摘要:

Abstractp‐Toluene sulfinic acid (TSA) of a high degree of purity, halide free and lowp‐toluene sulfonic acid (TOSA) content, was prepared. A cooled‐capillary dilatometer was constructed for the study of the bulk heterogeneous polymerization up to high conversions. Acids were found to show both cocatalytic and inhibitory activities, depending on their type and concentration. The bulk polymerization of acrylonitrile (AN) by TSA shows the usual autoacceleration, which was found however to be depressed or even eliminated by the addition of TSOA and other acids. An autoacceleration phenomenon was found in the solution polymerization of AN at 60°C. by TSA alone. In this case the addition of small amounts of TSOA eliminated the autoacceleration. On addition of TSOA to samples of constant TSA concentration, in bulk or in solution, the initial rate increases, reaches a maximum, and then decreases. A decrease in rate was also observed in the azo‐initiated bulk polymerization on addition of TSA + TSOA. Increasing the concentration of TSOA or H3PO4in the bulk polymerization, at constant TSA concentration, leads to a lowering of molecular weight. The order of the polymerization with respect to TSA was found to be between 1.1 and 1.5, depending on the TSOA concentration. The results are explained by an enhancement of the TSA initiation through its interaction with a proton, and the role of a TSA‐proton complex in a retardation

ISSN:0449-2994    

DOI:10.1002/polc.5070160303

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe ordinary bulk polymerization of acrylonitrile (AN) yields a powdery precipitate or an aggregated white polyacrylonitrile (PAN). Only one case has been reported, previous to our work (presented in this and in another paper5), in which AgNO3catalyst yielded a transparent PAN gel containing, however, 50% salt. We have found that conventional initiators can be employed in a bulk polymerization process, carried out under controlled conditions, to yield transparent rigid plastics of pure PAN. The process found involves a phenomenon of spontaneous transformation of the polymerizing system at high conversions from a heterogeneous polymer‐monomer mixture to a homogeneous transparent solid polymer. Processes employing benzoyl peroxide, α,α‐azobisiso‐butyronitrile,p‐toluene sulfinic acid, and mixtures of these, other catalysts, co‐catalysts, and additives are described. The transformation was found to depend on catalyst type and concentration, temperature, volume, and shape of the system as well as on the presence and supply of oxygen above the react

ISSN:0449-2994    

DOI:10.1002/polc.5070160304

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

年代:1967

数据来源: WILEY

摘要:

AbstractThis paper summarizes results obtained by studying solutions of poly (vinyl chloride) in various solvents by light‐scattering, sedimentation analysis, streaming birefringence, viscometry, and osmometry. Determination of certain molecular parameters (molecular weight, dimensions of maeromolecules, and optical anisotropy of segments) is described and attention is paid to the complications which arise from the presence of supermolecular structures occurring in the solutions of poly(vinyl) chloride even in good solvents. Some conditions are given for the occurrence of the sepermolecular structures in thermodynamically good, as well as poor solvents (both single and mixed), and the structures are partially characterized. The presence of supermolecular structures makes it impossible to determine directly certain parameters, in particular, molecular dimension

ISSN:0449-2994    

DOI:10.1002/polc.5070160305

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

年代:1967

数据来源: WILEY

摘要:

AbstractA potential energy function and an equation of state for amorphous polymers are developed by using a mathematical, quasi‐lattice model to represent the molecular structure. The potential energy function, obtained by dividing a polymer chain into a linked series of interaction centers, is described by three molecular parameters: e*, a force constant which measures the strength of interaction between two polymer segments,p*, a range parameter which measures the minimum separation between point centers on adjacent segments, andl, a structural parameter which indicates the size of the molecular units. A theoretical equation of state is then developed by defining a cell partition function for a polymer segment in terms of the potential energy function and one additional parameter, 3Cm, which is a measure of the number of external degrees of freedom possessed by an interaction center. It is shown that the theoretical equation for the thermal expansion at constant pressure simplifies to:\documentclass{article}\pagestyle{empty}\begin{document}$$ \mathop V\limits^{\rm \^} = V^* [0.935 + 10.8(l/\rho ^*)2] + V^* [0.824 + 24.9(l/\rho ^*)^2](3C_m \lambda k/2\varepsilon ^* \rho ^*)T $$\end{document}Similar expressions are developed for compressibility, internal pressure, and cohesive energy density. Experimental data for 13 polymers are then correlated using the theoretical equations. Densities, thermal expansion coefficients, and internal pressure measurements are used to evaluate the molecular parameters. Internal pressures over a range of temperatures are correlated to within 1% (in the best case). The cohesive energy density and the glass transition temperature are also interpreted in terms of the model. The molecular force parameters are also evaluated by a modified Slater‐Kirkwood calculation, and the results are compared to the experimentally determined values. A physical interpretation is then discussed in light of these calculations. The tentative conclusions are that the thermodynamic properties of amorphous polymers can be correlated with a model containing four molecular parameters. Two of these parameters,e*andp*, are associated with the nature of the interaction potential between structural units along the chain and can perhaps be estimated theoretically. The parameterl, a measure of the size of a structural unit on a polymer chain, has a strong effect on the repulsion between polymer segments and must be evaluated from experimental data. The parameter 3Cmis a measure of the mobility and freedom of a polymer chain and must be evaluated from experimental data. The change of a given polymer from a rubbery to a glassy state probably can be related to large changes in this latter parame

ISSN:0449-2994    

DOI:10.1002/polc.5070160306

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

年代:1967

数据来源: WILEY

摘要:

AbstractPhase separation during the formation of three‐dimensional polymers in the presence of inert diluents, by crosslinking of linear polymers, or by polymerization of multifunctional monomers, was treated under the assumption of thermodynamic equilibrium by using the Flory theory of swelling equilibria and rubber elasticity. The separation begins when the maximum swelling of the network in the diluent or diluent‐monomer mixture drops to the degree of dilution of the network; the two quantities remain equal even after separation of phases. The network formed in this way is a composite one. Relations have been derived for the dependence of composition and volume of the network phase upon initial conditions and degree of crosslinking or extent of polymerization. The results of calculations for binary and ternary model systems are discussed with respect to syneresis or formation of porous structures, as two possible modes of phase separat

ISSN:0449-2994    

DOI:10.1002/polc.5070160307

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe kinetics of the bulk polymerization of styrene in the presence of tetramethylthiu‐ramdisulfide ([TMTD]; 2.11 × 10−4‐1.67 × 10−1mole/1., and some other sulfur compounds at 80, 95, 115, 130, and 140°C, were studied. The rate of polymerization has been measured as a function of the concentration of the studied compound. The formal order of reaction (n) was determined with respect to the concentration of TMTD, which varies with the increase of the concentration of TMTD and temperature of polymerization in the range 0

ISSN:0449-2994    

DOI:10.1002/polc.5070160308

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

年代:1967

数据来源: WILEY

摘要:

AbstractCyclization ofcis‐1, 4 andtrans‐1, 4‐polybutadiene as of poly (2,3‐dimethyl butadiene‐1,3) was carried out with H2S4as the cyclization agent. The decrease of the original unsaturation as well as of total unsaturation were measured with IR spectroscopy and the iodine monochloride method, respectively. The kinetics of cyclization were measured and evaluated with an analog computer. Both methods indicate the length of cyclic segments as 25–45 cycles. In the case of poly(2,3‐dimethyl butadiene‐1,3) only monocycles are formed. Some indications of secondary reactions, including isomerization, accompanying the eyclization were given by analyses of IR spectra and ch

ISSN:0449-2994    

DOI:10.1002/polc.5070160309

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

年代:1967

数据来源: WILEY

摘要:

AbstractA modified precipitation chromatography apparatus, designed to operate with periodie temperature changes of the entire column, permitted fractionation of larger amounts of polymer. To verify the efficiency, 5 g. of a poly(methyl methacrylate) specimen were fractionated.

ISSN:0449-2994    

DOI:10.1002/polc.5070160310

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

年代:1967

数据来源: WILEY

摘要:

AbstractElectron spin resonance spectra of short‐lived free radicals formed by addition of HO. to vinyl acetate, vinyl propionate, and 1,3‐butadiene in aqueous solution were studied by means of a rapid flow technique. The observed spectra were assigned to be due to free radicals, CH2CHOCOCH3, CH2CHOCOC2H5, and CH2CH(CHCHS2), respectively. The observed hyperfine coupling constants give the spin density of 0.855, 0.848, and 0.629. Taking previously reported spin densities of propagating type free radicals of acrylic acid, methyl acrylate, and ethylene, as well as the present results into consideration, the order of the spin density is ethylene>methyl acrylate ≈ acrylic acid ≈ vinyl acetate>butadiene, which is in agreement with the order of the reactivity of the propagating radicals in addition polymerization. This is interpreted as an effect of resonance stabilization due to the side‐chain substituent of the vinyl monomers. In addition, there are differences between vinyl ester and acrylic ester radicals which tentatively are interpreted as related to the hindered rotation of the endgroups of the growi

ISSN:0449-2994    

DOI:10.1002/polc.5070160311

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe effects of solvent, molecular weight regulator, and concentration of initiator and emulsifier on the polymerization rate of chloroprene in the latex particle was studied. By a modification in the method for the determination of the latex particle size by means of soap sorption, errors of conductometric titration due to the liberation of hydrochloric acid and dilution of latex were reduced. The found data were used to calculate the velocity constant of the growth reaction of chloroprene and its temperature dependence in the range of 10–35

ISSN:0449-2994    

DOI:10.1002/polc.5070160312

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

年代:1967

数据来源: WILEY