Temperature-Responsive Polymers

Chapter 1 Poly(N‐isopropylacrylamide): Physicochemical Properties and Biomedical Applications

Marzieh Najafi, Erik Hebels, Wim E. Hennink and Tina Vermonden

Department of Pharmaceutics, Faculty of Science, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, 3508 TB Utrecht, The Netherlands

1.1 Introduction

Poly(N‐isopropylacrylamide) (PNIPAM) (Figure 1.1) has attracted a lot of attention during the past decades because of its thermoresponsive behavior in a biomedically interesting temperature window. This polymer exhibits inverse solubility in aqueous media and precipitates upon increasing the temperature [1, 2]. The temperature at which this polymer converts from a soluble state to an insoluble state, known as the cloud point (CP) or the lower critical solution temperature (LCST), is 32 °C [3]. The first study on the PNIPAM phase diagram was reported by Heskins and Guillet [2] Since then this polymer has been known as a thermosensitive polymer. PNIPAM has been prepared by a wide range of polymerization techniques such as free radical polymerization (FRP) [4], redox polymerization [5], ionic polymerization [6], radiation polymerization [7], and living radical polymerization [8].

Figure 1.1 Chemical structure of poly(N‐isopropylacrylamide) (PNIPAM).

The focus of this chapter is on polymerization techniques, and examples are given addressing ...