摘要:

The photopolymerization of methyl methacrylate (MMA) in visible light was studied at 40°C using the acridone-bromine (acridone-Br2) combination as the photoinitiator. The polymerization was found to proceed via a free radical mechanism, and the radical generation process was considered to follow an initial complexation reaction between monomer and each initiator component (acridone and Br2), followed by further interaction between these two initiator-monomer complexes. Kinetic data indicated a lower-order dependence of R on initiator concentrations (initiator exponent < 0.5). Initiator-dependent chain termination was signifi-cant along with the usual bimolecular mode of chain termination. The monomer exponent varied from about 1.00 to 2.00, depending on the nature of solvents used. The nonidealities in this system were also analyzed.

ISSN:0022-233X    

DOI:10.1080/00222338408062419

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Methyl methacrylate (MMA), methyl acrylate (MA), and ethyl acrylate (EA) have been graft copolymerized onto wool fiber in aqueous medium using the chromium acetylacetonate-tertiary-butyl hydroperoxide (Cr(acac)3-TBHP) system as initiator. The percentage of grafting has been determined as a function of the concentrations of monomer, chelate, and TBHP, and the time and temperature under optimum conditions. MMA produced a maximum grafting of 119.8%, MA produced a maximum grafting of 56%, while EA afforded maximum grafting to the extent of 41.9%. Different vinyl monomers were found to follow the following reactivity order toward grafting onto wool fiber in the presence of the Cr(acac)3-TBHP system: MMA > MA > EA.

ISSN:0022-233X    

DOI:10.1080/00222338408062420

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The copolymerization of styrene and 4-methoxystyrene by constant potential electrolysis in 1,2-dichloroethane was achieved at three different potentials. Amounts of the monomers in the resulting copolymers were found to be potential-dependent. The effect of polymerization potential on copolymer composition was also found to be related to anodic peak potentials (Ep,a) of the monomers.

ISSN:0022-233X    

DOI:10.1080/00222338408062421

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The kinetics of polymerization of ethyl methacrylate initiated by manganese (III) in sulfuric acid have been investigated. The overall rates of polymerization (Rp), disappearance of manganic ion (-Rm), and degree of polymerization (Xn) were measured with variation in [monomer], [Mn3+], [H+], μ, and temperature. Various rate parameters and thermodynamic parameters were evaluated and are discussed.

ISSN:0022-233X    

DOI:10.1080/00222338408062422

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The polymerization of 2,4,6-trimethylstyrene (vinyl mesitylene) has been investigated, and quasiliving polymerizations have been achieved under a comfortably wide experimental condition range. This monomer is particularly suitable for quasiliving polymerizations because the methyl groups in the 2 and 6 positions prevent chain transfer to monomer involving indanyl-skeleton formation. Quasiliving polymerizations readily occurred by the use of cumyl chloride/TiCl4or BCl3initiating systems in variousn-C6H14/CH2Cl2mixtures at -50°C. Because indanyl-skeleton formation is impossible, the rate of monomer addition can be safely decreased to very low values without risking chain transfer by intramolecular alkylation.

ISSN:0022-233X    

DOI:10.1080/00222338408062423

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The synthesis of poly(styrene-b-isobutylenes) by the sequential addition of styrene and isobutylene has been accomplished. First a stream of styrene was added to a cumyl chloride/TiCl4in nhexane/methylene chloride charge at -50°C under quasiliving conditions. After the polystyrene block has reached a desirable sequence-length (molecular weight), gaseous isobutylene was continuously introduced to the quasiliving polystyrene carbocation until the polyisobutylene block also reached a desirable molecular weight. TheMnversus monomer input plot was uninterrupted and linear over both monomer introduction phases, indicating quasi-living conditions over the entire regime of block copolymer synthesis. The block copolymers have been characterized by selective solvent extraction and GPC, and their compositions determined by1H-NMR spectroscopy.

ISSN:0022-233X    

DOI:10.1080/00222338408062424

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Forced ideal carbocationic copolymerization of isobutylene and isoprene has been achieved by continuous addition of monomer mixtures of different compositions to cumyl chloride/TiCl4charges at -50°C. The overall rate of copolymerization could be kept equal to that of addition rate with up to 10 mol% isoprene in the mixed monomer feed. In this monomer concentration range the composition of the copolymer was identical to that of the feeds. At higher diene concentrations in the feed, chain transfer to monomer and other side reactions (intramolecular cyclization, gel formation) could not be completely avoided. The number-average molecular weight of the copolymers increased almost linearly with the amount of consumed monomers at 10 mol% isoprene concentrations in the feed (i.e., in the quasiliving range). According to1H-NMR and13C-NMR spectroscopy, the products are random copolymers.

ISSN:0022-233X    

DOI:10.1080/00222338408062425

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Forced ideal carbocationic terpolymerization of styrene/α-methylstyrene/isobutylene systems has been achieved by continuous addition of mixed monomer feeds to 2-chloro-2,4,4-trimethylpentane/TiCl4initiator/coinitiator charges dissolved in n-hexane/methylene chloride solvent mixtures. The compositions of terpolymers were uniform and identical to those of the feeds in the concentration ranges studied. The number-average molecular weights increased monotonously with the amounts of monomers consumed; however, pronounced chain transfer to monomer was evident. The microstructure of the products was investigated13C-NMR spectroscopy. According to dual detector GPC,13C-NMR and DSC data true terpolymers have formed.

ISSN:0022-233X    

DOI:10.1080/00222338408062426

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

α-Methylstyrene/isobutene, α-methylstyrene/diisobutene, cyclopentadiene/isobutene, and cyclopentadiene/α-methylstyrene were copolymerized by cationic polymerization techniques. Several properties of the copolymers such as softening ranges and oxidation stability depend on their constitutional composition, and were controlled by variation of the conditions of their synthesis.

ISSN:0022-233X    

DOI:10.1080/00222338408062427

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The acid-catalyzed reaction of o-cresol with formaldehyde follows second-order kinetics. The reaction was carried out at 65, 70, 75, and 80°C and at pH values of 1.30, 1.80, 2.00, 2.50, and 3.00, using hydrochloric acid as a catalyst. The rate was found to increase with decreasing pH. The overall rate constant (k) has been resolved into stepwise rate constants (k1and k2) for the formation of monomethylol and methylene derivatives. Values of Arrhenius parameters and of the entropy of activation for the overall reaction were also calculated. A mechanism consistent with our kinetic data is given.

ISSN:0022-233X    

DOI:10.1080/00222338408062428

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor