摘要:

A new type of copolymerization is presented which proceeds without any added catalyst. A monomer of nucleophilic reactivity (MN) is mixed with the second monomer having electrophilic reactivity (ME) to produce a zwitterion+MN—ME-(1), which is responsible for initiation as well as propagation. By the following scheme of reactions, alternating copolymer is formed.

ISSN:0022-233X    

DOI:10.1080/00222337508065887

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Ionic polymerization received prominence about 35 years ago when isobutylene was commercially polymerized by two processes which, with some modifications, are still used today [1]. One process uses aluminum chloride as the initiator and the other uses boron trifluoride; both cationic polymerization processes are carried out at low temperatures. A number of additional commercial processes based on cationic and anionic polymerization have since been developed. Cyclic ethers, most prominently tetrahydrofuran, are polymerized cationically to relatively low molecular weight hydroxyl terminated polyethers which have found important uses in polyurethanes. Trioxane is copolymerized with a small amount of ethylene oxide to form a useful copolymer of polyoxymethylene. Other products which are of interest are the polymers of caprolactone and epichlorohydrin and polymers of various epoxides, mainly those of glycidyl ethers which are most commonly known as epoxy resins. Anionic polymerization on a commercial scale has developed along the lines of styrene and isoprene polymers. Stereorubber, stereoregular 1,4-cis isoprenes, are based on lithium initiators and were introduced in the middle 1950s. Triblock polymers based on A-B-A block polymers of isobutylene with styrene as endblocks and prepared from living polymers have been known since the early 1960s.

ISSN:0022-233X    

DOI:10.1080/00222337508065888

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A number of examples of addition and polymerization reactions is presented with special emphasis on the chemical behaviors of activated monomers and/or activated nucleophilic reagents. Lithium alkoxyethanolate forms a complex with lithium alkyl. Spectroscopic studies showed this complex to possess agent-separated ion pairs. The nature of the complex is characterized by the enhanced reactivity of styrene in the copolymerization reaction with butadiene initiated by the complex. Magnesium alkyl can be sufficiently activated by magnesium alkoxyethanolate to polymerize styrene and diene. Aluminum alkyl and zinc alkyl are able to induce the anionic polymerization of vinyl ketones, but not of unsaturated esters or nitriles. Aluminum or zinc alkoxyethanolates fail to activate their corresponding metal alkyls. Bipyridyl, sparteine, triphenylphosphine, HMPT, and related Lewis bases, however, activate aluminum alkyl enough to react with carbon-carbon double bonds of the unsaturated esters and nitriles. Crotononitrile can be polymerized by the AIR3-HMPT system to form a colorless polymer, where possible side reactions between CN and AIR3are prevented by HMPT. Mutual activation through complex formation is confirmed by a model system of a vinyl ketone with organozinc compounds. AIR3-HMPT does not polymerize vinyl ketones because of a lack of complex formation. N-Carboxy-α-alanine anhydride (NCA) can be polymerized with zinc alkyl as initiator. The formation of activated NCA by proton abstraction from the NH group is shown to be the essential stage for polymerization. Zinc alkyl is also activated by conventional acid anhydrides. The propylene oxide ring can be cleaved with the ZnR2-phthalic anhydride system, which is the initiation step in the alternate copolymerization between propylene oxide and the acid anhydride. The propagation mechanism of the CO2-epoxide copolymerization is also discussed.

ISSN:0022-233X    

DOI:10.1080/00222337508065889

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The main conclusions in studies on polymerization catalysts and the nature of chain transfer in the polymerization of cyclic imino ethers were that there is extensive chain transfer in the 2-alkyl oxazolines to produce polymer with a reactive end. Toward the end of polymerization, these chain-transferred molecules repolymerize back on the active center producing a multibranched star polymer. A theory for the data was developed.

ISSN:0022-233X    

DOI:10.1080/00222337508065890

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Oxonium ion ring-opening polymerization is reviewed with emphasis on unsolved problems. New findings in cationic ECH polymerization and in cyclic oligomer formation are given. Participation of the Cl of ECH in the cationic center is suggested.

ISSN:0022-233X    

DOI:10.1080/00222337508065891

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Work carried out in the past few years aimed at elucidating the mechanism of initiation of vinyl polymerization when a donor and an acceptor molecule, one or both of which may be vinyl monomers, is summarized. The emphasis of our investigation has been on polymerizable ether donors and strong electron acceptors which do not undergo polymerization, or the acceptor vinylidene cyanide. Alkyl vinyl ethers were polymerized in the presence of tetracyanoquinodimethane (TCNQ) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in polar solvents. Observation of the ESR spectrum of the DDQ radical anion and the isolation of a 1:1 addition product of DDQ and alkyl vinyl ether when the two are mixed in a 1:1 ratio and quenched in alcohol support an initiation mechanism involving a coupling reaction of the donor monomer (radical cation) and the acceptor initiator (radical anion). The reaction of vinylidene cyanide (VC) with the vinyl ethers p-dioxene, dihydropyran, ethyl vinyl ether, isopropyl vinyl ether, and ketene diethylacetal in a variety of solvents at 25°C spontaneously afforded poly(vinylidene cyanide), the cycloaddition products 7,7-dicyano-2,5-dioxo-bicyclo[4.2.0] octane, 8,8-dicyano-2-oxo-bicyclo[4.2.0] octane, the 1,1-dicyano-2-alkoxycyclo-butanes, and 1,1-diethoxy-2,2,4,4-tetracyanohexane, respectively, and with the exception of p-dioxene, homopolymers of the vinyl ethers. In the presence of AIBN at 80°C, alternating copolymers were obtained in addition to the homopolymers and cycloaddition products, supporting the involvement of donor-acceptor complexes. The reaction of styrene with VC spontaneously formed an alternating copolymer in addition to the 1:2 head-to-head cycloaddition product, 1,1,3,3-tetracyano-4-phenylcyclohexane. Mixing VC with any one of the cyclic ethers tetrahydrofuran, oxetane, 2,2-dimethyloxirane, 2-chloromethyloxirane, and phenyloxirane resulted in the polymerization of both the VC and the cyclic ether to afford homopolymers of both. The cyclic ethers trioxane, 3,3-bis(chloromethyl)oxetane, and oxirane initiated the polymerization of VC, but did not undergo ring-opening polymerizations themselves. Other ethers such as 1,3-dioxolane, tetrahydropyran, and diethyl ether did not initiate the polymerization of VC. In these polymerizations, VC and the cyclic ethers polymerize via anionic and cationic propagation reactions, respectively.

ISSN:0022-233X    

DOI:10.1080/00222337508065892

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

High-energy phosphonium compounds, the N-phosphonium salts of pyridines, were prepared by the oxidation of phosphorous acid and its esters with mercuric salts or halogens in pyridines, or by a hydrolysis-dehydration reaction of diphenyl and triaryl phosphites or phosphonites. These salts are very reactive to nucleophiles, activating carboxyl, amino, or hydroxyl compounds via the corresponding N-phosphonium salts to yield carboxylic amides and esters in high yields on further aminolysis, alcoholysis, and acidolysis. These reactions, especially the hydrolysis-dehydration reactions with phosphites, were successfully extended to the direct polycondensation reaction of dicarboxylic acids with diamines, of free α-amino acids or dipeptides, and of carbon dioxide and disulfide with diamines under mild conditions, yielding linear polymers of high molecular weight (polyamides, polypeptides, polyureas, and polythioureas).

ISSN:0022-233X    

DOI:10.1080/00222337508065893

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Polymerizations of N-carboxy anhydrides of L-phenylalanine, γ-benzyl-L-glutamate, O-carbobenzoxy-L-tyrosine, L-leucine, and sarcosine, as initiated by primary, secondary, and tertiary amines in N2or CO2atmospheres and in the presence or absence of NaH, indicate that they proceed via carbamate salt intermediates. This conclusion is supported by radiotracer studies as well as by NMR studies of the initial products of NCA-amine reaction mixtures.

ISSN:0022-233X    

DOI:10.1080/00222337508065894

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Polymerization with many triphenylmethyl salts was conducted for α-methylstyrene, isobutyl vinyl ether, t-butyl vinyl ether, and spiro[2,4]hepta-4,6-diene (SHD). The variation of polymer structure (the isotactic unit content for the first three monomer systems and the amount of the 1,4-addition structure for SHD) showed fairly simple correlations with the counteranion size. The results can be interpreted in terms of the tightness of the propagating ion pair within the framework of a theory of the cationic propagation which had been proposed. When the counteranion radius was greater than 3.5 Å, the counteranion exerts a parallel influence on the tightness of the growing ion pair without regard to the monomer structure. However, in the case of smaller counterions, the tightness appears to be determined by the relative sizes of counteranion and monomer. The penta-coordinated counteranions gave rise to the polymer structure which would arise from tighter ion pairs than expected from their sizes alone. The polymer structure was also affected by the initiator concentration in these cases. These results are attributed to peculiar characteristics of penta-coordinated anions.

ISSN:0022-233X    

DOI:10.1080/00222337508065895

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Photoinduced ionic polymerizations of the monomers α-methylstyrene, cyclohexeneoxide, nitroethylene, and acrylonitrile were carried out in the presence of electron acceptor or donor molecules. These polymerizations are proved to be initiated by ions formed through the dissociation of the photoexcited electron donor-acceptor complex and to proceed by ionic mechanism.

ISSN:0022-233X    

DOI:10.1080/00222337508065896

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor