Characterization of Surface Energy Effects on Morphology of Thin Diblock Copolymer Films by High Throughput Techniques

Published

January 1, 2001

Author(s)

A P. Smith, A Sehgal, Eric J. Amis, Alamgir Karim

Abstract

Block copolymers are widely used materials due to their unique capabilities as surfactants, adhesives and ordered templates. An understanding of the properties of these materials is crucial for their increased use as polymer materials. When symmetric diblock copolymer are cast as thin films preferential interfacial interactions induce ordering with the formation of lamella parallel to the substrate. The surface of the film remains smooth when the film thickness, h, is integral multiples of the bulk lamella spacing, L_o, and surface island and hole patterns form when the film deviates from these characteristic thicknesses. We have recently extended the study of these materials by applying high throughput, continuous gradient techniques to understand the entire morphological evolution of this surface pattern as a function of H. It has also recently been observed that changes in the morphology of the block copolymer film can be induced by modifying the substrate surface energy. The objective of the present work is to combine the thickness gradient technique previously utilized with a surface energy gradient to map out the effect of surface energy on the thin film block copolymer morphology. Previous studies have shown that when PS-b-PMMA is cast and annealed on a hydrophilic substrte the PMMA preferentially segregates to the substrate while the PS segregates to a hydrophobic substrate. The PS block segrates to the air interface in all cases and smooth films form for film thickness of h, = ml^o for the hydrophobic substrate and h, = (m + 1/2)L_o for the hydrophilic substrate Islands and holes are produced when the film thickness deviates from H_o. In films where the substrate is energetically nwutral, the block copolymer lamellae are found to form perpendicular to the substrate with a layer of PS across the air interface, producing a smooth film for any h. The objective of this research is to utilize continuous gradient techniques to systematically quantify film surface morphological transitions with changing substrate surface energy.

Citation

Polymer Preprints

Volume

42

Issue

No. 2

Pub Type

Journals

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Keywords

block copolymer ordering, combinatorial experiment, substrate energy, surface pattern formation

Citation

Smith, A. , Sehgal, A. , Amis, E. and Karim, A. (2001), Characterization of Surface Energy Effects on Morphology of Thin Diblock Copolymer Films by High Throughput Techniques, Polymer Preprints, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851900 (Accessed March 26, 2025)