L. Cipelletti et al., STATIC LIGHT-SCATTERING CHARACTERIZATION OF MICROPOROUS MEMBRANE FILTERS, Journal of molecular structure, 383(1-3), 1996, pp. 31-35
Some of the more commonly employed microporous membrane filters have b
een studied in quasi index matching solvents by means of small-angle s
tatic light scattering. We report data obtained from membranes made of
esters of cellulose with rated pore size p(s) ranging from 0.1 to 8 m
u m. The high q behaviour of the scattered intensity follows a power l
aw I(q) proportional to q(-alpha) where alpha is either 1.9 or 3.8 dep
ending on the membrane chemical composition. Such values reveal that o
n a short length scale the filters have a fractal nature. Furthermore,
the scattered intensity distribution exhibits a peak at a finite wave
vector q(m), like in spinodal decomposition processes (which indicate
s mass anticorrelation effects), a behaviour similar to that observed
in Vycor porous glasses via neutron and X-ray small angle scattering.
The peak position moves towards smaller q values when increasing p(s),
although the characteristic length Lambda = 2 pi/q(m) is always large
r than the pore size and it is not trivially related to it. In particu
lar, for membranes made of mixed-esters of cellulose, Lambda is found
to be roughly proportional to p(s) for small pore sizes, while for p(s
) > 1.2 mu m it increases only slightly with the pore size and eventua
lly tends to saturate. In conclusion, these results indicates that sma
ll-angle static light scattering promises to be a very useful techniqu
e for characterising microporous membrane filter morphology, and also
for quality control.