DIFFUSION-LIMITED SEGREGATION OF DIBLOCK COPOLYMERS TO A HOMOPOLYMER SURFACE

Citation
A. Budkowski et al., DIFFUSION-LIMITED SEGREGATION OF DIBLOCK COPOLYMERS TO A HOMOPOLYMER SURFACE, Israel Journal of Chemistry, 35(1), 1995, pp. 55-64
Citations number
34
Categorie Soggetti
Chemistry
Journal title
ISSN journal
00212148
Volume
35
Issue
1
Year of publication
1995
Pages
55 - 64
Database
ISI
SICI code
0021-2148(1995)35:1<55:DSODCT>2.0.ZU;2-C
Abstract
Using nuclear reaction analysis, we have measured the rate of surface segregation of an asymmetric diblock polyisoprene-polystyrene (PIPS) c opolymer to the free surface of polystyrene (PS) homopolymers within w hich it is incorporated at low bulk concentrations. We have also measu red the tracer diffusion coefficient of PIPS in PS under similar condi tions, and shown it to equal, within error, the self-diffusion coeffic ient of PS of a similar length. The equilibrium surface excess Gamma o f the diblock is low (<R(g), the radius of gyration of the PS block of the copolymer), so that the diffusion rate is not expected to be sign ificantly reduced by energy barrier effects. The rate of segregation a ppears considerably slower than a diffusion-limited picture based on a sink-boundary condition for the PIPS molecules at the PS surface woul d suggest. A much better description of our data is provided by a simp le kinetic model which assumes local equilibrium between unattached an d tethered diblocks at the free PS surface.