Overlap concentration of an aqueous poly(N‐vinylcaprolactam) solution in the dynamic and static states

Abstract

The overlap concentration of poly(N-vinylcaprolactam)s (PVCLs) of low molecular weights was studied with dynamic and static methods (with viscosity and refractive-index measurements) at three temperatures (25, 30, and 358C). This concentration, determined by viscometry, was lower than the overlap concentration determined by refractometry. Also, the influence of the temperature and molecular weight on the viscosity and refractive index was investigated, and the opposite effect of the temperature on the viscosity and refractive index of PVCL solutions was observed. The experimental overlap concentration values were compared with those calculated with the Rao, Huggins, and Fuoss equations. The results showed that the Huggins equation is the best equation to describe the dilute solution properties of this polymer.

Solution polymerization of N‐vinylcaprolactam in 1,4‐dioxane. Kinetic dependence on temperature, monomer, and initiator concentrations

“…Therefore, it is important to know the reason for these anomalous results, that is, a monomer reaction order higher than unity or a variation of k p / k t 0.5 with monomer concentration. One important factor to be analyzed when changing the polymerization parameters such as initiator and initial monomer concentrations and temperature is the viscosity, as was observed by Foroutan et al24 With the variation of the viscosity, we can observe a deviation from the normal kinetic and significant changes of mass and heat transfer and mainly changes of the termination rate constant k t , that is, the decrease of the mobility of macroradicals leads to a decrease of k t values, resulting in an autoacceleration of the reaction and an increase of the polymerization degree (gel effect) 25. The propagation rate constant k p is also dependent of the reactions conditions but it is less sensitive to the diffusion because of the mobility of the monomer molecules.…”

Synthesis of biocompatible and thermally sensitive poly(N‐vinylcaprolactam) nanogels via inverse miniemulsion polymerization: Effect of the surfactant concentration

“…8 PNVCL shows LCST in water at temperatures (35 to 38 C) near the physiological temperatures. 1 PNVCL is a biocompatible and suitable polymer for in vivo biomedical applications because it does not suffer hydrolysis in pure water. 6 It can be used as a carrier for drug delivery of active molecules for cosmetic applications with controlled release of active ingredients.…”

An experimental investigation of nucleate pool boiling in aqueous solutions of a polymer

“…This limiting value at infinite dilution is a direct measure of the molecular properties of the polymer, and it essentially quantifies the volume occupied by a unit mass of the macromolecule. Higher [η] suggests increased capability of a polymer to enhance the solution viscosity, and in general it is related to the molecular weight or degree of polymerization 28, 36, 37…”

“…The critical overlap concentration can also be determined from the intrinsic viscosity,28, 34, 36, 37 because [η] −1 approximately represents the concentration within the polymer, or its overlap concentration in a solvent, exceeding which molecules will touch and interpenetrate to form a semidilute solution. According to the Einstein model, which considers dilute dispersions of unsolvated spherical particles, when the volume fraction φ of the spherical particles is small the relative viscosity is given by the following function34: From the limiting condition of Eq.…”