KCD/MDEA/TA三元引发剂引发丙烯酸酯/液晶复合体系光聚合动力学

采用配有441.6 nm滤光片的光差示扫描量热仪研究了3,3'-羰基双(7-二乙胺香豆素)(KCD)/N-甲基二乙醇胺(MDEA)/2-(4-甲氧苯基)-4,6-双(三氯甲基)-1,3,5-三嗪(TA)三元引发剂引发丙烯酸酯/液晶复合体系光聚合动力学行为. 结果表明, 在KCD/MDEA复合引发剂中添加TA, 显著提高了丙烯酸酯/液晶复合体系的最大光聚合速率[R_p(max)]和单体转化率, 当TA质量分数为0.5%时, 体系的R_p(max)和单体转化率分别提高了100%和69%. 同时, 随着光照强度的增加, 该体系的R_p(max)和单体转化率呈增大的趋势, 当光强从1.5 mW/cm⁺²提高到35.2 mW/cm⁺²时, 其R_p(max)和最终单体转化率分别提高了2.5和2.8倍.     

PHOTOPOLYMERIZATION INITIATED BY DIMETHYLAMINOCHALCONE/DIPHENYLIODONIUM SALT COMBINATION SYSTEM SENSITIVE TO VISIBLE LIGHT

Several dimethylamino-substituted chalcone (i .e. dimethylaminobenzal acetophenone) (DBA) derivatives with intramolecular charge transfer transition character were used as visible light sensitizers for radical photopolymerization initiated by iodonium salt (DPIO). Initiating radical species is produced from DBA sensitized photolysis of DPIO through the single electron transfer, accompanying the bleaching of DBA, The activity of DBA decreases as a function of substituent attached to phenyl ring in the order: DBA-2 (OCH_3) >DBA-1(H)> DBA-3 (Cl). The kinetic study on photopolymerization of MMA was carried out in CH_3CN solution at 30 ℃by dilatometry. The polymerization rate was determined to be proportional to the concentration with exponents of 0.42, 0.25 and 0.86 for DPIO, DBA-1 and MMA, respectively.     

可见光促进的偕二氟烯烃制备与应用研究进展

偕二氟烯烃化合物在医药、材料、精细化工等领域具有广泛的应用,同时也是一类非常重要的用于制备各类复杂的有机氟化合物的有机合成中间体.可见光催化反应具有条件温和、绿色清洁等特点,已经成为有机化学中非常重要的合成手段之一.本文综述了近年来可见光促进的偕二氟烯烃化合物的制备及其在有机合成化学中的应用.     

Anionic polymerization of primary acrylates as promoted by lithium 2-(2-methoxyethoxy) ethoxide

Some primary acrylates, such as methyl, ethyl, n-butyl, and n-nonyl acrylate (MA, EA, nBuA and nNonA, respectively) have been anionically polymerized by using diphenylmethyl lithium (DPMLi) as an initiator, in the presence of a chelating μ-σ dual ligand, i.e., a polydentate lithium alkoxide, at low temperature. It has been found that lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM) is a very efficient ligand in preventing the anionic polymerization of these monomers from being disturbed by significant secondary transfer and termination reactions. Even for the difficult cases of ethyl and methylacrylate, that approach provides high polymerization yields and low polydispersity, allowing the molecular weight to be predetermined. LiOEEM/initiator molar ratio, solvent polarity, temperature and monomer concentration have proved to be key parameters in the control of the polymerization process. The efficiency of that control is however dependent on the monomer structure and improves with the length of the n-alkyl substituent, i.e., MA < EA < nBuA < nNonA. © 1997 John Wiley & Sons, Inc.     

Visible light irradiation promoted catalyst-free and solvent-free synthesis of pyrano[2,3-d]pyrimidine scaffolds at room temperature

A catalyst-free and solvent-free synthetic route for convenient one-pot synthesizing pyrano[2,3-d] pyrimidine scaffolds through Knoevenagel-Michael cyclocondensation is reported using visible light irradiation as a green promoter at room temperature based on green chemistry principles. Completing the reactions takes thoroughly less time while obtaining the products in outstanding yields. This green method includes the application of non-hazardous reaction circumstances, direct work-up without column chromatographic separation, catalyst-free, solvent-free, cost effective, simple synthesis, one-pot procedure, and high atom-economy.     

In-situ polymerization for PPy/g-C3N4 composites with enhanced visible light photocatalytic performance

Polypyrrole-modified graphitic carbon nitride composites (PPy/g-C₃N₄) are fabricated using an in-situ polymerization method to improve the visible light photocatalytic activity of g-C₃N₄. The PPy/g-C₃N₄ is applied to the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Various characterization techniques are employed to investigate the relationship between the structural properties and photoactivities of the as-prepared composites. Results show that the specific surface area of the PPy/g-C₃N₄ composites increases upon assembly of the amorphous PPy nanoparticles on the g-C₃N₄ surface. Owing to the strong conductivity, the PPy can be used as a transition channel for electrons to move onto the g-C₃N₄ surface, thus inhibiting the recombination of photogenerated carriers of g-C₃N₄ and improving the photocatalytic performance. The elevated light adsorption of PPy/g-C₃N₄ composites is attributed to the strong absorption coefficient of PPy. The composite containing 0.75 wt% PPy exhibits a photocatalytic efficiency that is 3 times higher than that of g-C₃N₄ in 2 h. Moreover, the degradation kinetics follow a pseudo-first-order model. A detailed photocatalytic mechanism is proposed with ·OH and ·O₂^? radicals as the main reactive species. The present work provides new insights into the mechanistic understanding of PPy in PPy/g-C₃N₄ composites for environmental applications.     

Visible light and base promoted O-H insertion/cyclization of para-quinone methides with aryl diazoacetates: An approach to 2,3-dihydrobenzofuran derivatives

A visible light and base promoted O-H insertion/cyclization of para-quinone methides with aryl diazoacetates is developed. This one-pot two step reaction offers a mild and efficient approach for the synthesis of biologically important 2,3-dihydrobenzofuran derivatives in good yields and moderate diastereoselectivities.     

Stereospecific radical polymerization of fluoroalkyl acrylates

The free‐radical polymerization of 2,2,2‐trifluoroethyl acrylate (TFEA), 1,1,1,3,3,3‐hexafluoro‐2‐propyl acrylate (HFiPA) and perfluoro‐tert‐butyl acrylate (PFtBA) was carried out under various conditions and the stereostructure of the obtained polymers was investigated. Most polymerizations of the three monomers afforded polymers rich in diad syndiotacticity (r) in bulk or in solution; the r‐specificity was higher in the HFiPA and PFtBA polymerization than in the TFEA polymerization. Although the tacticity was nearly independent of reaction temperature during the polymerization of TFEA, the r‐specificity increased by lowering the reaction temperature during the polymerization of the other two monomers. The polymerization stereochemistry was also affected by the reaction solvents including toluene, tetrahydrofuran, and fluoroalcohols. It was noted that the stereochemistry of the polymerization of HFiPA and PFtBA also depended on the monomer concentration, and a lower monomer concentration led to a higher r‐specificity. By optimizing the aforementioned reaction conditions, the poly(HFiPA) having r = 81% (polymerization in tetrahydrofuran at −98 °C at [M]_o = 0.2M) and the poly(PFtBA) having r = 77% (polymerization in toluene at −78 °C at [M]_o = 0.2M) were obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1024–1032, 2000     

Visible-Light Initiated Dispersion Photopolymerization of Styrene

Polystyrene (PS) particles were synthesized in ethanol/water mixture by dispersion polymerization using visible light irradiation, with either a N-heterocyclic carbene borane-based photoinitiating system (PIS) or a disulfide. With the full PIS and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as stabilizer, the size distributions were broad and the amount of PEGMA had a strong impact on the experiment reproducibility. The addition of a base solved the problem, leading to faster polymerizations, narrower size distributions and larger particles. With the disulfide as sole PIS, bigger and narrowly distributed PS particles were again formed. Quantitative conversion was achieved in each system, with particle size ranging between 100 and 350 nm. The use of poly(N-vinylpyrrolidone) as stabilizer led to significantly larger particles, up to 1.2 μm, with narrow size distributions. The production of such large latex particles by photoinitiated polymerizations is unprecedented.     

Modeling the free radical polymerization of acrylates

Acrylates have gained importance because of their ease of conversion to high‐molecular‐weight polymers and their broad industrial use. Methyl methacrylate (MMA) is a well‐known monomer for free radical polymerization, but its α‐methyl substituent restricts the chemical modification of the monomer and therefore the properties of the resulting polymer. The presence of a heteroatom in the methyl group is known to increase the polymerizability of MMA. Methyl α‐hydroxymethylacrylate (MHMA), methyl α‐methoxymethylacrylate (MC₁MA), methyl α‐acetoxymethylacrylate (MAcMA) show even better conversions to high‐molecular‐weight polymers than MMA. In contrast, the polymerization rate is known to decrease as the methyl group is replaced by ethyl in ethyl α‐hydroxymethylacrylate (EHMA) and t‐butyl in t‐butyl α‐hydroxymethylacrylate (TBHMA). In this study, quantum mechanical tools (B3LYP/6‐31G*) have been used in order to understand the mechanistic behavior of the free radical polymerization reactions of acrylates. The polymerization rates of MMA, MHMA, MC₁MA, MAcMA, EHMA, TBHMA, MC₁AN (α‐methoxymethyl acrylonitrile), and MC₁AA (α‐methoxymethyl acrylic acid) have been evaluated and rationalized. Simple monomers such as allyl alcohol (AA) and allyl chloride (AC) have also been modeled for comparative purposes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Visible light initiated polymerization of styrenic monolithic stationary phases using 470 nm light emitting diode arrays

Poly(styrene‐co‐divinylbenzene) monolithic stationary phases have been synthesized for the first time by photoinitiated polymerization. An initiator composed of (+)‐(S)‐camphorquinone/ethyl‐4‐dimethylaminobenzoate/N‐methoxy‐4‐phenylpyridinium tetrafluoroborate was activated using a 470 nm light emitting diode array as the light source. Spatially controlled polymerization of styrenic monoliths has been achieved within specific sections of a 100 μm id polytetrafluoroethylene‐coated fused‐silica capillary using simple photo masking. The sharpness of the edges was confirmed by optical microscopy, while SEM was used to verify a typical porous, globular morphology. Flow resistance data were used to assess the permeability of the monoliths and they were found to have good flow through properties with a flow resistance of 0.725 MPa/cm at 1 μL/min (water, 20°C). Conductivity profiling along the length of the capillary was used to assess their lateral homogeneity. Monoliths which were axially rotated during polymerization were found to be homogeneous along the whole length of the capillary. The monolithic stationary phases were applied to the RP gradient separation of a mixture of proteins. Column fabrication showed excellent reproducibility with the retention factor (k) having a RSD value of 2.6% for the batch and less than 1.73% on individual columns.     

Oxygen vacancies on the BiOCl surface promoted photocatalytic complete NO oxidation via superoxide radicals

One of the core issues in the photocatalytic oxidation of nitric oxide is the effective conversion of NO into the final product (nitrate). More than just improving the visible light photocatalytic performance of BiOCl, we aim to inhibit the generation of toxic by-product NO₂ during this process. In this study, we demonstrate that the oxygen vacancies (OVs) modulate its surface photogenerated carrier transfer to inflect the NO conversion pathway by a facile mixed solvent method to induce OVs on the surface of BiOCl. The photocatalytic NO removal efficiency under visible light increased from 5.6% to 36.4%. In addition, the production rate of NO₂ is effectively controlled. The effects of OVs on the generation of reactive oxygen species, electronic transfer, optical properties, and photocatalytic NO oxidation are investigated by combining density functional theory (DFT) theoretical calculations, the in situ FTIR spectra and experimental characterization. The OVs on the surface of BiOCl speed the trapping and transfer of localized electrons to activate the O₂, producing O₂⁻, which avoid NO₂ formation, resulting in complete oxidation of NO (NO + O₂⁻ → NO₃⁻). These findings can serve as the basis for controlling and blocking the generation of highly toxic intermediates through regulating the reactive species during the NO oxidation. It also can help us to understand the role of OV on the BiOCl surface and application of photocatalytic technology for safe air purification.     

Photoinduced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine on polyethylene membrane surface for obtaining blood cell adhesion resistance

Phospholipid polymer, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)], was grafted with polyethylene (PE) membrane using photoinduced polymerization technique to make the membrane resistant to cell adhesion. The water contact angle on the PE membrane grafted with poly(MPC) decreased with an increase in the photopolymerization time. This decrease corresponded to the increase in the amount of poly(MPC) grafted on the PE surface. The same graft polymerization procedure was applied using other hydrophilic monomers, such as acrylamide (AAm), N-vinylpyrrolidone (VPy) and methacryloyl poly(ethylene glycol) (MPEG). These monomers were also polymerized to form grafted chains on the PE membrane, and the grafting was confirmed with X-ray photoelectron spectroscopy. Analysis of amount and distribution of plasma proteins at the plasma-contacting surface of the original and the modified PE membranes were analyzed using immunogold assay. The grafting of poly(MPC) and poly(VPy) on PE membrane reduced the plasma protein adsorption significantly compared with that on the original PE membrane. However, the PE membranes grafted with poly(AAm) or poly(MPEG) did not show any effects on protein adsorption. Platelet adhesion on the original and modified PE membranes from platelet-rich plasma was also examined. A large number of platelets adhered and activated on the original PE membrane. Grafting with poly(AAm) did not suppress platelet adhesion, but grafting with poly(MPC) or poly(VPy) on the PE membrane was effective in preventing platelet adhesion. It is concluded that the introduction of the phosphorylcholine group on the surface could decrease the cell adhesion to substrate polymer.     

亚芳基环戊酮类可见光引发剂的结构与性质研究

合成了三种分别含有苯环、噻吩环和呋喃环的亚芳基环戊酮类可见光引发剂BDMA、BDTA和BDFA。采用紫外-可见吸收光谱、荧光发射光谱、激光闪光光解和电子自旋共振等方法研究了它们的光物理和光化学性质。和BDMA相比,杂环的引入使BDTA和BDFA的吸收光谱红移至黄绿光波段,从而能够和商用532nm激光器的发射光谱相匹配。光聚合动力学研究表明,在可见光光源照射下,这三种光引发剂均能直接引发丙烯酸酯单体PEGDA400发生自由基聚合,其中BDTA的引发效果最好,在可见光聚合中具有潜在的应用前景。     

Redox initiator systems for emulsion polymerization of acrylates

The performance of different redox initiator couples to initiate the emulsion polymerization of butyl acrylate at low temperature (40–50 °C) was investigated in both batch and seeded semibatch polymerizations. Polymerizations were carried out mimicking industrial conditions, that is, technical grade monomer and no N₂ purging was used during the polymerizations. The redox systems used contained as oxidants persulfates or hydroperoxides and as reducing agents ascorbic acid, formaldehyde sulfoxilate (SFS), tetramethyl ethylene diamine (TMEDA), Bruggolit 6 and 7 (FF6 and FF7), and sodium metabisulfites. Batch experiments showed that for systems using persulfates, the ammonium persulfate (APS)/TMEDA system provided the lower induction period and higher conversion, whereas for the systems with hydroperoxide oxidants, tert‐butyl hydroperoxide (TBHP)/FF7, TBHP/SFS, and H₂O₂/FF7 were the best alternatives. When these selected systems were used in seeded semibatch experiments of BA with allyl methacrylate, it was found that to obtain similar kinetics and microstructure (gel content and crosslinking density) than in case of using a thermal initiator at 80 °C, the polymerization could be run at 40 °C if the reactor was purged with N₂. Alternatively, in absence of N₂ polymerization, temperature should be increased to 50 °C and initiator concentration increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2917–2927, 2009     

Benzoylformamides as new photocaged bases for photo-latent anion polymerization

Benzoylfonnamide（BFA） derivatives are proposed as new photocagcd bases with good solubility in epoxy resin.Initially their structures were confirmed by ¹H NMR,¹³C NMR,and elemental analysis.Next,we detail their thermal stability,solubility behavior,and photolysis products.Furthermore,the model photo-latent anion polymerization（AP） of epoxide system in the presence of BFA-dBA（N,N-dibenzyl-2-oxo-2-phenylacetamide） as a photocaged base has been investigated,and excellent photopolymerization profile is obtained.     

Michael additions of amines to methyl acrylates promoted by microwave irradiation

A simple and efficient protocol has been developed for the Michael addition of amines to alpha,beta-unsaturated esters under microwave irradiation. Under these conditions there was a significant decrease in the reaction time, increases in the yields and increased purity of the products.     

Synthesis and polymerization of phosphorus‐containing acrylates

Novel phosphorus‐containing acrylate monomers were synthesized by two different routes. The first involved the reaction of ethyl α‐chloromethyl acrylate and t‐butyl α‐bromomethyl acrylate with diethylphosphonoacetic acid. The monomers were bulk‐ and solution‐polymerized at 56–64 °C with 2,2′‐azobisisobutyronitrile. The ethyl ester monomer showed a high crosslinking tendency under these conditions. The selective hydrolysis of the ethyl ester phosphonic ester compound was carried out with trimethylsilyl bromide, producing a phosphonic acid monomer. In the second route, ethyl α‐hydroxymethyl acrylate and t‐butyl α‐hydroxymethyl acrylate were reacted with diethylchlorophosphate. The bulk homopolymerization and copolymerization of these monomers with methyl methacrylate and 2,2′‐azobisisobutyronitrile gave soluble polymers. The attempted hydrolysis of the monomers was unsuccessful because of the loss of the diethylphosphate group. The relative reactivities of the monomers in the photopolymerizations were also compared. The ethyl α‐hydroxymethyl acrylate/diethylphosphonic acid monomer showed higher reactivity than the other monomers, which may explain the crosslinking during the polymerization of this monomer. The reactivities of other derivatives were similar, but the rates of polymerization were slow in comparison with those of methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3221–3231, 2002     

Preparation and polymerization of difluoramino-substituted alkyl acrylates and methacrylates

Several difluoramino-substituted alkyl acrylic acid esters were conveniently prepared by the debromination of difluoramino-substituted alkyl-2,3-dibromopropionates and 2,3-dibromoisobutyrates. The polymerization character of difluoramino-substituted alkyl acrylates and methacrylates was found to be similar to that displayed by other alkyl acrylic esters.