Short-time interdiffusion at polymer interfaces: A probe to study polymer motion

The aim of this work was to design experiments that could probe the motion of the polymer chains at the molecular level, and thereby suggest the mechanism of polymer-polymer interdiffusion. In the first experiment, a thin layer ($\sim$400-1500 A) of triblock polystyrene (HDH), wherein the central half of the chain was deuterated, was interdiffused into a thin layer of similar polymer (DHD), wherein the labeling was reversed, i.e., the two end fractions were deuterated. Since, the total deuteration was equal in both the polymers, initially, the concentration of H and D segments was 0.5 at all depths in the HDH/DHD bilayer. Upon interdiffusion, if the polymer chains reptate, i.e., move ends first, a local enrichment of D in the HDH, and H in the DHD, at the interface would develop. Upon further diffusion, this enrichment would decrease, and eventually vanish as the bilayers homogenize. On the contrary, if the chain ends and the chain centers diffused at the same rate, the initial concentration profile would be retained at all times. In the second experiment, interdiffusion between HDH/HPS (normal polystyrene) and HDH/DPS (deuterated polystyrene) was investigated. In the first, the change in the concentration profiles of D yielded the penetration depth of the chain centers, and in the latter, the concentration profiles of H reflected the diffusion of the chain ends. If reptation occurs, there would be a finite time, to, before which the chain centers do not cross the interface. Concentration profiles were measured with neutron reflectivity and secondary ions mass spectroscopy, up to the times of the order of the reptation time ($\tau\sb{\rm d}$) of the polymers. The following results were obtained.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Agrawal, Gaurav

• Engineering, Materials Science

Statement dc:rights

• Copyright 1994 Agrawal, Gaurav

Language dc:language

eng

Identifier

AAI9512280
(UMI)AAI9512280

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/20784