摘要:

AbstractLog‐normal particle size distributions in polymer solutions have been measured with the Coulter counter. Qualitative membrane diffusion measurements were performed to substantiate the presence in these solutions of particles in the micron size range. Particle size was found to be dependent upon the thermal history of a polymer solution and upon the shearing forces to which it had been subjected. Further, particle size decreased upon dilution of a polyelectrolyte solution or upon an increase in the salt content. It is concluded that polymeric aggregates are the species being counted. These aggregates apparently originated during the polymerization of the polystyrene or of the styrene maleic anhydride studied. Bimodal distributions were observed in polystyrene solutions and in polystyrene sulfonate (Na+) solutions. The latter bimodal systems were resolved by graphical means, and it was found that the two populations are present in the ratio 65:35. The two distributions have the same dispersions (0.04) and only slightly different means (3.7 versus 4.5 microns). The mechanism of formation of this bimodal system may be that proposed by van der Hoff; namely, that particles are formed consecutively in the micellar and in the aqueous phase of an emulsion polymerization system when the soap concentration is near the critical micelle concentratio

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010201

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractThe paper deals with theoretical and experimental data on polymeric products with semiconducting properties. The data show the possibility of producing, on the basis of polymers, particularly polyacrylonitrile, substances characterized by high electroconductivity and exponential dependence of the latter on temperature. Possible changes in electrophysical properties of the materials are discussed. A quasimetallic model of a polymeric semiconductor is described.

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010202

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010203

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractThe effect of oxygen on ESR spectra of various kinds of irradiated polymers has been examined by using a saturation technique developed in the present investigation. The radiation oxidation of some polymers has been studied by means of ESR as well as infrared spectroscopy. Results for polyethylene (PE) are given in this paper, with some general remarks as introduction. In PE three kinds of radicals are produced on irradiation: CH2CHCH2 (FRVI), CHCHCH (FRVII), and CH(CHCH)nCH2(FRI). On introduction of air, FRVIIgave the asymmetric singlet of the peroxide radical which showed anisotropy. Reversible oxygenation of FRVIItook place even as low as −113°C. Radiation oxidation of PE proceeds mainly via FRVII, which produced eventually about 12 carbonyl groups and about 5 hydroxyl groups in the course of post‐oxidation, thetrans‐vinylene group decreasing by an amount nearly equal to the amount of initial FRVII. FRVIplayed only a minor role in the oxidation. An oxidation mechanism involving chain reaction has been proposed. It suggests an intramolecular free‐back reaction of hydrogen to the peroxide radical of FRVII. FRI(polyenyl radicals of longer conjugations) is oxidized to form carbonyl and hydroxyl groups, although it does not give the spectrum of the peroxide radical. Polyenyl radicals

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010204

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractResults of ESR and infrared studies of radiation oxidation of polypropylene (PP) and poly(vinyl chloride) (PVC) are reported. The effect of oxygen on the free radicals, FRVIII(CH2Ċ(CH3)CH2) and FRIX(CH2Ċ(CH3)2), FRI′(polyenyl radicals with shorter conjugations), FRI(polyenyl radicals with longer conjugations) in PP and FRI′, FRIin PVC was studied. On introduction of air, FRVIIIand FRIXin PP and FRI′in PP and PVC showed the asymmetric singlet spectrum of the peroxide radical. Oxygenation of the radicals began at low temperatures: −135°C. for FRVIIIand FRIX, −144°C. for FRp in PP, and −170°C. for FRI′in PVC. By reevacuation, the oxygen molecule could be removed from the peroxide radical of FRI′in PP and PVC, while deoxygenation was impossible from FRVIIIand FRIX. Oxidation of the radicals in PP and PVC gave carbonyl and hydroxyl groups. The number of carbonyl groups produced per radical was estimated as 3.4 and 1.6 for

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010205

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractIt was observed in the gamma radiation‐induced graft polymerization of styrene to nylon that dilution of the styrene with methanol greatly accelerates the rate of styrene grafting. The compositions of the solutions absorbed by the nylon on equilibration with the various methanol—styrene solutions were determined. These results showed that the concentration of styrene available for the grafting reaction is much greater when the styrene—methanol solutions are employed than when undiluted styrene is employed. It was found that the values ofk p 2/ktfor these graft polymerizations are increased by a factor of 105compared to the corresponding value in homopolymerization. These increases in thek p 2/ktterm are ascribed to the greater viscosity of the medium in which the grafting reaction takes place and to the immobilization of the graft polymer chains by the Trommsdorff‐type effect of methanol. A discussion is presented of the applicability of steady‐state kinetics, as well as of the various competing reactions, in the gra

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010206

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractAllene has been polymerized to a high molecular weight by several transition metal salts reduced by aluminum triisobutyl. The polymer contained three types of unsaturation: vinylidene, vinyl, andcis;notransunsaturation was found. A hypothesized mechanism accounted for these facts by two competitive rates: reaction of a linear intermediate with monomer to form again the linear intermediate plus one vinylidene unit, and isomerization of the linear intermediate to a cyclic intermediate which ultimately yielded one vinylidene and one vinyl orcisunit after reaction with monomer. Thus, the ratio of the two rates was controlled by the concentration of allene. The suggested mechanism proved to predict accurately the effect of the conditions of polymerization upon the structures of the resulting polymers. The nature of the transition metal also proved of importance in determining the path of polymerization as did temperature, solvent, degree of agitation, and copolymerization. Polyallene was found to exist in three crystalline forms as well as an amorphous form.

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010207

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractObservations on the x‐ray scattering by ball‐milled cellulose and cellulose derivatives, amorphous oligosaccharides, and Fortisan H are reported and an approximate shape is established for the scattering curve of the noncrystalline component of celluloses. Using this shape measurements have been made of the minimum crystallinity which is consistent with the observed x‐ray diagram of regenerated cellulose.From a comparison of this minimum crystallinity with crystallinity determined by the infrared‐deuteration method, it is concluded that at least 14% of the total material cannot be truly described as either perfectly crystalline or perfectly amorphous. This fraction of material of intermediate order is registered as crystalline by x‐ray diffraction, but infrared spectroscopy suggests that it does not possess the precise molecular configuration characteristic of crystalline material. Support for this view of structure is reported from observations of differences in hydrogen‐bonding in amorphous regions of regenerated and bacterial celluloses. Infrared results show that OH groups which lie in the surface of crystallites are hydrogen‐bonded in a random amorphous manner and it is concluded that the material of intermediate order can be accounted for in terms of chains lying in the surface of crystallites of cross‐secti

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010208

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractThe homogeneous anionic polymerization of acrylonitrile in dimethylformamide withn‐butyllithium was studied. Two different termination reactions were found to exist depending on catalyst concentration. At high catalyst concentrations termination was bimolecular by chain transfer to monomer, while at relatively low catalyst concentrations termination was monomolecular, by an inner cyclization reaction of the growing chain end. The existence of chain transfer only at high catalyst concentrations suggests the possibility of free catalyst molecules participating in the transfer reaction. At intermediate catalyst concentrations, both monomolecular and bimolecular terminations were found to occur side by side, andDP=Kp[M]/(Ktr[C][M]+Kt). Study of the dependence of molecular weight on per cent conversion at low catalyst concentrations showed that, up to about 30% conversion, there is a linear relationship between molecular weight and concentration of monomer consumed which is independent of temperature and monomer. After this degree of conversion, molecular weight stopped to increase and remained constant due to monomolecular termination. All over the wide range of catalyst concentrations investigated, the catalyst efficiency in initiating polymerization was found to be low. In the lowest range where there is a linear dependence of molecular weight on per cent conversion it was also found that the molecular weights are proportional to [M]/[C], which is a property of “living” sy

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010209

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY

摘要:

AbstractThe copolymerization of acrylonitrile (AN) with sodiump‐styrenesulfonate (SSS) in aqueous solutions (of pH 3 and pH 7) has been investigated. Monomer reactivity ratios at 45°C. for AN and SSS are found to ber1= 0.10 ± 0.02,r2= 1.20 ± 0.10 at pH 3 andr1= 0.05 ± 0.01,r2= 1.40 ± 0.04 at pH 7, from which PriceQandevalues for SSS of 0.76 and −0.26 at pH 3 and of 1.25 and −0.43 at pH 7 are calculated. Initial rates of copolymerization at 45°C. with ammonium persulfate (APS) as initiators were determined over the entire range of composition from pure AN to pure SSS, and it has been found that there is a sharp rise in copolymerization rates within 0.2–5 mole‐% monomer feed, sometimes being eight times larger than those in the neighboring range. The copolymerization in SSS monomer feed of 0.2–5 mole‐% occurs in the transition phase from homogeneous to heterogeneous, and the system is very viscous and slightly cloudy. From the investigation of the effect of initiator concentration on the copolymerization rate and the direct observation by an electron microscope, the sharp rise in copolymerization rates may reasonably be interpreted in terms of the emulsion copolym

ISSN:0449-2951    

DOI:10.1002/pol.1963.100010210

出版商:John Wiley&Sons, Inc.    

年代:1963

数据来源: WILEY