Showing papers on "Ionic polymerization published in 2009"
TL;DR: Ionic liquids (ILs) are continuing as important media in which to effect various kinds of polymerizations, and it is particularly noteworthy that ionic polymerization are being developed in IL solvents and that atom transfer radical polymerization (ATRP) catalysts are being attached to ILs to make them more easily recoverable in living polymerizations as mentioned in this paper.
978 citations
TL;DR: The aim of this review was to establish ana-C2v-Ligated Catalysts as a stand-alone database of Lanthanide Complexes with a focus on the latter stages of their development in the second half of the 1990s.
Abstract: 1.3. Scope of Review 5161 2. Methacrylate Polymerization 5161 2.1. Lanthanide Complexes 5161 2.1.1. Nonbridged Lanthanocenes 5161 2.1.2. ansa-Lanthanocenes 5164 2.1.3. Half-Lanthanocenes 5166 2.1.4. Non-lanthanocenes 5166 2.2. Group 4 Metallocenes 5170 2.2.1. Nonbridged Catalysts 5170 2.2.2. ansa-C2v-Ligated Catalysts 5173 2.2.3. ansa-C2-Ligated Catalysts 5173 2.2.4. ansa-C1-Ligated Catalysts 5176 2.2.5. ansa-Cs-Ligated Catalysts 5177 2.2.6. Constrained Geometry Catalysts 5178 2.2.7. Half-Metallocene Catalysts 5180 2.2.8. Supported Catalysts 5180 2.3. Other Metallocene Catalysts 5180 2.4. Nonmetallocene Catalysts 5181 2.4.1. Group 1 and 2 Catalysts 5181 2.4.2. Group 13 Catalysts 5183 2.4.3. Group 14 Catalysts 5186 2.4.4. Transition-Metal Catalysts 5187 3. Acrylate Polymerization 5188 3.1. Lanthanocenes 5188 3.2. Group 4 Metallocenes 5189 3.3. Nonmetallocenes 5190 4. Acrylamide and Methacrylamide Polymerization 5191 4.1. Acrylamides 5191 4.2. Methacrylamides 5192 4.3. Asymmetric Polymerization 5193 5. Acrylonitrile and Vinyl Ketone Polymerization 5196 5.1. Acrylonitrile 5196 5.2. Vinyl Ketones 5196 6. Copolymerization 5197 6.1. Polar-Nonpolar Block Copolymers 5197 6.2. Polar-Nonpolar Random Copolymers 5199 6.3. Polar-Polar Copolymers 5204 7. Ion-Pairing Polymerization 5206 8. Summary and Outlook 5208 9. Acknowledgments 5208 10. References 5208
460 citations
TL;DR: This review highlights the mechanistic developments of the ROP of NCAs from the conventional to the living initiating systems/methods; the second is dedicated to the synthesis of polypeptide hybrids with different macromolecular architectures; and the third deals with surface-boundpolypeptides.
Abstract: Since 1906, when Leuchs synthesized the first R-amino acid N-carboxyanhydrides (NCAs),1 later referred to as Leuchs’ anhydrides, a great number of publications dealing with the ring-opening polymerization (ROP) of these monomers (Scheme 1) has accumulated. This interest stems from the wide variety of polypeptides that this polymerization can generate. The synthetic polypeptides produced from the NCAs, although far from being monodisperse or constructed from a precise sequence and composition of R-amino acid residues, possess the ability, as their natural relative-proteins, to form R-helix and -sheet motifs. These secondary structures contribute significantly to the self-assembling character of polypeptide chains, leading to novel supramolecular structures with potential biomedical and pharmaceutical applications.2 As for their natural counterparts, it is important for such synthetic polypeptides to be well-defined with high molecular and structural homogeneity in order to favor their selfassembly into precisely defined nanostructures, a requirement for appropriate functionality. It was not until 1997, when Deming3 reported the first living initiating system for the ROP of NCAs, that the synthesis of well-defined polypeptides was achieved. Following this first report, other alternative living initiating systems or methods have also been developed. These living systems lead to well-defined homo-/copolypeptides and hybrids, with high molecular weight and structural homogeneity. Nevertheless, the earlier studies served as the springboard for developments in the whole area of polypeptide synthesis. Several excellent reviews4 have been dedicated to the ROP of NCAs, elucidating the mechanistic aspects of this polymerization. However, only a few have addressed the synthesis of polypeptide-based materials with different macromolecular architectures.4c,5,6 This review is divided into three parts. The first highlights the mechanistic developments of the ROP of NCAs from the conventional to the living initiating systems/methods; the second is dedicated to the synthesis of polypeptides and polypeptide hybrids with different macromolecular architectures; and the third deals with surface-bound polypeptides. Surface-bound polypeptides were incorporated in the review due to the great interest in biologically active surfaces for medical diagnostics and sensors.7
454 citations
TL;DR: Ionic liquids have emerged as a new class of solvents for practical applications due to their unique combination of low volatility, chemical stability, high conductivity, wide electrochemical window, ability to dissolve organic and inorganic solutes and gases, and tunable solvent properties.
350 citations
28 Jan 2009
TL;DR: A comprehensive survey of the current literature on ring-opening polymers can be found in this paper, where the authors present a detailed survey of existing works in the area of ROP.
Abstract: THERMODYNAMICS AND KINETICS OF RING-OPENING POLYMERIZATION Introduction Thermodynamics of the Ring-Opening Polymerization Kinetics of Ring-Opening Polymerization GENERAL MECHANISMS IN RING-OPENING POLYMERIZATION Introduction Anionic Ring-Opening Polymerization Cationic Ring-Opening Polymerization Radical Ring-Opening Polymerization SILOXANE-CONTAINING POLYMERS Introduction Polydimethylsiloxanes Functional Silicones Polycarbosiloxanes SULFUR-NITROGEN-PHOSPHOROUS-CONTAINING POLYMERS Introduction Mechanism and Methods in Ring-Opening Polymerization (ROP) of Halogenated Cyclotriphosphazanes Ring-Opening Polymerization and Chemistry of Nonhalogenated Phosphazane Rings Incorporation of Sulfur into Phosphazane Ring Systems and Their Polymerization Chemistry POLYMERIZATION OF CYCLIC DEPSIPEPTIDES, UREAS AND URETHANES Introduction Polydepsipeptides Monomers Ring-Opening Polymerization Enzymatic Polymerization Ring Expansion Polyureas Polyurethanes POLYETHERS AND POLYOXAZOLINES Introduction Polyethers Polyoxazolines POLYAMIDES Introduction Mechanism of the Anionic Polymerization of Lactams Initiators for the Anionic Polymerization of Lactams Activators for Anionic Polymerization of Lactams Nonactivated Polymerization Cyclic Oligomers of Epsilon-Caprolactam Block Copolymers of Lactams Anionic Copolymerization of Epsilon-Caprolactam with Omega-Laurolactam Copolymerization of Lactams with Lactones (Epsilon-Caprolactone) Powdered Polyamide Nanocomposites Anionic Polymerization of 2-Pyrrolidone RING-OPENING METATHESIS POLYMERIZATION General Introduction Introduction to Ring-Opening Metathesis Polymerization (ROMP) Well-Defined Catalysts for ROMP 'Living? ROMP Selected Recent Applications and Developments POLYESTERS FROM BETA-LACTONES Introduction Beta-Lactones Preparation Ionic Polymerization Coordination Process Carbene-Based Polymerization Enzymatic Polymerization Illustrative Experimental Section POLYESTERS FROM DILACTONES Introduction General Concepts and ROP Promoted by Metallic Recent Advances in ROP Macromolecular Engineering Applications POLYESTERS FROM LARGE LACTONES Introduction Controlled Synthesis of Linear Polyesters Physical Properties of Polymers POLYCARBONATES Introduction Polymerization of Cyclic Carbonates: Homopolymers and Block Copolymers POLYMERIZATION OF CYCLOALKANES Introduction General Overview and Thermodynamic Requirements Structure-Reactivity Relationships Based on a Comprehensive Survey of the Current Literature METAL-FREE CATALYSIS IN RING-OPENING POLYMERIZATION Introduction Nucleophilic ROP Metal-Free Ionic ROP ENZYME-MEDIATED RING-OPENING POLYMERIZATION Introduction Characteristics of Enzymatic ROP Classes of Monomer Polymer Architectures Employing Enzymatic ROP
344 citations
TL;DR: A new class of "switchable" RAFT agents are reported, N-(4-pyridinyl)-N-methyldithiocarbamates, that provide excellent control over polymerization of LAMs and, after addition of 1 equiv of a protic or Lewis acid, become effective in controlling polymerizations of MAMs, allowing the synthesis of poly(MAM)-block-poly(LAM) with narrow molecular weight distributions.
Abstract: The polymerization of most monomers that are polymerizable by radical polymerization can be controlled by the reversible addition−fragmentation chain transfer (RAFT) process. However, it is usually required that the RAFT agent be selected according to the types of monomer being polymerized. Thus, RAFT agents (dithioesters, trithiocarbonates) suitable for controlling polymerization of “more activated” monomers (MAMs; e.g., styrene, acrylates, methacrylates, etc.) tend to inhibit polymerization of “less activated” monomers (LAMs; e.g., vinyl acetate, N-vinylpyrrolidone, etc.). Similarly RAFT agents suitable for polymerizations of LAMs (xanthates, certain dithiocarbamates) tend to give little or poor control over polymerizations of MAMs. We now report a new class of “switchable” RAFT agents, N-(4-pyridinyl)-N-methyldithiocarbamates, that provide excellent control over polymerization of LAMs and, after addition of 1 equiv of a protic or Lewis acid, become effective in controlling polymerization of MAMs, allow...
259 citations
TL;DR: Since lipase-catalyzed polyester synthesis provides a good opportunity for conducting "green polymer chemistry", the importance of this is described.
Abstract: Polyester synthesis by lipase catalyst involves two major polymerization modes: i) ring-opening polymerization of lactones, and, ii) polycondensation. Ring-opening polymerization includes the finding of lipase catalyst; scope of reactions; polymerization mechanism; ring-opening polymerization reactivity of lactones; enantio-, chemo- and regio-selective polymerizations; and, chemoenzymatic polymerizations. Polycondensation includes polymerizations involving condensation reactions between carboxylic acid and alcohol functional groups to form an ester bond. In most cases, a carboxylic acid group is activated as an ester form, such as a vinyl ester. Many recently developed polymerizations demonstrate lipase catalysis specific to enzymatic polymerization and appear very useful. Also, since lipase-catalyzed polyester synthesis provides a good opportunity for conducting "green polymer chemistry", the importance of this is described.
250 citations
TL;DR: A review of atom transfer radical polymerization (ATRP) in aqueous dispersed media is presented in this article, which covers the most important progress of ATRP in dispersed media from 1998 to 2009.
Abstract: During the last decade, atom transfer radical polymerization (ATRP) received significant attention due to its exceptional capability of synthesizing polymers with pre-determined molecular weight, well-defined molecular architectures and various functionalities. It is economically and environmentally attractive to adopt ATRP to aqueous dispersed media, although the process is challenging. This review summarizes recent developments of conducting ATRP in aqueous dispersed media. The issues related to retaining “controlled/living” character as well as colloidal stability during the polymerization have to be considered. Better understanding the ATRP mechanism and development of new initiation techniques, such as activators generated by electron transfer (AGET) significantly facilitated ATRP in aqueous systems. This review covers the most important progress of ATRP in dispersed media from 1998 to 2009, including miniemulsion, microemulsion, emulsion, suspension and dispersed polymerization.
119 citations
TL;DR: The integration of ring-opening metathesis polymerization (ROMP) and ring- opening polymerization of the amino acid N-carboxyanhydride (NCA) to allow facile synthesis of brush-like polymers containing polypeptide as the brush side chains is reported.
Abstract: We report here the integration of ring-opening metathesis polymerization (ROMP) and ring-opening polymerization of the amino acid N-carboxyanhydride (NCA) to allow facile synthesis of brush-like polymers containing polypeptide as the brush side chains. ROMP of N-trimethylsilyl norbornenes rendered the preparation of poly(norbornene)s bearing pendant N-TMS groups. With no need to purify the resulting polymers, such macromolecular initiators could subsequently initiate controlled NCA polymerizations. Brush-like poly(norbornene)s with grafted polypeptides or block copolypeptides were readily obtained with controlled molecular weights and narrow molecular weight distributions. Because numerous ROMP and NCA monomers are widely available, this novel polymerization technique will allow easy access to numerous brush-like hybrid macromolecules with unprecedented properties and broad applications.
111 citations
TL;DR: Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures.
Abstract: Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures. Depending upon the nature of the catalyst structure, two distinct molecular weight evolutions were observed. Polymerization conducted with catalysts bearing six-carbon tethers displayed rapid polymer molecular weight growth which reached a maximum value at ca. 70% monomer conversion, resembling a chain-growth polymerization mechanism. In contrast, five-carbon-tethered catalysts led to molecular weight growth that resembled a step-growth mechanism with a steep increase occurring only after 95% monomer conversion. The underlying reason for these mechanistic differences appeared to be ready release of five-carbon-tethered catalysts from growing polymer rings, which competed significantly with propagation. Owing to reversible chain transfer and the lack of end groups in REMP, the ...
102 citations
TL;DR: In this article, Cationic polymerization of isobutyl vinyl ether (IBVE) was examined using a variety of metal halides and the difference in the polymerization activity of these Lewis acids was significant.
Abstract: Cationic polymerization of isobutyl vinyl ether (IBVE) was examined using a variety of metal halides. In the presence of an appropriate added base, ester or ether, the living polymerization of IBVE proceeded for almost all Lewis acids (MCln; M: Fe, Ga, Sn, In, Zn, Al, Hf, Zr, Bi, Ti, Si, Ge, Sb) used in conjunction with an IBVE−HCl adduct in toluene at 0 °C. The difference in the polymerization activity of these Lewis acids was significant. As examples, polymerization with some acids, such as FeCl3, proceeded in the order of seconds, whereas it took more than a few weeks with others such as SiCl4 and GeCl4. The difference in activity is based on the strength of the interaction between the Lewis acid and the propagating end chloride anion and/or the basic carbonyl (or ether) oxygen atom of the added base, that is, the chlorophilic or oxophilic nature of each metal halide is a decisive factor. In addition, a suitable combination of a Lewis acid and an additive was indispensable for living polymerization. Wi...
TL;DR: In this paper, the surface-initiated polymerization with different initiator densities and different polymerization rates was investigated using molecular dynamics simulation method, and the authors found that the initiator density, together with the polymerization rate, greatly determines the polymer brush structure, the initiation efficiency and the graft density.
Abstract: The surface-initiated polymerization with different initiator densities and different polymerization rates is investigated using molecular dynamics simulation method. We find that the initiator density, together with the polymerization rate, greatly determines the polymer brush structure, the initiation efficiency, and the graft density, especially when the initiator density is high. The excluded volume effect also plays a crucial role in the system when the chains are densely grafted. By tuning the initiator density and modifying the polymerization rate, we can obtain the polymer brushes with different degrees of polydispersity. This study partially emphasizes the importance of considering the effects of polymerization rate in further investigations.
TL;DR: In this paper, an investigation for the initiation of a chain-growth polymerization, Kumada catalyst-transfer polycondensation, for the synthesis of poly(3-hexylthiophene) is described.
Abstract: An investigation for the initiation of a chain-growth polymerization, Kumada catalyst-transfer polycondensation, for the synthesis of poly(3-hexylthiophene) is described. A novel method for the generation of an active catalyst/initiator complex was developed utilizing the inexpensive, air stable Ni(PPh3)2Cl2 precursor to generate the active Ni(PPh3)4 catalyst in situ. Poly(3-hexylthiophene) polymerization reactions were carried out using aryl halides with various substituents on the phenyl ring as external initiators, and it was found that the type of the functional group present on the initiator plays a crucial role in the polymerization. The new method provided a more efficient way to initiate polymerization yielding polymers with higher regioregularity, larger molecular weight, and lower polydispersity than the previously reported methods.
TL;DR: The first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described in this article, where the utilized polymerization technique, namely ATRPP, provides MIP microspheres with obvious molecular imprintings towards the template, fast template binding kinetics and an appreciable selec- tivity over structurally related compounds.
Abstract: The first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described. The utilized polymerization technique, namely atom transfer radical precipitation poly- merization (ATRPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding kinetics and an appreciable selec- tivity over structurally related compounds. The living chain propagation mechanism in ATRPP results in MIP spherical particles with diameters (number-average diame- ter Dn � 3 lm) much larger than those prepared via traditional radical precipitation polymerization (TRPP). In addition, the MIP microspheres prepared via ATRPP have also proven to show significantly higher high-affinity binding site densities on their surfaces than the MIP generated via TRPP, while the binding association constants Ka and apparent maximum numbers Nmax of the high-affinity sites as well as the specific template bindings are almost the same in the two cases. V C 2009 Wiley
TL;DR: Water-soluble, high-molecular-weight polycobaltocenium polyelectrolytes have been prepared by ring-opening polymerization (ROP) techniques by forming oligomers with up to nine repeat units using a redox-active cobalt-containing polyElectrolyte.
Abstract: Water-soluble, high-molecular-weight polycobaltocenium polyelectrolytes have been prepared by ring-opening polymerization (ROP) techniques. Anionic polymerization of a strained 19-electron dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium chloride resulted in the formation of oligomers with up to nine repeat units. Thermal ROP of dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium nitrate resulted in the formation of high-molecular-weight polycobaltocenium nitrate, a redox-active cobalt-containing polyelectrolyte.
TL;DR: It is demonstrated here via the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAM) at low temperature that the negative function of water in aqueous ATRP is significantly suppressed.
Abstract: We demonstrate here via the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAM) at low temperature that the negative function of water in aqueous ATRP is significantly suppressed. By the addition of a small amount of water in a water-miscible organic solvent and maintaining low polymerization temperature, the ATRP of NIPAM is relatively fast and well controlled. We observed that the rate of the polymerization in pure organic solvent at a monomer concentration of 20 wt % is slow, and relatively low conversions were obtained. The low conversion of PNIPAM in pure alcoholic media (such as methanol, ethanol, and n-propanol) is attributed to the poor solubility of the resulting low molecular weight polymer in such solvents. The consequence is that the PNIPAM chains are aggregated, resulting in the inaccessibility of the embedded halide atom of the polymer chain ends by the copper catalyst. As expected, the ATRP of NIPAM in pure water was found to be fast and uncontrolled. These results have therefore prompted us to study the ATRP of NIPAM in aqueous-organic mixtures. Room temperature polymerization of NIPAM in mixed aqueous-organic solvent mixtures (organic:water = 4:1 or 3:1) revealed to be fast and uncontrolled. However, when the NIPAM polymerization was conducted at low temperature (0 degrees C) in such solvent systems, the polymerization turned out to be well-controlled as the molar masses progress linearly with conversion, and pseudo-first-order kinetic plots were obtained. Furthermore, monomodal GPC traces and narrow molecular weight distributions were obtained in all aqueous-organic solvent systems. Chain extension for aqueous ATRP of NIPAM revealed to proceed well at low temperature as compared to room temperature. Furthermore, we observe that the rates of the polymerization of NIPAM in different aqueous-organic mixtures follow the trend of polarity in the case of the polar aprotic solvents. However, in the case of polar protic solvent (such as methanol, ethanol, 1-propanol, and 2-propanol), the rate of the polymerization was found to increase with increasing solubility of the PNIPAM from methanol to 2-propanol.
TL;DR: The diene 3-methylenecyclopentene was synthesized from the naturally occurring monoterpene myrcene by ring-closing metathesis using Grubbs second generation catalyst to afford regiopure 1,4-poly-2.
Abstract: The diene 3-methylenecyclopentene (2) was synthesized from the naturally occurring monoterpene myrcene (1) by ring-closing metathesis using Grubbs second generation catalyst. Radical, anionic, and cationic polymerizations of 2 were investigated. The anionic polymerization of 2 with sec-butyllithium (s-BuLi) in cyclohexane gave poly-2 in quantitative yield, with a narrow molecular weight distribution and predictable molecular weight based on the molar ratio of 2 and s-BuLi. Radical polymerization of 2 was also successful using AIBN as the initiator. Samples of poly-2 obtained from the anionic and radical polymerization of 2 possessed mixed regiochemistry (i.e., 4,3 and 1,4 addition). The cationic polymerization of 2 proceeded smoothly to afford regiopure 1,4-poly-2. For example, the i-BuOCH(Cl)Me/ZnCl2/Et2O initiating system afforded 1,4-poly-2 with controlled molecular weight and narrow molecular weight distribution. Samples of 1,4-poly-2 were semicrystalline as determined by differential scanning calorim...
06 Aug 2009
TL;DR: The ability of a cyclic monomer to polymerize according to the ring opening mechanism is determined by two equally important factors -the conversion of monomer molecules into macromolecules (of linear or more complex topologies) must be allowed both thermodynamically and kinetically as discussed by the authors.
Abstract: Cyclic monomers that have been polymerized via ring opening encompass a variety of structures, such as alkanes, alkenes, compounds containing heteroatoms in the ring: oxygen [ethers, acetals, esters (lactones, lactides, and carbonates), and anhydrides], sulfur (polysulfur, sulfi des and polysulfi des), nitrogen [amines, amides (lactames), imides, N carboxyanhydrides and 1,3 oxaza derivatives], phosphorus (phosphates, phosphonates, phosphites, phosphines and phosphazenes), or silicon (siloxanes, silaethers, carbosilanes and silanes). For the majority of these monomers, convenient polymerization conditions have been elaborated, that result in the controlled synthesis of the corresponding polymers [1 – 13] . The ability of a cyclic monomer to polymerize according to the ring opening mechanism is determined by two equally important factors – the conversion of monomer molecules into macromolecules (of linear or more complex topologies) must be allowed both thermodynamically and kinetically. In practical terms this means that: (i) monomer macromolecule equilibrium must be shifted to the right hand (macromolecule) side; and (ii) the corresponding polymerization mechanism should exist, that could enable conversion of the monomer molecules into the polymer repeating units, within the operable polymerization time (Equation 1.1 ). The net equation of the polymerization process reads:
TL;DR: In this paper, a three-component photoinitiator system that employs the free radical promoted decomposition of diaryliodonium salts for the visible light induced cationic polymerization of epoxides is described.
Abstract: Herein is described the development of a three-component photoinitiator system that employs the free radical promoted decomposition of diaryliodonium salts for the visible light induced cationic polymerization of epoxides. A long wavelength, titanium-complex free radical photoinitiator is used to generate radicals that abstract hydrogen atoms from benzyl alcohol synergists. The resulting benzyl radical species efficiently reduce diaryliodonium salts thereby generating oxycarbenium ions that spontaneously fragment to form the corresponding aldehyde and a Br⊘nsted superacid. The superacid subsequently initiates the cationic ring-opening polymerization of a wide variety of epoxide monomers.
TL;DR: In this paper, the first ORTERP of n-butyl acrylate (BA) in emulsifier-free emulsion polymerization system was carried out for the first time, using the in situ nuclea.
Abstract: Organotellurium-mediated living radical polymerization (TERP) of n-butyl acrylate (BA) in emulsifier-free emulsion polymerization system was carried out for the first time, using the in situ nuclea...
TL;DR: Controlled hybridization of olefin-containing polymers prepared by two different polymerization methods, step-growth polymerization and chain- growth polymerization, was accomplished by macromolecular oleFin cross-metathesis.
TL;DR: The SEEP (surface electroinitiated emulsion polymerization) as mentioned in this paper is a grafting method that provides covalently grafted polymer films on conducting or semiconducting surfaces by radical polymerization in aqueous dispersed media.
Abstract: As recently reported, the SEEP process (surface electroinitiated emulsion polymerization) is a new grafting method that provides covalently grafted polymer films on conducting or semiconducting surfaces by radical polymerization in aqueous dispersed media. It relies on cathodic electroinitiation, which creates radical species able to start a radical polymerization. Contrary to the formerly described cathodic electrografting of vinylic polymers (CE), which also delivers submicrometer-thick and stable polymer films on conducting substrates but requires strictly anhydrous conditions and organic aprotic solvent, SEEP brings a major improvement in switching from a purely anionic mechanism to a radical one by adding an aryldiazonium salt in the reaction mixture, while retaining the same polymer films characteristics. Moreover, SEEP is not restricted to water-soluble monomers but can be performed even with hydrophobic ones, such as n-butyl methacrylate (BMA). In such cases, a surfactant is necessary to stabilize...
TL;DR: In this article, the controlled-radical polymerization of NBMA and o-nitrobenzyl acrylate (NBA) monomers has been evaluated using Atom Transfer Radical Polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated NMP.
Abstract: We report on the controlled-radical polymerization of the photocleavable o-nitrobenzyl methacrylate (NBMA) and o-nitrobenzyl acrylate (NBA) monomers. Atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated. polymerization (NMP) have been evaluated. For all methods used, the acrylate-type monomer does not polymerize, or polymerizes very slowly in a noncontrolled manner. The methacrylate-type monomer can be polymerized by RAFT with some degree of control (PDI similar to 1.5) but leading to molar masses up to 11,000 g/mol only. ATRP proved to be the best method since a controlled-polymerization was achieved when conversions are limited to 30%. In this case, polymers with molar masses up to 17,000 g/mol and polydispersity index as low as 1.13 have been obtained. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6504-6513, 2009
TL;DR: Polymerization of Divinylbenzene and Glycidyl Methacrylate Particles by Photo-initiated Precipitation Polymerization in Different Solvent Mixtures as discussed by the authors.
Abstract: Polymerization of Divinylbenzene and Divinylbenzene-co-Glycidyl Methacrylate Particles by Photoinitiated Precipitation Polymerization in Different Solvent Mixtures
TL;DR: OMRP was confirmed by an independent polymerization experiment starting from an isolated and purified [Co(tmhd)(2)](PVAc) macroinitiator and the reversal of relative effective OMRP rate constants k(eff) (4>1 in the absence of external donors, 4<1 in their presence) is rationalized through competitive steric effects on Co(III)-C and Co(II)-L bond strengths.
Abstract: Poly(vinyl acetate) by OMRP: Increasing the steric encumbrance of the β-diketonate R substituents in vinyl acetate (VAc) polymerization mediator [Co{OC(R)CHC(R)O}2] from Me to tBu sufficiently weakens the CoIIIPVAc bond of the polymer chain to allow it to operate by both associative (degenerative transfer) and dissociative (organometallic radical polymerization, OMRP) mechanisms (see scheme). The CoIIIPVAc species also acts as a transfer agent in the absence of Lewis bases, whereas the CoII complex shows catalytic chain transfer (CCT) activity.
The complex [CoII(tmhd)2] (4; tmhd=2,2,6,6-tetramethylhepta-3,5-dionato) has been investigated as a mediator for controlled radical polymerization of vinyl acetate (VAc) and compared with the analogue [CoII(acac)2] (1; acac=acetylacetonato). A relatively well controlled process occurs, after an induction time, with 2,2′-azobis(4-methoxyl-2,4-dimethylvaleronitrile) (V-70) as radical initiator at 30 °C. However, whereas the polymerization essentially stops after about six initiator half-lives in the presence of 1, it continues with a first-order rate law in the presence of 4. The successful simulation of the kinetic data shows that 4 operates simultaneously by associative (degenerative transfer, DT) and dissociative (organometallic radical polymerization, OMRP) mechanisms. The occurrence of OMRP was confirmed by an independent polymerization experiment starting from an isolated and purified [Co(tmhd)2](PVAc) macroinitiator. The polymer molecular weight evolves linearly with conversion in accordance with the expected values for one chain per Co atom when DT is the predominant mechanism and also during the pure OMRP process; however, observation of stagnating molecular weights at long reaction times with concomitant breakdown of the first-order rate law for monomer consumption indicates a competitive chain-transfer process catalyzed by an increasing amount of CoII. In the presence of external donors L (water, pyridine, triethylamine) the DT pathway is blocked and the OMRP pathway is accelerated, and polymerization with complex 4 is then about five times slower than with complex 1. The reversal of relative effective OMRP rate constants keff (4>1 in the absence of external donors, 4<1 in their presence) is rationalized through competitive steric effects on CoIIIC and CoIIL bond strengths. These propositions are supported by 1H NMR studies and by DFT calculations.
TL;DR: FeFeCl3·6H2O and FeCl2·4H 2O are found to be bulk polymerization catalysts for the ring opening polymerization of β-butyrolactone as mentioned in this paper.
Abstract: FeCl3·6H2O, RuCl3·H2O and FeCl2·4H2O are found to be bulk polymerization catalysts for the ring opening polymerization of ɛ-caprolactone, δ-valerolactone and β-butyrolactone. These polymerizations can be significantly enhanced by conducting them in the presence of appropriate amounts of different alcohols. The major initiation pathway in the polymerization is found to proceed via the activated monomer mechanism and depending on the nature of the alcohol used, poly(lactones) with different end groups can be synthesized. Such polymerizations constitute an economical process, employing readily available inorganics as catalysts and do not necessitate solvents. The overall system is green and eco friendly.
TL;DR: In this article, α-Azido,ω-hydroxypolyethers were prepared directly by monomer-activated anionic polymerization, and the azido function in the α-position of poly(ethylene oxide), poly(propylene oxide), protected polyglycidol and polyepichlorohydrin was used as initiator.
Abstract: α-Azido,ω-hydroxypolyethers were prepared directly by monomer-activated anionic polymerization. The introduction of the azido function in the α-position of poly(ethylene oxide), poly(propylene oxide), protected polyglycidol and polyepichlorohydrin was carried out by tetrabutylammonium azide used as initiator. A slight excess of triisobutylaluminum with respect to the ammonium salt ([i-Bu3Al]/[NBu4N3] = 1.5 to 5) was added to trigger the polymerization and get polyethers with controlled molar masses up to 30000 g/mol in a few hours. The terminal hydroxyl function was formed by deactivation of the active polymer ends. The successful and direct preparation of these N3-functionalized polyethers was proven by NMR spectroscopy, size exclusion chromatography and matrix-assisted laser desorption/ionization time-of-flight characterizations as well as “click” reactions.
TL;DR: Well-defined polymethylene-block-polystyrene (PM-b-PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene using a series of hydroxyl-terminated polymethylenes.
Abstract: Well-defined polymethylene-block-polystyrene (PM-b-PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene. A series of hydroxyl-terminated polymethylenes (PM-OHs) with different molecular weight and narrow molecular weight distribution were prepared using living polymerization of ylides following efficient oxidation in a quantitive functionality. Then, the macroinitiators (PM-MIs ($\overline M _{\rm n}$ = 1 900-15 000; PDI = 1.12-1.23)) transformed from PM-OHs in ≈ 100% conversion initiated ATRPs of styrene to construct PM-b-PS copolymers. The GPC traces indicated the successful extension of PS segment ($\overline M _{\rm n}$ of PM-b-PS = 5 000-41 800; PDI = 1.08-1.23). Such copolymers were characterized by (1) H NMR and DSC.
TL;DR: In this paper, the synthesis of polystyrene block-poly(p-hydroxystyrene-graft-ethylene oxide), PS-b-(PHOS-g-PEO), amphiphilic block−graft copolymers was presented.
Abstract: This work presents the synthesis of polystyrene-block-poly(p-hydroxystyrene-graft-ethylene oxide), PS-b-(PHOS-g-PEO), amphiphilic block−graft copolymers. The backbone diblock copolymers (PS-b-PHOS) were prepared by lithium-based anionic polymerization, followed by postpolymerization acid hydrolysis of the poly(p-tert-butoxystyrene), PtBOS, precursor block. The PEO side chains were synthesized by metal-free anionic ring-opening polymerization of ethylene oxide (EO), using the phosphazene base (t-BuP4) and the phenolic hydroxyl groups (PhOH) in the backbones as the complex multifunctional initiating system. In all cases, starlike block−graft copolymers with high molecular weights and low polydispersities were synthesized. Well-controlled polymerization was achieved even with the molar ratio of t-BuP4 to PhOH being equal to 0.2. Dynamic and static light scattering and fluorescence spectroscopy studies were carried out to investigate the solution behavior of the amphiphilic block−graft copolymers, including t...