Control of polymer structure by a chain-transfer reaction in the radical polymerization of acrylamide by β-mercaptopropionic acid and 1,2,6-hexanetriol trithioglycolate

 Star polymer synthesis by radical polymerization of acrylamide (AM) in the presence of thiol compounds was investigated. When 1,2,6-hexanetriol trithioglycolate (HTTG), as a trithiol compound, was used the molecular weights of the polymers were about 3 times those obtained in the presence of β-mercaptopropionic acid, as a monothiol compound, at the same concentration of thiol compounds in the feed. From viscosity measurements of the polymers and analysis of the ¹H NMR spectra of the polymers, we presumed that a star-shaped polymer of AM could be synthesized by radical polymerization in the presence of HTTG. Received: 9 June 2000 Accepted: 11 January 2001     

“Nascent” Cu(0) nanoparticles‐mediated single electron transfer living radical polymerization of acrylonitrile at ambient temperature

Zn(0)/ppm concentrations of CuBr₂ from 10 to 50 ppm was firstly used to catalyze radical polymerization of acrylonitrile at ambient temperature. The polymerization displayed typical living radical polymerization (LRP) characteristics, as evidenced by pseudo first‐order kinetics of polymerization, linear increase of number‐average molecular weight, and low polydispersity index (PDI) value. Effects of solvent, copper concentration, and initiator concentration on the polymerization reaction and molecular weight as well as PDI were investigated in detail. EC excelled NMP, DMF, and DMSO in terms of rate of polymerization as well as control of molecular weight and PDI. The increase of the copper concentration from 2.5 to 50 ppm leads to a higher rate of polymerization and a better control over the polymerization reaction. ¹H NMR and GPC analyses as well as chain extension reaction confirmed the very high chain‐end functionality of the resultant polymer. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). V. Kinetics of initial template polymerization

The influence of stereoregular poly(methyl methacrylate) (PMMA) as a polymer matrix on the initial rate of radical polymerization of methyl methacrylate (MMA) has been measured between ?11 and +60°C using a dilatometric technique. Under proper conditions an increase in the relative initial rate of template polymerization with respect to a blank polymerization was observed. Viscometric studies showed that the observed effect could be related to the extent of complex formation between the polymer matrix and the growing chain radical. The initial rate was dependent on tacticity and molecular weight of the matrix polymer, solvent type and polymerization temperature. The accelerating effect was most pronounced (a fivefold increase in rate) at the lowest polymerization temperature with the highest molecular weight isotactic PMMA as a matrix in a solvent like dimethylformamide (DMF), which is known to be a good medium for complex formation between isotactic and syndiotactic PMMA. The acceleration of the polymerization below 25°C appeared to be accompanied by a large decrease in the overall energy and entropy of activation. It is suggested that the observed template effects are mainly due to the stereoselection in the propagation step (lower activation entropy Δ S_p^?) and the hindrance of segmental diffusion in the termination step (higher activation energy Δ E_t^?) of complexed growing chain radicals.     

Bulk atom transfer radical polymerization of allyl methacrylate

A detailed investigation of the polymerization of allyl methacrylate, a typical unsymmetrical divinyl compound containing two types of vinyl groups, methacryloyl and allyl, with quite different reactivities, was performed with atom transfer radical polymerization (ATRP). Homopolymerizations were carried out in bulk, with ethyl‐2‐bromoisobutyrate as the initiator and with copper halide (CuX, where X is Cl or Br) with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst system. Kinetic studies demonstrated that during the early stages of the polymerization, the ATRP process proceeded in a living manner with a low and constant radical concentration. However, as the reaction continued, the increased diffusion resistance restricted the mobility of the catalyst system and interrupted the equilibrium between the growing radicals and dormant species. The obtained poly(allyl methacrylate)s (PAMAs) were characterized with Fourier transform infrared, ¹H NMR, and size exclusion chromatography techniques. The dependence of both the gel point conversion and molecular characteristics of the PAMA prepolymers on different experimental parameters, such as the initiator concentration, polymerization temperature, and type of halide used as the catalyst, was analyzed. These real gel points were compared with the ones calculated according to Gordon's equation under the tentative assumption of equal reactivity for the two types of vinyl groups. Moreover, the microstructure of the prepolymers was the same as that exhibited by those homopolymers prepared by conventional free‐radical polymerization; the fraction of syndiotactic arrangements increased as the reaction temperature was lowered. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2395–2406, 2005     

含芳酰胺结构的新型甲壳型液晶高分子PMPACS的聚合反应动力学研究

采用称量法和GPC,研究了以二甲基乙酰胺为溶剂,偶氮二异丁腈为引发剂,自由基溶液聚合制备含芳酰胺结构的新型甲壳型液晶高分子聚[乙烯基对苯二甲酸二(4-甲氧基苯胺)](PMPACS)的聚合反应动力学.研究发现,(1)MPACS的聚合反应在60℃时主要为双基偶合终止,所以反应后期聚合物分子量明显增大,分子量分布变窄;(2)该反应的聚合反应速率方程为Rp=kp[M][I]1/2,表观活化能Eα=44 kJ/mol,在60℃时的聚合反应常数kp=1.04 L·mol-1·h-1;(3)相同聚合条件下,单体的转化率和数均分子量随单体初始浓度[M]0的增加而增大,当引发剂浓度[I]0增加时,聚合物的分子量随之降低,分子量分布增大;(4)该研究虽采用普通自由基聚合,所得聚合物的分子量分布却较窄,仅为1.1～1.4.     

Atom Transfer Radical Polymerization (ATRP) of Ethyl Acrylate: Its Mechanistic Studies

Atom transfer radical polymerization (ATRP) of ethyl acrylate was carried out in bulk using ethyl 2-bromoisobutyrate as initiator, CuBr as well as CuCl as catalyst in combination with different ligands e.g., 2,2′ bipyridine (bpy)andN,N, N′,N″,N″-pentamethyldiethylenetriamine (PMDETA). In most of the cases very high conversion (72–98%) was achieved. The polymerization was well controlled with a linear increase of molecular weight (M_n^SEC) with conversion and relatively narrow molecular weight distributions (polydispersity index 1.2–1.3). Use of PMDETA as the ligand resulted in faster polymerization rate (98% conversion in 1 h) than those using bipyridine (72% conversion in 5 h). The MALDI-TOF-MS analysis of poly (ethyl acrylate) (PEA) prepared by using bpy as ligand showed the presence of halogen as the end group. On the contrary, when PMDETA was used as the ligand, the mass analysis showed no trace of this end group.     

A copper‐based reverse atom‐transfer radical polymerization process for the living radical polymerization of polyacrylonitrile

The reverse atom‐transfer radical polymerization (RATRP) technique using CuCl₂/2,2′‐bipyridine (bipy) complex as a catalyst was applied to the living radical polymerization of acrylonitrile (AN). A hexasubstituted ethane thermal iniferter, diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS), was firstly used as the initiator in this copper‐based RATRP initiation system. A CuCl₂ to bipy ratio of 0.5 not only gives the best control of molecular weight and its distribution, but also provides rather rapid reaction rate. The rate of polymerization increases with increasing the polymerization temperature, and the apparent activation energy was calculated to be 57.4 kJ mol^?1. Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed the chain extension polymerization in the presence of CuCl/bipy catalyst system via a conventional ATRP process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 226–231, 2006     

Photophysical Properties and Electropolymerization of Regioregular Head-to-Tail Oligothiophenes-Functionalized 9,9′-spirobifluorene Derivatives

The photophysical properties of oligothiophenes-functionalized 9,9′-spirobifluorene derivatives in solution and in solid state were investigated in detail. The enhanced red-shift was observed from the absorption and the photoluminescence (PL) spectra of these derivatives in dilute THF solution with the increase of thiophene unit at one branch of 9,9′-spirobifluorene identical with the increased p-electron delocalization and the more effective conjugation length of the whole molecular system. The investigation on the photophysical properties of these compounds further demonstrated that the sp3-hybrid carbon at the spiro-center completely obstructed the correlation between two branches of the 9,9′-spirobifluorene system and made every branch become an independent chromophore. The electrochemical polymerization of 6b as a representative was also investigated.     

结构规整有序的寡聚噻吩修饰9,9'-螺二芴衍生物的光物理性质及其电化学聚合

研究了结构规整有序的寡聚噻吩修饰的9,9'-螺二芴衍生物在溶液中和在固体膜状态下的光物理性质, 发现在四氢呋喃的稀溶液中, 随着有效共轭长度的增加这些化合物的最大吸收峰和发射峰发生了明显的红移. 实验结果表明, 9,9'-螺二芴骨架中的9位螺碳原子明显地阻断了二个共轭片段的共轭效应, 使它们成为了二个独立的共轭链节. 此外, 还进一步研究了这些化合物的电化学聚合性质.     

Effects of hydration and hydrophilicity on Na‐Clay‐supported aqueous‐phase catalysis for atom transfer radical polymerization

Hydrated sodium montmorillonite (Na‐clay) has been used as a catalyst support for the heterogeneous atom transfer radical polymerization of benzyl methacrylate in the presence of various concentrations of water, reducing agent, and CuBr₂ in anisole at ambient temperature. The polymerization was promoted via reduction of Cu^II to Cu^I through the addition of sodium ascorbate (NaAsc) as a reducing agent in aqueous solution. The polymerizaton proceeded in a controlled manner and produced poly(benzyl methacylate) with moderately narrow molecular weight distribution (MWD) when performed under optimum conditions of hydration (10 wt % ≤ H₂O/Na‐clay ≤ 21 wt %) and reducing agent (0.15 ≤ [NaAsc]/[I] ≤ 0.23). The polymerization was uncontrolled if hydration and NaAsc exceed above their optimum range of concentrations. Apparent rate of the polymerization (k_app) increased in the presence of decane–anisole (1/3, v/v) mixture solvent. Selective adsorption of decane at the interfaces of the hydrated clay was attributed for the rate enhancement due to increased polymer and hydrophobic interface interaction. The polymerization progressed in a controlled manner as confirmed by the first‐order time‐conversion plot, linear increase in molecular weights, and moderately narrow MWDs over conversion. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Radical polymerization of methyl methacrylate with ethane-1,1,2-triyltribenzene as an initiator and ethane-1,1,2-triyltribenzene-end polymers as macroinitiators

An unsymmetrical triphenylethane, ethane-1,1,2-triyltribenzene (ETB), was successfully prepared from phenyl lithium, trans-1,2-diphenylethylene, and methanol. Characterization of the compound was performed by ¹H and ¹³C nuclear magnetic resonance spectroscopy (NMR). The polymerization of methyl methacrylate (MMA) was performed in the presence of ETB at 85 °C or higher. The free radicals obtained were characterized by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF MS). Gel permeation chromatography (GPC) traces of the average molecular weight of poly(MMA) (PMMA) showed a series of translations with increasing time. The average molecular weight of PMMA indicated narrow polydispersity, and a linear relationship was found between ln([M]₀/[M]) and polymerization time. These results indicated the “living” nature of the polymerization of MMA in the presence of ETB. The structure of ETB was also introduced to the end of polystyrene (PS), polyisoprene (PI), and polyisoprene-b-polystyrene (PIS) chains which were obtained by living anionic polymerization. Hence, they initiated radical polymerization of MMA as ETB-end-macroinitiators to obtain block copolymers. Thus, living anionic polymerization and this radical polymerization method were combined together to prepare block copolymers without the intermediate transformation step.     

Catalytic aerobic radical polymerization in typical redox-non-innocent solvents as potential low-efficiency initiators

Abstract

Certain complexes of some transition metal cations in the high oxidation state could oxidize some organic substrates with labile C-H moieties, leading to the corresponding cations in the lower" oxidation state and some carbon-centered radicals. The former would form oxidative complexes with molecular dioxygen to continuously oxidize organic substrates, while the latter would initiate polymerization of vinylic monomers. Such catalytic oxidation is adopted to initiate radical polymerization of methyl methacrylate (MMA) and styrene (St) with cyclohexanone (CyHO) and benzylic hydrocarbons as both the solvent and the substrate. Although, a large array of complexes could trigger the polymerization, Cu^II/2,2′-bipyridine complexes display a maximum turnover frequency above 200?h^–1 during the catalytic aerobic radical polymerization of MMA in CyHO at 70–80?°C, but only less than 0.4% of CyHO is involved in chain formatting. Cu^II/ligand-catalyzed aerobic radical polymerization of St in CyHO exhibit comparable behaviors. Only Co^II complexes could catalyze the aerobic radical polymerization of MMA in para-xylene and cumene at 90?°C, but only 0.1% of PX and 0.3% of cumene are involved in chain forming.     

Controlled Radical Polymerization of Furfuryl Methacrylate

Atom transfer radical polymerization provides a new method of controlled radical polymerization. The most important advantage of ATRP is that it is tolerant to the different functional groups present in the initiator as well as in the monomer. Furfuryl Methacrylate (FMA) is a specialty monomer, which has applications in coatings, adhesives and in biomedicals. Conventional radical polymerization of FMA leads to excessive gel formation, which limits its applications. In this investigation homo and co-polymerization of FMA has been carried out via ATRP. ATRP of FMA was carried out using CuBr as catalyst and 1, 1, 4, 7, 10, 10 hexamethyltriethylenetetramine (HMTETA) as ligand. There was no gel formation during the polymerization. ATRP of FMA was well controlled with a linear increase of molecular weight (Mn) with monomer conversion. The polymers were characterized by using ¹HNMR, FT-IR and GPC analysis. Interestingly, it was observed that the furfuryl ring was not affected during polymerization.     

Living radical polymerization of acrylonitrile catalyzed by copper with a high concentration of radical initiator and its application in removal of Ag(I) after modification

In this study, we reported the synthesis of polyacrylonitrile (PAN) via living radical polymerization in N, N‐dimethylformamide using carbon tetrachloride as initiator, copper(II) chloride (CuCl₂)/hexamethylenetetramine as catalyst system, and 2,2‐azobisisobutyronitrile as a high concentration of thermal radical initiator. The polymerization proceeded in controlled/living manner as indicated by first‐order kinetics of the polymerization with respect to the monomer concentration, linear increase of the molecular weight with monomer conversion and narrow polydispersity. Higher polymerization rate and narrower molecular weight distributions were observed with CuCl₂ less than 50 ppm. The rate of polymerization showed a trend of increase along with temperature. The modified PAN containing amidoxime group was used for extraction of Ag(I) ions from aqueous solutions. The adsorption kinetics data indicated that the adsorption process followed pseudo‐second‐order rate model. The isotherm adsorption process could be described by the Freundlich isotherm model. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

六甲氧基甲基三聚氰胺-多元醇-丙烯酸酯混杂聚合体系的研究

六甲氧基甲基三聚氰胺 (HMMM) 多元醇 丙烯酸酯 酸催化剂混杂聚合体系在高温下同时进行缩聚和自由基聚合并表现出协同效应 .体系中的活泼亚甲基在HMMM的催化下被空气氧化成过氧化氢物 ;过氧化氢物在酸催化下分解成自由基进而引发自由基聚合反应 .研究结果表明 ,体系中存在固化加速的协同效应 ;同时体系中还存在热互补效应 ,丙烯酸酯的自由基聚合反应放出的热可以传递给缩聚反应 ,满足缩聚反应吸热的要求 .混杂聚合得到的高分子合金膜具有优良的机械性能和耐溶剂性能 ,这是由于在混杂聚合过程中形成了互穿聚合物网络 (IPN)结构 .使用潜酸催化剂作为酸的来源 ,可以提高体系的储存稳定性 ;交联 引发剂的使用可以拓宽它的使用范围 ;对超枝化聚合物在混杂体系中的应用也进行了初步研究     

Well-defined higher-molecular-weight polyacrylonitrile via RAFT technique in the presence of disulfide compounds as a source of chain transfer agent

Well-defined polyacrylonitrile with a higher number-average molecular weight () up to 200,000 and a lower polydispersity index (PDI, 1.7-2.0) was firstly obtained via reversible addition-fragmentation chain transfer (RAFT) process. This was achieved by selecting a stable, easy way to prepare disulfide compound intermediates including bis(thiobenzoyl) disulfide (BTBDS) and bis(thiophenylacetoyl) disulfide (BTPADS) to react with azobis(isobutyronitrile) to directly synthesize RAFT agents in situ. The polymerization of acrylonitrile (AN) displays the characteristics of controlled/living radical polymerization as evidenced by pseudo first-order kinetics of polymerization, linear evolution of molecular weight with increasing monomer conversion, and narrow PDIs. The polymerization rate and the efficiency for producing RAFT agent of BTPADS system are obviously higher than those of BTBDS system, whereas the control of the latter over the polymerization is superior to that of the former. ¹H NMR analysis has confirmed the dithioester chain-end functionality of the resultant polymer. The RAFT copolymerizations of AN and the comonomers including methyl acrylate, itaconic acid, methyl methacrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, and acrylamide were also successfully carried out using the same polymerization system.     

新型水溶性共轭嵌段含糖聚合物的合成与表征

以两端溴化的聚9,9-二己基芴作为大分子引发剂, 6-O-甲基丙烯酰基-1,2∶3,4-二-O-异亚丙基-D-吡喃型半乳糖(6-O-Methacryloyl-1,2∶3,4-di-O-isopropylidene-D-galactopyranose, MaIpGa)为单体, 氯化亚铜/1,1,4,7,10,10-六甲基三乙基四胺为催化剂, 通过原子转移自由基聚合(ATRP), 合成了一种新型的具有良好光学性能的三嵌段共聚物聚甲基丙烯酸羟基保护半乳糖酯-聚芴-聚甲基丙烯酸羟基保护半乳糖酯(PMaIpGa-PF-PMaIpGa). 在酸性条件下进一步水解, 得到水溶性的聚甲基丙烯酸半乳糖酯-聚芴-聚甲基丙烯酸半乳糖酯(PMaGa-PF-PMaGa)三嵌段聚合物, 其结构和分子量(分布)通过核磁共振、红外光谱和凝胶渗透色谱(GPC)确证, 并研究了其紫外-可见和荧光光谱特性.     

Atom Transfer Radical Polymerization of Butadiene Initiated by Benzyl Chloride/MoCl5 Substituted by 1-octanol/PPh3

A novel initiator system, benzyl chloride/MoCl₅ substituted by 1-octanol/triphenyl phosphine (PPh₃), was applied to the atom transfer radical polymerization (ATRP) of butadiene. The characterization revealed the linear increase of the number average molecular weight with the monomer conversion and the rather wide molecular weight distributions of the polymerization products. The microstructure of the butadiene was detected by IR and ¹H-NMR. The chlorine atom at ω –end group of the polymer and the change of valence states of molybdenum detected by UV–Vis spectra revealed that the polymerization accorded primarily with the mechanism of ATRP.     

New approaches towards the synthesis and characterization of alkoxy substituted spirobifluorenes and spirosilabifluorenes for organic optoelectronics

Alkoxy substituted spirobifluorene derivatives namely 2,2′,7,7′-tetrabromo-3,6-bis(methoxy)-9,9′spirobifluorene (MSBF), 2,2′,7,7′-tetrabromo-3,6-bis(ethoxy)-9,9′spirobifluorene (ESBF), 2,2′,7,7′-tetrabromo-3,6-bis(butoxy)-9,9′spirobifluorene (BSBF), 2,2′,7,7′-tetrabromo-3,3′,6,6′-tetra(methoxy)-9,9′-spiro-9-silabifluorene (MSSiBF) and their key intermediates have been synthesised successfully. All compounds have been fully characterised by ¹H and ¹³C NMR, FTIR, UV-visible spectroscopy, MS spectrometry. TGA analysis revealed good thermal stability. The systematic investigation on the solubility, thermostability and photophysical property of synthesized compound showed that alkoxy substituted spirobifluorene were unique in rigidity and have wide range of applications in molecular electronics and can be used as building units for optoelectronics material.     

Synthesis and kinetic analysis of DPE controlled radical polymerization of MMA

The 1,1‐diphenylethene (DPE) controlled radical polymerization of methyl methacrylate was performed at 80 °C by using AIBN as an initiator and DPE as a control agent. It was found that the molecular weight of polymer remained constant with monomer conversion throughout the polymerization regardless of the amounts of DPE and initiator in formulation. To understand the result of constant molecular weight of living polymers in DPE controlled radical polymerization, a living kinetic model was established in this research to evaluate all the rate constants involved in the DPE mechanism. The rate constant k₂, corresponding to the reactivation reaction of the DPE capped dormant chains, was found to be very small at 80 °C (1 × 10^?5 s^?1), that accounted for the result of constant molecular weight of polymers throughout the polymerization, analogous to a traditional free radical polymerization system that polymer chains were terminated by chain transfer. The polydispersity index (PDI) of living polymers was well controlled <1.5. The low PDI of obtained living polymers was due to the fact that the rate of growing chains capped by DPE was comparable with the rate of propagation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009