Kinetics and Mechanism of Polymerization of Methyl Methacrylate using Selenonium Ylide as a Novel Initiator

Polymerization of Methyl methacrylate (MMA) was carried out in dioxan at 60 ± 1°C for 90 min in dilatometer under nitrogenous atmosphere using diphenylselenonium 2,3,4,5-tetraphenylcyclopentadienylide (selenonium ylide) as a novel initiator. The exponent values for initiator and monomer were computed as 0.32 and 1.59, respectively. The overall activation energy and k_p ²/k_t were found 42.1 k J mol^?1 and 0.819 l mol^?1s^?1, respectively. The free radical mode of polymerization was confirmed by ESR spectroscopy. The FT-IR, ¹H-NMR and ¹³C-NMR spectroscopic techniques were used for its characterization.     

C60与甲基丙烯酸甲酯共聚物的制备及光电导性能的研究

通过自由基聚合的方法制备了一系列甲基丙烯酸甲酯和C₆₀的共聚物,实验结果表明,增加引发剂的含量可以大大提高共聚物的产率。用元素分析、GPC和DSC等方法对共聚物进行表征。首次尝试研究了不含导电高分子的C₆₀共聚物体系的光电导性能,结果表明,该类共聚物光电导性能良好。     

C60(Fullerene)及其卤化衍生物在阴离子聚合中的研究

综述了近年来C60及其卤化衍生物在阴离子聚合中的研究进展。在阴离子聚合中，C60可以直接与反应而进入主链，形成超枝化结构；C60可作为阴离子聚合的偶联剂，形成星形和线形结构；C60阴离子可以引发阴离子聚合。介绍了偶联产物结构控制的方法，以及偶联产物的稳定性。氯化富勒烯也可以作为阴离子聚合的偶联剂，生成星形结构聚合物。     

苯乙烯-甲基丙烯酸甲酯嵌段共聚物的合成与表征

采用阴离子聚合技术合成了一系列苯乙烯-甲基丙烯酸甲酯的两嵌段共聚物(PS－b－PMMA)．采用GPC、FTIR、NMR(¹HNMR、¹³CNMR和固体NMR)和DMA等手段进行了表征．结果表明,所得产物为高分子量、窄分布、具有微相分离结构的两嵌段共聚物．     

Synthesis of Dendrimers with Porphyrine Core and their Supramolecular Complexes with Fullerene C60

Dendritic branches of poly(arylether) with peripheral butyl chains have been attached to a porphyrine core. Dendrimers of first, second and third generation were synthesized. Viability to form supramolecular complexes with fullerene C₆₀ was studied with two dendrimers of second and third generation. The supramolecular complexes were characterized by ¹H, ¹³C NMR in solution, FTIR, UV-vis spectroscopy and elemental analysis.     

Graft Copolymerization of Methyl Methacrylate onto Nylon 6 Using Thallium(III) Ions as Initiator

Abstract

Graft copolymerization of methyl methacrylate onto nylon 6 was investigated in aqueous perchloric acid medium using thallium(III) ions as initiator. The rate of grafting was evaluated by varying the concentrations of monomer, initiator, acid, and temperature. The rate of grafting was found to increase with an increase of both monomer and initiator concentrations. The graft yield was found to increase with an increase in the acid concentration up to 0.49 mL^?1, and beyond this concentration of perchloric acid the graft yield was found to decrease. It also increased with an increase of temperature. From the Arrhenius plot the overall activation energy was found to be 3.9 kcal/mol. The effects of inhibitors, various solvents, inorganic salts, and swelling agents on graft yield were studied. A suitable kinetic scheme has been proposed and a rate equation has been derived.     

聚甲基丙烯酸2,2,3,3-四氟丙酯及其单体与甲基丙烯酸甲酯共聚物的合成与表征

含氟甲基丙烯酸酯聚合物中的氟原子可使其折光指数n_D很低。这是光导纤维皮材的首要条件^[1]。这类材料的大分子主链与作为芯材使用的聚甲基丙烯酸甲酯(PMMA)具有相同的结构,因此其间的相容性和粘结性好,有利于光的全反射;其热稳定性也好^[2,3],可用于共挤出法制造塑料光导纤维.     

有机催化剂存在下原位生成烷基碘化物的甲基丙烯酸甲酯的可逆-休眠自由基聚合

以四丁基溴化铵(BNBr)或四丁基碘化铵(BNI)作为有机催化剂,碘(I_2)与偶氮二异丁腈(AIBN)原位生成烷基碘化物为引发剂在本体聚合中实现了甲基丙烯酸甲酯(MMA)的可逆催化络合聚合(RCMP).首先,比较了2种催化剂对该体系催化活性的大小,相同实验条件下,BNI作为催化剂时对聚合的控制效果优于BNBr,即在该体系中BNI的催化活性大于BNBr;其次,较为详细地研究了催化剂BNI的用量对MMA可控聚合的影响,结果表明,BNI的浓度在9.43~117.81 mmol/L范围内均有较好的控制效果,当[MMA]∶[I_2]∶[AIBN]∶[BNI]=100∶0.5∶0.75∶0.25,即催化剂的浓度为23.56 mmol/L时反应速率较快,理论分子量与实测分子量(通过GPC进行表征)几乎完全吻合,分子量多分散指数(PDI=M_w/M_n)较小(PDI1.27);最后,通过1H-NMR对所得聚合物的结构进行表征,证明为碘原子封端,M_(n,NMR)与M_(n,GPC)相吻合,端基保有度达到98.8%.     

Vitamin C Functionalized Poly(Methyl Methacrylate) for Free Radical Scavenging

Abstract

In the present work, a strategy was developed to use mild and highly selective enzymatic methods to covalently couple the primary hydroxyl group of vitamin C with methyl methacrylate monomer, followed by a second enzymatic reaction catalyzed by horseradish peroxidase to polymerize the vinyl monomer yielding a vitamin C functionalized poly(methyl methacrylate) (PMMA). Vitamin C, L‐ascorbyl methylmethacrylate and PMMA, when used at concentrations up to 133 µM, fully scavenged 2,2‐diphenyl‐1‐picryl hydrazyl free radicals (0.2 mM). Thus, the formation of vinyl polymers with active pendent antioxidant compounds, in this case vitamin C, retained an ability to scavenge radicals while in polymeric form. The functionalized antioxidant on a PMMA backbone has implications for consumer‐related applications like foods, pharmaceuticals, and personal care products.     

He+C60↔(He@C60)的反应势垒研究

The reaction barriers of (He+C60(He＠60)) have been calculated by the quantum-chemical method EHMO/ASED in the following four paths: (1) penetrate through the pentagon on the C60 cage; (2) penetrate through the hexagon on the C60 cage,(3) penetrate through the short bond; (4) penetrate through the long bond. Corresponding to each path, there are two choices: (a) while He penetrate C60 cage, the distances of the C’s which are the most adjacent to He are changed with a planar extension and a concerned window is formed; (b) while He penetrate C60 cage, the distances of the C’s which are the most adjacent to He are changed with a spherical extension and a concerned window is formed. The results are given in Figs. 1-2 and Tables 1-2. It is shown that the reaction through path(4) with choice (a) has the least reaction barrier, being optimum. At that case, a window of 9-membered ring is formed. Because the window extension of C6H6 is more free than that of C60, the barrier of He penetrating through C6H6 will be lower than that of He penetrating through C60.     

A Comparative Study of Methyl Methacrylate/Butyl Acrylate Copolymerization Kinetics by Atom‐Transfer and Conventional Radical Polymerization

Methyl methacrylate and butyl acrylate monomers are copolymerized by atom‐transfer radical polymerization, affording polymers with well‐controlled molecular weight and low polydispersity. A kinetic analysis of this system is compared with the corresponding free‐radical polymerization system. The copolymerization rate follows an opposite trend to that observed in conventional copolymerization. This fact is attributed to a smaller population of radicals generated in the reaction, since the relative fraction of propagating radicals is the same as that in classical copolymerization.     

Loss of characteristic absorption bands of C60 conjugation systems in the addition with aliphatic amines

The characteristic absorption bands disappear and the shortest band at approximately 244 nm in cyclohexane or 282 nm in toluene remained only with long smoothing tail as C60 reacts adequately with aliphatic amines under sunlight radiation at approximately 40 degrees C. Simultaneously, fluorescence emission shifts from a weak band initially at longer wavelength to another strong one finally at shorter wavelength. The results might imply that the pi-conjugation system of C60 parent molecule is isolated into smaller separated parts. Therefore, some possible isolation models associated with observed experimental results are designed under some reasonable assumptive conditions.     

Preparation of Latexes with Poly(Methyl Methacrylate) Cores and Hydrophilic Polymer Shells Containing Amino Groups

Abstract

Functional latexes with poly(methyl methacrylate) (PMMA) cores and amino‐containing, water‐soluble polymer shells were synthesized via direct graft copolymerization of methyl methacrylate from water‐soluble polymers induced by a small amount of tert‐butyl hydroperoxide (TBHP) at 80°C for 2 h. Amphiphilic graft copolymers and PMMA homopolymers were generated concurrently to form highly monodispersed latexes. The effects of water‐soluble polymer containing different amino group, reaction temperature, TBHP concentration, molecular weight of the polymer and pH of the solution on conversion and grafting efficiency of the monomer and particle size were investigated. Transmission electron microscopic images of the PMMA/poly(ethyleneimine) (PEI) and PMMA/poly(allylamine) (PAA) particles clearly show well‐defined core‐shell morphologies, where PMMA cores are coated with either PEI or PAA shell. The amino‐containing polymer shells were also confirmed with zeta‐potential measurements. Furthermore, the amino‐containing latexes can be produced with a solids content up to 22 wt.%. Thus, this method provides a commercially viable route to functional latexes.     

Simultaneous thermoanalytical investigations of (C6H5)4AsCl and (C6H5)4PCl under air and argon atmospheres

The thermoanalytical curves of (C₆H₅)₄AsCl (I) and (C₆H₅)₄PCl (II) were generated simultaneously by using a Netzsch simultaneous thermal analyser 409 under static air and dynamic argon atmospheres. The ranges of thermal stability of I and II were found to be 145–310°C and 137–365°C, respectively, and their melting points to be 261 and 278°C. The DTA profiles of I and II differ and can be used for their distinction.     

Preparation and Characterization of Fullerene C_(60) and Phthalocyanine Co-grafted Poly(epoxy propyl carbazole)

Fullerenes and its derivatives have attracted great interest from the viewpoints of both fundamental science and potential application. Fullerene-doping polymeric photoconductors have been extensively investigated due to their potential technological application. The enhancement of the photoconductivity of the poly (N-vinylcarbazole) (PVK) films by dopong with fullerenes (a mixture of C60 and C70) was for the first time reported by Wang1. He proposed that enhanced photoconductivity was attr…     

Kinetic Studies on Star Polymerization of Styrene,MA and MMA Using New Three and Four Arm Chain Transfer Agents (CTAs): The Role of R-Group Structure Present in the CTA on RAFT Polymerization

Polystyrene, poly(methylacrylate) and poly(methyl methacrylate) four and three-arm stars were synthesized by Reversible Addition Fragmentation chain-Transfer (RAFT) polymerization by using two new dithioester-derived chain transfer agents [CTA or R-S-(C = S)Z]), CTA-1 and CTA-2. CTA-1 is a four arm CTA while CTA-2 is a three-arm CTA. These were easily synthesized from commercially available reagents and were characterized by spectroscopic techniques such as ¹H-NMR, ¹³C-NMR, IR and mass spectrometry. It is demonstrated that the two new CTAs enable the growth of arms away from the core (i.e., core first approach). An attempt has been made to study the effect of the structure of the R-group, which is present as the core in the CTA, on the polymerization, by analyzing the detailed kinetics. This study suggests that CTA-2, with a benzylic R group, enables the controlled star polymerization of styrene while CTA-1, with a R group similar in structure to the propagating radical derived from the polymerization of methyl acrylate (MA), enables the controlled polymerization of MA although to a lesser extent. This study also reveals that the temperature of free radical initiated RAFT (star) polymerization should be chosen in such a way that it is a compromise between reasonable rate of homolysis of the initiator and the CTA (R-group).     

Synthesis and Characterization of Novel Methacrylic Copolymers: Determination of Monomer Reactivity Ratios

A new methacrylic monomer, 4‐nitro‐3‐methylphenyl methacrylate (NMPM) was prepared by reacting 4‐nitro‐3‐methyl phenol dissolved in methyl ethyl ketone (MEK) in the presence of triethylamine as a catalyst. Copolymerization of NMPM with methyl methacrylate (MMA) has been carried out in methyl ethyl ketone (MEK) by free radical solution polymerization at 70±1°C utilizing benzoyl peroxide (BPO) as initiator. Poly (NMPM‐co‐MMA) copolymers were characterized by FT‐IR, ¹H‐NMR and ¹³C‐NMR spectroscopy. The molecular weights (M_w and M_n) and polydispersity indices (M_w/M_n) of the polymers were determined using a gel permeation chromatograph. The glass transition temperatures (T_g) of the copolymers were determined by a differential scanning calorimeter, showing that T_g increases with MMA content in the copolymer. Thermogravimetric analysis of the polymers, performed under nitrogen, shows that the stability of the copolymer increases with an increase in NMPM content. The solubility of the polymers was tested in various polar and non‐polar solvents. Copolymer compositions were determined by ¹H‐NMR spectroscopy by comparing the integral peak heights of well separated aromatic and aliphatic proton peaks. The monomer reactivity ratios were determined by the Fineman‐Ross (r₁ =7.090:r₂=0.854), Kelen‐Tudos (r₁=7.693: r₂=0.852) and extended Kelen‐Tudos methods (r₁=7.550: r₂= 0.856).     

Water-soluble polyketones and esters as the main stable products of ozonolysis of fullerene C60 solutions

Stable ozonolysis products of C₆₀ solutions in CCl₄, toluene, and hexane were studied by elemental analysis, HPLC, and UV and IR spectroscopy. Polyketones and esters were established for the first time to be the main stable products, whose content increased during the whole ozonolysis time (1 h). Epoxides C₆₀O _n (n = 1—6) are accumulated within 1—3 min, and after 5 min of ozonolysis their concentration decreases to zero. Fullerene C₆₀ disappears from the reaction solution due to its conversion to oxides and mechanical capturing of C₆₀ by these oxides to form a precipitate. The oxidation of C₆₀ is completed in the solid phase by the formation of the C₆₀O₁₆ oxide in which 9.68 O atoms fall on fullerene polyketones, 6 O atoms are attributed to esters, and 0.32 O atoms fall per epoxides. The optimum medium for preparation of the C₆₀ oxides is CCl₄ rather than traditional toluene, which reacts with ozone in the side reaction to form products containing active oxygen. The C₆₀ cage is raptured during ozonolysis because of the C=C bond cleavage to form two C=O groups at the ends of the open hexagon. Ozonolysis of C₆₀ solutions in CCl₄ is efficient for synthesis of water-soluble fullerene oxides due to the high yield and solubility of polyketones and esters in water.     

C60/C70键联1,4-二-(咔唑-9-亚甲基)苯的电化学行为与双光子吸收

设计合成了C60键联1,4-二-(咔唑-9-亚甲基)苯(5)和C70键联1,4-二-(咔唑-9-亚甲基)苯(6), 用红外、核磁共振和MALDI-TOF质谱进行了表征, 确认了化合物5和6的结构, 用循环伏安法研究了化合物5和6的电化学性质, 并用Z扫描对其双光子吸收性质进行了研究.     

Preparation and Characterization of Thin-Film Solar Cells with Ag/C60/MAPbI3/CZTSe/Mo/FTO Multilayered Structures

New solar cells with Ag/C₆₀/MAPbI₃/Cu₂ZnSnSe₄ (CZTSe)/Mo/FTO multilayered structures on glass substrates have been prepared and investigated in this study. The electron-transport layer, active photovoltaic layer, and hole-transport layer were made of C₆₀, CH₃NH₃PbI₃ (MAPbI₃) perovskite, and CZTSe, respectively. The CZTSe hole-transport layers were deposited by magnetic sputtering, with the various thermal annealing temperatures at 300 °C, 400 °C, and 500 °C, and the film thickness was also varied at 50~300 nm The active photovoltaic MAPbI₃ films were prepared using a two-step spin-coating method on the CZTSe hole-transport layers. It has been revealed that the crystalline structure and domain size of the MAPbI₃ perovskite films could be substantially improved. Finally, n-type C₆₀ was vacuum-evaporated to be the electronic transport layer. The 50 nm C₆₀ thin film, in conjunction with 100 nm Ag electrode layer, provided adequate electron current transport in the multilayered structures. The solar cell current density–voltage characteristics were evaluated and compared with the thin-film microstructures. The photo-electronic power-conversion efficiency could be improved to 14.2% when the annealing temperature was 500 °C and the film thickness was 200 nm. The thin-film solar cell characteristics of open-circuit voltage, short-circuit current density, fill factor, series-resistance, and Pmax were found to be 1.07 V, 19.69 mA/cm², 67.39%, 18.5 Ω and 1.42 mW, respectively.