Polymer In Tetrahydrofuran Research Articles

Rheological properties of dilute and concentrated solutions of polyvinylchloride branched by irradiation

AbstractFollowing a previous study of two commercial poly(vinyl chloride) polymers, with Mw values of 130,000 and 70,000, the influence of γ radiation on the concentrated solutions of two other polymers in tetrahydrofuran was investigated. Their Mw values were 51,000 and 700,000, respectively; the second sample being crosslinked by copolymerization with a polyfunctional monomer.The irradiation‐induced changes were investigated by osmometry, light‐scattering, gel permeation chromatography and dilute and concentrated solution viscometry. From the experimental data obtained, it can be seen that the viscosity‐molecular weight relations are strongly affected by the molecular weight distribtuion and the presence of branching in the samples. By assuming the Stockmayer distribution, and using the equations developed by Kilb, the viscosities of the irradiated samples have been described satisfactorily.

The Instrument Spreading Correction in GPC. I. The General Shape Function Using a Linear Calibration Curve

Abstract A general shape function is proposed for describing the instrumental spreading behavior in gel permeation chromatography (GPC) columns due to axial dispersion and skewing effects. The general shape function contains statistical coefficients which describe the axial dispersion, skewing, and flattening of ideal monodisperse standards. A method denoted as the “method of molecular weight averages” is used to derive equations to correct GPC number- and weight-average molecular weights and intrinsic viscosities calculated from linear molecular weight calibration curves. The validity of these equations is experimentally verified with data for polystyrene, polybutadiene, and polyvinyl chloride polymers in tetrahydrofuran. The physical significance of the correction equations and their statistical coefficients is discussed in relation to the observed GPC chromatograms. Application of this shape function to the numerical Fourier analysis method for correcting differential molecular weight distribution (DMW...

Polymerization of Cyclosiloxanes. I. Kinetic Studies on Living Polymer—Octamethylcyclotetrasiloxane Systems

AbstractThe kinetics of the anionic polymerization of octamethylcyclotetrasiloxane (D4) initiated by α‐methylstyrene living polymer in tetrahydrofuran was studied. The following kinetic scheme was postulated: Initiation: equation image Propagation: equation image where S‐ and M represent the initiator and D4, respectively. At a living end concentration of 0.0377 mole/l. and a monomer concentration of 1.5 mole/l. in tetrahydrofuran at 25°C. the following kinetic data were obtained: k1 = 2.3 × 10−4 l./mole‐sec., k2 < 2.3 × 10−5 sec.−1, k3 = 2.75 × 10−2l./mole‐sec. k4 ≈ 1.17 × 10−2 sec.−1, K1 > 10 l./mole and K2 ≈ 2.35 l./mole. The rate constants k1 and k3 were found to be dependent on the concentration of anions. This is attributed to the dissociation of ion pairs to free ions at lower concentration. Under the experimental conditions studied the majority of the anions were present in the form of ion pairs. The reactivity of the free ions is about 100 times greater than that of ion pairs. There is no temperature effect on K2, indicating zero ΔH and positive ΔS in the propagation reaction.