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NEUTRON REFLECTIVITY STUDY OF POLY(STYRENE MALEIC ANHYDRIDE) ON THE
WATER-AIR INTERFACE
C. Malardier-Jugroot 1) , T.G.M. v.d. Ven 1) , M.A. Whitehead ) , R. Richardson 2) , T. Cosgrove 2)
1) Department of Chemistry, McGill University, Montreal, Canada
2) School of Chemistry, University of Bristol, United Kingdom
email: theo.vandeven@mcgill.ca
ABSTRACT
Poly(styrene maleic anhydride) (SMA) is an interesting alternating copolymer, used in paper treatment
applications. Previous studies showed interesting behavior of SMA in aqueous solutions, characterized by
self-association, depending on pH and ionic strength. The neutron reflectivity study was performed to see if
surface properties show similar interesting behavior.
The results for the ethyl esters in DO 2 were indistinguishable from the reflectivity of pure DO, 2 indicating
that the adsorption layer is very thin. The data can be accurately fitted to the theoretical reflectivity of DO, 2
using a surface roughness of 2-3 Å.
The neutron reflectivity data on the ethyl ester of SMA in NRW showed surprisingly little effect on pH. The
2
data were analyzed by plotting
RQ vs. Q. A linear relation was obtained from which the adsorbed amount
Γ and the adsorption layer thickness δ can be obtained from the intercept and the slope respectively. We
found an interesting relaxation effect for the reflectivity of the ethyl ester SMA at pH 7, absent at other pH’s.
The results obtained after 4 hours were significantly different from the initial data. With time, Γ decreased
from 1.34 to 1.11 mg/m 2 and δ decreased from 12.6 to 9.6 Å (for the ethyl deuterated ethyl ester of SMA).
The adsorption at pH 3 was identical to the relaxed adsorption at pH 7. The styrene deuterated compound
always showed a slightly higher adsorbed amount compared to the ethyl deuterated one: Γ = 1.2 and 1.1
mg/m 2 resp.
The results at pH 13 showed that the ethyl ester of SMA was partially hydrolyzed, resulting in a reflectivity
profile close to that of SMA at the same pH.
The adsorbed amounts for SMA were found to be extremely low, both for pH 7 and pH 13, with adsorbed
amounts of 0.38 and 0.24 mg/m 2 resp. The thickness of the adsorption layer was in the range 13 – 16 Å.