Investigation of solution properties of poly(N-isopropylacrylamide) in water with its thermohistory

"Single-chain" microgels were synthesized successfully from the cross-linkable poly(N-isopropylacrylamide) (PNIPAM) copolymer. This type of microgel has the exact chemical structure, molecular weight and molecular weight distribution of its precursor. It provides a direct way to compare the properties of linear polymers with those of their networks. The viscosity properties show that the microgels have lower critical solution temperatures (LCST) that are even higher than those of the corresponding linear copolymers. This can be attributed to the crosslinking points, which retard the change of the conformation of the network chains.

Synthesis and solution properties of single‐chain microgels from poly(N‐isopropylacrylamide) copolymer

Zhou

Yan

et al. 2003

Investigation of the self‐association behavior of a thermosensitive copolymer with lower critical solubility temperature near human heat by dynamic laser light scattering

Yin

Yang

Zhang

et al. 2005

ABSTRACT:The special thermosensitive copolymer with lower critical solubility temperature near human heat of 37°C in aqueous solution has been prepared successfully by copolymerizing N-isopropylacrylamide (NIPAM) and N-isopropylmethacrylamide (NIPMAM) randomly at an appropriate monomer ratio. The self-association behavior of the poly[NIPAM-ran-NIPMAM] copolymer has been studied by dynamic laser light scattering (DLLS) at a concentration higher than the critical concentration of the self-association calculated from viscosity data according to cluster theory. The effect of the concentration and temperature on the self-association behavior in water has been discussed respectively.

Application of time–temperature superposition principle to polymer transition kinetics

Cheng

Yang

2005

ABSTRACT:The time-temperature equivalence equation is deduced simply in view of the transition kinetics of a polymer. The independent variables time and temperature are separated in the two sides of the resulting equation. Thus, a physical property of the polymer, which is temperature dependent, can be matched with the theoretical calculated curve from a supposed model of transition kinetics in which only time is involved as the independent variable. By comparing different models, one may judge which model is probably more correct. The procedure of data fitting is described. As an application example, the measured viscosity data at different temperatures for the coil-globule transition of poly(N-isopropylacrylamide) in aqueous solution is tested to judge its transition mechanism. A transition mechanism involving a two-stage reversible reaction fits the experimental data in a satisfactory way.