The effect of stereoregularity
upon the adsorption behavior of high molecular weight poly(isopropyl acrylate)
Ruth Botham and Curt Thies
Polymer Research Section, Materials Research, National
Cash Register Co., Dayton, Ohio 45409, U.S.A.
Received 13 February
1969. Available online 6 July 2004.
Abstract
The adsorption of high molecular weight atactic, syndiotactic, and isotactic poly(isopropyl acrylate) (PIPA) on finely divided silica has been studied
at 24°C. Trichloroethylene was used as the solvent. The PIPA isotherms are
typical for polymers and differences in stereoregularity cannot be detected from the isotherm data.
Infrared-bound fraction determinations show that all adsorbed PIPA samples have
a high fraction of their segments attached directly to silica. However, surface
coverage and length of agitation affect bound fraction values, p. Below
surface saturation, atactic and syndiotactic PIPA have values of p = 0.36−0.52 while
for isotactic PIPA p = 0.47−0.58. In these
cases, prolonged agitation causes an increases in
values of p. At surface saturation, values of p for atactic and syndiotactic PIPA
decrease to 0.34–0.39, and length of agitation has little effect on p. It
was difficult to obtain reliable values of p for isotactic PIPA at surface saturation due to dispersion
instability. Silica was always readily removed from dispersions that contained
isotactic PIPA. In contrast, a substantial fraction of
silica could not be removed from dispersions that contained excess atactic and syndiotactic PIPA,
even after prolonged centrifugation. Many of these observations are consistent
with a bridging model for flocculation of colloidal dispersions by polymers.
|
Journal of
Colloid and Interface Science |