摘要:

AbstractA detailed investigation was made by ESCA of the gross structural features and chemical composition of ultrathin plasma polymer films prepared from tetrafluoropyridazine. The data reveal evidence of extensive rearrangement that accompanied polymerization and that the C:F and C:N stoichiometries of the polymer films were similar to those of the starting monomer. From an initially high contact angle with water the surfaces became completely wettable with time and this is attributed to surface hydrolysis. A comparison is made between surface and bulk compositions. Brief consideration is also given to sleeve effects.

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220101

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractPlasma polymers synthesized by inductively coupled RF techniques have been investigated as a function of operating parameters for the isomeric perfluorinated diazines (pyrazine, pyrimidine, and pyridazine). A combination of ESCA and microanalytical studies shows that plasma polymers are produced by rearrangement mechanisms: the C/F and C/N stoichiometric ratios are similar to those of the starting monomers over a range of operating parameters. A comparison of rates of formation of plasma polymer films reveals distinctive differences between the isomeric diazines that suggest that equilibration of valence isomers occurs on a substantially slower time scale than for isomeric fluorinated benzenes5–9which, in general, polymerize at essentially the same rates. In contrast to the remarkably low critical surface tension of plasma polymers based on perfluorobenzenes (ca. 20 dynes cm−2), the plasma polymer films from the perfluorinated diazines which are initially hydrophobic become hydrophilic in contact with water droplets. This is attributed to the hydrolytic instability of films associated with the labilizing influence of nitrogen on nucleophilic displacement of fluoride which is a feature of the chemistry of monom

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220102

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractCationic polymerization of 1,4,6‐trioxaspiro [4,4]‐nonane (1) with (CH3)3O+SbF6−(2) and CH3OSO2CF3(3) initiators has been investigated. Although the observed rates of initiation and propagation are relatively slow, they consist of rapid reversible elementary reactions. In1H‐NMR spectra, a broadening of the monomer signal was observed, indicating a fast exchange between “free” monomer and monomer engaged in the active species. The variety of orthoester bonds were observed in the polymer formed at the early stages of monomer conversion. The final polymer has, however, structure of a linear poly(ester–ether) including two subsequent ester or ether linkages. To account for these new facts, the mechanism of polymerization was proposed, consisting of a rapid reversible opening of one of the rings in the monomer molecule involved in the growing species, followed by the slower opening of the second ring with formation of the ester linkages. It appears that the rings originally present in the chains rearrange into the linear units int

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220103

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractAlternating copolymers of phenylvinyl ethyl ether (I) and phenylvinyl sec‐butyl ether (II) with maleic anhydride (MAn) were prepared in bulk or in benzene solution by high‐energy irradiation at dose rates of 42, 160, and 540 Gy/h, respectively. The overall energies of activation in copolymerization ofIandIIwith MAn were 15.5 and 18.8 kJ/mol, respectively. The reaction proceeds by the free‐radical mechanism and was found to be largely dependent on the bulkiness of the alkyl group. In the copolymerization ofIand MAn, the molecular weight increases with conversion. By applying the model described by Shirota and co‐workers, it was established that participation of charge‐transfer‐complex monomers increases with the increase of the total monomer concentration and with the bulkiness of the alkyl group in electron do

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220104

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractStudies were conducted on grafting of acrylamide (AM) and sodium‐2‐acrylamido‐2‐methylpropane sulfonate (NaAMPS) comonomers onto dextran utilizing Ce(IV) induced initiation. The effects of reaction temperature, the Ce(IV)/dextran ratio, and the AM/NaAMPS ratio on grafting yield were investigated. The graft copolymerization behavior can be explained by exchange of the AMPS anion with one of the ligands on the Ce(IV) initiator. Oxidative modification of the dextran substrate improved the yield of graft copolymer. The dextran‐g‐poly(acrylamido‐co‐sodium‐2‐acrylamido‐2‐methylpropane sulfonate) samples prepared by this method were characterized as to copolymer composition and molecular weight utilizing elemental analysis, dilute solution viscometry, and aqueous size exclusion chromatography. Relationships of molecular weight and charge density to kinematic viscosity and salt se

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220105

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe concentration‐dependence measured by steady‐state permeation and unsteady‐state dyeing methods for a system of acid dye C.I.Acid Blue 182–nylon 6 film in the presence of inorganic salts such as NaCl, Na2SO4, and K2SO4, was analyzed in terms of parallel diffusion with simultaneous multimodal adsorption. It would found that the dyeing process with added NaCl was governed by surface diffusion with two kinds of Langmuir adsorption, whereas with added Na2SO4and K2SO4it was governed by surface diffusion with three kinds of Langmuir ads

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220106

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractLaser flash photolysis of diphenyliodonium salts produces phenyliodinium radical cation (PhI+·), which was also generated independently by flash‐induced electron transfer from iodobenzene to a phenanthrolinium salt. Apparent second‐order rate constants were determined for reaction of the transient (PhI+·) with nucleophiles, including iodobenzene and cyclohexene oxide. Quantum yields of formation of acid from stationary photolysis of diphenyliodonium hexafluoroarsenate were found to be significantly higher than yields of iodobenzene. These results may be explained by facile reaction of PhI+·with PhI to yield a new iodonium salt together with a proton. High reactivity of PhI+·with cyclohexene oxide suggests that the transient may directly initiate cationic polymerization of e

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220107

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractPhotoinitiated cationic polymerization by photosensitization of diphenyliodonium and triphenylsulfonium salts is shown to proceed by two distinct electron transfer process: (1) direct electron transfer from excited‐state photosensitizers and (2) indirect electron transfer from photogenerated radicals. The efficiency of the former process is attributed to the instability of the reduction products (from diphenyliodonium and triphenylsulfonium salts), which dissociate in competition with undergoing energy‐wastage reverse electron transfer. Amplification of photons in the production of protons (or other reactive cations) is postulated to account for the high quantum yields observed in the latter process. Potential advantages of utilizing the indirect redox process in the design of UV curable hybrid systems, which contain functionality for both radical and cationic polymerization, are noted. The results also provide evidence against the importance of triplet states of the onium salts in photoinitiator activ

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220108

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe effect of solvent in homo‐ and copolymerizations of methacryloyl fluoride (MAF) was investigated in various aromatic solvents. In these solvents, there is a significant effect on the rate of polymerization, on the tacticity of the resulting poly(methacryloyl fluoride), and on the copolymerization of MAF with methyl methacrylate (MMA). The equilibrium constants between MAF and aromatic solvents were determined from NMR spectroscopic measurements. These results indicated that the solvent effect on the MAF polymerization stems from changes in reactivity of MAF induced by the strong MAF–solvent interaction as well as stabilization of the MAF radical by solvents. Copolymerization of MAF with bothp‐methoxystyrene (MSt) andp‐nitrostyrene (NSt) was also

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220109

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe thermodynamical properties of the star‐branched polymers on the tetrahedral lattice are studied taking into account nearest‐neighbor interactions. The excess free energy and energy and heat capacities are computed for wide ranges of chain lengths, reduced potential ϵ/kT, and number of branches. A significant influence of the degree of branching on long‐range interactions in the polymer random coil is observed. The possibilities of phase transitions in both linear and branched systems are discussed on the basis of the Monte Carl

ISSN:0360-6376    

DOI:10.1002/pol.1984.170220110

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY