摘要:

AbstractThe tendency of poly (vinyl alcohol) in water to form aggregations was studied by light‐scattering measurements. On standing at 25°CC for several days an organized phase structure was formed. This could be seen in a change of the scattering functions (angular dependence of scattered light). At small scattering angles intensity increased and weak side maxima showed up in the scattering functions. This aging process is also characterized by negativeA2‐values, by a decreasing limiting viscosity number, and by increasing Huggins‐k′‐values. Speed and character of this change was found to be dependent on the concentration of the solution and the molecular weight of the sample. Models are discussed, which can lead to the observed irregular scattering functions. The most probable explanation is, that during aging gel particles are formed, which have a negative surrounding function, which has an analogous effect as weak

ISSN:0360-8905    

DOI:10.1002/polc.5070440113

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe process of formation of the supermolecular order (SMO) in aqueous solutions of poly(vinyl alcohol) (PVA) has been studied by the method of turbidity spectrum in a turbulent flow produced by a blade stirrer rotating at a rate of 1,500 rpm.The kinetics of SMO formation has been investigated depending upon the polymer molecular weight (Mw) and concentration (C) and temperature (T) of the solution. The rate of formation of SMO was characterized in the first stage of the process by a relative increment in τ at 540 nm per hr. The concentration dependence,K = K(C), is extremal in character having its maximum atC= 0.5–1 g/dl. WhenTwas increased from 20 to 50°CC,Kdecreased, whereas average equivalent size of supermolecular particles,rλ, remained unchanged. The colloid disperse phase of supermolecular particles (SMP) appears to be in a quasi‐equilibrium with the molecular‐disperse solution, since, after removal of SMP, the process of formation of SMO is resumed at the same rate. To a greater extent the character of SMO formation depends on the chemical structure of PVA (Kdrops off to zero with increasing content of the acetate groups up to 7.6%) and physical prehistory of the PVA sample (an increase inKafter thermal treatment of the polymer in the condensed state). PVA films cast from stirred solutions revealed (by IR spectra) a greater degree of crystallinity then those cast from unstirred solutions. All other conditions being equal,Kin a turbulent flow is higher by one to two orders of magnitude thanKunder static conditions. The data obtained have been explained from the point of view of crystallization of PVA when intensified by the turbulent regime of solution

ISSN:0360-8905    

DOI:10.1002/polc.5070440114

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe temperature dependence of the second virial coefficient,A2, in an aqueous solution of poly (vinyl alcohol) (PVA) has been studied by the light‐scattering method within the temperature range from 20 to 130°CC.The experiment was carried out under conditions which rule out the aggregation of macromolecules. The temperature dependence ofA2has the form of an extremum with an unpronounced minimum between 80–90°CC. In the temperature region studied here,A2>0, this condition is regarded as a proof of the stability of the system with respect to amorphous separation. Consequently, the supermolecular order which forms in the PVA‐water system over this range of temperatures (see Chem. Abst, (1967),66:11295u; (1971)73, 56516x; (1971)74, 23183d) has a crystalline nature.The literature noting an increase in the degree of sweiling with increasing temperature in the PVA‐water system in the interval 20–80°CC, which seems contradictory to a decrease in the solvent power (decrease inA2), may be explained by a decrease in the degree of crystallinity (degree of physical crosslinking) of

ISSN:0360-8905    

DOI:10.1002/polc.5070440115

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe sorption of water vapor by poly (vinyl alcohol) films at moderate vapor activities was followed by mass regain and electrical conductance. A slow rearrangement of polymer structure in the swollen state is indicated by the observed sorption overshoot.

ISSN:0360-8905    

DOI:10.1002/polc.5070440116

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

年代:1974

数据来源: WILEY

摘要:

AbstractUnder the action of an electric field at a frequency of 1000 Hz, an interaction occurs between spherical latex particles in aqueous solution. These spheres arrange themselves in linear aggregates along the lines of the force field. The formation of these aggregates is studied by the electric light scattering method. The case is investigated where the aggregates disintegrate after the electric field is switched off. Some preliminary theoretical ideas are presented concerning the electrooptics of the phenomenon. The constant of coagulation and the electric polarizability of the spheres are estimated, their radius being constant and known. The investigations carried out could be the beginning of the development of an electrooptical method for the determination of the electric polarizability of spherical particles in solution. In addition this investigation shows that electrooptical effects by solutions of spherical particles are possible.

ISSN:0360-8905    

DOI:10.1002/polc.5070440117

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

年代:1974

数据来源: WILEY

摘要:

AbstractAn optical‐mechanical device is described with which the length of a gel and the transmitted light can be registered. The swelling curves of gels of the crosslinked polystyrene in cyclohexane have been measured in the temperature range from 10 to 70°CC. Glycol dimeth‐acrylate was used as the crosslinking agent varying from 0.05 to 3% by weight of the polymer. The swelling curves are in good agreement with those determined gravimetrically. From the slightly crosslinked gels nearly 50% soluble polymer could be extracted.The results are compared with those of other authors and are discussed on the basis of statistical theories of swollen netw

ISSN:0360-8905    

DOI:10.1002/polc.5070440118

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

年代:1974

数据来源: WILEY

摘要:

AbstractGeneral expressions are obtained for the nucleation rate taking into account explicitly the contribution of the free energy change when nucleation follows two different mechanisms, both monomolecular and multimoleuclar, i.e., with folded and extended chains.Nucleation with folded chains is the more probable for flexible random coiled macromolecules. However, upon decreasing the degree of coiling without affecting the origin of the uncoiling, the probability of the formation of multimolecular nuclei increases while that of the formation of monomolecular nuclei decreases. At some critical degree of uncoiling a reverse situation as compared to the initial probabilities is attained.A general thermodynamic and thermokinetic interpretation is given of the influence of the equilibrium or induced rigidity on the morphology of crystallization of polymers from solutions and melts.

ISSN:0360-8905    

DOI:10.1002/polc.5070440119

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe light scattering equation ℋ︁c2(1 + cos2θ)/Rθ= dΠ/RTdc2+ (16 π2〈r2〉/3λ2)M2−1sin2θ/2 for moderately concentrated polymer solutions derived previously from a gradient dependent free energy will here be rederived with the help of the so‐called direct correlation function,C(s), first introduced by Ornstein and Zernike.The equation will be used to calculate 〈r2〉/M2for polystyrene in cyclohexane near the consolute (or critical) point from light scattering measurements of Debye, Coll, and Woermann in combination with those of Scholte We found [〈r2〉/M2]1/2= 3.5 (± 0.1) nm mol1/2g−1/2forM2rang

ISSN:0360-8905    

DOI:10.1002/polc.5070440120

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

年代:1974

数据来源: WILEY

摘要:

AbstractStages of formation in the structure of precipitated polymer phase have been found by the method of spectroturbidimetric titration (STT) during precipitation titration of a number of polymer systems. In the first stages of formation of polymer particles, a sharp decrease was observed in the particle size,rCλ, which may be related to a fall in large fluctuations in the postcritical region if the transition of the system through the binodal curve were to be identified with phase transition of the second kind. In the second stage,rλremains constant at the minimal level,rλ=rλ(γ) =rλ0 const. The extension of plateaurλ0 in terms of γ depends on the polymer‐solvent‐precipitant system(P‐S‐P) and conditions of titration. The value ofrλ0 differs insignificantly for different systems,rλ0 = 0.2–0.3 μm, which is possibly related to the existence of an optimum of particle size in colloid systems of this type. The third stage is determined by the process of particle coagulation, here the kinetics are subject to the equation of Smolukhowskii and the rate depends on the P‐S‐P system. A value ofvwas determined which appears to be antibate to the effectiveness of attractive forces produced between polymer particles and defines the coagulation process in a specific P‐S‐P system. General conditions for the preservation of particle size during titration were established. Under these conditions, however, an effective separation of fractions with respect to molecular weights can not be attained from the point of view of relaxation thermodynamics. These contradictions are minimized by the use of the STT method. It is shown that the coagulation of particles during turbidimetric titration by the conventional approach leads either to fallacious underestimation or overestimation of the polymolecularity of a polymer depending on the time of beginning of such coagulation, before or after complete

ISSN:0360-8905    

DOI:10.1002/polc.5070440121

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

年代:1974

数据来源: WILEY

摘要:

AbstractLocal concentration fluctuations in polymer/solvent systems are probed by laser light‐scattered linewidth measurements. Dilute polystyrene solutions are studied over the molecular weight range 4 × 103to 1.7 × 107and as a function of concentration. The diffusion coefficient at zero concentration can be expressed aswhile the concentration dependence of the diffusion coefficientDis used as a measure of thermodynamic and hydrodynamic virial coefficients and compared with available theory. Results are also presented for light‐scattered linewidths from some polystyrene/tetralin gels of known concentration and crosslink de

ISSN:0360-8905    

DOI:10.1002/polc.5070440122

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

年代:1974

数据来源: WILEY