Dynamics of PIPA-d₇ on Silica Surface

Piyawan Krisanangkura
Frank D. Blum, Missouri University of Science and Technology

This document has been relocated to http://scholarsmine.mst.edu/chem_facwork/2404

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Molecular motion of polymer chains is an important determinant in understanding the physical properties of polymeric materials. Glass transition temperature (Tg) is a physical property of polymers, which is of primary interest. The study of the dynamics of polymer segments assists in understanding the dependence of Tg on polymer structure.1 For decades, studies have addressed the molecular motion in various polymers. Some of them have probed the dynamics of polymer backbones.2,3 the properties of a polymer at an interface may change because of the type of polymer, the substrate, or other variables. The side chain of a polymer can also play an important role in terms of the interaction between a polymer and a substrate at an interface.4 the strength of the surface-segment interaction affects the mobility of polymer-chain segments. Several techniques have been used to investigate the effects, including modulated differential scanning calorimetry (MDSC)5,6 and nuclear magnetic resonance (NMR).2,3,7,8 in this work, relatively narrow polydispersity poly(isopropyl acrylate)-d7 (PIPA-d7) has been selected for study. The large and bulky group on the PIPA side-chain, would provide a different probe for segmental mobility than that of previously studied poly(methyl acrylate)-d3 (PMA-d3).9-11 the PIPA sidechain contains two methyl groups, branched at a methane carbon atom. Additionally, when different amounts of polymers are deposited on a surface, individual unique behaviors become evident that are different from the behavior of bulk polymers. Deuterium solid-state NMR was used to characterize the polymer segmental motions in both bulk deuterium-labeled PIPA and polymer thin films on silica. The 2H quadrupole-echo NMR spectra were collected as a function of temperature. The interpretation of those spectra can provide valuable information on the molecular motion and the physical properties of the polymer including glass transition temperatures. Calorimetry, the most widely accepted technique for measuring the glass transition temperature (Tg), was also performed for comparison. This work is an update of that previously presented.12