L. E. MILLERAND F. A. HAMM
110
Vol. 67
11IAClWMOLECULAR PROPERTIES OF POLYVINYLPYItItOLIDONE : MOLECULAR WEIGHT DISTRIBUTION BY L. E. MILLER’ AND F. A. H A M M ~ General Sniline & F i l m Corporation, Central Research Laboratory, Easton, Pennsylvania Received July 16. 1956
This paper discusses the application of the well known Svedberg equation to polyvinylpyrrolidone, a synthetic high polymer. The dependenoe of sedimentation constant on concentration and molecular weight is described. The configuration of the molecule in sslution in terms of axial ratios and root mean square distance between the ends of the randomly kinked chain is d i m m e d ; viscosity and translational diffusion data were used. From the empirical relation between sedimentation constant and molecular weight, several equations are derived for defining different type average molecular weights. Speoial emphasis was placed on the quantitative analyses for polydispersity. Four methods are compared. It is demonstrated that the b e ~ method t for describing the molecular heterogeneity is based on a recent procedure in which the number distribution of mdirnentatios owstants, g(s) v m u s s, i s determined from ultracentrifugal velocity diagrams. The limitations on the attempt to plot “true” molecular weight distributions (y(s) us. M ) are discussed; an approach to such a distribution is outlined.
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Introduction
listed in Table I, only those which are pertinent to the discuesiona have been inoluded.
Samples.-The polymer PVP is a hygroscopic white solid. The amount of water retained by the “dry” material is a function of the relative humidity; it may be as high as 15%. Although the esperimentntion was not limited to the samples
ing to Longsworth,lo the st.raight line rclationship is a criterion t,hat the diffusion ac,rossthe boundary interface was not significantly disturbed. Thc boundaries were made by positioning the cell coniponent,s in the conventional way. It, was not necessary 60 sharpen t,lie boundaries by capillary wit,Iidrawal of the solvent evcn for t.hc niore dilute solutions. The zero tinics recorded were of ( h e Hame order of magnitude as others quoted in the literature.’l hlthough tlie apparent
The samples represent both The synthetic high polymer, .polyvinylpyrroli- large and small scale experimental preparations. done, has recently acquired a national interest as a TABLE I blood plasma extender. Its preparation, properFikentscher Samples Description K ties and applications in the blood field and in other branches of medicine have been summariaed in I Unfract. material 33 First fraction of I book form.s This polymer in 3.S% aqueous soluI1 38 tion containing physiological inorganic salts has Second fraction of I 37 I11 Fifth fraction of I been known in Germany as “Periston.” The IV 29 V Unfract. material medical profession in Germany, both military and 20 VI civilian, has used this material as a blood plasma First fraction of V 21 extender since about 1940. It was the primary VI1 29 Unfract. material VI11 Unfract. high mol. n.t. purpose of this investigation to determine the 71 IX molecular weights of a representative number of Unfract. very high mol. wt. 109 samples, with special emphasis on their molecular Samples 11, 111 and IV are the precipit.ates which result weight distributions. This latter aspect is im- from an incrementd addition of diethyl et.her to a 20% portant because of’ the extended clinical evalua- (initial concehtration) solution of sample I in methanol. work in this Laboratory,6 as well as theoretical tions being conducted here as well as abroad. Subsequent considerations by Flory6 and Scott,’ have established that Throughout the remaining test this polymer will be less polydispcrsed fractions can be obtained by precipitareferred to as PVP.4 t,ion from more dilute solutions. (The solute concentrat#ion The macromolecular properties of PVP hair? at first signs af precipitat,ion is about one third of the initial Sample VI represents a different type of fractionabeen studied by means of sedimeiitatioii yelocity, value.). tion procedure. An acetone slurry was made sample V; diff usioii and viscosity techniques and compared it was stirred for four hours, and then the of mixture was with the results of earlier workers. Although an allowed to layer overnight. The clear supeinat,ant acetonc esteiided viscosity program6 has been carried out layer contained the soluble lonw molecular weight, portions. acetone was removed using’a steam-bath and vacuum. in this Laboratory, only a brief consideratioil, The The residue after dissolution in water was spray dried. sufficient to corroborate the other discussions, is This sample of PVP is represented by number VI. Tnc given herein. Fikentscher8 K - d u e s given in Table I were determincd A critical evaluation of the existing methods for from the relative viscosity of 1% aqueous solutions. Thew values are often used as a qualitative indication of the polydispersity analysis by means of the sedimenta- w i g h t average molecular weight. tion velocity and diffusion diagrams and the results Diffusiometry.-The translational diffusion coefficients obtained by applying each of these techniques to ( D )report,ed in this work were determined in a Kletts electhe same experimental data is presented and com- trophoresis apparatus using a Tiselius type 11 cc. analytical cell. The boundaries were recorded by mcans of the Longspared. wort,h scanning technique. A plot of 1/H2,,, us. time for each csperimeiit yielded a straight line which intercepted Experimental the tiiiie axis between minus 3000-5000 seconds. Accord-
(1) Bell Tela1)lioiie I,al)oratoriea, Inc., Allentown Lalmrators, 555 Union Bouiavaid, Allerituwii, Penn. (2) Burroughs .tddiiig Rlechiue Conrpany, Research Activity, 511 No. Broad St., Philadelphia, Penna. (3) “PVP Polyvinylpyrrolidone,“ Compiled and Published b y General Aniline & Film Corporation, Development Department, 230 Park Avenue, New York, N. Y . , March, 1951. (4) Sterilt! so111tions of IJolyvinylpyrrolidone for physiological uBe are niai,keted by the General Aniline & Filin Corporation under the trade name “Plasdone.” (5) S. Siggia and 0. 0 . Stoner, this Laboratory; unpublished
works.
(6) P. J. Flory, J . Chcm. P h m , l a , 425 (1944). (7) R . L. Scott, ibid., l a , 178 (1945). (8) H. Fikentscher, Ccllulosechemie, 13, 60 (1932). (9) Klet,t -Tiseliiis Electrolihoresis Apparatus, N e t t hlfp. Co., 178 East 87tli St., Kew York 28, N. 1’. (10) L. G. Longsworth, A n n . A’. Y. Acad. Sci., 41, 269 (1911). (11) I
