Polymerization Of 2-oxazolines Research Articles

Dormant Polymers and Their Role in Living and Controlled Polymerizations; Influence on Polymer Chemistry, Particularly on the Ring Opening Polymerization.

Living polymerization discovered by Professor Szwarc is well known to all chemists. Some of the living polymerizations involve dormancy, a process in which there is an equilibrium (or at least exchange) between two types of living polymers, namely active at the given moment and dormant at this moment and becoming active in the process of activation. These processes are at least equally important although less known. This mini review is devoted to these particular living polymerizations, mostly polymerizations by the Ring-Opening Polymerization mechanisms (ROP) compared with some selected close to living vinyl polymerizations (the most spectacular is Atom Transfer Radical Polymerization (ATRP)) involving dormancy. Cationic polymerization of tetrahydrofuran was the first one, based on equilibrium between oxonium ions (active) and covalent (esters) dormant species, i.e., temporarily inactive, and is described in detail. The other systems discussed are polymerization of oxazolines and cyclic esters as well as controlled radical and cationic polymerizations of vinyl monomers.

The use of sulfonyl halides as initiators of cationic polymerization of oxazolines

The kinetic investigations of the cationic polymerization of 2-ethyl-2-oxazoline are performed with the use of aromatic sulfonic acid halides as initiators. The rate constants of chain propagation and the activation energy are calculated. It is found that the polymerization predominantly proceeds via the livingchain, rather than the pseudoliving, polymerization mechanism.

Synthesis of Thermochromic Iron(II) Tris(bipyridine)-Centered Star-Shaped Polyoxazolines and Their Bipyridine-Centered Macroligand Counterparts

Iron tris(bipyridine) complexes [Fe{4,4‘-bis(chloromethyl)-2,2‘-bipyridine}3], 1a, and the corresponding iodide analogue generated in situ using NaI, 1b, were explored as initiators for the polymerization of a series of 2-R-2-oxazoline monomers (R = ethyl, EtOX; methyl, MeOX; phenyl, PhOX; and undecyl, UnOX). The resulting labile core, red-violet Fe-centered star polymers fragment during molecular weight analysis by gel permeation chromatography (GPC). Thus, samples were subjected to chemical cleavage in aqueous K2CO3 to generate metal-free bipyridine-centered polyoxazolines, bpyPROX2. When combined with ferrous ammonium sulfate, these bpyPROX2 macroligands chelate to Fe(II), regenerating the [Fe(bipyridine)3]2+ chromophores. Both preparative and analytical kinetics experiments generally produce polymers with reasonably narrow molecular weight distributions (∼1.1−1.5). Molecular weight vs % monomer conversion plots with either the iodide or chloride initiating system were nearly linear for all monomers ; however, only PEOX and PUOX products show good correlation with Mn(calcd) based on monomer/initiator loading. For most monomers, reactions with iodide initiators are faster than the chlorides, and linear first-order kinetics plots were observed. Polymerization of oxazolines with 4,4‘-bis(halomethyl)-2,2‘-bipyridines produced polymers with very narrow molecular weight distributions but with molecular weights higher than targeted based on monomer loading. 1H NMR data illustrates that termination with dipropylamine is efficient for EtOX polymerizations. Thermal analysis by DSC and TGA reveal few differences between Fe-centered stars and their bpy-centered PROX macroligand counterparts. Variable-temperature UV/vis data is provided for an Fe-centered PEOX thin film sample.

POLYMERS WITH METAL BINDING UNITS: BIPYRIDINE AND TERPYRIDINE CONTAINING POLYOXAZOLINES

2,2'-Bipyridines functionalized with one bromomethyl group in the 5-position were used as metallo-supramolecular initiators for the living cationic polymerization of 2-oxazolines utilizing cobalt(II), iron(II) and ruthenium(II) transition metal ions. The central metal ions could be removed using basic conditions resulting in uncomplexed polymers with a free metal binding side. The obtained polymers were characterized using NMR, UV/Vis spectroscopy, GPC and MALDI-TOF mass spectrometry. The termination of the living end groups with an amino-functionalized terpyridine during the polymerization process opens the possibility for the construction of polymers with different metal binding sides. Due to the exact control of molecular weight, defined end groups and the variability of the oxazoline monomers new supramolecular polymers can be obtained.

Synthesis of α-alkyl ω-trimethoxysilane polyoxazolines and their application as coatings on glass fibres

A novel class of telechelic α-alkyl ω-trimethoxysilane poly(N-propionylethylene imine)s (TMS-PPEls) has been synthesized by living cationic ring-opening polymerization of 2-oxazolines. A new route for the termination reaction of the living polyoxazoline is described. These block copolymers have been tested as coatings for glass fibres. The polymers were applied by means of a solvent dip test. It is supposed that the affinity of the polyoxazoline block for glass surfaces promotes the reaction of the silane with the silanol groups of the glass substrate. Because of the presence of the apolar α-block, the surface tension of the glass surface will be lowered, as was shown by contact angle measurements. The presence of the polymer on the glass surface was also demonstrated by XPS measurements. The interfacial properties of coated glass plates and polymer matrices were determined by performing lap-shear tests.

Block and graft copolymers of 2-oxazolines

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

Polymerization of oxazolines initiated with chloroformates

Polymerization of oxazolines initiated with chloroformates

Reactivity of N-alkylated cyclic imino ether salts having vinyl group

Two copolymers of 2-isopropenyl-2-oxazolinium tetrafluoroborate with methyl methacrylate and with methyl acrylate were prepared, from which the polymerization of 2-oxazolines (2-methyl and 2-t-butyl) was initiated to prepare graft copolymers.

Ring-opening polymerization of 2-oxazolines initiated by chloromethyl groups introduced onto carbon black surface

The ring-opening polymerization of 2-oxazolines (OXZs) was found to be initiated by chloromethyl groups introduced onto carbon black surface. The introduction of chloromethyl groups onto the surface was achieved by the reaction of carbon black with 3,3′-bischloromethylbenzoyl peroxide in carbon tetrachloride. During the polymerization, poly-OXZs were grafted from carbon black based on the propagation of the polymers from the surface: percentage of grafting increased with an increase of conversion and reached 40–60%. The polymerization was accelerated by the addition of potassium iodide. Poly-OXZ-grafted carbon black produced stable colloidal dispersions in both hydrophobic and hydrophilic solvents.

Synthesis of acryl- and methacryl-type macromonomers and telechelics by utilizing living polymerization of 2-oxazolines

Preparation des macromonomeres poly(-ethyleneimine) par polymerisation avec ouverture de cycle d'alkyl-2 oxazolines-2, hydrolyse basique du polymere vivant puis reaction de l'alcool forme avec le chlorure d'acryloyle ou de methacryloyle ou par terminaison du polymere vivant avec un anion methacrylate ou acrylate. Preparation des polymeres telecheliques en utilisant un sel de bis-oxazolinium amorceur et en terminant la polymerisation avec l'eau, l'ammoniaque ou une amine

Polymerization of 2-Oxazolines. IV. The Structure and the Reactivity of 2-Substituted-2-oxazolines and Oxazolinium Perchlorates

Abstract In order to elucidate the structure and the stability of the growing cationic end in the polymerization of 2-oxazolines, the reactions of 2-bromoethylbenzamide with silver salts such as silver perchlorate, tetrafluoroborate, nitrate, nitrite, cyanate, and acetate were investigated. The reactions with silver perchlorate and tetrafluoroborate gave the 2-phenyl-2-oxazolinium salt (intramolecular O-alkylation product) quantitatively, whereas the reaction with silver nitrate gave the corresponding alkyl nitrate (staight-chain product). For the reactions with silver nitrite, cyanate and acetate, both products were obtained. In order to elucidate the ring-opening reactivity of the oxazolinium cation, the ring-opening addition reaction of N-methyl-2-oxazolinium perchlorates with pyridine was investigated. It was found that N-methyl-2-phenyl-2-oxazolinium perchlorate was more reactive toward the nucleophilic ring-opening reaction than was N-methyl-2-methyl-2-oxazolinium perchlorate. The mutual copolymerization of 2-phenyl-2-oxazoline with the other 2-substituted-2-oxazoline such as 2-methyl-, 2-isopropyl-, and 2-benzyl-2-oxazoline indicated that the monomer reactivity ratio r2 was much larger than unity, whereas r1 was very much smaller. Based on these results, the influence of the structure and the reactivity of the monomer and the growing cationic end of the polymerizability of 2-oxazolines are discussed.

Polymerization of 2-Oxazolines. III. Influence of Polymerization Media on the Propagation Reaction in the Cationic Polymerization of 2-Phenyl-2-oxazoline

Abstract The influence of solvent on the cationic polymerization of 2-phenyl-2-oxazoline initiated with 2-phenyl-2-oxazalinium perchlorate was studied in connection with the physical properties of the solvents used. The polymerizations in all solvents used proceeded successively with little termination and transfer reactions. The propagation rate constant in polar solvents was larger than in nonpolar solvents. The propagation rate constant increased with a decrease in nucleophilicity of the solvent used. In binary solvent systems composed of components with similar nucleophilicities and with different dielectric constants, the propagation rate constant increased with an amount of the polar solvent. In binary solvent systems composed of components with similar dielectric constants and with different nucleophilicities, the propagation rate constant decreased with the amount of the solvent having more nucleophilicity. The activation energy (Ea) of the propagation reaction was about 17-27 kcal/mole, and the a...

Polymerization of 2-Oxazolines. II. Kinetics of the Cationic Polymerization of 2-Phenyl-2-oxazoline Initiated by Oxazolinium Perchlorate in N, N-Dimethylacetamide Solution

Abstract The solution polymerization of 2-phenyl-2-oxazoline in N, N-dimethylacetamide media was carried out at 120-150°C with the use of the oxazolinium salt of monomer and perchloric acid as an initiator. A marked acceleration in rate was observed in the early stage of polymerization. After the period of acceleration the polymerization rate and the moles of polymer chains were shown to remain constant, whereas the number-average degree of polymerization increased almost proportionally with an increase in the degree of conversion. The kinetic discussion, divided into two stages, gave the following results: an early stage of polymerization with slow initiation where the moles of the active propagating species increased, and a later stage with a stationary state where the moles of the active propagating species remained constant and the growth of polymer chains proceeded. The kinetics was reformulated as a function of the differential monomer concentration. The simulation of the kinetics with the use of th...

Polymerization of 2-Oxazolines. I. Cationic Polymerization of 2-Phenyl-2-oxazoline Initiated by Various Oxazolinium Salts of Monomer with Brbnsted Acids

Abstract Various kinds of the complexes of 2-phenyl-2-oxazoline with various Bronsted acids were prepared. From the elementary analysis and spectroscopic analysis of the complex, it was identified to be an equimolar oxazolinium salt. The monomer could be polymerized with the oxazolinium salt to give N-benzoyl-polyethylenimine. The polymer yield in bulk polymerization was linearly proportional to the reaction time, and the number-average degree of polymerization of the polymer obtained at the complete conversion was proportional to the initial molar ratio of the monomer to the complex. The catalytic activities of the oxazolinium salts increased with a decrease in the pKavalue of Bronsted acid in water. The results of the infrared spectroscopy and nuclear magnetic resonance spectroscopy of the oxazolinium salt at room temperature and elevated temperature indicated that the change of the double bond character of the imino and ether linkages is brought about by the complexation. On the basis of these results,...