Showing papers on "Ionic polymerization published in 2012"
Book•
01 Jan 2012
TL;DR: Polymer Science: A Comprehensive Reference as mentioned in this paper provides a broad and in-depth coverage of all aspects of polymer science from synthesis/polymerization, properties, and techniques to nanostructures, sustainability and energy, and biomedical uses of polymers.
Abstract: The progress in polymer science is revealed in the chapters of Polymer Science: A Comprehensive Reference. In Volume 1, this is reflected in the improved understanding of the properties of polymers in solution, in bulk and in confined situations such as in thin films. Volume 2 addresses new characterization techniques, such as high resolution optical microscopy, scanning probe microscopy and other procedures for surface and interface characterization. Volume 3 presents the great progress achieved in precise synthetic polymerization techniques for vinyl monomers to control macromolecular architecture: the development of metallocene and post-metallocene catalysis for olefin polymerization, new ionic polymerization procedures, and atom transfer radical polymerization, nitroxide mediated polymerization, and reversible addition-fragmentation chain transfer systems as the most often used controlled/living radical polymerization methods. Volume 4 is devoted to kinetics, mechanisms and applications of ring opening polymerization of heterocyclic monomers and cycloolefins (ROMP), as well as to various less common polymerization techniques. Polycondensation and non-chain polymerizations, including dendrimer synthesis and various "click" procedures, are covered in Volume 5. Volume 6 focuses on several aspects of controlled macromolecular architectures and soft nano-objects including hybrids and bioconjugates. Many of the achievements would have not been possible without new characterization techniques like AFM that allowed direct imaging of single molecules and nano-objects with a precision available only recently. An entirely new aspect in polymer science is based on the combination of bottom-up methods such as polymer synthesis and molecularly programmed self-assembly with top-down structuring such as lithography and surface templating, as presented in Volume 7. It encompasses polymer and nanoparticle assembly in bulk and under confined conditions or influenced by an external field, including thin films, inorganic-organic hybrids, or nanofibers. Volume 8 expands these concepts focusing on applications in advanced technologies, e.g. in electronic industry and centers on combination with top down approach and functional properties like conductivity. Another type of functionality that is of rapidly increasing importance in polymer science is introduced in volume 9. It deals with various aspects of polymers in biology and medicine, including the response of living cells and tissue to the contact with biofunctional particles and surfaces. The last volume is devoted to the scope and potential provided by environmentally benign and green polymers, as well as energy-related polymers. They discuss new technologies needed for a sustainable economy in our world of limited resources. * Provides broad and in-depth coverage of all aspects of polymer science from synthesis/polymerization, properties, and characterization methods and techniques to nanostructures, sustainability and energy, and biomedical uses of polymers* Provides a definitive source for those entering or researching in this area by integrating the multidisciplinary aspects of the science into one unique, up-to-date reference work* Electronic version has complete cross-referencing and multi-media components* Volume editors are world experts in their field (including a Nobel Prize winner)
362 citations
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TL;DR: In this paper, a well-controlled polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) was conducted with 300 ppm or lower of a copper catalyst and tris(2-pyridylmethyl)amine (TPMA) ligand in the presence of an excess of halide salts.
Abstract: Activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) was successfully implemented in aqueous media for the first time. A well-controlled polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) was conducted with 300 ppm or lower of a copper catalyst and tris(2-pyridylmethyl)amine (TPMA) ligand in the presence of an excess of halide salts. Ascorbic acid was continuously fed into the reaction mixture to regenerate the activator complex. The effects of the halide salt concentration, ligand concentration, feeding rate of the reducing agent, and copper concentration were systematically studied to identify conditions that provide both an acceptable rate of polymerization and good control over the polymer properties. The optimized polymerization conditions provided linear first-order kinetics, linear evolution of the molecular weight with conversion, and polymers with narrow molecular weight distributions (Mw/Mn < 1.3) at high monomer conversions (∼70%) ...
312 citations
TL;DR: In this paper, photochemically mediated atom transfer radical polymerization using a copper catalyst concentration as low as 50-100 ppm was achieved for methyl methacrylate at 35 °C.
Abstract: Well-controlled polymerization of methyl methacrylate at 35 °C was achieved by photochemically mediated atom transfer radical polymerization using a copper catalyst concentration as low as 50–100 ppm. Irradiation at λ > 350 nm provided both a reduction of initially added copper(II) catalyst complexed with either PMDETA or TPMA ligand to a copper(I) activator and a sufficient rate of polymerization. Poly(methyl methacrylate) with a narrow dispersity and predictable molar mass was obtained when an initiator, such as 2-bromopropionitrile, was used. Successful chain-extension polymerization confirmed the living character of the photopolymerization system.
202 citations
TL;DR: The controlled growth of polymer brushes under ambient conditions using surface-confined eATRP and the multiple reuse of the polymerization solution is reported.
Abstract: Controlled/“living” surface-initiated radical polymerization offers the possibility to generate brushlike polymeric thin films with controllable thickness, composition, and architecture. Polymer brushes have found widespread applications as model responsive and non-biofouling surfaces, in protein binding and immobilization studies, chromatography supports, in membrane applications, antibacterial coatings, actuation, and low friction surfaces. Among the many controlled polymerizations, atom-transfer radical polymerization (ATRP) is most widely used, particularly for surface grafting in aqueous solution. In standard surface-initiated ATRP, a Cu complex is used as the catalyst and high monomer concentrations are required to maximize the polymer growth. However, polymerization solutions often cannot be reused without purification, leading to inefficient use of the monomers. Furthermore, trace amount of oxygen will oxidize Cu to the deactivating Cu species and therefore, brush growth is usually carried out in an inert atmosphere. The conditions can be relaxed by employing advanced variations on ATRP as shown by Matyjaszewski et al. Recently, the same group reported electrochemically mediated ATRP (eATRP) to control the polymerization of methacrylate monomers by a one-electron reduction of an initially added air-stable Cu salt. Electrochemical generation of catalytically active Cu has been exploited in a surface “click” reaction between alkynes and azides. Here, we report the controlled growth of polymer brushes under ambient conditions using surface-confined eATRP and the multiple reuse of the polymerization solution. Scheme 1 shows the mechanism of polymer brush growth using eATRP. The reaction was carried out in an electrochemical cell with a three electrode system. A constant potential was applied to generate the CuCl/bipyridine (bipy) complex through one-electron reduction of CuCl2/bipy in the vicinity of initiator-decorated gold surface to initiate the polymerization. Prior to brush growth, cyclic voltammograms (CVs) of an initiator-modified electrode were carried out to identify the potential window for accurate manipulation of the reduction/oxidation state of the catalyst. As shown in Figure 1a and 1b, no redox process occurred within the potential window from 0.6 to 0.3 V versus the saturated calomel electrode (SCE) when using w-mercaptoundecyl bromoisobutyrate (SH-C15-Br) decorated electrode because of the impedance of the monolayer to charge transfer. The charge transfer resistance (Rct) calculated from the electrical impedance spectrum of the surface is as large as 71 kWcm (theRct of bare gold is only 6Wcm ). When a shorter-chain alkanethiol initiator (2-mercaptoethyl-2bromo-2-methylpropanoate, SH-C6-Br) modified electrode was used, a redox reaction occurred because of the low interfacial Rct (1138Wcm , Figure 1b red curve and Table 1).
146 citations
TL;DR: Different polyaromatic structures (truxene derivatives and tris(aza)pentacene) are presented as new metal-free organic photocatalysts (OPC) to promote free radical polymerization FRP and ring-opening polymerization (ROP) under halogen lamp, household LED bulb, and laser diode (405 nm) as discussed by the authors.
Abstract: Different polyaromatic structures (truxene derivatives and tris(aza)pentacene) are presented as new metal-free organic photocatalysts (OPC) to promote free radical polymerization FRP and ring-opening polymerization (ROP) under halogen lamp, household LED bulb, and laser diode (405 nm). These OPCs exhibit interesting light absorption properties and lead, through an oxidative catalytic cycle, to the formation of radicals and ions that can initiate both free radical polymerization FRP and ring-opening polymerization ROP. Interestingly, excellent polymerization profiles are obtained even upon visible light exposure. Using these very soft irradiation conditions, acrylate/epoxide blends are also easily polymerized under air and lead to the formation of interpenetrated polymer networks IPN exhibiting no phase separation.
137 citations
TL;DR: Kinetic studies reveal that the propagating intermediates for the polymerization in low dielectric solvents maintain cyclic architectures with two chain ends in close contact through Coulombic interaction, which facilitates quasi-living polymerization behavior in cyclic zwitterionic species.
Abstract: N-Heterocyclic carbene (NHC)-mediated polymerizations of N-butyl N-carboxyanhydride (Bu-NCA) to produce cyclic poly(N-butyl glycine)s (c-NHC-PNBGs) have been investigated in various solvents with NHCs having differing steric and electronic properties. Control over the polymer molecular weight (MW) and polymerization rate is strongly dependent on the solvent and the NHC structure. Kinetic studies reveal that the propagating intermediates for the polymerization in low dielectric solvents (e.g., THF or toluene) maintain cyclic architectures with two chain ends in close contact through Coulombic interaction. The NHCs not only initiate the polymerization, but also mediate the chain propagation as intramolecular counterions. Side reactions are significantly suppressed in low dielectric solvents due to the reduced basicity and nucleophilicity of the negatively charged chain ends of the zwitterions, resulting in quasi-living polymerization behavior. By contrast, the two charged chain ends of the zwitterionic spec...
136 citations
TL;DR: The ring-opening polymerization (ROP) of lactide with DBU (1,8-diazabicyclo[5.4.0] undec-7-ene) is described in this paper.
Abstract: The ring-opening polymerization (ROP) of lactide with DBU (1,8-diazabicyclo[5.4.0] undec-7-ene) is described. Room temperature polymerization using the neutral amine catalyst DBU in the absence of any other initiator produces polymers with narrow polydispersities and shows a linear relationship between molecular weight and conversion. The resulting polymers were characterized and determined to be cyclic. DFT calculations support a mechanistic hypothesis involving a zwitterionic acyl amidinium intermediate.
130 citations
TL;DR: In this article, the catalytic behavior of several inexpensive and simple N-heterocyclic organic catalysts in ring-opening polymerization of ω-pentadecalactone (PDL) and e-caprolactone(CL) has been studied.
Abstract: The catalytic behavior of several inexpensive and simple N-heterocyclic organic catalysts in ring-opening polymerization (ROP) of ω-pentadecalactone (PDL) and e-caprolactone (CL) has been studied. The polymerization reactions, carried out in bulk monomer and in toluene solution at 100 °C, identified 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with benzyl alcohol (BnOH) as initiator as the only active catalyst for the ring-opening polymerization of PDL and for the copolymerization of PDL and CL. The guanidine N-methyl-TBD (MTBD), 1,2,3-triisopropylguanidine, the amidine 1,8-diazabicycloundec-7-ene (DBU), and other N-heterocyclic organic catalysts such as dialkylaminopyridine (DMAP), imidazole, indoles, and N-heterocyclic carbenes (NHC’s) tested in this study proved to be inactive in the ROP of PDL even for the long reaction times. The polymerization mechanism, kinetic studies, temperature, and monomer concentration effects were investigated both in solution and in bulk monomer. The pseudolivin...
119 citations
TL;DR: In this article, the synthesis and characterization of bis(8-quinolinato)aluminum ethyl complexes, substituted at the 2-, 5-, and 7 positions on the 8quinolinol ligand, are presented.
95 citations
TL;DR: In this article, the authors reported new acid/base switchable N-aryl-N-pyridyl dithiocarbamates (R = −CH2CN, Z = −N(Py)(Ar)) which vary in substituent at the 4 position of the aryl ring and the use of these to control molecular weight and dispersity.
Abstract: The structures of the “Z” and “R” substituents of a RAFT agent (Z–C(S)S–R) determine a RAFT agent’s ability to control radical polymerization. In this paper we report new acid/base switchable N-aryl-N-pyridyl dithiocarbamates (R = −CH2CN, Z = −N(Py)(Ar)) which vary in substituent at the 4-position of the aryl ring and the use of these to control molecular weight and dispersity. In their protonated form, the new RAFT agents are more effective in controlling polymerization of the more activated monomer, methyl acrylate (MA), whereas in their neutral form they provide more effective control of the polymerization of less activated monomers, N-vinyl carbazole (NVC) and vinyl acetate (VAc). For each polymerization, the apparent chain transfer coefficient (Ctrapp) shows a good correlation with Hammett parameters. Dithiocarbamates with more electron-withdrawing aryl ring substituents have the higher Ctrapp. This demonstrates the influence of polar effects on Ctrapp and supports the hypothesis that the activity of...
TL;DR: An ethoxy-bridged dinuclear indium catalyst was used for the ring opening polymerization of the cyclic ester β-butyrolactone to form the biodegradable polyester poly(hydroxybutyrate) (PHB).
TL;DR: Evidence suggesting that the polymers bind the lectin concanavalin A at the same site as natural carbohydrates, showing the potential of these polymers to mimic natural polysaccharides.
Abstract: Enantiopure poly-amido-saccharides (PASs) with a defined molecular weight and narrow dispersity are synthesized using an anionic ring-opening polymerization of a β-lactam sugar monomer. The PASs have a previously unreported main chain structure that is composed of pyranose rings linked through the 1- and 2-positions by an amide with α-stereochemistry. The monomer is synthesized in one-step from benzyl-protected d-glucal and polymerized using mild reaction conditions to give degrees of polymerization ranging from 25 to >120 in high yield. Computational modeling reveals how the monomer’s structure and steric bulk affect the thermodynamics and kinetics of polymerization. Protected and deprotected polymers and model compounds are characterized using a variety of methods (NMR, GPC, IR, DLS, etc.). On the basis of circular dichroism, the deprotected polymer possesses a regular secondary structure in aqueous solution, which agrees favorably with the prediction of a helical structure using molecular modeling. Fur...
TL;DR: extremely fast tandem ring-opening/ring-closing metathesis polymerization of a monomer containing two rather unreactive functional groups: cyclohexene and a terminal alkyne is reported.
Abstract: We report extremely fast tandem ring-opening/ring-closing metathesis polymerization of a monomer containing two rather unreactive functional groups: cyclohexene and a terminal alkyne. When a third-generation Grubbs catalyst was used at low temperature, this tandem polymerization produced polymers with controlled molecular weights and narrow polydispersity indices. To explain this extremely fast polymerization, its reaction mechanism was studied. This new type of controlled polymerization allowed for the preparation of block copolymers using other conventional living metathesis polymerizations. The diene on the backbone of the polymer was postfunctionalized by sequential Diels–Alder and aza-Diels–Alder reactions, which led to selective functionalization depending on the stereochemistry of the diene.
TL;DR: In this paper, photoinitiating systems based on boron-dipyrromethene dye (bodipy)/iodonium salt and optionally tris(trimethylsilyl)silane are proposed for the polymerization of divinylether and epoxy monomers upon visible-light exposure.
Abstract: New photoinitiating systems based on boron-dipyrromethene dye (bodipy)/iodonium salt and optionally tris(trimethylsilyl)silane are proposed for the polymerization of divinylether and epoxy monomers upon visible-light exposure. The presence of the silane increases the epoxide rate of polymerization and conversion. Using acrylate/vinyl ether blends, the synthesis of cross-linked polymer networks (possessing two Tg values: −11 and 111 °C) is also successfully achieved through concomitant cationic and radical polymerization pathways. The chemical mechanisms associated with these initiating systems are investigated by steady-state photolysis and ESR experiments.
TL;DR: In this paper, the free secondary amine bearing monomer 2,2,6,6-tetramethylpiperidin-4-yl methacrylate (TMPMA) was polymerized by means of different controlled radical polymerization techniques (ATRP, RAFT, NMP).
Abstract: This work describes the polymerization of the free secondary amine bearing monomer 2,2,6,6-tetramethylpiperidin-4-yl methacrylate (TMPMA) by means of different controlled radical polymerization techniques (ATRP, RAFT, NMP). In particular, reversible addition-fragmentation chain transfer (RAFT) polymerization enabled a good control at high conversions and a polydispersity index below 1.3, thereby enabling the preparation of well-defined polymers. Remarkably, the polymerization of the secondary amine bearing methacrylate monomer was not hindered by the presence of the free amine that commonly induces degradation of the RAFT reagent. Subsequent oxidation of the polymer yielded the polyradical poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate), which represents a valuable material used in catalysis as well as for modern batteries. The obtained polymers having a molar mass (Mn) of 10,000–20,000 g/mol were used to fabricate well-defined, radical-bearing polymer films by inkjet- printing. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
TL;DR: The results suggest that Cu(0) acts as a supplemental activator and reducing agent of Cu(II)Br(2)/L to Cu(I)Br/L, which seem to be responsible for the activation of SET-LRP.
Abstract: The field of transition-metal-mediated controlled/"living" radical polymerization (CLRP) has become the subject of intense discussion regarding the mechanism of this widely-used and versatile process Most mechanistic analyses (atom transfer radical polymerization (ATRP) vs single-electron transfer living radical polymerization (SET-LRP)) have been based on model experiments, which cannot correctly mimic the true reaction conditions We present, for the first time, a determination of the [Cu(I)Br]/[L] (L=nitrogen-based chelating ligand) ratio and the extent of Cu(I)Br/L disproportionation during CLRP of methyl acrylate (MA) in dimethylsulfoxide (DMSO) with Cu(0) wire as a transition-metal catalyst source The results suggest that Cu(0) acts as a supplemental activator and reducing agent of Cu(II)Br(2)/L to Cu(I)Br/L More importantly, the Cu(I)Br/L species seem to be responsible for the activation of SET-LRP
TL;DR: A highly efficient strategy for one-pot synthesis of programmable, crystalline-amorphous stereomultiblock PLA from rac-lactide.
TL;DR: The Kumada-Tamao coupling polymerization of Grignard pyridine monomers yields well-defined poly(pyridine-3,5-diyl) with a broad molecular weight distribution as discussed by the authors.
Abstract: Recent developments in catalyst-transfer condensation polymerization, which proceeds in a chain-growth polymerization manner, have made it possible to synthesize well-defined π-conjugated polymers with controlled molecular weight and low polydispersity, as well as block copolymers and gradient copolymers. However, catalyst-transfer condensation polymerization has been limited to the polymerization of donor monomers (such as thiophene) for the synthesis of p-type π-conjugated polymers. Here, we highlight several recent advances in catalyst-transfer condensation polymerization leading to n-type π-conjugated polymers. The Kumada–Tamao coupling polymerization of Grignard pyridine monomers yields well-defined poly(pyridine-3,5-diyl) and poly(pyridine-2,5-diyl) with a broad molecular weight distribution. Monomers consisting of strong acceptor and weak donor moieties also undergo catalyst-transfer polymerization; well-defined poly(fluorene benzothiaziazole) was obtained by Suzuki–Miyaura coupling polymerization ...
TL;DR: In this article, a review summarizes recent work on side-chain metallocene-containing polymers prepared by controlled and living polymerizations, which include living anionic polymerization (LAP), ring-opening metathesis polymerization, and controlled radical polymerization.
Abstract: This review summarizes recent work on side-chain metallocene-containing polymers prepared by controlled and living polymerizations, which include living anionic polymerization (LAP), ring-opening metathesis polymerization (ROMP) and controlled radical polymerization (CRP) such as atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated polymerization (NMP). The majority of efforts in the field are focused on side-chain ferrocene-containing polymers, while cobaltocenium-containing polymers have recently started to draw attention. Future direction on the development of other metallocene-containing polymers is discussed.
TL;DR: A novel polymerization methodology for efficient synthesis of hyperbranched polyethylene amphiphiles by chain walking polymerization followed by RAFT polymerization has been developed and can self-assemble to form supramolecular polymer vesicles in aqueous solution.
Abstract: A novel polymerization methodology for efficient synthesis of hyperbranched polyethylene amphiphiles by chain walking polymerization (CWP) followed by RAFT polymerization has been developed. Hyperbranched polyethylene with hydroxyl ends (HBPE-OHs) is first synthesized via chain walking copolymerization of ethylene with 2-hydroxyethyl acrylate with Pd-α-diimine catalyst. The hydroxyl groups of hyperbranched polyethylene are then converted into thiocarbonyl thio moieties by an esterification reaction with trithiocarbonate 3-benzylsulfanylthiocarbonyl sulfanylpropionic acid (BSPA). The hyperbranched polyethylene with thiocarbonyl thio moiety ends (HBPE-BSPAs) is used as a macro-RAFT agent for the synthesis of hyperbranched polyethylene amphiphiles, HBPE-PDMAEMAs, by RAFT polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA). The resultant HBPE-PDMAEMAs can self-assemble to form supramolecular polymer vesicles in aqueous solution. A preliminary investigation on thermo- and pH-responsive behaviors of the polymer is also reported.
TL;DR: In this article, molecular brushes of poly(2-oxazoline)s were prepared by living anionic polymerization of 2-iso-propenyl-2-oxyazoline to form the backbone and subsequent living cationic ring-opening polymerization for pendant chain grafting.
Abstract: Molecular brushes of poly(2-oxazoline)s were prepared by living anionic polymerization of 2-iso-propenyl-2-oxazoline to form the backbone and subsequent living cationic ring-opening polymerization of 2- n - or 2- iso -propyl-2-oxazoline for pendant chain grafting. In situ kinetic studies indicate that the initiation effi ciency and polymerization rates are independent from the number of initiator functions per initiator molecule. This was attributed to the high effi ciency of oxazolinium salt and the stretched conformation of the backbone, which is caused by the electrostatic repulsion of the oxazolinium moieties along the macroinitiator. The resulting molecular brushes showed thermoresponsive properties, that is, having a defi ned cloud point (CP). The dependence of the CP as a function of backbone and side chain length as well as concentration was studied.
TL;DR: A positive effect: the bis(allyl)bismuth cation in [Bi(C(3)H(5))(2)(thf)(2)] is superior to neutral tris(allyL) bismuth in the additive-free allylation of unsaturated C-heteroatom functionalities and the controlled living radical polymerization of activated olefins.
Abstract: A positive effect: the bis(allyl)bismuth cation in [Bi(C(3)H(5))(2)(thf)(2)][B(C(6)H(3)Cl(2))(4)] is superior to neutral tris(allyl)bismuth in the additive-free allylation of unsaturated C-heteroatom functionalities and the controlled living radical polymerization of activated olefins.
TL;DR: In this paper, a parallel enzymatic polymerization system was developed as an advanced extension of the vine-twining polymerization to obtain the inclusion complex from a strongly hydrophobic guest polymer.
Abstract: This paper reviews preparation and applications of amylose supramolecules by means of phosphorylase-catalyzed enzymatic polymerization. When the enzymatic polymerization of α-d-glucose 1-phosphate (G-1-P) as a monomer was carried out in the presence of poly(tetrahydrofuran) (PTHF) of a hydrophobic polyether as a guest polymer, the supramolecule, i.e., an amylose-PTHF inclusion complex, was formed in the process of polymerization. Because the representation of propagation in the polymerization is similar to the way that vines of plants grow twining around rods, this polymerization method for the preparation of amylose-polymer inclusion complexes was proposed to be named “vine-twining polymerization”. Various hydrophobic polyethers, polyesters, poly(ester-ether), and polycarbonates were also employed as the guest polymer in the vine-twining polymerization to produce the corresponding inclusion complexes. To obtain the inclusion complex from a strongly hydrophobic guest polymer, the parallel enzymatic polymerization system was developed as an advanced extension of the vine-twining polymerization. In addition, it was found that amylose selectively includes one side of the guest polymer from a mixture of two resemblant guest polymers, as well as a specific range in molecular weights of the guest PTHF. Amylose also exhibited selective inclusion behavior toward stereoisomers of poly(lactide)s. Moreover, the preparation of hydrogels through the formation of inclusion complexes of amylose in vine-twining polymerization was achieved.
TL;DR: Kinetic data reveal activity for styrene polymerization among the fastest reported to date and initial studies implicate a multimechanism system.
Abstract: Tetradentate amine-bis(phenolate) iron(III) halide complexes containing chloro substituents on the aromatic ring are extremely efficient catalysts for controlled radical polymerization. Molecular weights are in good agreement with theoretical values and polydispersity indexes (PDIs) are as low as 1.11 for styrene and methyl methacrylate polymerizations. Complexes containing alkyl substituents on the aromatic ring are less efficient. Kinetic data reveal activity for styrene polymerization among the fastest reported to date and initial studies implicate a multimechanism system. Despite the highly colored polymerization media, simple work-up procedures yield pure white polymers.
15 Mar 2012
TL;DR: The position of radical polymerization (RP) in the context of polymer industry is highlighted in this paper, where the mechanistic steps of RP are discussed from an industrial point of view, including photoinitiators, chain transfer agents, and monomer stabilizers.
Abstract: The position of radical polymerization (RP) in the context of polymer industry is highlighted. The mechanistic steps of RP are discussed from an industrial point of view. An overview of industrial initiators including photoinitiators, chain transfer agents, and monomer stabilizers is given. The most important polymerization processes with focus on emulsion polymerization (EP) and dispersion polymers as well as types of polymerization reactors are presented. The progress of controlled RP toward commercialization is reviewed.
Keywords:
industrial radical polymerization;
industrial monomers;
initiators;
photoinitiators;
copolymerization;
chain transfer agents;
polymerization inhibitors;
monomer stabilization;
oxygen inhibition;
polymerization processes;
controlled radical polymerization
TL;DR: In this article, molecular brushes of poly(2-oxazoline)s were prepared by living anionic polymerization of 2-isopropenyl-2-oxyazoline to form the backbone and living cationic ring-opening polymerization to form random and block copolymers.
Abstract: Molecular brushes (MBs) of poly(2-oxazoline)s were prepared by living anionic polymerization of 2-isopropenyl-2-oxazoline to form the backbone and living cationic ring-opening polymerization of 2- n -propyl-2-oxazoline and 2-methyl-2-oxazoline to form random and block copolymers. Their aqueous solutions displayed a distinct thermoresponsive behavior as a function of the side-chain composition and sequence. The cloud point (CP) of MBs with random copolymer side chains is a linear function of the hydrophilic monomer content and can be modulated in a wide range. For MBs with block copolymer side chains, it was found that the block sequence had a strong and surprising effect on the CP. While MBs with a distal hydrophobic block had a CP at 70 ° C, MBs with hydrophilic outer blocks already precipitated at 32 ° C.
TL;DR: In this article, photochemical input of photochemistry to the Co(acac)2 mediated radical polymerization (CMRP) of n-butyl acrylate and vinyl acetate is investigated for the first time upon UV irradiation.
TL;DR: In this article, the authors investigated the carbocationic polymerization of isobutylene (IB), co-initiated by GaCl3 or FeCl3·dialkyl ether 1:1 complexes.
Abstract: The carbocationic polymerization of isobutylene (IB), co-initiated by GaCl3 or FeCl3·dialkyl ether 1:1 complexes has been investigated in hexanes in the −20 to 10 °C temperature range. In contrast to AlCl3·diisopropyl ether (AlCl3·i-Pr2O) complexes,(1) GaCl3·i-Pr2O and FeCl3·i-Pr2O readily co-initiate polymerization with 2-chloro-2,4,4-trimethylpentane (TMPCl) or tert-butyl chloride (t-BuCl) in the presence or absence of proton trap. In the absence of proton trap, chain transfer to monomer readily proceeded, resulting in close to complete monomer conversion and up to 85% exo-olefinic end group content. Diisopropyl ether complexes gave the highest polymerization rates, while nonbranched alkyl ether complexes were completely inactive. A polymerization mechanism is proposed to involve ether-assisted proton elimination to yield PIB exo-olefin, and the abstracted proton can subsequently start a new polymer chain by protonation of IB. Alternatively PIB+ may be deactivated by ion collapse to yield PIBCl, which c...