Aggregation States of Poly(2-methoxyethylacrylate)/ Poly(methylmethacrylate) Blend Films at Water Interface
Toyoaki HIRATA1, Yoshihisa FUJII1, Hisao MATSUNO1, Masaru TANAKA2,and Keiji TANAKA1
1
Department of Applied Chemistry, Kyushu University, Fukuoka 819-0395, Japan2
Department of Biochemical Engineering, Yamagata University, Yamagata 992-8510,
Japan
Introduction
Poly(2-methoxyethyl acrylate) (PMEA) has been regarded as one of promisingblood-compatible polymers and used as a coating material for artificial organs.
Nevertheless, the manifestation mechanism of such a surface functionality remains
incompletely understood. Although the surface aggregation states of PMEA should beclarified as the first benchmark, such has not been realized yet. This is because a thin
PMEA film supported on a solid substrate can be easily broken. In our previous study,
we succeeded to prepare and characterize a stable surface covered with PMEA bymixing it with poly(methyl methacrylate) (PMMA) under an ambient condition. In
this study, we have applied neutron reflectivity (NR) to a PMEA/deuterated PMMA(dPMMA) bilayer so that the aggregation states of PMEA at air and water interfaces
can be discussed.
Experimental
PMEA (number-average molecular weight (Mn): 26k and molecular weight
distribution (Mw/Mn): 3.23) and monodisperse dPMMA (Mn: 296k and Mw/Mn: 1.06)
were used. PMEA/dPMMA bilayer was preparedby a double spin-coating method. Firstly, dPMMA (a) 1
10
1. in airwas spin-coated on a quartz substrate as a bottom
100
2. in D O
layer and the obtained film was annealed at 423 K for
10-1
24 h. Then, PMEA was spin-coated on the dPMMA
10-2
layer and the obtained bilayer film was again
10-3
annealed at 403 K for 24 h. Aggregation states of110-4
the bilayer in air and D2O were investigated by NR
10-52measurement.
Reflectivity

210-61) Tanaka et al, Langmuir, 2008, 24, 296 – 301.

00.2

0.4 0.6
q / nm-1

0.8

1.0(b)
72dPMMA

6b/V·10-4 / nm-2

Results and Discussion
Fig. 1(a) shows the scattering vector (q)dependence of NR for the PMEA/dPMMA bilayer
contacting air and D2O phases. The Kiessig fringeswere less visible in water than those in air. Inaddition, the fringes shifted to a higher q side in D2O.
These results make it clear that the bilayer became
thicker in D2O than in air and that the D2O/PMEA
interface became more diffuse compared to theair/PMEA one. Panel (b) of Fig. 1 shows the model
scattering length density (b/V) profiles used to obtain
the best-fit reflectivity. The b/V value in the interregion of the PMEA layer in D2O was higher thanthat in air. This result indicates that D2O molecules
are sorbed in the PMEA layer. In addition, thethickness of PMEA layer increased in D2O from 48.0
to 52.6 nm. This increment was striking comparedto the homogeneous dPMMA film.1)

54310

SiO2PMEA

21100

1.
2.

in airin D2O80 60 40 20Film thickness / nm

0Fig. 1 (a) NR for a PMEA/dPMMA
bilayer in air and D2O. Circles are theexperimental data, and solid curves
denote the calculated reflectivity on thebasis of the scattering length density
profiles shown in (b). Solid anddotted curves denote the b/V profiles inair and D2O, respectively. For clarity,
the data in D2O is off-set by twodecades.