Showing papers on "Ionic polymerization published in 1994"

Cationic zirconocene olefin polymerization catalysts based on the organo-Lewis acid tris(pentafluorophenyl)borane. A synthetic, structural, solution dynamic, and polymerization catalytic study

Abstract: We have isolated and systematically studied the structural and chemical properties of a series of electron-deficient cationic zircocene alkyl and hydrido complexes with high olefin polymerization activities. The single crystal X-ray diffraction-derived solid state and NMR-derived solution structures of these complexes correlate well with each other and afford considerable insight into the nature of these species. Through the use of the novel organoborane, we have, for the first time, unambiguously demonstrated the role of the key metallocene-cocatalyst interaction that has been proposed for MAO, alkyl aluminum halides, and dehydroxylated alumina. 56 refs., 10 figs., 19 tabs.

A Visible Light Initiating System for Free Radical Promoted Cationic Polymerization

Abstract: : A new visible light free radical promoted cation in chain polymerization is reported. The system is based on electron transfer photoreduction of xanthene dye triplets by aromatic amines possessing a hydrogen on the alpha carbon atom to the nitrogen. Subsequent deprotonation of the amine radical cation followed by onium salt oxidation leads to formation of an (alpha- amino carbenium ion and the latter initiates polymerization. Critical to the success of the system are the basicity of the amine, the oxidation potential of the onium salt, and the presence or absence of nucleophilic centers in the monomer to be polymerized. The scope and details of the system are discussed in the publication. Visible light photoinitiating system, Free radical promoted cationic polymerization.

Reactive surfactants in emulsion polymerization

Abstract: Covalent binding of the surfactants to the polymers obtained from emulsion polymerization is expected to improve some properties of the resulting latexes and also of the films formed from these latexes. This is possible if the surfactants include functional groups capable of interacting with the radical polymerization process. These functional groups may be a polymerizable function so that the surfactant is a comonomer, named in this review SURFMER. Alternatively it may be an initiator (INISURF) or a transfer agent (TRANSURF). The paper is a literature review of the state of the art and illustrates the increasing interest in this field. The main trends and some prospects are discussed in the conclusions.

Polymerization of .epsilon.-Caprolactone by Divalent Samarium Complexes

Abstract: It is shown that a variety of samarium (II) complexes generate ring-opening polymerization systems with e-caprolactone in reactions which initially involve oxidation of the metal. The (C 5 Me 5 ) 2 Sm(THF) x is found to be an active polymerization system which maintains activity after all the initial batch of monomer is consumed. The molecular weight, polydispersity and tendency of the polymer to be degraded by catalyst appear to be sensitive to the nature of the ligands attached to the metal

Catalyst mediated method of interfacial polymerization on a microporous support, and polymers, fibers, films and membranes made by such method

Abstract: The invention pertains to the polymerization of molecules having electrophilic and nucleophilic substituents on the same or different molecules, such polymerization mediated by aminopyridine catalysts which are substantially regenerated during polymerization. The invention also pertains to polymer products of such polymerization, to permselective membranes containing such polymers, and to processes and apparatus for separating fluids.

Dendrimers as macroinitiators for anionic ring-opening polymerization. Polymerization of ε-caprolactone

Abstract: Experimental results show that by using dendrimers of high generation, the anionic polymerization of e-caprolactone can be put under kinetic control. The other advantage of this initiator is the possibility to form hybrid linear-globular AB block copolymers containing aliphatic polyester as the linear block that are not readily accessible via the end-capping techniques applied earlier

Process for producing ethylene/alpha-olefin copolymer

Abstract: A process for producing an ethylene/α-olefin copolymer is provided in which ethylene is copolymerized with an α-olefin having three or more carbons by use of an olefin polymerization catalyst at a polymerization temperature of not lower than 120°C. The olefin polymerization catalyst comprises, as constitutional components, a) a metallocene compound, b) an ionizing ionic compound, and c) an organoaluminum compound, the ionizing ionic compound (b) being a compound which is capable of changing the metallocene compound (a) into a cationic form and does not further react with the cationic form of the metallocene compound.

MCM-41 and related materials as media for controlled polymerization processes

Abstract: The synthesis of mesoporous MCM-41 type materials based on transition metal oxides and the polymerization of several monomers within MCM-41 is presented with the aim to specifically investigate the effects of the interface and confinement on host-guest interactions. In addition to standard MCM-41, material based on transition metal oxides is obtained although template removal has been unsuccessful for such compounds until now. In situ polymerization of styrene, methyl methacrylate and vinyl acetate is possible within the mesopore system. The properties of some of the encapsulated polymers differ markedly with those obtained in the bulk.

Introduction to synthetic polymers

Abstract: Part 1 Introduction: definitions and nomenclature some historical perspectives the synthetic polymers industry general features of polymerization processes. Part 2 Average molecular masses and polydispersity: definitions and illustrations experimental determinations liquid-phase osmometry. Part 3 Microscopic features of bulk polymers: general aspects microcrystallinity and drawing amorphous polymers glass transition temperatures melting temperatures measurement of temperatures concluding remarks. Part 4 Major techniques for analysis and structure determination: infrared absorption and spectroscopy nuclear magnetic resonance (NMR) spectroscopy X-ray scattering. Part 5 Step-growth polymerizations: general features linear step-growth systems with two monomers some important linear step-growth polymers network polymers. Part 6 Addition polymerization via free radicals: general features physical forms of synthesis media initiation processes the growth and termination of chains the control of chain growth generation of side-chains. Part 7 Addition polymerization via ionic and co-ordination mechanisms: general features of ionic polymerization cationic polymerization anionic polymerization co-ordination polymerization. Part 8 Properties of common polymers in bulk: crystallinity variation of glass transition temperature drawn thermoplastics elastomers polymer degradation and recycling. Part 9 Some speciality polymers: graft co-polymers and comb co-polymers liquid crystal polymers high-temperature polymers polycarbonate ionomers and polymeric solid electrolytes. Part 10 Looking to the future: the synthesis of block co-polymers side-chain liquid crystals synthetic metals polymers with active surfaces concluding remarks. Appendix: Systematic names of common monomers.

Protection and polymerization of functional monomers. 21. Anionic living polymerization of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate

Abstract: The two hydroxy groups of 2,3-dihydroxypropyl methacrylate (1) were protected in the dioxolane form, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate (2). The anionic polymerization of 2 in THF at -78°C with various initiators proceeded to give living poly(2) quantitatively in each case. Complete hydrolysis of the acetal protective group of poly(2) produced water-soluble poly(1). Addition of 2 to poly(styryl)lithium capped with 1,1-diphenylethylene in the presence of LiCl gave the block copolymers

Anionic ring-opening polymerization of macrocyclic esters

Abstract: The ring opening polymerization of macrocyclic esters has been investigated in comparison with caprolactone. It is concluded that macrocyclic esters considered as low-polymerizable monomers easily undergo ring-opening polymerization by common anionic initiators. The propagation rates of macrocyclic esters were found to increase with increasing the s-character of the methylene carbon

Highly reactive yttrium alkoxide as new initiator for the polymerization of β-butyrolactone

Abstract: It is shown that 2-methoxyethoxide is a very efficient initiator for the polymerization of β-butyrolactone and exhibits outstanding reactivity at room temperature. Moreover, the polymerization shows some living character

Kinetic and structural EPR studies of radical polymerization. Monomer, dimer, trimer and mid-chain radicals formed via the initiation of polymerization of acrylic acid and related compounds with electrophilic radicals (˙OH, SO4–˙ and Cl2–˙)

Abstract: A continuous-flow system has been used in conjunction with EPR spectroscopy to study the initial stages of polymerization of acrylic acid and methacrylic acid in aqueous solution at pH 2 and 9, brought about with inorganic radicals (e.g.˙OH) formed from metal–peroxide redox couples. Structural characteristics of monomer adduct-radicals, as well as corresponding dimers and trimers, are reported, together with evidence for rapid intramolecular hydrogen-abstraction of the appropriate tetramer to give a mid-chain radical. Computer-based simulation of steady-state concentrations leads to estimates of rate constants for initiation, propagation and termination reactions under these conditions.

Synthesis of Sequence-Ordered Polysilane by Anionic Ring-Opening Polymerization of Phenylnonamethylcyclopentasilane

Abstract: Sequence-ordered polysilane ([Si(Me) 2 ] 4 Si(Me)(Ph)) n has been obtained by anionic ring opening polymerization of phenylnonamethylcyclopentasilane

Polyoxazoline auf fettchemischer Basis

Abstract: A new, economic techniques was developed for the production of 2-alkyl-2-oxazolines with saturated, unsaturated or OH-functionalized alkylrests. In the process the fatty acids are changed into polymerizable monomers. The cationic polymerization of fattyalkyl-2-oxazolines was investigated in unpolar solvents and in bulk. It reacts in a living mechanism. The polymerization is remarkable inert against impurities like water or ethanolamide. A reaction enthalpy of ΔH= 85,9 kJ/mol was found for the bulk polymerization of 2-pentadecyl-2-oxazoline

Ultrasonic polymerization process

Abstract: Polymerization of ethylenically unsaturated monomers such as methyl methacrylate can be initiated in solutions containing monomer and a special non-polymeric initiator with intense ultrasound. The number average molecular weight of the poly(methyl methacrylate) that forms is about 300,000 gmol-1 as compared with polystyrene standards. The conversion of the polymerization is about 50% for poly(methyl methacrylate). Variations of the polymerization rate with time and the amount of the initiator are explained by a simple reaction mechanism.

Initiation via Haloboration in Living Cationic Polymerization. 1. The Polymerization of Isobutylene

Abstract: We have discovered that, using polar solvents in the presence of a proton trap, BCl 3 alone can initiate the polymerization of isobutylene. The polymerization rate increased in the order CH 3 Cl, CH 2 Cl 2 , 1,2-dichloroethane. Increasing the BCl 3 concentration increases the rate; however the molecular weights are similar at similar conversions. Change in temperature in the studied range -25 to -60°C had no effect on the polymerization rate or on the molecular weights. The products are low molecular weight asymmetric telechelic polymers carrying a BCl 2 - head group and a tertiary chloro end group. A new initiation mechanism via haloboration is proposed to explain the apparent livingness of the polymerization and the structure of the polymers

Homogenous, stabilized, reduced metal addition polymerization catalysts, process for preparation and method of use

Abstract: Complexes useful as addition polymerization catalysts, a process for their manufacture and addition polymerization processes wherein the complex comprises a Group 4 metal in the + 3 oxidation state, a delocalized n-bonding moiety, and at least one stabilizing ligand.

Anionic Polymerization of Acrylates. 8. Kinetics of the Anionic Polymerization of Butyl Acrylate Initiated with the Complex Initiator Lithium Ester Enolate/Lithium tert-Butoxide

Abstract: The kinetics of the anionic polymerization of butyl acrylate initiated with the system tert-butyl 2-lithioisobutyrate (Li-t-BIB)/lithium tert-butoxide (t-BuOLi) in the mixed solvent toluene/THF was studied at -70 to -40°C. At -60°C, the external reaction order is unity with respect to the concentrations of both the monomer and propagating species. Semilogarithmic conversion curves indicate a certain extent of self-temination at higher degrees of conversion. The termination reaction process formally as a first-order reaction with respect to active centers. Kinetic calculations show that while the rate constant of propagation is concentration-independent, the rate constant of termination increases with the initial concentration of the monomer

High Modulus and High Tg Thermally Stable Polymers from Di-p-ethynylbenzoyl Ester Monomers: Synthesis, Solid State Polymerization; Processing, and Thermal Properties

Abstract: Seven novel crystalline p-ethynylbenzoyl ester momoners (EBEs) have been synthesized and characterized. Five of the monomers polymerized without melting. Thermal polymerization in N 2 produced highly cross-linked resins with polymerization exotherms centered between 204 and 250°C. The monomers are liquid crystalline or crystalline during polymerization and yield polymers retaining some order. They polymerize to high conversion in spite of their rigid matrix, which was attributed to the fact that their ethynyl groups interdigitate to a certain degree

Living cationic polymerization of cyclohexyl vinyl ether

Abstract: The cationic polymerization of cyclohexyl vinyl ether (CHVE) initiated by α-halogeno ethers in the presence of a Lewis acid activator has been investigated first. In conditions leading to a living polymerization of alkyl vinyl ethers (ethyl, isobutyl, etc.), an extremely fast polymerization, accompanied by chain transfer reactions, is observed with CHVE. In fact, we have shown that the polymerization of this monomer may be directly initiated by the HI and HCl adducts of CHVE, in the absence of any electrophilic activator. However, even in these conditions, the polymerization cannot be controlled. A “living” polymerization of CHVE was finally obtained by addition of ammonium salts (NBu4X; X = Cl, Br, I) to the systems free of electrophilic activators. The added salts stabilize the α-halogeno ether chain ends and reduce the overall reactivity. Using this procedure, we have synthesized poly(CHVE)s with Mn's ranging from 6 · 103 to 4 · 104 g · mol−1 (in good agreement with the predicted values assuming the formation of one polymer chain per initiator molecule) and narrow molecular weight distributions (Mw/Mn < 1,2). Though most of poly(alkyl vinyl ether)s exhibit glass transition temperatures far below 0°C, the glass transition temperature of the poly(CHVE) is close to +50°C, indicating that this monomer can be used as a precursor to rigid poly(vinyl ether) blocks.