Random Copolymer Adsorption at the Polymer Melt/Substrate Interface:  Effect of Substrate Type

Abstract

Using low-energy forward recoil spectrometry (LE-FRES) and dynamic secondary ion mass spectrometry (DSIMS), we measure the interfacial excess, z*, and the volume fraction profiles of a bromine functionalized polymer chains at the polymer/inorganic substrate interface. Specifically, we investigate a blend of polystyrene (PS) homopolymer and a deuterium-labeled poly-d-(styrene-ran-4-bromostyrene) (dPBrxS) random copolymer, where the mole fraction of 4-bromostyrene units in the chain is x ) 0.06. Our aim is to measure the strength of interaction of bromine functionalized segments of dPBr0.06S with silicon oxide, SiOx, and hydrogen-terminated silicon, SiH, surfaces. The results from both LE-FRES and DSIMS show that dPBr0.06S segregates at both polymer/SiOx and polymer/SiH interfaces, demonstrating that that the bromine groups do interact favorably with both surface types. We also use the self-consistent mean-field model (SCMF) to calculate the dPBr0.06S concentration profile and z* at the polymer/substrate interface and to determine the value of the interaction energy between 4-bromostyrene segments and the substrate. The comparison of experimental and SCMF results provides the interaction energy between the brominated polystyrene repeat unit and both substrate types, namely dPBr1S SiOx ) -0.18kT and dPBr1S SiH ) -0.22kT. These results show that the interaction of the brominated segment with SiH surface is ca. 20% stronger than that with the SiOx surface.

Block Copolymer Adsorption from a Homopolymer Melt to Silicon Oxide: Effects of Nonadsorbing Block Length and Anchoring Block−Substrate Interaction

“…Note that this value is 1 order of magnitude weaker than the ε between PMMA and SiO x . This observation is consistent with those of Oslanec et al , Therefore, only one input parameter Σ PMMA - SiO x (or Σ PDMAEMA - SiO x ) was systematically varied until the SCMF profile fell into good agreement with the experimental profile (cf. Figures and ).…”

“…In fact, few experimental studies attempt to measure the strength of these interactions. [1][2][3][4][5][6][7][8][9] However, the polymer conformation near interfaces has been studied theoretically 2,9-11 and experimentally. [12][13][14][15][16] The goals of our study are to investigate the effects of the nonadsorbing block length on the conformation of adsorbed molecules at the polymer/substrate interface and to understand how these interfacial characteristics depend on the polymer-substrate interaction by changing the adsorbing block type.…”

“…Although interfacial properties are determined by these two factors, the interaction strength between a polymer and a substrate cannot be easily determined experimentally and is not readily available in the literature. In fact, few experimental studies attempt to measure the strength of these interactions. − However, the polymer conformation near interfaces has been studied theoretically ,− and experimentally. − The goals of our study are to investigate the effects of the nonadsorbing block length on the conformation of adsorbed molecules at the polymer/substrate interface and to understand how these interfacial characteristics depend on the polymer−substrate interaction by changing the adsorbing block type.…”

Surface ordering in thin films of liquid‐crystalline polymers containing fluorinated and protonated segments: Neutron‐reflectometry study

“…This study addresses the structure of thin films of a polymeric liquid crystal that consists of short alternating methylstilbene units and fluorinated cyclobutane segments. When polymers and liquid crystals are cast into thin films, the interfacial interactions become significant, determining the structure of the film 1–10. Among the most notable effects is surface‐induced segregation, enhancing ordering.…”

“…In the polymer under consideration, the interfacial structure is affected by all of the aforementioned parameters. Extensive experimental1–10 and theoretical studies11–19 address surface segregation of polymers, blends, and diblock copolymers. Theoretical studies11–14 of binary polymer blends have indicated that surface segregation is mainly driven by the difference of surface energies of the polymers.…”