Reversible Chain Transfer Catalyzed Polymerization with Alkyl Iodides Generated from Alkyl Bromides by in Situ Halogen Exchange

Reversible chain transfer catalyzed polymerization(RTCP) is a practical and efficient process for the precise synthesis of polymers with special architecture by using simple phenols(2,4,6-trimethylphenol, TMP) or hydrocarbons(xanthene, XT) as efficient organocatalysts. Herein,alkyl iodide(R-I), which was generated from in situ bromine-iodine transformation of alkyl bromide(R-Br) with sodium iodide(NaI), was served as initiator to mediate RTCP with TMP or XT. MMA and other functional methacrylate...     

Stereoregular Polymerization of Alkyl Propiolate Catalyzed by Rh Complex

Abstract

The polymerizations of alkyl esters of propiolic acid by Rh complex catalysts were investigated. [Rh(norbornadiene)Cl]₂, which was the most active among the catalysts examined, gave rise to poly(alkyl propiolate) in a fairly high yield (～80%) in the presence of alcohol as the polymerization solvent. The polymers formed were a pale yellow powder soluble in common organic solvents except for poly(methyl propiolate). The structures of the polymers obtained were investigated by IR, ₁₃C-NMR, CP MAS ₁₃C-NMR, and laser Raman spectroscopies, together with the x-ray diffraction method. Based on these spectroscopic data, it was concluded that this Rh complex can be called a stereoregular polymerization catalyst of alkyl propiolate because the poly(alkyl propiolate) obtained has a cis-transoidal structure.     

Organocatalytic copolymerization of mixed type monomers

Triggered by environmental concerns and the rising demands for metal-free polymers in e.g.bio-related and microelectronic applications,studies on organocatalytic polymerization have been launched and developed unprecedentedly during the last 15 years.A wide range of organic molecules are now available in polymer chemists' toolbox to choose from as catalysts for polymerization of (hetero)cyclic and polar vinyl monomers.Apart from the intrinsic merits such as lower toxicity and better solubility compared with (transition) metal catalysts/initiators,organocatalysts have also shown,in many cases,excellence to achieve high polymerization rates and/or good control (selectivity).In addition,particular natures and catalytic/activating mechanisms of organocatalysts have led to new opportunities for rational design and efficient synthesis of macromolecular architectures,i.e.chain structures,topological structures and functionalities.This mini-review is specially themed on pathways to construct copolymer chain structures by organocatalytic copolymerization of mixed type monomers (comonomers bearing different polymerizing moieties) and will be sectioned by different comonomer combinations,including cyclic monoesters of different sizes,cyclic monoesters and lactides,cyclic esters and cyclic carbonates or epoxides,heterocycles and vinyl monomers.     

Polymerizations with hydrido and alkyl transition metal complexes in aqueous media

Hydrido pentacyanocobaltate(III) and alkyl pentacyanocobaltate(III) have been studied as initiators for the polymerization of isoprene and butadiene in aqueous emulsion systems. The microstructure of the polymers is consistent with a free radical process. Other transition metal hydrides are relatively ineffective as polymerization initiators or act as inhibitors for the radical polymerization of the same dienes.     

Alkyl halide/tertiary amine as novel initiators for free radical polymerizations of methyl methacrylate,methyl acrylate and styrene

A series of combinations of alkyl halide with tertiary amine such as ethyl α-bromophenylacetate/tris[2-(dimethylamino)ethyl)]amine (αEBP/Me₆TREN), ethyl 2-bromoisobutyrate/triethylamine (EBiB/TEA), and ethyl 2-chloropropionate/N,N,N′,N′,N′′-pentamethyldiethylenetriamine (ECP/PMDETA) have been developed as novel free radical initiators and used for the polymerizations of methyl acrylate (MA), methyl methacrylate (MMA) and styrene (St). The effects of the structure of alkyl halide and tertiary amine on the polymerization of MA were investigated. Gel permeation chromatograph (GPC) and proton nuclear magnetic resonance (¹H NMR) have been utilized to analyze the end group of the obtained poly(methyl acrylate). Electron spin resonance (ESR) spectroscopy was employed to identify the structure of the radicals produced by αEBP/Me₆TREN, and the results indicated that αEBP reacted with Me₆TREN via a single electron transfer (SET) nucleophilic mechanism to produce corresponding ethyl α-phenylacetate radicals which subsequently initiated the polymerization of MA. As both alkyl halide and tertiary amine are commercially available at low cost, non-explosive, and ease of use and storage in comparison with conventional azo, peroxide or persulfate initiators, the combination of alkyl halide and tertiary amine as a free radical initiator is promising for large-scale practical applications.     

Molar Mass Dispersity Control by Iodine-mediated Reversible-deactivation Radical Polymerization

Dispersity(D)of polymers has a great effect on the properties of polymeric materials,and therefore how to control D is very important but still a huge challenge in polymer synthesis,especially for reversible-deactivation radical polymerization(RDRP)strategy.Herein,we successfully developed a novel strategy to adjust D of polymers by visible light-controlled reversible complexation mediated living radical polymerization(RCMP)and combination of single-electron transfer-degenerative chain transfer living radical polymerization(SET-DTLRP)at room temperature.In RCMP system,2-iodo-2-methylpropionitrile(CP-I)and ethyl 2-iodo-2-phenylacetate(EIPA)were used as alkyl iodide initiators,by using methyl methacrylate(MMA)as the model monomer and n-butylacrylate(BA)as the end-capping reagent to regulate D of polymers.Subsequently,we successfully prepared the block copolymer PMMA-b-PBA with adjustable D by reactivating the polymer end-chains via SET-DTLRP in the presence of copper wire,fully demonstrating that it is a promising strategy that can keep the"living"feature of polymers while regulating their molar mass dispersities easily.     

Highly heterotactic polymerization of methacrylates — Higher order stereoregulation and stereochemical significance

A combination of tert-butyllithium (t-BuLi) and bis(2,6-di-t-butylphenoxy)methylaluminium (MeAI(ODBP)₂) was found to be an efficient initiator for heterotactic living polymerization of certain alkyl methacrylates in toluene at low temperatures. The polymerization of methyl methacrylate (MMA) with t-BuLi/MeAI(ODBP)₂ (AI/Li=5 mol/mol) in toluene at −78°C gave heterotactic-rich poly(methyl methacrylate) (PMMA) with narrow molecular weight distributions (MWDs) (heterotactic triad fraction mr = 68%, ratio of weight- to number-average molecular weights M̄w/M̄n = 1.06-1.17). Other alkyl methacrylates also gave heterotactic polymers under the same conditions; in particular, ethyl and butyl methacrylates gave polymers with heterotactic triad fractions of 87%. The highest triad heterotacticity of 91.6% was obtained for the polymerization of ethyl methacrylate at −95°C. Some characteristic features of this stereospecific polymerization were discussed based on the polymerization results combined with other structural information of the polymer such as chain-end stereostructure and stereosequence distribution in the main chain.     

Effects of initiators and photo-acid generators on nitroxide-mediated photo-living radical polymerization of methyl methacrylate

The effects of the structure of initiators and photo-acid generators on the nitroxide-mediated photo-living radical polymerization of methyl methacrylate were explored. The bulk polymerization was performed at room temperature using nine different initiators in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate as the photo-acid generator. 2,2′-Azobisisobutyronitrile, 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2′-azobis(2-methylpropionate), and 2,2′-azobis(N-butyl-2-methylpropionamide) produced the polymers with a molecular weight distribution (MWD) around 1.6, while the racemic- and meso-(2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) provided a 1.4 MWD. 2,2′-Azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane-1-carbonitrile), and 1-(cyano-1-methylethoxy)-4-methoxy-2,2,6,6-tetramethylpiperidine produced a broad MWD over 4.0. The structure of the photo-acid generator also had an influence on the molecular weight control. The photo-acid generator of sulfonium salts supporting the alkyl, methoxy, phenoxy, methylthio, and tert-butoxycarbonylmethoxy groups, coupled with halogens with the exception of the iodide had no effect on the MWD. On the other hand, the salts containing the iodide, phenylthio, and naphthyl groups produced polymers with broad MWDs and with uncontrolled high molecular weights.     

α-亚甲基-β-丁内酯的区域选择性聚合:合成线形与环状聚酯

设计不同的催化体系或引发剂实现了α-亚甲基-β-丁内酯(MβBL)单体的区域选择性聚合,合成不同拓扑结构的聚酯.选用偶氮二异丁腈(AIBN)自由基引发剂,选择性聚合MβBL的α位上亚乙烯基双键,形成线形含有四元环内酯单元的聚酯.使用SalenAlCH3金属配合物催化剂,区域选择性在MβBL的酰-氧键断裂,生成双键保留以间同结构为主的结晶性线形聚酯.有机强碱是MβBL的高效开环聚合催化剂,获得以酰-氧键断裂为主的线形聚酯.而使用简单碘化钠催化MβBL开环聚合,形成以烷-氧键断裂为主的结晶性环状聚酯.     

Polymerization of surface-active monomers. II. Polymerization of quarternary alkyl salts of dimethylaminoethyl methacrylate with a different alkyl chain length

The cationic monomers (C_NBr), obtained by quarternization of dimethylaminoethyl methacrylate with n-alkyl bromide containing varying carbon number (N = 4, 8, 12, 14, and 16) were polymerized with radical initiators in water and various organic solvents. The degree of polymerization of the resulting polymers was determined by GPC measurements on poly(methyl methacrylate) samples derived from them. The rate of polymerization of the micelle-forming monomers (N = 8, 12, 14, and 16) in water increases with increasing a chain length of alkyl group, whereas it is little dependent on N in isotropic solution in dimethylformamide. The data on the degree of polymerization for the polymers of C₄Br, C₈Br, and C₁₂Br show that the polymerization of C₁₂Br with azo initiators in water and benzene gives polymers with a very high degree of polymerization. The results obtained here suggest that highly developed or relatively rigid, aggregated structures of monomers in solution are responsible for the formation of the polymers with a very high degree of polymerization, in addition to an enhanced rate of polymerization. Also considered are the relation of the molecular weight of poly(C₁₂Br) to the viscosity data in chloroform and methanol.     

Ring‐opening polymerization of 1,3‐benzoxazines by p‐toluenesulfonates as thermally latent initiators

p‐Toluenesulfonic acid (TsOH) and several alkyl p‐toluenesulfonates, that is, methyl p‐toluenesulfonate (TsOMe), cyclohexyl p‐toluenesulfonate (TsOCH), and neopentyl p‐toluenesulfonate (TsONP), were evaluated as initiators for the ring‐opening polymerization of benzoxazines. TsOH and TsOMe were highly efficient initiators that induced the polymerization at 60 and 80 °C, respectively. In contrast, TsOCH and TsONP did not initiate the polymerization below 100 °C, while they induced the polymerization at elevated temperatures, 120 and 150 °C, respectively. When TsOCH was used as an initiator, the corresponding polymerization rate was comparable to that observed for the polymerization with using TsOH as an initiator. These results suggested that neutral TsOCH and TsONP can be regarded as “thermally latent initiators,” which underwent the thermal dissociation at the elevated temperatures to generate the corresponding alkyl cations and/or TsOH as the initiators of the polymerization. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

End capping ring-opening olefin metathesis polymerization polymers with vinyl lactones

The selective placement of a functional group at the chain end of a ring-opening metathesis polymer using ruthenium carbene initiators has been a significant limitation. Here we demonstrate a highly effective and facile end-capping technique for ROMP with living ruthenium carbene chain ends using single-turnover olefin metathesis substrates. Vinylene carbonate and 3H-furanone are introduced as functionalization and termination agents for the ruthenium-initiated ring-opening metathesis polymerization. This leads directly to the formation of functional polymer end groups without further chemical transformation steps. Aldehyde and carboxylic acid end groups can be introduced by this new method which involves the decomposition of acyl carbenes to ruthenium carbides. The high degrees of chain-end functionality obtained are supported by (1)H NMR spectroscopy, MALDI-ToF mass spectrometry, and end-group derivatization.     

Effect of Substituents on the Homopolymerization Activity of Methyl Alkyl Diallyl Ammonium Chloride

Among nitrogen-containing cationic electrolytes, diallyl quaternary ammonium salt is a typical monomer with the highest positive charge density, which has attracted the most attention, especially in the research on homopolymers and copolymers of dimethyl diallyl ammonium chloride (DMDAAC), which occupy a very unique and important position. In order to improve the lipophilicity of substituted diallyl ammonium chloride monomers under the premise of high cationic charge density, the simplest, most direct, and most efficient structure design strategy was selected in this paper. Only one of the substituents on DMDAAC quaternary ammonium nitrogen was modified by alkyl; the substituents were propyl and amyl groups, and their corresponding monomers were methyl propyl diallyl ammonium chloride (MPDAAC) and methyl amyl diallyl ammonium chloride (MADAAC), respectively. The effect of substituent structure on the homopolymerization activity of methyl alkyl diallyl ammonium chloride was illustrated by quantum chemical calculation and homopolymerization rate determination experiments via ammonium persulfate (APS) as the initiator system. The results of quantum chemistry simulation showed that, with the finite increase in substituted alkyl chain length, the numerical values of the bond length and the charge distribution of methyl alkyl diallyl ammonium chloride monomer changed little, with the activation energy of the reactions in the following order: DMDAAC < MPDAAC < MADAAC. The polymerization activities measured by the dilatometer method were in the order DMDAAC > MPDAAC > MADAAC. The activation energies E_a of homopolymerization were 96.70 kJ/mol, 97.25 kJ/mol, and 100.23 kJ/mol, and the rate equation of homopolymerization of each monomer was obtained. After analyzing and comparing these results, it could be easily found that the electronic effect of substituent was not obvious, whereas the effect of the steric hindrance was dominant. The above studies have laid a good foundation for an understanding of the polymerization activity of methyl alkyl diallyl ammonium chloride monomers and the possibility of preparation and application of these polymers with high molecular weight.     

Alkyl chloride initiators for SET‐LRP of methyl acrylate

Single‐electron transfer living radical polymerization (SET‐LRP) proceeds by an outer‐sphere single‐electron transfer mechanism that induces a heterolytic bond cleavage of the initiating and propagating R‐X (where X = Cl, Br, and I) species. Therefore, unlike the homolytic bond cleavage mechanism claimed for ATRP, SET‐LRP is expected to show a small dependence of the nature of the halide group on the apparent rate constant of activation. This means the R‐X with X = Cl, Br, and I must all be efficient initiators for SET‐LRP and no chain transfer must be observed in the case of initiators with X = Br and I. Here, we report the SET‐LRP of methyl acrylate initiated with the alkyl chlorides methyl‐2‐chloropropionate (MCP) and chloroform (CHCl₃) and catalyzed by Cu(0)/Me₆‐TREN/CuCl₂ in DMSO at 25 °C. A combination of kinetic and structural analysis was used to elucidate the MCP and CHCl₃ initiating behavior under SET‐LRP conditions, and to demonstrate the very small dependence of the SET‐LRP apparent rate constant of propagation on X while providing polymers with well defined architecture. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4917–4926, 2008     

Block and graft copolymers of 2-oxazolines

The cationic ring-opening polymerization of 2-oxazolines is known to be initiated by alkyl halides, Lewis acids and esters of strong acids. The polymerization proceeds by a living mechanism. Numerous block and graft copolymers have already been described. Recently it was found that chloroformates (R-O-CO-CI) are also useful initiators. The mechanism of the initiation and propagation is discussed. This type of initiators allows the synthesis of different novel two-block and three-block copolymers, star-shape polymers, and a graft copolymer with a polyvinylacetate backbone.     

固相聚合合成聚噻吩衍生物及烷基链对固相聚合的影响

New poly(bis-3, 4-ethylenedioxythiophene methine)s derivatives with typical electro-optical moieties of thiophene, carbazole and fluorene as the side chains are obtained by facile solid state polymerization (SSP) or melt state polymerization (MSP). Detail characterizations of these polymers are carried out and some key monomers' crystals are obtained for structures analysis. It is found that existence of alkyl chains decrease monomers onset temperatures for SSP (T_onset) due to the weakening of the intermolecular interaction in crystals.     

Kinetic Study of the Polymerization of Alkyl Vinyl Ethers by HI/12 Catalyst

The polymerization of alkyl vinyl ethers initiated by hydrogen iodide and iodine catalyst has been studied in detail. The polymerization showed living behavior in nonpolar solvents at low (-15°) temperatures as reported earlier by others. The observed rate of polymerization under the reaction conditions was linearly dependent on the initial concentration of hydrogen iodide and iodine, respectively. However, the monomer concentration did not influence the rate of polymerization (apparent zero order). From the observed rate equation, two possible reaction schemes were proposed and attempts were made to distinguish them by using UV/visible spectroscopy and ¹³ C-NMR spectroscopy. In both schemes a reversible interaction between monomer and an iodine molecule was postulated as a necessary elemental reaction to fit the observed expression for rate of polymerization. From the spectroscopic analysis results, the interaction between the iodide compound (chain end) and the iodine molecule seems to be very weak compared to the interaction between monomer and the iodine molecule.     

Cu(0) Wire-mediated Single-electron Transfer-living Radical Polymerization of Oligo(ethylene oxide) Methyl Ether Acrylate by Selecting the Optimal Reaction Conditions

The efficient Cu(0) wire-catalyzed single-electron transfer-living radical polymerization (SET-LRP) in organic solvents and mixtures of the organic solvents with water has been thoroughly investigated.Oligo(ethylene oxide) methyl ether acrylate was used as an exemplar oligomer monomer to determine the optimum polymerization conditions for rapid,controlled,and quantitative production of well-defined polymers.The effects of Cu(0)-wire length (12.5 or 4.5 cm),ligand type (tris(dimethylaminoethyl)amine,Me6-TREN,or tris(2-aminoethyl)amine,TREN),and solvent type (dipolar aprotic solvents,cyclic ethers,alcohol,or acetone) on the polymerization have been evaluated.Kinetic experiments were performed for all polymerizations to assess the "living" behavior of each system employed.Importantly,TREN could be used as a replacement for Me_6-TREN in Cu(0) wire-catalyzed SET-LRP of oligomer monomer,which probably provides the most economical and efficient methodology since TREN is 80 times less expensive than Me6-TREN.The high chain-end fidelity of resulting polymer was experimentally verified by thiol-Michael addition reaction at the a-Br chain end and subsequent chain extension with methyl acrylate.     

Coordination polymerization of ω-alkenoates and ω-epoxyalkanoates

As functional polymers have become more and more used, the need for a general synthesis of addition polymers with functional groups became greatly important. We have achieved the polymerization of ω-alkenoates with coordination initiators of the Ziegler-Natta initiation type using titanium trichloride-based transition metal initiators modified with dialkylaluminum chloride. To accomplish this polymerization required that the ω-alkenoates be precomplexed with dialkylaluminum chloride. High molecular weight homopolymers and copolymers with olefins have been obtained. The polymerization of ω-epoxyalkanoates with coordinative anionic polymerization systems based on triethylaluminum/water/acetylacetone (1.0/0.5/1.0) has also been accomplished. Homo- and copolymers of high molecular weight and of relatively narrow molecular weight distribution have been prepared. All polymers and copolymers of functional olefins and epoxides have been characterized and the study of the reactivity of the functional groups attached via a flexible spacer to the polymer main chain has been started. Special attention was given to the classical cationic copolymerization of trioxane with derivatives of ω-epoxyundecanoate to prepare novel functional polyoxymethylenes of potential commercial interest.     

Preparation and polymerization of methylenecyclobutene and 1-methyl-3-methylenecyclobutene

Methylenecyclobutene (MCB) and 1-methyl-3-methylenecyclobutene (MMCB) were synthesized, characterized, and polymerized by anionic and cationic initiators. Structural analyses of the polymers were carried out by infrared and NMR spectros-copy. The cationic polymerization of MCB appeared to proceed entirely by a 1,5-propagation mechanism to form low molecular weight polymers in low yields. Anionic polymerization of this monomer, on the other hand, proceeded primarily through a 1,2-propagation path, again forming only low molecular weight polymeric products in low yield. In contrast to MCB, the methyl-substituted monomer, MMCB, polymerized readily with cationic initiators to produce unusually high molecular weight polymers in high conversions. On the basis of both infrared and NMR spectroscopic analyses, it was concluded that the polymers also contained essentially only 1,5-addition repeating units. Anionic initiators such as n-BuLi were unable to induce polymerization of this monomer, but polymerization by Ziegler-Natta catalysts proceeded readily to yield polymers virtually identical in structure and molecular weight to those obtained with cationic initiators.