Latent Solid-Phase Extraction with Thermoresponsive
Soluble Polymers
SERGIO O. GONZALEZ, STEVEN FURYK, CHUNMEI LI, SHANE E. TICHY, DAVID E. BERGBREITER,
ERIC E. SIMANEK
Texas A&M University, Department of Chemistry, College Station, Texas 77842-3012
Received 12 July 2004; accepted 6 August 2004
DOI: 10.1002/pola.20465
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: The use of soluble thermoresponsive polymers to sequester or scavenge
hydrophobic guest molecules from dilute aqueous solutions on heating is described. In
these studies, a homopolymer of N-isopropylacrylamide was shown to sequester 46 –
83% of a soluble monochlorotriazine from 0.1–10 ppm aqueous solutions when heating
above this polymer’s lower critical solution temperature (LCST). Substitution of the
reactive piperidine-containing 20:1 copolymer poly(N-isopropylacrylamide)-c-poly[N-4-
(acrylamidomethyl)piperidine] for this unreactive polymer led to 98% scavenging of
these same triazines when heating above this reactive polymer’s LCST. The monochlo-
rotriazine guests studied included the herbicide atrazine and two dye-labeled analogues
of this herbicide. In one case, an atrazine analogue was designed so as to contain a
dansyl group for fluorescence analysis. In the second case, an atrazine analogue was
labeled with a methyl red group to facilitate visual and spectrophotometric analysis.
Atrazine concentrations were measured with liquid chromatography–mass spectrome-
try. The enhanced efficiency of the reactive piperidine-containing copolymer scavenger
in removing triazines from solution is attributed to covalent bond formation by nucleo-
philic aromatic substitution of the chlorine of the monochlorotriazines by the piperidine
nucleophile on the copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem
42: 6309 – 6317, 2004
Keywords: polymeric reagents; stimuli-sensitive polymers; separation techniques;
water-soluble polymers; atrazine
INTRODUCTION
Solid-phase extractions with insoluble crosslinked
polymer supports are well established as a
method to separate or concentrate trace contam-
inants from solution.
1,2
Reactive insoluble poly-
mer-bound reagents are also routinely used as
scavengers for reagents, byproducts or products
in solution-state high-throughput synthesis.
3
Here, we describe how poly(N-isopropylacryl-
amide) (PNIPAM) and PNIPAM derivatives can
be used as latent solid phase supports for the
physical sequestration or reactive scavenging of
low concentrations of hydrophobic contaminants
from aqueous solutions. PNIPAM is a thermore-
sponsive polymer that is soluble in water at low
temperatures, but it has the feature that it quan-
titatively precipitates from solution above a lower
critical solution temperature (LCST).
4
This be-
havior has been exploited in the design of smart
materials for catalysis,
5,6
in the design of ther-
mally responsive coatings,
7
in the preparation of
soluble polymeric ligands,
8
in the development of
supports for heavy-metal scavenging,
9
and to de-
sign temperature or pH-sensitive materials in
Correspondence to: D. E. Bergbreiter (E-mail:
bergbreiter@tamu.edu
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 42, 6309 – 6317 (2004)
© 2004 Wiley Periodicals, Inc.
6309