originating from the donors was observed in fluorescence spectra, illustrating that intrachain energy transfer is highly efficient along the polymer chain.     

三苯基吡啶-芴交替共轭聚合物的合成与光致发光性能研究

通过Suzuki偶合反应得到了两种间位连接的三苯基吡啶同分异构体和9,9-二辛基芴的交替共聚物PFOTPP1和PFOTPP2.并对它们的紫外-可见吸收光谱、光致发光光谱以及电化学性能等进行了初步研究.结果表明,将间位连接的三苯基吡啶基引入聚芴主链能使聚合物的LUMO能级降低,光致发光光谱发生蓝移,得到了两种有望应用于电致炼光发光器件的共轭聚合物蓝光发光材料.     

Anionic alternating copolymerization of α‐arylacrylates with methyl methacrylate: Effect of monomer sequence on fluorescence

Anionic polymerizations of acrylates possessing 1‐pyrenyl (Py1), 1‐naphthyl (Np1), 2‐naphthyl (Np2), and 2‐fluorenyl (Fl2) groups as α‐substituents were investigated as well as the properties of the obtained polymers. Py1 and Np1 did not undergo polymerization, whereas Np2 and Fl2, annulated α‐phenylacrylates at 3,4‐position of the phenyl group, afforded homo‐oligomers and alternating copolymers with methyl methacrylate (MMA). The oligomer of Fl2 [oligo(Fl2)] exhibited strong excimer emission in diluted solution. In contrast, dominant monomer emission was observed for the alternating copolymer with MMA [poly(Fl2‐co‐MMA)]. In the alternating copolymer, MMA units could function as spacers preventing the association of pendant fluorene moieties to suppress the excimer formation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2806–2814     

Dynamics and energetics of the self-assembly of a hydrophobically modified polyelectrolyte: Naphthalene-labeled poly(acrylic acid)

Steady-state and time-resolved fluorescence studies were performed on aqueous solutions of poly(acrylic acid) hydrophobically modified with two very different levels of naphthalene (Np). It is demonstrated that unique information on association phenomena involving hydrophobe-modifed polymers can be obtained from an extended fluorescence study by using data for a less-modified polymer as a reference. For the more highly modified polymer, the presence of excited-state (as well as ground-state) dimers in addition to monomer emission due to locally excited naphthalene gives evidence for hydrophobic association between naphthalene groups. This association becomes, as expected, much less important at higher pH due to the electrostatic repulsion between different chain segments. However, it is noted that even at high pH there is a significant self-association. The coexistence of static and dynamic quenching phenomena of the Np monomer label was also revealed in the time-resolved fluorescence data. The data are compatible with the existence of two types of monomers and one excimer and suggest that the essential contribution to the monomer emission comes from isolated chromophores, whereas excimer formation arises from both a dynamic route (excited Np chromophores able to produce a dynamic excimer) and a static route (excitation of ground-state Np dimers). At room temperature, the dissociative reaction, excimer-to-monomer, can be neglected, and thus the rate constant for excimer formation and decay could be obtained with and without considering the influence of preformed dimers. Temperature has shown to induce different behavior in the polymer photophysics. In the case of the less-labeled polymer, the decays were found to be single-exponential with the fluorescence lifetime decreasing with increasing temperature. From the temperature dependence of the steady-state fluorescence data, the activation energy for excimer formation and the binding energy of the excimer were evaluated at different pH values, through the Stevens-Ban-type plots of the excimer-to-monomer intensity ratio. With the time-resolved data, measured in the temperature range of 5-60 degrees C, it was possible to extract the intrinsic activation energies for excimer formation. The thermodynamic driving force for the intrapolymeric association was found to be dependent on a balance between hydrophobic and electrostatic interactions, which are dependent on the pH, temperature, and hydrophobic content of the polymer.     

From vanadium naphthalene (V(n-1)Np(n)) sandwich clusters to VNp sandwich nanowire: structural, energetic, electronic, and magnetic properties

The structural, energetic, electronic, and magnetic properties of a series of vanadium naphthalene (V(n-1)Np(n)) sandwich clusters (SWCs) and the VNp sandwich nanowire (SWN) were investigated by means of density functional theory computations. In the energetically most preferred configuration of each V(n-1)Np(n) SWC and SWN, the two nearest-neighbor Np rings form a 45° rotation angle, the two second-nearest-neighbor Np rings are parallel to each other, and V atoms align in a zigzag chain. The local magnetic moments in V(n-1)Np(n) SWCs favor antiferromagnetic coupling due to the superexchange mechanism. Especially, both electron and hole injection can switch V(n-1)Np(n) SWCs and VNp SWN from the antiferromagnetic state to the ferromagnetic state, thus manipulating the magnetization direction. These results suggest the potential applications of V(n-1)Np(n) SWCs and VNp SWN in spintronics.     

共轭双烯与丙烯酸甲酯交替共聚物的~(13)C-NMR谱研究

用~(13)C-NMR方法研究了丁二烯(BD)-丙烯酸甲酯(MA)、异戊二烯(IP)-MA和氯丁二烯(CP)-MA交替共聚物(分别简称为PBM、PIM和PCM)的联接方式和微观结构。在PBM中,BD单元以反-1,4-结构存在,并有少量的顺-1,4-和1,2-结构,其比例为88:7:5;在PIM和PCM中,IP与CP单元也主要以反-1,4-结构存在,与MA以“头-头”方式相连接。在PCM中还有少量CP-CP相连接的结构,交替度较低,而PBM和PIM则完全是交替结构。     

以氯代钒酸酯-三异丁基铝催化体系合成丁二烯-丙烯交替共聚物的研究

本文比较了各种氯代钒酸酯-三异丁基铝体系催化丁二烯、丙烯交替共聚的活性,得出氯代钒酸二新戊酯-三异丁基铝体系催化活性最高。能制得高分子量的交替共聚物。研究了该催化体系的特点和聚合规律及提高共聚物[η]的途径。在-76--45℃温度范围内可以制得正[η]为1.7-2.6dl/g的丁丙交替共聚物,单体转化率在80％以上。通过分析鉴定,证明产物交替度在95％左右,反式1,4丁二烯组分含量在95％以上。     

Controlling conformations in alternating dialkylsilylene-spaced donor-acceptor copolymers by a cooperative Thorpe-Ingold effect and polymer folding

A series of dialkylsilylene-spaced copolymers 6 and 7, which contain Me(2)Si and iPr(2)Si spacer groups, respectively, and have alternating donor and acceptor chromophores, have been designed and regioselectively synthesized by hydrosilylation. The ratio of the donor and acceptor chromophores for each repeat unit is 2:1, and the two donor chromophores are linked by a trimethylene bridge. A 4-aminostyrene moiety is used as the donor and a series of acceptor chromophores with different reduction potentials are employed. Both steady-state and kinetic measurements reveal that the photoinduced electron transfer (PET) in 6 obeyed the Marcus theory in which normal and inverted regions are observed. On the other hand, the iPr(2)Si-spaced copolymers 7 exhibit absorption and emission from the charge-transfer complexes exclusively due to ground-state interactions between the donor and acceptor chromophores. The discrepancy in photophysical behavior may have arisen from the difference in distance between the adjacent donor and acceptor chromophores. The bulkiness of the substituents on the silicon atom (i.e., Me versus iPr) may exert the Thorpe-Ingold effect on the local conformation around the silicon atom. The differences in the small energetic barriers for each of the conformational states may be amplified by extending the distance of the folding structure, which results in perturbing the conformation of the polymers. These results suggest that the electronic interactions between adjacent donor-acceptor pairs in these copolymers are controlled by the synchronization of the substitution effect and corresponding polymeric structures.