摘要:

AbstractThe polymerization of styrene with two catalyst systems, consisting of Al(i‐C4H9)3in combination with ZrCl4and ZrCl3respectively, has been examined in toluene at 40°C. The catalyst complexes formed in both the systems exhibited the dual effect of accelerating and retarding the polymerization reaction. The rate of polymerization with respect to monomer and the total catalyst concentration was found to be first‐order for ZrCl4‐Al(IC4H9)3and second‐order for ZrCl3‐Al(i‐C4H9)3. The second‐order dependence on total catalyst concentration in the latter system has been explained on the assumption that the solid catalyst species interact bimolecularly to produce an active center, which takes part in the polymerization reaction. Thus the order with respect to active‐center catalyst concentration remains 1. The overall activation energy of polymerization was 14.74 kcal./mole for ZrCl4‐Al(i‐C4H9)3and 10.3 kcal./mole for ZrCl3‐Al(i‐C4H9)3. These catalysts exhibited very high rates of polymerization and gave low molecular we

ISSN:0449-2994    

DOI:10.1002/polc.5070220102

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe radiation‐induced ionic polymerization of bulk styrene has been studied under extremely dry conditions. It was found that the rate of propagation increases with more rigorous drying of the monomer, and this effect is accompanied by a change in the exponent n for the doserate dependence of rate of polymerization from n values near unity to 0.6. A mechanism involving bimolecular termination of free ions is thereby indicated. The kpvalue is estimated to be>3.5×1061. mole−1sec.−1by the electrical conductivity method. The large kpvalue is explained as a characteristic ion dipole reaction for the free‐ion propagation process and by the considerable freedom of the growing end of a free ion in comparison with that of an ion pair end. Similar results were observed with isobutene, nitroethylene, and cyclic monomers such as trioxane and BCMO. The initiation mechanism induced by the ion radical formed by radiation was confirmed by direct observation with ESR, optical absorption, and mass spec

ISSN:0449-2994    

DOI:10.1002/polc.5070220103

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

年代:1968

数据来源: WILEY

摘要:

AbstractSeveral possible chemical structures for poly(α‐phenylethylisonitrile) are examined, and the structure is proposed for the polymer as it originally forms. The isolation of acetophenone from hydrolysates of the polymer suggests, although not conclusively, that the polymer may have undergone a tautomeric rearrangement to the structure Ultraviolet and infrared spectral data are cited as partial evidence of either of the proposed structures. The steric implications of the proposed structures are considered, and the probability that the polymerization and the presumed rearrangement are stereoregular chemical reactions is discussed. Debye‐Scherrer x‐ray patterns are presented for poly(α‐phenylethylisonitrile) and for poly(σ‐toly

ISSN:0449-2994    

DOI:10.1002/polc.5070220104

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

年代:1968

数据来源: WILEY

摘要:

AbstractCharge‐transfer complexes in solutions of comonomers such as divinyl ether and maleic anhydride have been identified by use of ultraviolet spectroscopy. Equilibrium constants and molar extinction coefficients were determined for several of these complexes. It appears reasonable that the cyclic units formed in these copolymers result from free‐radical initiation of the charge‐transfer complex, which preorients the comonomers into a conformation favorable for formation of copolymer in the observed comonomer ratio of 1:2. Copolymers prepared and studied were those of divinyl ether with N‐substituted maleimides having the following substituents on nitrogen: (a) hydrogen, (b) methyl, (c) ethyl, (d) n‐propyl, (e) isopropyl (f) n‐butyl, (g) isobutyl, (h) benzyl, (i) α‐naphthyl, (j) phenyl, (k) p‐methoxyphenyl. These copolymers were characterized by elemental analyses to establish the comonomer ratios and by viscosity measurements and in certain instances by determination of molecular weights by the vapor‐pressure osmometry method. The copolymer of divinyl ether and maleic anhydride has been found to be an effective antitumor agent by the Cancer Chemotherapy National Service Center, National Institutes of Health. Consequently, these copolymers were also submitted for evaluation in this program, and several have been found to possess favorable inhibiting acti

ISSN:0449-2994    

DOI:10.1002/polc.5070220105

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe copolymerization of dichloroprotoanemonin with methyl methacrylate is accompanied by the elimination of half of the chlorine that originally entered the copolymer. This result is consistent with a 1,4‐addition mechanism, the product of which would readily eliminate hydrogen chloride. A strong infrared band at 1770 cm.−1and a weak band at 1810 cm.−1indicates that the loss of hydrogen chloride proceeds primarily by 1,4‐elimination but to a small extent by 1,2‐elimination. The copolymerization of dichloroprotoanemonin with styrene results in the elimination of 10 to 20% of the total chlorine that entered the copolymer. Infrared bands at 1765 and 1800 cm.−1reveal the presence of both conjugated and nonconjugated lactone carbonyl groups. Treatment of the copolymer with hot pyridine resulted in further elimination, up to about 30% of the total chlorine. The decrease in the intensity of the 1800 cm.−1band relative to the 1765 cm.−1band as a result of the pyridine treatment confirmed the conversion of the nonconjugated structure into the conjugated one. The failure to achieve 50% elimination indicates that in the styrene case copolymerization may have occurred in part by 1,2‐addition, the product of which would not be expected to lose hydrogen chloride. These results suggest that the ratio of 1,4‐ to 1,2‐addition may depend in part upon the nature of the comonomer. Thermal homopolymerization of dichloroprotoanemonin at 210°C. results in a solid, black polymer, insoluble in the common solvents. The elimination of 76% of the total chlorine suggests that under the conditions of the polymerization the lactone ring opens, giving an α‐chloroketone, which then unde

ISSN:0449-2994    

DOI:10.1002/polc.5070220106

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

年代:1968

数据来源: WILEY

摘要:

AbstractTo clarify the polymerization mechanism of vinyl chloride (VCl) and chloroprene (CP) with titanium tetrabutoxide‐aluminum alkylchlorides some work was carried out. Carbon tetrachloride surprisingly enhanced polymerization without decreasing the molecular weight, whereas carbon tetrabromide transferred the polymer chain. The monomer reactivity ratios in the copolymerization of VCl with vinylidene chloride (VdCl), rVCl= 0.30 and rVdCl= 0.90, differed from those in free‐radical polymerizations. In the polymerization of perdeuterovinyl chloride an ethyl radical originating from AlCl(C2H5)2was found to be incorporated into the polymer. Polymerization of chloroprene with the same catalyst in carbon tetrachloride was kinetically investigated, and a square‐root dependence of the catalyst concentration on the rate was seen. With vanadyl or cobalt acetylacetonate polymers of identical microstructure were obtained. Copolymerization with butadiene and styrene revealed the same behavior as that in free‐radical polymerization. It is suggested that in the polymerization with this catalyst an ionic or coordinated mechanism is included besides the usual radical me

ISSN:0449-2994    

DOI:10.1002/polc.5070220107

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

年代:1968

数据来源: WILEY

摘要:

AbstractA study of radical polymerization in the absence of radical initiator, in which imidazole or imidazyl groups may participate, was made. Polymerization of 1‐vinyl‐2‐methylimidazole was found to proceed easily at low temperatures in the presence of macromolecule, carbon tetrachloride, and water. Kinetic results showed that the polymerization concerned was of radical character, the overall activation energy being estimated to 13.7 kcal./mole. Vinyl polymerization could be also initiated in the presence of imidazole and carbon tetrachloride, and it was found that the polymerization was accelerated by the addition of some macromolecules in the system. The initiation mechanism is disc

ISSN:0449-2994    

DOI:10.1002/polc.5070220108

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe polymerization of 4‐vinylpyridine (4VP) in an electrochemical cell in liquid NH3solutions was studied. With monomer concentrations of 5 to 25 vol.‐% in the temperature range −33 to −78°C. rapid polymerization takes place when current is passed through the cell. Polymer yields of 80 to 90% are easily obtained in a few hours with NaN3or NaCl as electrolyte and smooth Pt electrodes in a stirred three‐compartment cell. Current densities of 1 × 10−2to 10 ma./cm.2and applied voltages of 2.5 to 50 v. were employed. Different anodic materials were used, including Pt and pyrolitic graphite. The electrochemical yield is about 1 mole of polymer per faraday for current densities of ⩽ 1 × 10−2ma./cm.2, and it becomes 0.5 and lower at higher current densities. The rate of polymerization was found to increase, and the molecular weight of the polymer to decrease, with increasing current density. It is concluded that the initiation step consists of electron transfer between the cathode and the monomer. Depending on the amount of polymer deposited on the cathode and on the current density, initiation may occur on the cathode surface or within the polymer deposit on the cathode or in the free liquid solvent. The consequence of the electron transfer to monomer is the formation of radical anions. Electrochemical yields of about 1.0 mole of polymer per faraday suggest that radical anion dimerization does not take place extensively, while dimerization may predominate when electrochemical yields are about 0.5. Subsequent chain growth occurs through an anionic mechanism, as evidenced by the nonterminating nature of the polymerization, the presistent red color of the polymer formed, and the sensitivity of the polymerization to the addition of protic substances. Polymer molecular weights were in the range of 10,000 to 360,000. Molecular weight distributions with Mw/Mnratios of 1.21 or larger were found. Softening points, solubility characteristics, and infrared spectra of the electrochemical polymer are presented and discussed in comparison with those of poly(4‐vinylpyridine) prepared with

ISSN:0449-2994    

DOI:10.1002/polc.5070220109

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

年代:1968

数据来源: WILEY

摘要:

AbstractWe investigated the polymerization of methyl methacrylate, initiated by decay products of the complex formed by maleic anhydride and tetrahydrofuran and by the action of visible light. The polymerizations were effected in solid and melted paraffin at temperatures of 6 to 60°C., mostly with an 80% paraffin content. The solid‐paraffin mixtures showed high polymerization rates, a higher efficiency of photoinitiated polymerization, and an entire lack of thermal polymerizati

ISSN:0449-2994    

DOI:10.1002/polc.5070220110

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

年代:1968

数据来源: WILEY

摘要:

AbstractStar‐shaped macromolecules have been obtained by anionic block copolymerization of a monofunctional monomer and a divinyl compound with cumylpotassium or butyllithium as initiator. The polymer molecule is a crosslinked nodulus, to which n linear, solvated chains are attached. The shielding effect of these chains is such that more than 40% difunctional monomer is necessary to induce gel formation in the reaction medium. Star‐shaped polystyrenes, polyisoprenes, polyvinylpyridines and poly(methyl methacrylate) were obtained by this method, the crosslinking agent being divinylbenzene or glycol dimethacrylate. The individual branches of the star molecules may be considered identical, but a polydispersity arises from the fact that within a sample the number of branches of the star molecules fluctuates appreciably. Fractionation remains possible, though it is not very easy to get monodispersed samples. The molecular dimensions of the star‐shaped polymers, as determined from their intrinsic viscosities or from their radii of gyration, are smaller than those of the corresponding linear polymers, and this may be considered a proof of their highly branched stru

ISSN:0449-2994    

DOI:10.1002/polc.5070220111

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

年代:1968

数据来源: WILEY