摘要:

AbstractPoly(4(5)‐vinylimidazole) poly(4(5)‐Vlm) has been shown to be an effective catalyst, as compared to monomeric imidazole, for the hydrolysis of various nitrophenyl esters. The catalytic activity of synthetic macromolecules in general and poly(4(5)‐VIm) in particular has been attributed to the approximation of substrate and catalyst by electrostatic‐ or apolar‐bonding and to certain bifunctional interactions. In an effort to exploit the enhancement in catalytic activity derived through hydrophobic interactions between polymer and substrate, 1‐methyl‐5‐vinylimidazole, 1‐methyl‐4‐vinylimidazole, 1‐butyl‐5‐vinylimidazole, and 1‐butyl‐4‐vinylimidazole, have been synthesized and polymerized. The kinetics of the poly‐1‐methyl‐4‐vinylimidazole (poly‐1,4‐Me) and the poly‐1‐methyl‐5‐vinylimidazole (poly‐1,5‐Me) catalyzed hydrolysis of various nitrophenyl esters will be discussed presently. Poly‐1,5‐Me has been proven to be an efficient catalyst, as compared to the model compound, 1,5‐dimethylimidazole (1,5‐DMIm), towards the hydrolysis of nitrophenyl esters. The poly‐1,5‐Me catalyzed hydrolysis of the negatively charged ester 3‐nitro‐4‐acetoxybenzoic acid exhibits a bell‐shaped pH‐rate profile with a maximum at pH 5 where about 40% of the pendant imidazole groups are protonated. When long‐chain nitrophenyl esters are hydrolyzed by poly‐1,5‐Me, order of magnitude rate enhancements over 1,5‐DMIm are realized. The kinetics of the poly‐1,5‐Me catalyzed hydrolysis of long‐chain nitrophenyl esters has been analyzed in terms of the rate‐determining decomposition of an intermediate polymer‐substrate complex. In support of such a mechanism, saturation and inhibition phenomena typical of enzymatic systems have been observed.Graft copolymers have been prepared from linear and branched polyethylenimine. These graft copolymers were studied as catalysts for the hydrolysis of activated esters in an aqueous system.The rate enhancements for the hydrolysis catalyzed by the polymer were attributed to electrostatic and hydrophobic effects.A study of the hydrolysis of p‐nitrophenyl acetate at varying pH showed that there were no cooperative effects between imidazoles or between imidazole and amine. The lack of cooperativity was attributed to the stereochemistry of the system.Electrostatic effects were investigated by a study of the hydrolysis of 4‐acetoxy‐3‐nitrobenzoic acid at varying pH. A bell‐shaped pH‐rate profile was obtained indicative of an electrostatic attraction between the positive polymer and negative substrate at the maximum rate.The large rate enhancements obtained in the hydrolysis of the esters of long‐chain fatty acids were explained by hydrophobic effects. This syste

ISSN:0360-8905    

DOI:10.1002/polc.5070500103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070500104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractTwo types of photoinitiating systems are considered in this paper: (i) Group VII transition metal carbonyls in the presence of fluoro‐olefins and (ii) vanadium chelates and their derivatives.(i) The photoinitiating activities of Mn2(CO)10and Re2(CO)10in association with CF2:CFCl, CF2:CHF, CF2:CH2, or CHF:CH2have been studied. Methyl methacrylate was the monomer and the incident wavelengths were 436 nm and 365 nm for the manganese and Re2(CO)10at relatively low [T]. The kinetics of photoinitiation have been investigated. With rhenium derivatives, respectively. Of the above fluoro‐olefins, only CF2:CFCl forms a photoinitiating system with Mn2(CO)10while all are active with Re2(CO)10.In all the active systems the rate of polymerization ω increases with increasing fluoro‐olefin (T) concentration but finally reaches a plateau value; plateau conditions are achieved with Mn2(CO)10/CF2:CFCl (the system studied in most detail) the “sharpness” of the ω ‐ [CF2:CFCl] relation increases as the incident intensity decreases and the rate of consumption of manganese carbonyl is equal to the rate of initiation over the whole range of [CF2:CFCl]. Quantum yields of photoinitiation have been determined for the various systems; they range from unity for Re2(CO)10/CF2:CHF to 0.35 for Re2(CO)10/CF2:CH2.Polymers prepared with the aid of these photoinitiators carry terminal groups in which the metal is covalently attached to the polymer chain through a unit derived from the fluoro‐olefin; for example with Mn2(CO)10/CF2:CFCl the terminal groups are (CO)5MnCF2CFCl. The initiating radicals are therefore formed by addition of an activated metal carbonyl species to the fluoro‐olefin and not by halogen abstraction as in systems such as Mn2(CO)10/CCl4, Mn2(CO)10/CBr4.On the basis of these and other results a mechanism is proposed in which photolysis of manganese carbonyl in methyl methacrylate solution leads reversibly to dissimilar fragments, only one of which forms an initiating radical with the fluoro‐olefin.The activity of fluoro‐olefins in these reactions (compared to the inertness of common vinyl monomers) is attributed to their ability to form relatively strong transition metal‐carbon bonds.(ii) Chloro‐oxobis‐(2,4‐pentanedionato) vanadium (V), VO(acac)2Cl, irradiated with light of Λ = 365 nm, initiates free‐radical polymerization of methyl methacrylate with a quantum yield of 0.02. The primary act is scission from the molecule of a chlorine atom, which is the initiating species. In the presence of an electron‐donor D (e.g., dimethylsulfoxide) ionic complexes a−are formed and photoiniate with much higher quantum yields (29‐fold in the case of dimethylsulfoxide). We believe that in these systems the primary act is electron‐transfer leading to D+and VO(acac)2; subsequent reactions of D±then generate initiating radical species.Photolysis of the chelate VO(Q), OMe, in which Q iepresents the 8‐quinolyloxo ligand, generate initiating radicals which comprise both CH, O and CH, OH. These results provide to route to photosensitive polymers with side‐chains carrying vanadium chelates which may be used to synthesize graft copolymers and polymer networks. Preliminary experiments ha

ISSN:0360-8905    

DOI:10.1002/polc.5070500105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractResults are reviewed on cationic polymerizations initiated by γ‐rays, by carbocation salts, and by strong acids, especially HClO4, with the conclusion that in no case are all criteria for true living polymerization satisfied.Detailed information is presented on bimodal molecular weight distributions found in polystyrenes initiated by HClO4in CH2Cl2between 0 and −97°C, showing that at all temperatures, polymerization can take place via both pseudo‐cationic and true ionic species, with the former in numerical preponderance. Transfer reactions prevent these species from being in simple ionization/recombination equilibria with each other, hence precluding a true living polymerization situation.The chief reason for these kinetic complexities is concluded to be a strong monomer‐complexation of the HClO4initiator and of propagating species. Indications of similar complexation in styrene/H2SO4and Ph3CClO4, and between HClO4and five other monomers suggests it may be a fairly widespread feature in cationic polyme

ISSN:0360-8905    

DOI:10.1002/polc.5070500106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070500107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070500108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractA new improved linear graphic method allowing simple and reliable determination of the reactivity ratios and estimation of the adequacy of the composition equation (i.e., of the mechanism of copolymerization) is presented.After a brief description of the basic principles of the hot radical theory, a complete treatment of the binary copolymerization, with the aid of this theory, is given. A kinetic analysis shows that for the complete characterization of the copolymerization, 13 parameters are required. According to this theory, four parameters of the classical theory depend on concentration and dilution, and only one value is a real constant. The requirements of experimentation and computation for the real estimation of all 13 parameters are elaborated.

ISSN:0360-8905    

DOI:10.1002/polc.5070500109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractA classification of the electroinitiation processes which takes into account the nature of the electrodic processes undergone by the different substances present in the reaction mixture is proposed.Some of the most recent results obtained in the author's laboratories on both electroinitiated and electroinfluenced polymerizations are briefly described and discussed.An algebraic treatment is also illustrated, which stresses the importance of the diffusion phenomena thus far neglected by most researchers. The theoretical results of this treatment are shown to closely agree with the experimental results.

ISSN:0360-8905    

DOI:10.1002/polc.5070500110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractChemical reactions are a useful tool in the investigation of structure and properties of macromolecules. They can be used to prove the tacticity of noncrystallizable polymers. The chain conformation of polymers and helix‐coil transformations in solution can be studied by spin labeling, introducing stable free radical groups into the polymers. Competition of inter‐ and intramolecular reactions of macromolecules gives information on interpenetration of coils. The structure of crosslinked polymers can be studied by chemical cleavage of the netw

ISSN:0360-8905    

DOI:10.1002/polc.5070500111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY

摘要:

AbstractThe 1:2 regularly alternating copolymer of divinyl ether and maleic anhydride produced via the cyclocopolymerization mechanism has been converted to a number of derivatives, and certain of these derivatives have been found useful as antitumor agents. Citraconic anhydride was substituted for maleic anhydride in the above cyclocopolymerization and its derivatives also exhibited antitumor properties, as did the derivatives of the copolymers of furan with maleic anhydride and with itaconic anhydride, respectively. The divinyl ether‐maleic anhydride copolymer reacts with dimethylformamide to yield a copolymer possessing polyelectrolyte character. The completely methylated copolymer was found to be useful in determining the molecular weight distribution of the original copolymer by gel permeation chromatography.A second series of reactive polymers were prepared by cationic initiation of o‐, m‐, and p‐(2‐vinyloxy)ethoxy‐β‐nitrostyrenes, propagation occurring only through the vinyloxy group. The polymer of the p‐isomer was crosslinked through anionic initiation on the nitrovinyl group. The m‐ and p‐isomers were converted to linear polymers through the nitrovinyl group via anionic initiation which underwent crosslinking through the vinyloxy group upon standing in air. The o‐isomer was not converted to polymer via anionic initiation. This unusual “ortho effect” appears to be a steric effect, as the only ortho derivative of β‐nitrostyrene which has been polymerized by anionic initiation is o‐fluoro‐β‐nitrostyrene. Poly‐m‐β‐dinitrostyrene was converted to the polyanion by sodium methoxide.A third series of reactive polymers were synthesized via anionic initiation on the o‐, m‐, and p‐(2‐vinyloxy)ethoxystyrenes. Propagation occurred through the styrene double bond leaving the vinyloxy group pendant. Hydrolysis of this vinyl ether was accomplished in all cases to yield the poly‐2‐hydroxyethylstyrenes. Further reactions of these polymers with acrylonitrile, phenyl isocyanate, and diisocyanates led to new polymeric systems. Hydrolysis of the vinyloxy group of the original styrenes followed by esterification with acrylyl chlorides led to monomers that were cyclopolymerized by a radi

ISSN:0360-8905    

DOI:10.1002/polc.5070500112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1975

数据来源: WILEY