INGREDIENT PROFILE
by Michael J. Fevola, PhD
Polyquaternium-6
Michael J. Fevola, PhD,
is a manager in the New
Technologies group at
Johnson & Johnson Consumer
and Personal Products
Worldwide in Skillman, NJ,
where he leads R&D in polymer
and surface chemistry. Fevola
has authored 12 peer-reviewed articles and book
chapters, is an inventor on six US patents, and
is a member of both the Personal Care Product
Council’s International Nomenclature Committee
and the Society of Cosmetic Chemists.
Editor’s note: The content of
the “Ingredient Profile” column is
provided for informational purposes
only and is not intended as legal,
regulatory or ingredient safety
guidance. The author assumes no
responsibility for misuse of the
information presented herein.
Figure 1. Chemical structure of
polyquaternium-6
Chemistry and Manufacture
Polyquaternium-6 (PQ-6) is the
polymeric quaternary ammonium salt
derived from the homopolymerization
of diallyldimethylammonium chloride
(DADMAC) monomer, as shown in
Figure 1.1, 2 The grades of PQ-6 supplied
to the personal care industry typically
have weight-average molecular weight
(Mw) values of ca. 150,000 g/mol,
although grades with Mw values as low as
15,000 g/mol are available.3 PQ-6 is a
strong polyelectrolyte, i.e. it is comprised of repeating units that remain
fully ionized in aqueous solutions
independent of the solution pH value.
In addition, PQ-6 has a relatively high
cationic charge density because each
repeating unit bears a positive charge.
DADMAC monomer is synthesized
commercially by the reaction of two key
commodity precursors, dimethylamine
and allyl chloride (see Figure 2).4, 5
Overall, two equivalents of allyl chloride
are reacted with dimethylamine to yield
the quaternary ammonium monomer
and one equivalent of sodium chloride
(NaCl). In this process, the hydrochloride salt of the monoallyldimethylamine
intermediate, i.e. allyldimethylammo-nium chloride, is neutralized in situ with
one equivalent of sodium hydroxide to
facilitate the addition of the second
equivalent of allyl chloride. Depending
on the specific process employed and
the desired monomer purity, the NaCl
may be left in the monomer product or
separated from the DADMAC.
PQ-6 is produced by the free-radical
addition polymerization of DADMAC
in aqueous solution, as shown in
Figure 3.2, 5 The polymerization is
typically initiated using thermal initiators such as ammonium persulfate
at temperatures of 60–80°C, or at lower
temperatures using redox initiators
such as potassium bisulfate (reducer)
in combination with potassium persulfate (oxidizer). The reaction is
conducted under a nitrogen atmosphere
to prevent radical inhibition by oxygen.
Chelating agents such as disodium
ethylenediamine tetraacetic acid may
also be added to the reaction to bind
any free metal ions that would otherwise
interfere with polymerization.6
Figure 2. DADMAC monomer synthesis
150 | Cosmetics & Toiletries® magazine www.CosmeticsandToiletries.com
Vol. 126, No. 3/March 2011
