Ultracentrifugal Characterization of Poly(ethylene terephthalate) in Dilute Solutions

Abstract

ABSTRACT:The well-fractionated poly(ethylene terephthalate) (PET) samples ranging in weight average molecular weight Mw from 0.9 to 16 X 10 4 have been studied by sedimentation velocity and equilibrium, and viscometry in hexafluoroisopropanol (HFIP) and m-cresol at 30°C. The second virial coefficient A2 determined in HFIP by the sedimentation equilibrium method is found to have high dependence on Mw expected for the helical wormlike chains in very good solvents. The constant l/J 113 P-1 in the Mandelkern-Flory equation is 2.54X10 6 for PET in HFIP and 2.57X10 6 in mcresol, being in excellent agreement with that reported for several polymer-solvent systems. In spite of an important polymer that has been widely used for a variety of industrial purposes, poly(ethylene terephthalate) (PET) is not still completely disclosed about its molecular characteristics and solution properties. I-s For example, there is significant disagreement among the constants of K' and a of the Mark-HouwinkSakurada (MHS) relationship, eq 1, compiled for several PET-solvent systems in "Polymer Handbook"; 9where [7]] is the intrinsic viscosity and M is the molecular weight. The reasons for this are that PET is soluble only in a limitted number of rather peculiar and dangerous solvents, such as trifluoroacetic acid (TFA) and achlorophenol (o-CP), and that the establishments of most MHS equations are based on the number average molecular weight Mn using the unfractionated samples. The reliable unperturbed chain dimensions, therefore, have not been determined in terms of the MHS relation proposed.The molecular weight and its distribution for several commercial PET samples have recently been measured in hexafluoroisopropanol (HFIP) by Naoki et al. 10 with light scattering and gel permeation chromatography (GPC). On the other hand, a series of preliminary experiments11·12 revealed that HFIP is an easy handling and very good solvent for PET. In this work, we direct our efforts toward the establishment of rigorous MHS relations for PET in HFIP and m-cresol. For this purpose, the polymer was first fractionated by a column elution method 13 and then the fractions obtained were characterized by sedimentation experiments and viscometry. The results for m-cresol solutions were compared with tTo whom all correspondence should be addressed. those obtained in m-cresol by Meyerhoff and Shimotsuma.2 Sedimentation equilibrium offers the weight average molecular weight Mw and requires least correction for polydispersity. HFIP is available with high refractive index increment dn/dc allowing a measurement at low polymer concentraion and providing good precision in Mw. The viscosity-molecular weight relations thus determined are available for the reliable evaluation of unperturbed chain dimensions ( < r 2 >ofM ) 112 from which the chain conformational parameter CJ is derived by the Stockmayer-Fixman method. 14 According to rather old-fashioned theory of the polymer solutions, 15 the dependences of a part of the molecular parameters obtained on molecular weight ar...

Morphological changes of poly(ethylene terephthalate‐co‐isophthalate) during solid state polymerization

“…Measurements were performed in duplicates. The IV values were converted to molecular weight through the Mark–Houwink–Sakurada equations32: where IV is given in dL g −1 and M n is the number‐average molecular weight of the polymer sample, given in g mol −1 .…”

Ultrafast Homogeneous Glycolysis of Waste Polyethylene Terephthalate via a Dissolution-Degradation Strategy

“…As one of the engineering plastics, the solubility of PET in different solvents has already been investigated; the commonly used solvents include m -cresol, chloroform/hexafluoroisopropanol, 1-methyl-2-pyrrolidinone (NMP), and nitrobenzene . However, these solvents are reported to be used as mobile phase for gel permeation chromatography or to recycle PET waste by dissolution-reprecipitation method .…”

Simple Length Determination of Single-Walled Carbon Nanotubes by Viscosity Measurements in Dilute Suspensions

“…Techniques to obtain the molecular weight (or length) of polymers include dynamic and static light scattering, ultracentrifugation, gel permeation chromatography or size exclusion chromatography, matrix-assisted laser desorption/ionization, , membrane and vapor pressure osmometry, and intrinsic viscosity measurements − by capillary viscometers. Until recently, none of these methods have been applied successfully to determine the average length of individual SWNTs.…”

“…[16][17][18][19][20][21] SWNT length is believed to play a role in other applications such as the formation of sheets and coatings [22][23][24][25][26] and may affect the interaction of SWNTs with living organisms. [27][28][29][30] Techniques to obtain the molecular weight (or length) of polymers include dynamic 31 and static light scattering, 31 ultracentrifugation, 32 gel permeation chromatography or size exclusion chromatography, 33 matrix-assisted laser desorption/ ionization, 34,35 membrane and vapor pressure osmometry, 36 and intrinsic viscosity measurements [37][38][39] by capillary viscometers. Until recently, none of these methods have been applied successfully to determine the average length of individual SWNTs.…”