Showing papers on "Ionic polymerization published in 1997"

Controlled/“Living” Radical Polymerization of Styrene and Methyl Methacrylate Catalyzed by Iron Complexes1

Abstract: Controlled/“living” radical polymerization of styrene and methyl methacrylate has been achieved by atom transfer radical polymerization (ATRP) catalyzed by iron halide complexes under both homogene...

Preparation of novel homo- and copolymers using atom transfer radical polymerization

Abstract: The present invention is directed to a process of atom (or group) transfer radical polymerization for the synthesis of novel homopolymer or a block or graft copolymer, optionally containing at least one polar group, with well defined molecular architecture and narrow polydispersity index, in the presence of an initiating system comprising (i) an initiator having a radically transferrable atom or group, (ii) a transition metal compound, and (iii) a ligand; the present invention is also directed to the synthesis of a macromolecule having at least two halogen groups which can be used as a macroinitiator component (i) to subsequently form a block or graft copolymer by an atom or group transfer radical polymerization process; the present invention is also directed to a process of atom or group transfer radical polymerization for the synthesis of a branched or hyperbranched polymer; in addition, the present invention is directed to a process of atom or group transfer radical polymerization for the synthesis of a macroinitiator which can subsequently be used to produce a block or graft copolymer.

Controlled/“Living” Radical Polymerization of Methyl Methacrylate by Atom Transfer Radical Polymerization

Abstract: One of the most important goals of synthetic polymer chemistry is to gain control not only over the molecular weights and polydispersities of polymer chains, but also their architecture and end-groups. Living polymerizations, in which neither transfer nor termination takes place, appeared to be the best technique to reach this target.1 Mainly performed by anionic,2 cationic,3 or group transfer polymerization,4 living polymerizations require specific experimental conditions that often make their industrial application difficult. Recently, controlled/ “living” approaches to radical polymerizations were reported.5-11 In these processes, the contribution of termination and transfer reactions remains very low,7 although they cannot be completely eliminated. One of the most successful controlled/“living” radical polymerization methods developed is atom transfer radical polymerization9 (ATRP). It has its roots in organic chemistry’s atom transfer radical addition12,13 (ATRA), which is sometimes called Kharasch addition.14 ATRP has been proven to be effective for a wide range of monomers15 and appears to be a powerful tool for the polymer chemist, providing new possibilities in structural and architectural design16 and allowing the development of new materials with monomers currently available.17,18 This communication reports that atom transfer radical polymerization can be used successfully to control the polymerization of methyl methacrylate (MMA) over a broad range of molecular weights, reaching very low polydispersities, with easy reaction conditions and relatively rapid kinetics. As reported by Sawamoto,10,19 ATRP based on ruthenium catalytic systems allows for control of the polymerization of MMA untilMn ) 20 000 with slow reaction rates (typically 80% conversion in 20-30 h). By using a homogeneous ATRP catalytic system based on copper bromide and a substituted bipyridyne, we were able to synthesize poly(MMA) with polydispersities as low as 1.1 (Mn ) 20 000) in a few hours while controlling molecular weights until Mn ) 180 000. MMA was polymerized with p-toluenesulfonyl chloride (p-TSCl) in conjunction with copper(I) bromide (CuBr) and 4,4′-bis(5-nonyl)-2,2′-bipyridine (dNbipy)20 in diphenyl ether (DPE) at 90 °C.21 p-Toluenesulfonyl chloride was used as an initiator for styrene polymerization22,23 and in metal-catalyzed ATRA. When aiming at PMMA of Mn ) 20 000 at 100% conversion (Figures 1 and 2), /2 equiv of catalyst to initiator was used in order to reduce the amount of radicals in the medium. Complexation of copper by 4,4′-bis(5-nonyl)-2,2′-bipyridine allowed the reaction mixture to be homogeneous. As shown in Figure 1, 80% conversion was reached in 5 h, and semilogarithmic kinetic plots are linear, indicating that the radical concentration is constant during the polymerization. A linear increase of number average molecular weight, Mn,SEC, vs monomer conversions up to 95% was found (Figure 2). The Mn,SEC is very close to the theoretical one, Mn,th, defined by eq 1,24 which assumes that one molecule of initiator generates one growing polymer chain:

Kinetic Study of the Homogeneous Atom Transfer Radical Polymerization of Methyl Methacrylate

Abstract: The homogeneous controlled/“living” radical polymerization of methyl methacrylate (MMA) using the atom transfer radical polymerization (ATRP) with CuCl/4,4‘-di(5-nonyl)-2,2‘-bipyridine catalytic system and diphenyl ether as the solvent generated well-defined polymers with polydispersities Mw/Mn ≤ 1.2. The evolution of the molecular weights of the polymers follows the ratio of the mass of the consumed monomer to the initial initiator concentration. The rate of polymerization follows first-order kinetics with respect to the decrease of monomer concentration. The polymerization rate reaches a maximum when the ratio of ligand-to-CuICl is one-to-one. ATRP of MMA shows first-order kinetics with respect to both CuICl and the initiator, alkyl or sulfonyl chloride. The rate of polymerization did not obey simple negative first-order kinetics with respect to the concentration of CuIICl, partially due to a persistent radical effect, which resulted in the increase of [CuIICl] in the initial stage of polymerization. Th...

Preparation of Hyperbranched Polyacrylates by Atom Transfer Radical Polymerization. 2. Kinetics and Mechanism of Chain Growth for the Self-Condensing Vinyl Polymerization of 2-((2-Bromopropionyl)oxy)ethyl Acrylate

Abstract: The self-condensing vinyl polymerization (SCVP) of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) has resulted in the formation of hyperbranched polyacrylates. The polymerization mechanism used to polymerize the BPEA was atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization. This paper details the study of the kinetics of polymerization and the growth of the macromolecule during the polymerization. The results obtained in the polymerization were compared to the theoretical predictions for SCVP. It was determined that the polymerization deviated from the ideal case, as a consequence of the establishment of a dynamic equilibrium in ATRP resulting in the addition of more than one monomer unit in a single activation step.

Preparation of Hyperbranched Polyacrylates by Atom Transfer Radical Polymerization. 3. Effect of Reaction Conditions on the Self-Condensing Vinyl Polymerization of 2-((2-Bromopropionyl)oxy)ethyl Acrylate

Abstract: The homopolymerization of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) by atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization system, has yielded a hyperbranched polymer. Variation of the reaction conditions and especially the concentration of copper(II) in the polymerization system affects not only the rate of polymerization but also the chain architecture. The copper(II) concentration in the polymerization medium is affected by solvent, the ligand used to complex copper, and temperature. The effects of temperature and ligand on the polymerization rate and the resulting chain architecture were studied.

Evidence for Living Radical Polymerization of Methyl Methacrylate with Ruthenium Complex: Effects of Protic and Radical Compounds and Reinitiation from the Recovered Polymers1

Abstract: The effects of additives such as methanol, water, and radical scavengers (TEMPO and galvinoxyl) were studied in the living polymerization of methyl methacrylate (MMA) with the PhCOCHCl2/RuCl2(PPh3)...

Block Copolymers by Transformation of “Living” Carbocationic into “Living” Radical Polymerization

Abstract: This communication reports that polystyrene with chlorine termini synthesized by living cationic polymerization without any transformation is an efficient macroinitiator for living atom transfer radical polymerization of styrene and (meth)acrylates

Identifying the Nature of the Active Species in the Polymerization of Methacrylates: Inhibition of Methyl Methacrylate Homopolymerizations and Reactivity Ratios for Copolymerization of Methyl Methacrylate/n-Butyl Methacrylate in Classical Anionic, Alkyllithium/Trialkylaluminum-Initiated, Group Transfer Polymerization, Atom Transfer Radical Polymerization, Catalytic Chain Transfer, and Classical Free Radical Polymerization

Abstract: Reactivity ratios have been determined for the monomer pair methyl methacrylate and n-butyl methacrylate under a range of polymerization conditions. The value of using reactivity ratios as a mechanistic probe is discussed. Reactivity ratios determined where M1 = MMA and M2 = n-BMA are 1.04, 0.81, classical anionic; 1.10, 0.72 , alkyllithium/trialkylaluminum initiated; 1.76, 0.67, group transfer polymerization; 0.98, 1.26, atom transfer radical polymerization; 0.75, 0.98, catalytic chain transfer; and 0.93, 1.22, classical free radical polymerization. The data suggest ATRP and CCTP proceed via radical type propagation. Li/Al-initiated polymerization undergoes an anionic mechanism, while strong evidence is found for an associative, catalyst dependent mechanism for GTP. Galvinoxyl is demonstrated to inhibit GTP as well as free radical polymerization, and it is suggested that neither the use of inhibition nor polymer stereochemistry can be used to distinguish between anionic and radical processes.

Macromolecular design of polymeric materials

Abstract: Rational design of well-defined polymeric materials. Part 1 Control of polymerization toward molecular design of polymers: structural control by living radical polymerization living cationic polymerization - design of polymerization and macromolecular structure macromolecular engineering by carbocationic polymers by living anionic polymerization controlled polymer synthesis with metalloporphyrins group transfer polymerization for controlled polymer architecture industrial applications of living polymerization stereospecific living polymerization of methacrylate and construction of stereoregular polymer architecture stereochemistry of anionic polymerization of polar vinyl monomers helical polymers and oligomers with molecular dissymetry activated monomer polymerization of cyclic monomers ring-opening polymerization of cyclic sulfides and imines macromolecular engineering of polylactones and polylactides by ring-opening polymerization coordination polymerization with high-activity catalyst and soluble coordination catalysts macrocyclic oligomers as precursors of high polymers in-site polycondensation for synthesis of high performance polymers design of reactive polymers and their applications polymer reactions for the synthesis of functional polymers synthetic design by modification of natural materials highly branched polymers - dendrimers and hyperbranched polymers star polymer synthesis molecular design of network polymers. Part 2 Molecular design of specialty polymers: acrylic copolymers by radical and anionic mechanisms and their practical applications fluoropolymers and fluoroelastomers. (Part contents).

Polymerization of Methyl Methacrylate Using Zirconocene Initiators: Polymerization Mechanisms and Applications

Abstract: The polymerization of methyl methacrylate (MMA), initiated by zirconocene complexes Cp2ZrMe2 (1) and [Cp2ZrMe(THF)][BPh4] (2), provides partially syndiotactic poly(methyl methacrylate) (PMMA) in hi...

Very large counteranion modulation of cationic metallocene polymerization activity and stereoregulation by a sterically congested (perfluoroaryl)fluoroaluminate

Abstract: We communicate here the unusual structural and cocatalytic features of a new, stable (perfluoroaryl)aluminate anion, tris(2,2`,2``-nonafluorobiphenyl)flouroaluminate (PBA{sup -}). Noteworthy features include very large ion pairing/metallocenium ancillary ligand structural effects on olefin polymerization activity and stereoselectivity. These results considerably expand what is known about the consequences of strong cation-anion interactions for group 4-mediated olefin polymerization. For anions that coordinatively `intrude` into the cation coordination sphere, the effects can be dramatic. 15 refs., 1 tab.

Catalysis in precision polymerization

Abstract: Transition Metal Catalysis: Part 1. Transition Metal Catalysis: Part 2. Rare Earth Metal Catalysis. Radical Polymerization Catalysis. Anionic Catalysis. Cationic Catalysis. Enzymatic Catalysis. Polymerization Without Catalyst. Index.

Ring-Opening-Metathesis Polymerization for the Preparation of Carboxylic-Acid-Functionalized, High-Capacity Polymers for Use in Separation Techniques

Abstract: Ring-opening-metathesis polymerization (ROMP) was used for the modular, molecular design of stationary phases. New materials for solid-phase extraction (SPE) as well as for air and water clean-up have been prepared by ring-opening-metathesis suspension polymerization of 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene (I) and its copolymerization with the functional monomer endo,endo[2.2.1]bicyclohept-2-ene-5,6-dicarboxylic anhydride (II), using the well-defined Schrock catalyst Mo(N-2,6-i-Pr2-C6H3)CHCMe2Ph(OCMe(CF3)2)2 (III). The resulting cross-linked polymers have been investigated in terms of influence of the polymerization sequence as well as of the stoichiometries I/II and II/III on swelling behavior, surface area, capacity, accessability of the functional groups, and their possible use in SPE, respectively. In order to obtain further information about the new resins, the microstructure of poly(II) was determined by NMR techniques. Investigations revealed that it represents an all cis, ...

Noncoordinating anions in carbocationic polymerization

Abstract: The initiation and catalysis of isobutylene polymerization from several new metallocene and nonmetallocene initiator-catalysts that contain the noncoordinating anions (NCA), B(C6F5)4− and RB(C6F6)3−, is reported. Application of these initiator-catalysts is extended to styrenics and vinyl ethers. The NCA does not contribute to termination and can be used in low concentrations compared with conventional Lewis acids. These qualities provide for isobutylene polymerizations that yield low Mn oligomers or high Mn polymer, dependent upon the initiator and polymerization conditions. Mechanistic aspects of initiation, transfer and termination as well as the participation of adventitious water are considered for each class of initiator-catalyst. The influence of the NCA on the stereoregularity of cationic styrene polymerization is also considered. NCAs do not cause the stereospecific carbocationic polymerization of styrene. We suggest that under conditions not conducive to carbocationic polymerization, NCA/metallocenes mediate the coordination polymerization of styrene. © 1997 John Wiley & Sons, Inc.

Controlled radical polymerization of 4-vinylpyridine

Abstract: 2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO)-mediated free radical polymerization of 4-vinylpyridine is found to proceed in a “controlled” manner. A linear increase of molecular weight along with an increase in conversion occurs at varying temperatures. Polymerization of styrene with a poly(4-vinylpyridine) block as macromer results in block copolymers with narrow polydispersity. The polymers are characterized by different size exclusion chromatography methods and converted to cationic polyelectrolytes as well as to polysulfo- and polycarbobetaines.

Specific Salt Effect of Lithium Perchlorate in Living Anionic Polymerization of Methyl Methacrylate and tert-Butyl Acrylate

Abstract: Living anionic polymerization of methyl methacrylate can be achieved at −40 °C in tetrahydrofuran (THF) and at −78 °C in toluene/THF (9/1 v/v) using (1,1-diphenylhexyl)lithium as the initiator in the presence of lithium perchlorate (LiClO4) as the additive. Polymerization of tert-butyl acrylate also proceeds in a living manner at −78 oC in THF. Polymers with narrow molecular weight distributions and high initiator efficiencies can be obtained. The use of lithium perchlorate retards the rate of polymerization. The ratio of LiClO4 to initiator has a greater influence in determining the control of polymerization. The beneficial effect of lithium perchlorate is attributed to its efficient interaction with growing ester−enolate ion pairs.

Radical Polymerization Kinetics of Poly(ethylene oxide) Macromonomers

Abstract: Radical polymerization of poly(ethylene oxide) macromonomers carrying a methoxy group on the one end and a p-vinylbenzyl or a (p-vinylphenyl)butyl group on the other end was investigated in benzene and water. The overall rate of polymerization was found to be more than 50 times higher in water than that in benzene. Apparent rate constants of propagation and termination were evaluated based on ESR measurements under irradiation, while initiator efficiency was estimated from inhibition period measurements. Very rapid polymerization in water was then reasonably attributed to a combined result of locally concentrated propagating radicals and monomers in their micellar organization, together with high initiator efficiency, enhanced rate of propagation, and reduced rate of termination there.

Bis-macromonomers of 2-alkyl-2-oxazolines - synthesis and polymerization.

Abstract: Poly(2-alkyl-2-oxazoline)s having an acrylate group at both chain ends were synthesized by terminating living bifunctional poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline) with acrylic acid. These macromonomers have been polymerized to the corresponding polyoxazoline networks. Thermal as well as UV-initiated free radical polymerization were applied and the influence of the polymerization conditions and molecular weight of the prepolymer used on the properties of the networks were investigated. Both methods of polymerization produced high fractions of soluble material, probably due to the low concentration of the acrylate end groups.

Two-Dimensional Polymerization of Lipid Bilayers: Visible-Light-Sensitized Photoinitiation

Abstract: The sensitized polymerization of synthetic lipid bilayers via visible-light irradiation of membrane-bound cyanine dyes is reported. Visible-light-initiated polymerizations were successful with liposomes composed solely or partly of either 1-palmitoyl-2-[10-(2‘,4‘-hexadienoyloxy)decanoyl]-sn-glycero-3-phosphatidylcholine (mono-SorbPC), 1,2-bis[10-(2‘,4‘-hexadienoyloxy)decanoyl]-sn-glycero-3-phosphatidylcholine (bis-SorbPC), or 1,2-bis(2,4-octadecadienoyl)-sn-glycero-3-phosphatidylcholine (DenPC). The ballasted sensitizing dyes reported here were conveniently incorporated into liposomes. The sensitizing dye N,N‘-dioctadecyl-3,3,3‘,3‘-tetramethylindocarbocyanine perchlorate, DiIC(18)3, was used in many of these studies because its absorption properties were especially well matched to the spectral output of the light source. The lipid product from the sensitized photoconversion of mono-SorbPC was transesterified and analyzed by size exclusion chromatography, which revealed the presence of a polymer with a rel...

N -benzyl and N -alkoxy pyridinium salts as thermal and photochemical initiators for cationic polymerization

Abstract: Cationic polymerizations induced by thermally and photochemically latent N-benzyl and N-alkoxy pyridinium salts, respectively, are reviewed. N-Benzyl pyridinium salts with a wide range of substituents of phenyl, benzylic carbon and pyridine moiety act as thermally latent catalysts to initiate the cationic polymerization of various monomers. Their initiation activities were evaluated with the emphasis on the structure-activity relationship. The mechanisms of photoinitiation by direct and indirect sensitization of N-alkoxy pyridinium salts are presented. The indirect action can be based on electron transfer reactions between pyridinium salt and (a) photochemically generated free radicals, (b) photoexcited sensitizer, and (c) electron rich compounds in the photoexcited charge transfer complexes. N-Alkoxy pyridinium salts also participate in ascorbate assisted redox reactions to generate reactive species capable of initiating cationic polymerization. The application of pyridinium salts to the synthesis of block copolymers of monomers polymerizable with different mechanisms are described.

Cationic Ring-Opening Polymerization of Trimethylene Urethane: A Mechanistic Study

Abstract: The cationic ring-opening polymerization of trimethylene urethane (TU; systematic name, tetrahydro-2H-1,3-oxazin-2-one, (1)) in the melt at 100 °C with methyl trifluoromethanesulfonate (TfOMe), trifluoromethanesulfonic acid (TfOH), and BF3·OEt2 as initiators yields poly(trimethylene urethane) (poly(TU), (2)) with a uniform microstructure. The reaction mechanism is examined for TfOMe and TfOH as initiators. According to NMR spectroscopic results, with both initiators the polymerization proceeds via an active chain end mechanism with protonated cyclic endo iminocarbonates (5) as active species. The propagation step involves a nucleophilic attack of the active species at the monomer followed by a double isomerization process and regeneration of the active species. The polymerization kinetics was investigated yielding a polymerization rate constant of 4.2 × 10-4 L·mol-1·s-1 for the TfOMe-initiated process. Comparison of the kinetic data of the TfOMe- and the TfOH-initiated polymerizations reveals a qualitativ...