Synthesis and Phase Behavior of Poly(N-isopropylacrylamide)-b- Poly(L-Lysine Hydrochloride) and Poly(N-Isopropylacrylamide- co-Acrylamide)-b-Poly(L-Lysine Hydrochloride).

Milica Spasojević,Mark Jansen,Paul De Vos,Arend Schouten,Joop Vorenkamp

doi:10.3390/ma7075305

Abstract

The synthesis of poly(N-isopropylacrylamide)-b-poly(L-lysine) and poly(N-isopropylacrylamide-co-acrylamide)-b-poly(L-lysine) copolymers was accomplished by combining atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP). For this purpose, a di-functional initiator with protected amino group was successfully synthetized. The ATRP of N-isopropylacrylamide yielded narrowly dispersed polymers with consistent high yields (~80%). Lower yields (~50%) were observed when narrowly dispersed random copolymers of N-isopropylacrylamide and acrylamide where synthesized. Amino-terminated poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide-co-acrylamide) were successfully used as macroinitiators for ROP of N6-carbobenzoxy-L-lysine N-carboxyanhydride. The thermal behavior of the homopolymers and copolymers in aqueous solutions was studied by turbidimetry, dynamic light scattering (DLS) and proton nuclear magnetic resonance spectroscopy (1H-NMR).

Highlights

Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most intensively studied synthetic polymers for use in controlled drug delivery [1,2,3], cell-sheet engineering [4,5,6,7], as a biosensor [8,9,10] or in tissue engineering [11,12,13]
The PNIPAAm-b-PLL diblock copolymer can be prepared by combining atom transfer radical polymerization and ring opening polymerization as described in Scheme I
The same synthesis route can be used for the preparation of the PNIPAAm-PAAm-b-PLL copolymer where the AAm monomer is copolymerized with NIPAAm via atom transfer radical polymerization (ATRP) to give a random copolymer PNIPAAm-AAm in the first synthesis step

Summary

Introduction

Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most intensively studied synthetic polymers for use in controlled drug delivery [1,2,3], cell-sheet engineering [4,5,6,7], as a biosensor [8,9,10] or in tissue engineering [11,12,13]. The most interesting feature of poly(N-isopropylacrylamide) is the reverse solubility upon heating in water This thermo-responsive behavior originates from the ability of the polymer to undergo a change from a dissolved coil to a collapsed globule when the temperature is raised above 32 °C. This transition temperature is known as the lower critical solution temperature (LCST). Recent reports have shown that PNIPAAm polymer brushes do not always collapse above the LCST and proteins do not adsorb to all PNIPAAm coatings or hydrogels above the LCST [5,6,7,14,15]

Methods

Results

Discussion

Conclusion