Showing papers on "Ionic polymerization published in 1989"

A study of the mechanism of aniline polymerization

Abstract: A chemical polymerization of aniline is quenched at specific reaction time intervals and the amounts of unreacted aniline and formed p-aminodiphenylamine is observed. Oxidation of aniline to generate p-aminodiphenylamine is observed. Oxidation of aniline to generate p-aminodiphenylamine is the slow step in the plymerization. Furthermore, the tetramer of aniline is used as starting material for polymerization under the same conditions as polymerization of aniline. Direct coupling of two tetramers leading to polymer is not observed. A mechanism of polymerization of aniline is proposed

Autoacceleration and kinetics of electrochemical polymerization of aniline

Abstract: A convenient method is presented for determining the rate of polyaniline formation in the electrochemical polymerization of aniline in aqueous HCl solution utilizing cyclic potential sweep techniques. In this method, the mass of polyaniline deposited on a platinum electrode is correlated with the polymer anodic peak current that is recorded during the polymerization. The rates of polymer deposition were therefore monitored by the increases in the anodic peak current at various concentrations of aniline. A kinetic expression obtained for the polymerization accounts well for the autoacceleration process in the electrochemical polymerization of aniline and supports the mechanism of polymerization in which monomeric aniline is incorporated in the growing polymer.

Living and highly syndiotactic polymerization of methyl methacrylate and other methacrylates by tert‐butyllithiumtrialkylaluminium in toluene

Abstract: Highly syndiotactic poly(methyl methacrylate)s (PMMAs) with narrow molecular weight distribution (MWD) were prepared by polymerization of MMA in toluene at low temperatures, initiated with tert-butyllithium (t-C4H9Li) combined with trialkylaluminium compounds such as triethyl-, tributyl-, and trioctylaluminium (mole ratio Al/Li ≥ 3). Polymerization was initiated by the t-C4H9 anion and proceeded in a living manner. Several alkyl methacrylates were also polymerized with t-C4H9Li-(n-C4H9)3Al to give highly syndiotactic polymethacrylates with narrow MWD. Highly syndiotactic block and random copolymers of MMA and ethyl methacrylate were obtained by this initiator.

A novel photo-sensitized polymerization of pyrrole

Abstract: A novel photo-sensitized polymerization of pyrrole by the use of tris(2,2′-bipyridine)ruthenium(II) as a photo-sensitizer has been investigated in aqueous solution and in polymer matrix for the fabrication of fine conducting polymer patterns.

Biocatalytic synthesis of polymers. II. Preparation of [AA–BB]x polyesters by porcine pancreatic lipase catalyzed transesterification in anhydrous, low polarity organic solvents

Abstract: Enzyme-catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures. (1) Such polymerizations may allow the polymer to retain functionality that would be destroyed under normal polymerization conditions. (2) The selectivity provided by enzyme catalysts may permit polymers, including optically active polymers, to be prepared that are either not accessible or accessible only with difficulty by other methods. (3) The characteristics of the enzyme and the mild polymerization conditions may permit formation of polymers having highly regular sizes and backbone structures. This report describes the first successful use of an enzyme-catalyzed polycondensation to prepare a chiral (AA–BB)x polyesters of more than a few repeat units. Polymerization of bis(2,2,2-trichloroethyl) alkanedioates (BB) with diols (AA) using the enzyme porcine pancreatic lipase (PPL) as a catalyst is detailed. The polycondensations were carried out at ambient temperature in anhydrous, low polarity organic solvents such as ether, THF, and methylene chloride. End group analysis by NMR provided Mn values of 1300–8200 daltons while GPC provided Mw values of 2800–14900 daltons for the polymers. Based on proton NMR spectra obtained during the polymerization, relatively rapid formation of an AA–BB “dimer” and an AA–BB–AA “trimer,” slower formation of a BB–AA–BB “trimer,” and subsequent condensation of these to give higher polymers are suggested to be components of the polymerization mechanism.

Direct synthesis by living cationic polymerization of nitrogen-containing polymers

Abstract: A method is provided for the direct synthesis by living cationic polymerization of novel polymeric materials functionalized with desirable nitrogen-containing functional groups such as terminal azido, cyano, carbonylamino, cyanato, thiocyanato or thiocarbonylamino groups. Polymerization and functionalization occur in a substantially simultaneous manner. All necessary reactants for the functionalization are present when polymerization is initiated. The nitrogen-containing functional group is provided as a part of a molecule having a release moiety which is preferably resonance stabilized or a tertiary alkyl type and which acts to aid the nitrogen-containing species in functioning as a leaving group.

Polymerization of monomers containing functional silyl groups. 6. Anionic polymerization of 2-(trialkoxysilyl)-1,3-butadiene

Abstract: Polymerisation des derives trimethoxysilyl et triisopropoxysilyl. Copolymerisation sequencee avec l'isoprene

Kinetics of photopolymerization of acrylamide in AOT reverse micelles

Abstract: The kinetics of the photoinitiated polymerization of acrylamide in toluene/AOT/water inverse microemulsions have been examined for systems initiated by AIBN or a dye: triethanolamine redox reaction. The rates of polymerization were determined by dilatometry, the data being corrected for the effect of reaction exotermicity. For both the oil-soluble and the water-soluble initiating systems, the rate of polymerization was found to be proportional to the first power of the incident light intensity. For AIBN-initiated systems, the rate of polymerization was also found to be proportional to the first power of the initiator concentration. The molecular weights of the polymers produced were independent of the rates of polymerization and initiation. These results suggest that exclusively monoradical termination, involving a degradative chain transfer, is occurring in these systems

Heteropolyacids — new efficient initiators of cationic polymerization

Abstract: We have found, that heteropolyacids (HPA) are efficient initiators of cationic polymerizations, including polymerizations of cyclic ethers and acetals, providing high-molecular-weight polymers. In several systems (e. g. THF, 1,3-dioxolane) the degree of polymerization is given by the ratio of concentrations of monomer and initiator, as for the living system. In the polymerization of cyclic formaldehyde trimer: 1,3,5-trioxane, the comparable polymerization rates may be obtained with ≈ 25 times less an initiator consumption on weight basis (≈ 103 times less on molar basis) than for typical initiators like BF3 · OR2.

Group Transfer Polymerization process employing supported initiators

Abstract: Group Transfer Polymerization (GTP) process for preparing a "living" polymer, the process comprising contacting under polymerizing conditions in a polymerization medium, at least one acrylic or maleimide monomer with an initiator which is a tetracoordinate organosilicon, organotin or organogermanium compound having at least one GTP initiating site and a catalyst which is or is a source of an anion selected from the group consisting of bifluoride, fluoride, cyanide, azide or a selected oxyanion, or a selected Lewis acid or Lewis base, the process further characterized in that the initiator or the anion or Lewis acid catalyst is chemically attached (grafted) to a solid support that is insoluble in the polymerization medium.

Water effects on the zwitterionic polymerization of cyanoacrylates

Abstract: This paper presents a number of qualitative and semi-quantitative observations on the effect of small concentrations of water on the polymerizations of butyl cyanoacrylates by tertiary amines in THF. It reports also that, in the absence of other bases, large concentrations (approx. 1 mol/l) of water can cause the polymerization of ethyl cyanoacrylate, in THF, even in presence of normally inhibiting amounts (10−5 mol/l) of p-toluenesulfonic acid. A formal kinetic scheme of a stationary-state polymerization, initiated by hydroxyl anions, is presented and discussed.

Active species in the anionic ring‐opening polymerization of cyclic carbonates

Abstract: Anionic ring opening polymerization of 5,5-dimethyl-1,3-dioxan-2-one (2,2-dimethyltrimethylene carbonate) (1) initiated by sec-butyllithium, sodium methoxide or potassium dihydronaphthylide was found to proceed via alcoholate anions. This finding is based on 31P NMR spectroscopic studies of the polymer end groups, which result from the reaction of the living polymer with diphenyl chlorophosphate.

Curable resin composition

Abstract: PURPOSE:To obtain the title composition excellent in solvent resistance and useful for sealing electronic components etc., by adding talc to a curable polybutadiene resin composition. CONSTITUTION:A curable polybutadiene resin composition (A) is obtained by mixing 100pts.wt. curable polybutadiene resin (a) having an MW of 500-5,000 and polymerizable functional groups which can undergo radical polymerization, ionic polymerization, etc. by heat or light with, optionally, 230pts. or below reactive compound (b) which is other than component (a) and a reactive monomer or oligomer having polymerizable terminal groups which can undergo radical polymerization, ionic polymerization, etc. with component (a) by heat or light (e.g., isobornyl acrylate), a curing agent, a polymerization initiator (e.g., alpha-hydroxyisobutyrophenone), etc. 20-200pts.wt. talc of a mean particle diameter of 0.5-30mum is added as a filter to 100pts.wt. component A.

Semisuspension polymerization processes

Abstract: A process for the preparation of polymeric particles which comprises mixing at least one monomer with a polymerization initiator, a crosslinking component and a chain transfer component; effecting bulk polymerization until partial polymerization results; dispersing the aforementioned partially polymerized monomer product in water containing a stabilizing component to obtain a suspension of particles in water and polymerizing the resulting suspension.

Anionic polymerization of p-xylenesulfonium salts

Abstract: Recent investigations indicate that the base-promoted polymerization reaction of a 1,4-phenylenebis(methylene)disulfonium salt in a aqueous solution involves the formation of a highly reactive p-xylylene intermediate, which polymerizes through formation of a sulfur ylide active center by an anionic mechanism. If so, it would be expected that the concentration of this intermediate should be very important in controlling both polymer yield and molecular weight, so it should be possible to increase the concentration of that intermediate by removing the organic sulfide released in the initial elimination reaction by extraction into an organic solvent. This expected effect was verified by the very large increases in both reaction conversion and polymer intrinsic viscosity obtained when the polymerization reaction was carried out in the presence of pentane. The effect was greater with the cyclic sulfide monomer than with the dimethyl sulfide monomer, presumably because of the higher water solubility of the latter.

Heat-latent, cationic polymerization initiator and resin compositions containing the same

Abstract: Benzyl pyridinium or ammonium salts of a non-nucleophilic anion are useful as a cationic polymerization initiator having a heat latency. A variety of resinous compositions containing this initiator is also disclosed.

Process for the suspension polymerization of 4-acetoxystyrene and hydrolysis to 4-hydroxystyrene polymers

Abstract: Poly(4-hydroxystyrene) is prepared by aqueous suspension polymerization of 4-acetoxystyrene monomer followed by hydrolysis with ammonium hydroxide.

Functionalized polymers prepared by anionic polymerization

Abstract: Novel polymers prepared by anionic polymerization techniques containing phenol, silyl ether, aminophenyl functionality or carboxylic acid or ester.

UV‐induced polymerization of maleimides in solution

Abstract: Maleimide and N-ethylmaleimide were irradiated in various solvents with a high pressure mercury lamp at 30°C. The polymerization of maleimides is promoted in the presence of hydrogen donating solvents such as tetrahydrofuran, 1,4-dioxane, ethanol and basic solvents such as dimethylformamide, dimethyl acetamide, pyridine. ESR spectra suggest that a radical mechanism is responsible for the polymerization in the former solvents and an anionic mechanism in the latter solvents.