摘要:

The determination of the individual conversion rate of each monomer in a radical copolymerization allows the absolute concentration of each kind of growing radical to be derived, provided the reactivity ratios and the homopropagation rate constants are known. The procedure is applied to the following binary copolymerizations: styrene-methyl methacrylate, vinyl chloride-vinyl acetate, acrylonitrile-vinyl acetate, and acrylonitrile-vinyl chloride. In the two latter cases, the anomalous behavior, probably caused by the internal cyclization reaction involving CN bonds, is well evidenced.

ISSN:0022-233X    

DOI:10.1080/00222337508065870

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The intramolecular cyclization reaction involving the polymerization of cyano groups reported in a previous paper for the system acrylonitrile-vinyl chloride is studied for other comonomers with acrylonitrile including vinyl acetate, vinylidene chloride, butadiene, styrene, methyl acrylate, and methyl methacrylate. It is shown that the extent of the reaction is governed by the reactivity of the comonomer-unit ended radical, but the cyclization reaction cannot explain all the kinetic deviations observed.

ISSN:0022-233X    

DOI:10.1080/00222337508065871

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

2,3-Dihydropyran (DHP) and ethyl vinyl ether (EVE) were co-polymerized with maleic anhydride (MA) with benzoyl peroxide at 60°C, and 1:1 alternating copolymers were obtained. The rates were maximum at 1:1 monomer composition. Spontaneous copolymerization and solvent effect on the rate were observed in the copolymerization of DHP with MA, in which initial rates were slower in more polar solvents. Participation of charge transfer complex was considered. EVE copolymerized rapidly with MA, reaching the theoretical limiting conversion of 1:1 alternating copolymerization. Although DHP-MA comonomer pair and EVE-MA comonomer pair formed similar 1:1 charge transfer complexes, DHP copolymerized slowly with MA to produce a low molecular weight copolymer, and the limiting conversion was much lower than the theoretical one. To explain these, degradative chain transfer to DHP monomer is proposed as the initial rate of DHP-MA copolymerization is proportional to the initiator concentration to the power 1.1. Q and e values of DHP were calculated to be 0.013 and -0.93, respectively, from the monomer reactivity ratios of copolymerization of DHP with acrylonitrile [r1(DHP)=0.003 ± 0.006 and r2(AN)=3.6 ± 0.3].

ISSN:0022-233X    

DOI:10.1080/00222337508065872

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A more precise determination of Q and e values for vinyl monomers can be attained through the use of a linear least squares technique.

ISSN:0022-233X    

DOI:10.1080/00222337508065873

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The copolymerization of 1-hexene and propylene in the presence of a Ziegler-Natta type catalyst (AlEt2Cl-TiCl3) has been studied. The gas chromatography method used for the kinetic study allowed determination of reactivity ratios of both monomers from the classical copolymerization equation which was found to be followed. The copolymers composition has been confirmed by NMR analyses and the theoretical sequence distribution computerized, thus giving an a priori description of the macromolecules useful for further studies of the properties of these copolymers. The drift in copolymer composition and thus in the distribution of monomer units occurring with conversion has been found important, and to avoid this heterogeneity in composition, some copolymers were prepared at constant monomer feed composition using a very simple manometric device.

ISSN:0022-233X    

DOI:10.1080/00222337508065874

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The cathode-initiated copolymerization of styrene and methyl methacrylate (MMA) in dimethylformamide yielded a copolymer which was found to be a mixture of the high and low molecular weight copolymers. The composition of the former, rich in MMA, was similar to that of a typical anionic copolymer. The latter, of anomalously high styrene content, was assumed to be produced on the cathodic surface via an anionic process, where styrene monomer was preferentially adsorbed. This was confirmed by capacitance measurement of the electrode and sequence analysis of the copolymer.

ISSN:0022-233X    

DOI:10.1080/00222337508065875

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Syntheses of cyclic oligomer and polymer were attempted with magnesiacyclohexane as the initiator in HMPA. The oligomer of α-methylstyrene, initiated by magnesiacyclohexane, was treated with dimethyldichlorosilane in order to obtain a stable cyclic oligomer. The products were investigated by GPC, IR, NMR, and elemental analysis. It was found that magnesia-cyclohexane could not be activated enough by HMPA, and that the magnesium-carbon bond was not stable in HMPA, and that the chain transfer reaction might occur repeatedly during the polymerization. Consequently, the yield of cyclic oligomer was so low that cyclic compounds could not be discriminated from the linear oligomer.

ISSN:0022-233X    

DOI:10.1080/00222337508065876

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

trans-Stilbene, 1, 1-diphenylethylene, and α-methylstyrene were allowed to react with dibenzylmagnesium to form their oligomers in hexamethylphosphortriamide (HMPA). One and two molecules of stilbene and 1, 1-diphenylethylene were incorporated into the magnesium carbon bond, and the carbanions obtained in HMPA were stable in analogy with the anionic living polymer having alkali cation as the gegenion in eithers. Intense coloration was observed during the reaction between α-methylstyrene and dibenzylmagnesium as well as in the case of stilbene and 1, 1-diphenylethylene. The low molecular weight products which were formed after a long time in the reaction between α-methylstyrene and dibenzylmagnesium were found to have no magnesium-carbon bond. It was considered that the cleavage of the propagating chain occurred gradually after the rapid propagation had proceeded to consume the monomer.

ISSN:0022-233X    

DOI:10.1080/00222337508065877

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The barium salt of the dimeric dianion of 1,1-diphenylethylene (Ba-DPhE) initiates polymerization and copolymerization of monomers capable of anionic polymerization (butadiene, isoprene, styrene) in ethereal and hydrocarbon solvents. Ba-DPhE is more stereospecific in butadiene polymerization (up to 70% of cis-1, 4-units in hydrocarbon medium) than initiators based on other metals of Groups I and II. The relative reactivity of monomers in copolymerization processes in THF decreases in an order typical for anionic polymerization: styrene > butadiene > isoprene. The most interesting feature of organobarium initiators is their ability to form random butadiene-styrene copolymers with high cis-1,4-butadiene unit content when copolymerization proceeds in a hydrocarbon medium.

ISSN:0022-233X    

DOI:10.1080/00222337508065878

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The cationic and anionic polymerization of 1,3,5-tri(1,3,5,7-tetra)methyl-1,3,5-tri (1,3,5,7-tetra)-10-carbomethoxydecylcyclotri (tetra) siloxane, catalyzed by sulfuric acid and alkali metal naphthalenes, respectively, was studied. With sulfuric acid the polymer yield increased with increasing catalyst concentration, while the molecular weights decreased. With potassium naphthalene the polymerization reaction was first order to monomer, and the molecular weights increased linearly with increasing the percent conversion in accordance with a “living” polymerization. In both cases the polymerization was an equilibrium reaction and the conversion was about 85%. Only low molecular weight polymers were obtained due to steric effects of the bulky long-chain substituents.

ISSN:0022-233X    

DOI:10.1080/00222337508065879

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor