Crosslinker-Based Regulation of Swelling Behavior of Poly(N-isopropylacrylamide) Gels in a Post-Polymerization Crosslinking System.

Shohei Ida,Motoharu Nakamura,Yoshitsugu Hirokawa,Mitsuhiro Tsujio,Akimitsu Katsurada

doi:10.3390/gels6010002

Abstract

A fundamental understanding of the effect of a crosslinker on gel properties is important for the design of novel soft materials because a crosslinking is a key component of polymer gels. We focused on post-polymerization crosslinking (PPC) system utilizing activated ester chemistry, which is a powerful tool due to structural diversity of diamine crosslinkers and less susceptibility to solvent effect compared to conventional divinyl crosslinking system, to systematically evaluate the crosslinker effect on the gel properties. A variety of alkyldiamine crosslinkers was employed for the synthesis of poly(N-isopropylacrylamide) (PNIPAAm) gels and it was clarified that the length of alkyl chains of diamine crosslinkers strongly affected the gelation reaction and the swelling behavior. The longer crosslinker induced faster gelation and decreased the swelling degree and the response temperature in water, while the crosslinking density did not significantly change. In addition, we were able to modify the polymer chains in parallel with crosslinking by using a monoamine modifier along with a diamine crosslinker. This simultaneous chain modification during crosslinking (SMC) was demonstrated to be useful for the regulation of the crosslinking density and the swelling behavior of PNIPAAm gels.

Highlights

Crosslinking is a key reaction for construction of network structure of a polymer gel, which is a soft and wet material anticipated for various applications such as biomedical devices, actuating systems and catalyst platforms [1,2,3,4,5,6,7,8]
We focused on the post-polymerization crosslinking (PPC) utilizing activated ester chemistry to understand the effect of the crosslinker
We focused on the PPC utilizing activated ester chemistry to understand the effect of the structure on the swelling properties of PNIPAAm gels

Summary

Introduction

Crosslinking is a key reaction for construction of network structure of a polymer gel, which is a soft and wet material anticipated for various applications such as biomedical devices, actuating systems and catalyst platforms [1,2,3,4,5,6,7,8]. Properties and functions of a polymer gel are generally controlled by choosing an appropriate monomer consisting the network chains for the desired characteristics because it is a main component of polymer gels. A polymeric crosslinker gives an amphiphilic network structure having unique swelling property in both of water and organic solvents [14,15,16,17,18,19]. Despite of these examples, the fundamental research on the effect of a crosslinker on gel properties is still limited in the general synthetic method of vinyl polymer gels probably due to the poor structural diversity

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Conclusion