ISSN 1070-4272, Russian Journal of Applied Chemistry, 2015, Vol. 88, No. 1, pp. 124−128. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © N.V. Baranova, L.A. Pashina, A.P. Necheporenko, A.V. Kostochko, 2015, published in Zhurnal Prikladnoi Khimii, 2015, Vol. 88, No. 1,
Acid and Base Sites of the Surface of Cellulose Nitrates
N. V. Baranova, L. A. Pashina, A. P. Necheporenko, and A. V. Kostochko
Kazan National Research University of Technology, ul. Karla Marksa 68, Kazan, Tatarstan, 420015 Russia
Received February 3, 2015
Abstract—The distribution of adsorption sites with repsect to the acid–base type and intensity on the surface of
cellulose nitrates with different degrees of substitution was studied by the indicator method with spectrophoto-
metric determination of the amount of sites. Acid–base sites capable to act as active sites of adhesion interaction
on the polymer surfaces were determined. All the surfaces studied are bifunctional and contain both base and
acid sites, with the acid sites prevailing. The aqueous medium inﬂ uences the activity of some of the revealed
sites: Lewis base site (–NO
) with рK
= 9.9 and one of the Brønsted acid sites (СН) at the С(6) carbon atom.
The results obtained can serve as a basis for understanding the mechanism of adhesion interaction on the phase
boundary with cellulose nitrate as one of the phases.
Interfacial phenomena in polymeric composite
materials are the major factor determining their
properties. Understanding of the mechanism of interfacial
interactions is impossible without determining the
contribution of contacting surfaces of each component,
which is largely determined by the chemical composition
and structural features.
Numerous approaches are used for studying the
surface properties; some of them are described in [1–8].
They allow prediction of various properties: from the
reactivity and catalytic activity to the adhesion interaction
In particular, in some cases it is sufﬁ cient to use
the integral acidity parameter [9, 10], whereas for
understanding the interaction mechanism a wider
spectrum of characteristics is required : local acidity
and distribution of sites with respect to the type and
strength; protic or aprotic nature of the sites; correlation of
these characteristics with structural-chemical parameters.
Cellulose nitrates (CNs) are widely used for production
of various composites, in particular, for new branches
of engineering. The application ﬁ elds of this polymer
continue to expand in connection with its use for
fabricating semipermeable membranes, selective
sorbents, and other kinds of high-tech products. The
diversity of applications makes it topical to study in
detail the surface properties of this cellulose ester from
the viewpoint of prediction of the adhesion interaction
in composites based on it.
To identify the active interaction sites on the surface
of cellulose nitrates with different degrees of substitution
from the standpoint of the acid–base concept of the
molecular adhesion theory, we used the indicator method
for monitoring the adsorption site distribution (ASD) on
the surface of solids.
The investigation objects were cellulose nitrates with
different degrees of substitution: CN 13.1% N (209.3 cm
NO/g), CN 12.9% N (206.2 cm
NO/g), and CN 12% N
NO/g), placed in an aqueous medium. The
local acidity of sites on the sample surface was evaluated
by the adsorption of indicators with рK
from –4.4 to
12.8 from aqueous solution. The set of probe molecules
(a total of 30 species) included Hammett indicators
and indicators used by Tanabe and other researchers
[1, 11–17] for evaluating the local and mean acidity of
the surface of solids belonging to different classes. The
analysis procedure is described in .