甲基丙烯酸2-羟乙酯水溶液聚合与硫氰化钠的效应

<正> 甲基丙烯酸2-羟乙酯(HEMA)是一带有羟基的功能性单体,它可以在自由基聚合引发剂如过氧化苯甲酰、偶氮二异丁腈、过氧化二碳酸二异丙酯或氧化还原引发体系过硫酸盐-乙酸二甲胺基乙酯的作用下进行自由基聚合,我们已报道带有羟基的单体如HEMA、甲基丙烯酸羟丙酯(HPMA)及甲基丙烯酯3-甲氧基-2-羟丙酯(MHPMA)可用     

Copper(I)-mediated radical polymerization of methacrylates in aqueous solution

α-Methoxypolyethylene oxide methacrylate was polymerized by copper(I)-mediated living radical polymerization in aqueous solution to give polymers with controlled number-average molecular masses and narrow polydispersities. When equimolar quantities of initiator with respect to copper(I) bromide were used, the reaction was extremely fast with quantitative conversion achieved in less than 5 min at ambient temperature. However, the molecular weight distribution was broad, and control over the number-average molecular weight (M_n) growth was extremely poor; this is ascribed to an increase in termination because of the increased rate as a result of the coordination of water at the copper center. The complex formed between copper(I) bromide and N-(n-propyl)-2-pyridylmethanimine, bis[N-(n-propyl)-2-pyridylmethanimine]copper(I), was demonstrated to be stable in aqueous solution by ¹H NMR over 10 h at 25 °C. However, on increasing the temperature to 50 °C, decomposition occurred rapidly. Thus, polymerization temperatures were maintained at ambient temperature. When longer alkyl chains were utilized in the ligand, that is, pentyl and octyl, the complex acted as a surfactant leading to heterogeneous solutions. When the catalyst concentration was reduced by two orders of magnitude, the rate of polymerization was reduced with 100% conversion achieved after 60 min with the M_n of the final product being higher than that predicted and the polydispersity equal to 1.43. Copper(II) was added as an inhibitor to circumvent these problems. When 10% of Cu(I) was replaced by Cu(II) {[Cu(I)] + [Cu(II)]/[I] = 1/100}, the mass distribution showed a bimodal distribution, and the rate of polymerization decreased significantly. With a catalyst composition [Cu(I)]/[Cu(II)] = 0.5/0.5 {[Cu(I)] + [Cu(II)]}/[I] = 1/100, polymerization proceeded slowly with 80% conversion reached after 22 h. Thus, the concentration of Cu(I) was further reduced with [Cu(I)]/[Cu(II)] = 10/90, {[Cu(I)] + [Cu(II)]}/[I] = 1/100. The system then contained [Initiator]/[Cu(I)] = 1000/1 and [I]/[Cu(II)] = 1000/9. Under these conditions, the reaction reached 50% after 5 h with the polymer having both an M_n close to the theoretical value and a narrow polydispersity of PDi = 1.15. Optimum results were obtained by increasing the amount of catalyst. When a ratio of [Cu(I)]/[Cu(II)] = 10/90 with a ratio of [Cu]/[I] = 1/1, a conversion of 100% was achieved after less than 20 h, leading to a product having M_n = 8500 and PDi = 1.15. Decreasing the amount of Cu(II) relative to Cu(I) to [Cu(I)]/[Cu(II)] = 0.5/0.5 (maintaining the overall amount of copper) led to 100% conversion after 75 min: M_n = 9500, PDi = 1.10. Block copolymers have been demonstrated by sequential monomer addition with excellent control over M_n and PDi. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1696–1707, 2001     

CoⅡ(salen*)存在下的氯丁二烯自由基聚合

研究了N,N'-双(3,5-二叔丁基水杨醛)-1,2-环己二胺钴(Ⅱ)[Co^Ⅱ(salen*)]存在下氯丁二烯(CP)的自由基聚合, 考察了不同溶剂、 引发剂用量及配体对聚合反应的影响. 结果表明, 随着引发剂用量的增加, 聚合反应的诱导期缩短, 以[ABVN]₀/[ Co^Ⅱ(salen*)]₀=3/1配比投料, 聚合反应表现出较好的可控聚合特征. 在苯、 甲苯、 四氢呋喃(THF)和乙酸乙酯(EA) 4种溶剂中按照[CP]₀/[Co^Ⅱ(salen*)]₀/[ABVN]₀=400/1/3的配比投料, 在苯中的可控聚合程度最好: 在低转化率(40%以下)实测聚合物分子量(M_n,GPC)与理论值(M_n,th)吻合, 且分子量随转化率增加呈线性增长. 研究了THF、 三乙胺(NEt₃)、 吡啶(Py)及水等不同配体对聚合反应的影响, 发现在添加THF时, 低转化率(40%以下)下M_n,GPC与M_n,th相符, 分子量分布(PDI)相对较窄.     

6,6′-Bisfunctionalized 2,2′-bipyridines as metallo-supramolecular initiators for the living polymerization of oxazolines

[Cu(I) {6,6′-bis(bromomethyl)-2,2′-bipyridine}₂](PF₆) complexes were used as metallo-supramolecular initiators for the polymerization of 2-oxazolines resulting in defined polymers with a central 6,6′-disubstituted 2,2′-bipyridine unit. The living character of the polymerization was demonstrated with the linear relationship between the weight-average molecular weight M̄_w and the [monomer]/[initiator] ratio as well as in the synthesis of block copolymers. The metal ions could be removed resulting in uncomplexed polymers with a free central metal binding unit.     

以2,2′-联吡啶与丙二腈为添加剂的苯乙烯活性自由基聚合的研究

研究了稳定自由基存在下苯乙烯的活性聚合 .发现在 2 ,2′ 联吡啶的存在下 ,苯乙烯聚合的分子量控制效果提高 ,分子量可控 ,分子量分布较窄 .在与丙二腈共同作用时 ,可在 4h内达到 85 %的转化率 ,分子量分布在 1 5以下 ,分子量控制误差在 2 0 %以下 .设计分子量在 1× 10 4 ～ 9× 10 4 的范围内 ,实测分子量和理论分子量相近 .     

Separation and enantioseparation of derivatized amino acids and biogenic amines by high-performance liquid chromatography with reversed and chiral stationary phases

A lignosulfonate sample was fractionated according to the solubility in ethanol-water. The fractions were analysed by aqueous size exclusion chromatography (SEC) combined with in-line multi-angle laser light scattering (MALLS), and by static MALLS. Satisfactory SEC results were obtained with aqueous phosphate buffer containing DMSO and SDS. The refractive index increment (dn/dc) varied from 0.186 to 0.205 ml/g, depending on Mw and the degree of sulfonation. The second viral coefficient (A2) was 7 x 10(-3) ml mol/g2. The weight-average molecular weight (Mw) of the fractions varied from 4600 up to 398 000 g/mol. and the polydispersity (Mw/Mn) varied between 1.3 and 3.5.     

Reaction and stabilizing mechanism of the cross-type macromonomers in the dispersion polymerization of styrene

The cross-type (C-VUM) and linear-type (L-VUM) bifunctional vinyl urethane macromonomers and polystyrene (PS) using these macromonomers were synthesized in the dispersion polymerization in ethanol, and the reaction and stabilizing mechanism of the macromonomers was proposed. The structural verification of the macromonomers and PS was studied using (1)H NMR. The weight-average particle size of C-PS (PS prepared with C-VUM) and L-PS (PS prepared with L-VUM) decreased from 4.41 to 1.36 microm and from 3.56 to 1.52 microm, whereas the average-molecular weight of those increased from 34,100 to 100,500 g/mol and from 32,200 to 71,800 g/mol, respectively. The XPS result showed that the C-PS was anchored with a larger amount of PEG than that of the L-PS on the particle surface. Thus, the reaction and stabilizing mechanism of the macromonomers for the formation of PS particles is proposed as the following. The particle surface of the C-PS is surrounded by a large amount of tail shaped macromonomers leading to higher molecular weights and smaller particle sizes. On the other hand, the particle surface of the L-PS is comprised of relatively small amounts of loop shaped macromonomers inducing lower molecular weights and larger particles of L-PS than C-PS.     

Novel organosoluble polynorbornene bearing a polar,pendant, ester‐bridged epoxy group via living ring‐opening metathesis polymerization

A novel organosoluble polynorbornene bearing a polar, pendant, ester‐bridged epoxy group [poly(oxiran‐2‐ylmethyl 2‐methylbicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate) (polyOMMC)] was prepared via the living ring‐opening metathesis polymerization (ROMP) of active norbornenes with a Ru catalyst. PolyOMMC exhibited excellent solubility in a variety of solvents. The number‐average molecular weight of polyOMMC linearly increased with the [M]/[I] ratio (where [M] is the monomer concentration and [I] is the initiator concentration), and a narrow polydispersity of 1.09–1.19 was observed; this was considered a living polymerization. When ROMP of oxiran‐2‐ylmethyl 2‐methylbicyclo[2.2.1]hept‐5‐ene‐2‐carboxylate with [M]/[I] = 350 was carried out at 30 °C in CH₂Cl₂, the number‐average molecular weight (7.01 × 10⁴; polydispersity index = 1.07) was close to the calculated molecular weight (7.28 × 10⁴), and a diblock copolymer was observed after the addition of another monomer ([M]/[I] = 350) with an increase in the number‐average molecular weight (1.60 × 10⁵; polydispersity index = 1.11), which was close to the calculated molecular weight (1.61 × 10⁵). The modified polynorbornenes retained good solubility in methylene chloride, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, N,N‐dimethylacetamide, and N‐methyl‐2‐pyrrdione. High‐performance polynorbornenes with active epoxy groups could be designed with great potential for applications in photoresists, UV curing, and elastomers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4428–4434, 2006     

Optimum conditions for preparing micron-sized PMMA beads in the dispersion polymerization using PVA

The optimum conditions for preparing micron-sized monodisperse polymethylmethacrylate (PMMA) beads by dispersion polymerization in a methanol/water mixture were proposed. PMMA forming microspheres having an average molecular weight of 55,300 g/mol, 2.6 μm weight-average diameter, with a 5.3% coefficient of variation and 91% conversion, were successfully obtained in the presence of 15 wt.% of polyvinylalcohol (PVA), 100/50 (g/g) of MeOH/water mixtures at 70°C; the reaction lasted for 8 h. Compared to dispersion polymerization using polyvinylpirrolydone, PVA proved to be an extremely stable steric stabilizer in the dispersion polymerization of methylmethacrylate.     

十二烷基苯磺酸钡存在下负离子聚合控制聚苯乙烯立构规整性研究

以正丁基锂(n-BuLi)为引发剂,环已烷为溶剂,通过添加十二烷基苯磺酸钡/四氢呋喃(SDBB/THF),对苯乙烯负离子聚合进行了研究.该体系可在60℃聚合得到立构规整性聚苯乙烯,其丁酮不溶物含量可达80%左右.13C-NMR表征结果显示其微观序列组成以等规结构为主,三元组mm和等规五元组mmmm含量可达57%和45%;DSC谱图中不仅有聚苯乙烯玻璃化温度(100℃),而且在211℃有一熔融峰.GPC结果表明,实测分子量与设计分子量差别较大,且分子量分布较宽。     

Continuous precipitation polymerization of vinylidene fluoride in supercritical carbon dioxide: molecular weight distribution

The surfactant-free precipitation polymerization of vinylidene fluoride (VF2) in supercritical carbon dioxide was studied in a continuous stirred autoclave. The polymerization temperature ranged from 65 to 85°C, the average residence time in the reactor varied from 10 to 50 min., and the pressure was between 210 and 305 bar. Diethyl peroxydicarbonate was used as the initiator. The fractional conversion of monomer varied from 7 to 26%, the number-average molecular weight of the polymer was between about 14,000 and 79,000, and the weight-average molecular weight was between about 21,000 and 700,000. In many cases, the polymer exhibited a bimodal molecular-weight distribution, especially at high monomer concentrations.     

Ring‐opening polymerization of the cyclic dimer of poly(trimethylene terephthalate)

Poly(trimethylene terephthalate) (PTT) was prepared by the ring‐opening polymerization of its cyclic dimer. Antimony(III) oxide, titanium(IV) butoxide, dibutyltin oxide, and titanium(IV) isopropoxide were used as catalysts. Among the catalysts, titanium(IV) butoxide was the most effective for the same reaction conditions. A weight‐average molecular weight of 63,500 g/mol was obtained from ring‐opening poly merization at 265 °C for 2 h in the presence of 0.5 mol % titanium(IV) butoxide. The PTTs obtained from the polymerization catalyzed with increasing amounts of antimony(III) oxide showed increasing weight‐average molecular weights and reaction conversions. When 1 mol % antimony(III) oxide was used, the weight‐average molecular weight was 32,000 g/mol and the conversion was 82% after 1 h of polymerization at 265 °C. In the case of the polymer catalyzed by titanium(IV) butoxide under the same conditions, the weight‐average molecular weight and conversion were 40,000 g/mol and 77% when 0.25 mol % was used, whereas 0.5 mol % catalyst produced a weight‐average molecular weight of 27,000 g/mol and a conversion of 95%. To get an acceptable molecular weight and relatively high reaction conversion, a catalyst concentration of at least 0.5 mol % was found to be necessary, in contrast to conventional condensation polymerizations, which require only about one‐tenth of this amount of the catalyst. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6801–6809, 2006     

Photochemically grafted polystyrene layer assisting selective au electrodeposition

We describe the selective electrodeposition of submicrometer gold (Au) patterns achieved by a thin film resist layer of polystyrene (PS) that was exposed to ultraviolet (UV) light on a photoreactive monolayer of a benzophenone-containing alkylthiol formed on a Au-plated substrate and patterned by thermal nanoimprint lithography. The presence of a PS graft layer caused by the benzophenone monolayer photochemistry at an interface between the PS resist layer and photoreactive monolayer played the important role of suppressing the unfavorable growth of tiny Au grains in regions masked with the PS resist layer, resulting in the selective Au electrodeposition in aperture regions of PS resist patterns. The suppressive effect on selective Au electrodeposition depended on the molecular weight of PS used as a resist material. Among unimodal PSs having weight-average molecular weights (M(w)'s) of 2100, 10?900, and 106?000 g mol(-1), the PS of M(w) = 10?900 g mol(-1) functioned most effectively as the resist layer. Au electrodeposition at a low current density allowed the preparation of Au lines having widths of submicrometers and a uniform height independent of line widths in resist aperture regions. Submicrometer bump structures of Au lines could be fabricated on transparent silica substrates by the subsequent wet etching of a Au electrode layer and then a chromium adhesive layer.     

Determination of the width of a narrow molecular weight distribution by gel-permeation chromatography

A recycle gel-permeation chromatography (GPC) method for extrapolating to infinite resolution is proposed. From the GPC calibration curve, the extrapolated elution peak width volume can be converted into peak width in decades of molecular weight. For an essentially Gaussian distribution, the weight-average/number-average molecular weight ratio can be determined from a calculated conversion table.     

Kinetic analysis of surface‐initiated SET‐LRP of poly(N‐isopropylacrylamide)

The single‐electron transfer living radical polymerization (SET‐LRP) of N‐isopropylacrylamide (NIPAM) from silicon wafer modified with an initiator layer composed of 2‐bromopropionyl bromide (2‐BPB) fragments is described. The amount of Cu(0) generated in situ by the disproportination of Cu(I) to Cu(0) and Cu(II) in the presence of 2,2′‐bipyridine (2,2′‐bpy) ligand and N,N‐dimethylformamide (DMF) solvent at 90 °C is dependent on the ratio of [CuBr]/[CuBr₂]. By proper selection of the [CuBr]/[CuBr₂] ratio, well‐controlled SET‐LRP polymerization of NIPAM was observed such that the thickness of the layer consisting of chains grown from the surface increased linearly with the molecular weight of chains polymerized in solution in identical. In addition, the calculation of grafting parameters, including surface coverage, σ (mg/m²); grafting density, Σ (chain/nm²); and average distance between grafting sites, D (nm), from the number‐average molecular weight, M _n (g/mol), and ellipsometric thickness, h (nm), values indicated the synthesis of densely grafted poly(NIPAM) films and allowed us to predict a “brush‐like” conformation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

邻-酚羟基取代N-杂环卡宾[C,O]螯合双配体镍/MAO催化降冰片烯加成聚合的研究

3种邻-酚羟基取代的N-杂环卡宾[C,O]螯合双配体镍配合物在甲苯中以甲基铝氧烷(MAO)为助催化剂,催化降冰片烯(NBE)聚合.考察了反应温度、时间、n(Al)/n(Ni)以及n(NBE)/n(Ni)等因素对催化活性和所得聚降冰片烯相对分子质量及其分布的影响.结果表明,0℃时催化体系的聚合活性可达,1.34×107gPNBE/(molNi.h);所得聚降冰片烯(PNBE)重均相对分子质量(Mw)可达2.0×106,相对分子质量分布(Mw/Mn)为3.3~1.5,热分解温度在440℃附近,且在室温下可溶于环己烷和三氯苯.通过对聚合产物FTIR,13C-NMR和WAXD分析表明,该聚合反应以烯烃加成聚合方式进行,且聚合物是非晶态结构.     

Synthesis of Poly(IB‐co‐VBDC)‐g‐PMMA via Photo‐initiated Free Radical Graft Polymerization

Abstract

Photoinitiated free radical graft polymerization of methyl methacrylate (MMA) with poly[isobutene‐co‐(4‐vinyl benzyl N,N‐diethyldithiocarbamate)] [poly(IB‐co‐VBDC)] as macromolecular iniferter was investigated. The polymerization proceeds to give a high yield graft copolymer, however it was observed that even in the early stage of the polymerization there formed an insoluble polymer. In the presence of tetraethylthiuram disulfide (TETD) the gel fraction of the yield graft copolymer was drastically reduced and the polymerization was retarded as well. When the [TETD]/[VBDC] increased from 0 to 1.0, the gel fraction of the graft copolymer decreased from 33.2% to 1.6% (wt) while the fraction of the homopolymer of the MMA increased from 4.5% to 10.5% (wt). With the increasing of the UV irradiation time, both the MMA conversion and the molecular weight of the graft copolymer increased readily.     

Molecular weight effects in the third-harmonic generation spectroscopy of thin films of the conjugated polymer MEH-PPV

Thin spin-cast films of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) were prepared from samples whose weight-average molecular weight (Mw) was varied in the range of 10-1600 kg/mol. We have characterized the films by means of transmission and reflection ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy to derive the linear optical constants, and third-harmonic generation spectroscopy with variable laser wavelengths to get the modulus and phase angles of the complex third-order nonlinear optical susceptibility chi(3). Increasing molecular weight yields films with significantly larger chi(3) values, absorption coefficients, and refractive indices. The chi(3) values of films from the largest and lowest Mw differ by a factor of 4, which is caused by chain orientation effects, local field effects, and changes of the effective conjugation length.     

Unsymmetrical N-Heterocyclic Carbene: 1-Isopropyl-3-benzylimidazol-2-ylidene as Catalyst for Ring-Opening Polymerization of ϵ-Caprolactone

An unsymmetrical N-heterocyclic carbene, namely 1-isopropyl-3-benzylimidazol-2-ylidene, is a highly active catalyst for ring-opening polymerization of ?-caprolactone (CL) to give polycaprolactone (PCL) with number average molecular weight (Mn) as high as 2.66 × 10⁴ at 0°C in 100 min in tetrahydrofuran (THF). The effects of monomer/initiator molar ratio ([M]/[I]), catalyst/initiator molar ratio ([C]/[I]), monomer concentration, as well as polymerization temperature and time have been investigated. The kinetic studies of CL polymerization have indicated that the polymerization rate is first-order with respect to both monomer and catalyst concentrations. The apparent activation energy amounts to 56.04 kJ/mol. The proposed mechanism is a monomer-activated process.     

Similarities and differences of epoxide, aldehyde and peroxide initiators for Cp2TiCl-catalyzed styrene living radical polymerizations

Cp₂TiCl is the first example of a single electron transfer (SET) agent that both provides initiating radicals from three different types of functionalities (i.e. radical ring opening of epoxides and reduction of aldehydes and peroxides) and doubles as mediator for the living radical polymerization of styrene (St) by reversibly endcapping the growing polymer chains. An initiator (I) comparison was performed using 1,4-butanediol diglycidyl ether (BDE), benzaldehyde (BA) and benzoyl peroxide (BPO) as models. The investigation of the effect of reaction variables was carried out over a wide range of experimental conditions ([Cp₂TiCl₂]/[I] = 0.5/1-4/1; [Zn]/[Cp₂TiCl₂] = 0.5/1-3/1, [St]/[I] = 50/1-400/1 and T = 60-130 °C) to reveal living polymerization features such as a linear dependence of molecular weight on conversion and narrow molecular weight distribution (M_w/M_n) for each initiator class. However, progressively lower polydispersities and larger initiator efficiencies are obtained with increasing the [Cp₂TiCl₂]/[I] and [Zn]/[Cp₂TiCl₂] ratios and with decreasing temperature. Accordingly, optimum conditions correspond to [St]/[I]/[Cp₂TiCl₂]/[Zn] = [50-200]/[1]/[2-3]/[4-6] at 70-90 °C. By contrast to peroxides, aldehydes and the more reactive epoxides provide alcohol end groups useful in block or graft copolymers synthesis.