This article summarizes possibilities of tailoring polyacrylates and polymethacrylates prepared by anionic polymerization initiated with combined (mixed) initiators especially those containing alkali metal tert-alkoxides as stabilizing additives. First part gives a short overview of side reactions in anionic polymerization of polar vinyl monomers and the ways of solving the problem. Second part is devoted to the anionic polymerization of acrylic and methacrylic esters initiated with mixed initiators. Examples of synthetic methods are given for the preparation of special polymeric products based on acrylates, and the necessity of using different polymerization conditions for individual acrylic esters is demonstrated with respect to branching of the ester alkyl group. 相似文献
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. 相似文献
The synthesis and polymerization of representative acrylic-type esters containing a terminal acetylene group, CH2?C(R)COO(CHR′)m? C?CH, where R and R′ are H and CH3 and m = 1 or 2, by anionic initiation to linear polymers are described. In contrast, crosslinked polymers were formed when radical and cationic initiators were used. Crosslinked polymers were also obtained with organolithium compounds but not with sodium naphthalene and sodium benzalaniline; this observation is discussed and compared to the behavior of the acetylenic acrylic esters which do not contain a terminal acetylenic hydrogen. The unpolymerized acetylenic bonds in the resulting linear polymers were shown to be present by infrared spectroscopic methods and by the following post-reactions of these bonds: (1) the heat- and radical-initiated crosslinking of the polymers through the acetylenic bonds; (2) the post-bromination of the acetylenic bonds; and (3) the reaction of decaborane with the acetylenic bonds. The anionic copolymerization of acrylonitrile and styrene with these acetylenic monomers were performed and compared to the copolymerizations with 1-acryloxy-2-butyne and 1-methacryloxy-2-butyne. Dibromination of the linear polymers affords self-extinguishing polymers, while decaboronation yields soluble polymers which do not soften up to 300°C. The linear polymers may be classified as “self-reactive” polymers which yield thermosetting polymers. 相似文献
The growth center in the anionic polymerization of methacrylic esters is stabilized with alkaline alkoxides, sodium tert-butoxide in particular. The lifetime of the growth center was investigated in the polymerization of methyl methacrylate by evaluating yield and molecular weight distribution of the polymer formed when the monomer was added in two doses. The average lifetime of the original growth center stabilized by sodium tert-butoxide at 20°C under the given conditions was longer than several minutes. The stabilization of the growth center was also used in the stepwise copolymerization of n-butyl methacrylate and methyl methacrylate. The copolymer thus obtained in high yield was characterized as a block copolymer on the basis of its solubility, nuclear magnetic resonance (NMR) spectra, and measurements of the complex shear modulus. 相似文献
Polybenzyls were prepared from benzyl chloride with different catalysts and solvents and at different temperatures. A model compound reaction for the polymerization was studied by reacting benzyl chloride with an excess amount of diphenylmethane to determine the effect of reaction conditions on substitution distribution. The degree of branching of polybenzyl samples was characterized from the infrared absorption spectra by using peaks assigned to para and ortho disubstitution products and monosubstitution units. The degree of branching so obtained correlated well with the results from the model compound reactions and with the thermal stabilities of the polymers. Anthracene unit formation was also related to the isomer content, and addition of complexing agents such as SO2 or tetranitromethane caused a reduction in branching during polymerization. An unusual glass transition behavior was observed in these polymers. 相似文献
The polymerization behavior of N-(p-vinyl)phenylacrylamide, synthesized from p-aminostyrene and acryloyl chloride by means of the Schotten-Baumann reaction was studied. Due to a marked difference in electron density between the two double bonds, this monomer provided soluble polymers by both cationic and anionic polymerization procedures, the cationic and anionic polymers mainly carrying, as side chains, the acrylamide and styrene moieties, respectively. The polymerization behavior of the residual double bonds was also investigated for both polymers, leading to crosslinked, insoluble products. 相似文献
In the emulsion polymerization of allyl methacrylate (AMA), the reactive crosslinked polymer microspheres or microgel-like polymers with abundant pendant allyl groups were easily obtained because AMA possesses two types of vinyl groups, methacrylic and allylic double bonds, having greatly different reactivities. The resulting microgel-like poly(allyl methacrylate) microspheres (PAMA microspheres) were characterized by light scattering and viscometry. Then, the characteristic polymerization behaviour of PAMA microspheres was explored by the copolymerizations with diallyl terephthalate (DAT) and allyl benzoate (ABz). 相似文献
The effect of various aluminum alkyls at varying concentrations on the rate and stereospecificity of propylene polymerizations with titanium trichloride was examined. It was concluded that dialkylaluminum halides were merely chemisorbed on the surface of the titanium trichloride while the trialkylaluminums reacted more extensively with the surface. In the case of diethylaluminum chloride standard chemisorption kinetics were observed. The rate of polymerization was also found to be a function of solvent, with certain aromatic solvents causing significant rate increases. With diethylaluminum chloride essentially no termination occurs; the polymers are “living polymers.” 相似文献
The polymerization reactivities of α,β,β‐trifluorovinyl compounds (CF2=CF—R) and α‐trifluoromethylvinyl compounds (CH2=C(CF3)—R) are discussed since these monomers have scarcely been investigated and hardly yielded corresponding homopolymers, although tetrafluoroethylene and chlorotrifluoroethylene have been studied under radical polymerization conditions. In the case of α,β,β‐trifluorostyrene, a homopolymer is obtained in low yields by anionic polymerization and it is concluded that the reaction takes place without any side reactions once the reaction has started, since simple addition polymerization is observed and the molecular weight distribution is very narrow. Anionic polymerization of hexafluorobuta‐1,3‐diene is successfully achieved by the addition reaction of living end to the 2‐carbon of hexafluorobuta‐1,3‐diene followed by isomerization to produce excellently high thermostable polymers. ω‐Trifluorovinyloxyfluoroalkyl alcohol produces a polyether via a polyaddition reaction under anionic conditions. The homopolymers of α‐trifluoromethylacrylates are quantitatively obtained under anionic polymerization conditions. α‐Trifluoromethylstyrene derivatives are likely to polymerize under radical conditions, but are not well‐studied. The radical polyaddition reaction of perfluoroisopropenyl esters in 1,4‐dioxane, diethyl ether or 1,2‐dimethoxyethane yields the polymers possessing the solvent moiety in the polymer main chain, respectively. It is clearly demonstrated that each fluorinated vinyl monomer discussed in this article demands its own reaction conditions. Therefore, more experimental data on the polymerization of these individual monomers is needed, including research on developing the reactions discovered in the organofluorine chemistry field to the preparation of polymers. 相似文献
The homopolymerization of acrylic and fluoroacrylic esters mediated by benzyl dithiobenzoate and dibenzyl trithiocarbonate proceeds in the controlled mode via the reversible addition-fragmentation chain-transfer mechanism, while the controlled radical polymerization of methacrylic esters is not effected under these conditions. The molecular-mass characteristics of the copolymers of acrylic and methacrylic esters may be satisfactorily controlled by benzyl dithiobenzoate-mediated copolymerization when the content of acrylic esters is no less than 50 mol %. If a reversible addition-fragmentation chain-transfer agent active with respect to only one of the monomers is used, compositionally homogeneous narrowly dispersed copolymers are formed via the azeotropic copolymerization of the monomers up to high conversions. The controlled copolymerization of N-vinylpyrrolidone and fluoroacrylates allows the synthesis of alternating narrowly dispersed amphiphilic copolymers with properties different from those of alternating copolymers with a broad molecular-mass distribution. 相似文献
Abstract The course of the isothermal bulk polymerization of methacrylic acid and some methacrylic acid esters differing in the length of the ester group was studied by differential scanning calorimetry at different temperatures. The enthalpies of polymerization, the residual monomer content, the overall reaction rate constants, and the overall activation energies were calculated. The molecular weight averages of the synthesized polymers before and after the gel effect were measured by gel permeation chromatography. 相似文献
Innovative Pd0 heterogeneous catalysts were prepared upon using cross-linked, gel-type, functional acrylic polymers as the supports, along a simple route in use in our laboratories since long. The supports were obtained by polyaddition co-polymerization of N,N-dimethylacrylamide with either 2-acrylamido-2-methylpropane sulfonic acid, methacrylic acid or 4-vinylpyridine, and ethylene glycoldimethacrylate (cross-linker). The performance of these catalysts in the hydrogenation of cyclohexene, trans-methylcinnamate and 4-chloro-2-nitroanisole was compared with that of commercial Pd0/EnCat 30NP, produced by Reaxa. One of the catalysts (sulfonic resin as the support) behaved very well as far as activity, stability and selectivity are concerned. These results suggest that heterogeneous metal catalysts supported on polyaddition resins could be developed to become interesting materials for technical applications. 相似文献
Summary: Copolymerization of propylene and 1,4‐divinylbenzene was successfully performed by a MgCl2‐supported TiCl4 catalyst, yielding isotactic poly(propylene) (i‐PP) polymers containing a few pendant styrene groups. With a metalation reaction with butyllithium and a hydrochlorination reaction with dry hydrogen chloride, the pendant styrene groups were quantitatively transformed into benzyllithium and 1‐chloroethylbenzene groups, respectively, which allowed the synthesis of i‐PP‐based graft copolymers by living anionic and atom transfer radical (ATRP) polymerization mechanisms.
The incorporation of styrene pendant groups into isotactic poly(propylene) using a Zeigler–Natta catalyst gave functionalized polymers able to undergo living anionic and atom transfer radical (ATRP) polymerizations. 相似文献
The catalytic activity of the complexes prepared by the reaction of Grignard reagents with ketones, esters, and an epoxide as polymerization catalysts of methyl and ethyl α-chloroacrylates was investigated. The modifiers which gave isotactic polymers were α,β-unsaturated ketones such as benzalacetophenone, benzalacetone, dibenzalacetone, mesityl oxide, and methyl vinyl ketone, and α,β-unsaturated esters such as ethyl cinnamate, ethyl crotonate, and methyl acrylate. Catalysts with butyl ethyl ketone, propiophenone, and propylene oxide as modifiers produced atactic polymers but no isotactic polymers. It was revealed that the complex catalysts having a structure ? C?C? O? MgX (X is halogen) gave isotactic polymers. The mechanism of isotactic polymerization was discussed. In addition, for radical polymerization of ethyl α-chloroacrylate, enthalpy and entropy differences between isotactic and syndiotactic additions were calculated to give ΔHi* ? ΔHs* = 910 cal/mole and ΔSi* ? ΔSs* = 0.82 eu. 相似文献
A novel approach for ATRP has been developed which enables the polymerization of vinyl monomers including those bearing carboxylic acid groups such as acrylic/methacrylic acid in the free acid form with ppm amounts of copper. The quantity of copper used in the polymerization is comparable to those left in purified polymers obtained by a conventional ATRP process. 相似文献