Fluorescent Labeling of RAFT-Generated Poly(N-isopropylacrylamide) Via a Facile Maleimide-Thiol Coupling Reaction
Document Type
Article
Publication Date
5-1-2006
Department
Polymers and High Performance Materials
Abstract
We report a facile labeling technique in which the telechelic thiocarbonylthio functionality of well-defined poly(N-isopropylacrylamide) (PNIPAM) prepared by room temperature RAFT polymerization is first converted to the thiol and subsequently reacted with a maleimido-functional fluorescent dye, N-(1-pyrene)maleimide (PM). Nearly monodisperse PNIPAM (Mn = 39 500 g/mol, Mw/Mn = 1.07) was synthesized using a trithiocarbonate-based CTA, 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP), and a conventional azo-initiator, namely, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), as the primary source of radicals. The key to successful conjugation of PM to PNIPAM is the implementation of a two-step reduction process involving (1) the cleavage of the trithiocarbonate with a strong reducing agent, in this case, NaBH4, to form a mixture of polymeric thiols and disulfides and (2) the conjugation of PM to the pure polymeric thiol in the presence of tris(2-carboxyethyl)phosphine·HCl (TCEP). We show that TCEP efficiently eliminates the formation of polymeric disulfides and thus allows for the desired addition of the free polymeric thiol across the maleimide double bond. This concept is demonstrated using SEC-MALLS and UV−vis spectroscopy measurements.
Publication Title
Biomacromolecules
Volume
7
Issue
5
First Page
1389
Last Page
1392
Recommended Citation
Scales, C. W.,
Convertine, A. J.,
McCormick, C. L.
(2006). Fluorescent Labeling of RAFT-Generated Poly(N-isopropylacrylamide) Via a Facile Maleimide-Thiol Coupling Reaction. Biomacromolecules, 7(5), 1389-1392.
Available at: https://aquila.usm.edu/fac_pubs/2370