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

Abstract

The kinetics of the solution free radical polymerization of N-vinylcaprolactam, in 1,4-dioxane and under various polymerization conditions was studied. Azobisisobutyronitrile and 3-mercaptopropionic acid were used as initiator and as chain transfer agent (CTA), respectively. The influence of monomer and initiator concentrations and polymerization temperature on the rate of polymerizations (R p ) was investigated. In general, high conversions were obtained. The order with respect to initiator was consistent with the classical kinetic rate equation, while the order with respect to the monomer was greater than unity. The overall activation energy of 53.6 kJ mol À1 was obtained in the temperature range 60-80 C. The decreasing of the absolute molecular weights when increasing the CTA concentration was confirmed by GPC/ SEC/LALS analyses. It was confirmed by UV-visible analyses the effect of molecular weights on the lower critical solution temperature of the polymers. It was also verified that the addition of the CTA influenced the kinetic of the polymerizations.

Effect of the molecular architecture on the thermosensitive properties of chitosan-g-poly(N-vinylcaprolactam)

“…The results of yields are also shown in the Table 1. In general, the applied strategy of syntheses gives acceptable results in terms of yield and molecular dispersity, which are consistent with previous reports (Medeiros et al, 2013;Medeiros, Barboza, Ré, Giudici, & Santos, 2010;Ponce-Vargas et al, 2013;Wan et al, 2008).…”

“…Type III is characterized by one zero limiting critical concentration and two off-zero limiting critical concentrations (Meeussen et al, 2000). According to previous studies, PVCL solutions present Type I classical Flory-Huggins behavior, as the LCST is chain-length dependent (Beija et al, 2011;Medeiros et al, 2010;Meeussen et al, 2000). In this sense, the thermoresponsive behavior of PVCL varies with the polymer molecular weight and its concentration.…”

Poly(N-vinylcaprolactam), a comprehensive review on a thermoresponsive polymer becoming popular

“…Furthermore, the magnitude of conformational change is smaller for PNVCL. The mesoglobules formed above LCST for PNVCL consist of a globular structure with a hydrophobic core stabilized by more Page 13 of 155 A c c e p t e d M a n u s c r i p t 13 hydrophilic units on the surface [38]. The addition of ionic surfactants, like sodium dodecyl sulfate and cetylpyridinium chloride to dilute PNVCL solutions, leads to an increase in the LCST [7] since aggregation is prevented due to ionic stabilization; a similar case was observed for PNIPAAm aqueous solutions.…”

Synthesis of well-defined alkyne terminated poly(N-vinyl caprolactam) with stringent control over the LCST by RAFT

“…NVCL is a classic non-activated monomer, as vinyl acetate (VAc), N -vinylpyrrolidone (NVP) 52 and vinyl chloride, 53 since electron density around the double bond is very low. This feature turns radicals very reactive and therefore difficult to control.…”