摘要:

Ethenylbenzene-terminated poly(2-acetoxyethyl methacrylate) macromonomer, 2-methyl-2-propenoate-terminated poly (2-acetoxyethyl methacrylate) macromonomer, and 2-methyl-2-propenoate-terminated poly (methyl methacrylate) macromonomer were synthesized. The number-average molecular weight of the macromonomers could be controlled by adjusting the feed composition. Comb-type polymers and graft copolymers were prepared by homopolymerization and copolymerization of macromonomer with comonomer. Unreacted macromonomer in the resulting polymers could be determined by calculating the areas of the macromonomer peaks on gel permeation chromatograms (GPC).

ISSN:0022-233X    

DOI:10.1080/00222338508056612

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Polymerization of α-aminoisobutyric acid NCA by alkaline salts of various basicity as well as amines has been investigated. The study was focused on the effect on the initial polymerization rate of additives such as N-acetylglycine NCA and some other less electrophilic additives (l-acetyl-2-pyrrolidone, 3-acetyl-2-oxazolidone, 1-acetyl-3-methylhydantoin) which are all models of the growing chain end produced by the NCA anion pathway. The acetyl endgroup was detected by 250 MHz1H-NMR in all the polymers of α-aminoisobutyric acid NCA obtained in the presence of l-acetyl-3-methylhydantoin and triethyl amine or sodium methoxide initiators, whereas the additives influenced variously the kinetics of polymerization according to the nature of the initiator used. The results were interpreted in the light of a multiple mechanism supposing the simultaneous presence of the initiator anion, its conjugate acid, and NCA anion for basic salt initiation. Thus, the observed effect has to be considered as the sum of an elementary acceleration due to NCA anion and of an elementary deceleration due to the initiator anion. Predominance of the pathways involving NCA anion could be shown this way. This conclusion could be extended to γ-benxyl-L-glutamate NCA which is a more reactive NCA. However, the deceleration observed with some additives led us to believe that a nonnegligible participation of initiator anion during initiation cannot be excluded.

ISSN:0022-233X    

DOI:10.1080/00222338508056613

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The kinetics of polymerization of methyl methacrylate (MMA) initiated by the potassium peroxodisulfate (K2S2O8)-malonic acid (MA) redox system catalyzed by Ag(I) was studied in aqueous solution at 35°C. The rate of polymerization (R) was proportional to [MMA]1.4, [K2S2O8]0.27, [MA]0.23, and [Ag+]0.5. The overall energy of activation was calculated to be 13.5 kcal·K−1·mol−1between 20 and 45°C.

ISSN:0022-233X    

DOI:10.1080/00222338508056614

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Free-radical polymerization of styrene initiated by α,α1-azobisiso-butyronitrile (AIBN) has been studied in the presence of a 1,3-dipolar compound (methylnitrile ylide, MNY) by a dilatometric technique. The MNY retards the reaction by decreasing the rate of propagation and increasing the energy of activation. Polar solvents have very little influence on the rate of polymerization, but non-polar solvents favor retardation. MNY has no influence on the average degree of polymerization, and the system attains a steady state.

ISSN:0022-233X    

DOI:10.1080/00222338508056615

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Cationic polymerizations of β-propriolactone (Prop), -caprolactone (Capr), and glycolide (Glyc) were initiated by various alkylsulfonates, such as methyl fluorosulfate, ethyl fluorosulfate, methyl trifluoromethanesulfonate (triflate), methyl methanesulfonate, methyl p-nitrobenzene sulfonate, γ-propane sultone, and δ-butane sultone. Systematic variation of reaction time and temperature revealed that only methyl fluorosulfate and methyl triflate can give high yields, yet the temperature must be kept in a narrow range (50 ± 10°C). Due to the living character of the cationic endgroups, high temperatures may cause rapid degradation of the initially formed polylactones. However, at appropriate temperatures, the living chain ends permit the synthesis of block copolyesters. The sequences of the two-block copolyesters built up of Prop and Glyc or Capr and Glyc units were characterized by means of13C-NMR spectra and compared to random copolylactones. The DSC curves of the two-block copolyesters display the expected two melting endotherms, whereas those of the random copolyesters do not.

ISSN:0022-233X    

DOI:10.1080/00222338508056616

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The conformations of minimum total energy of bi-, tri-, and poly-flavonoids, constituting the polymeric condensed tannins, are elucidated. Maps of minimum total energy and spacial conformations are shown and discussed. The maps show the different conformations of rotational isomers for the different interflavonoid linkages. Considerations regarding the relative abundances of the various structures tie up with findings in both nature and by synthetic means. Van der Waals forces are predominant. H-bonds are present but have considerably lower importance in determining the conformations of minimum energy. H-bonds locations and values are reported. The helix confirmations of a few polyflavonoids are reported and discussed.

ISSN:0022-233X    

DOI:10.1080/00222338508056617

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The synthesis, characterization, and evaluation of bifunctional synthetic enzymes via alternating copolymerization was carried out. It was desired to obtain copolymers containing alternating placements of complementary functional groups to determine whether “cooperativity” between the groups (in the hydrolysis of ester substrates) would be greater than in the corresponding random copolymers containing the same functional groups. The bifunctional alternating copolymer, N-(β-vinyloxyethyl)imidazole-N-hydroxymaleimide, was synthesized and evaluated as a catalyst in the hydrolysis of p-nitrophenyl acetate. The effectiveness of this copolymer as an esterolysis catalyst was compared with imidazole and the homopolymer of N-hydroxymaleimide. Monomer syntheses, polymerization, and copolymer properties are also reported.

ISSN:0022-233X    

DOI:10.1080/00222338508056618

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0022-233X    

DOI:10.1080/00222338508056611

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor