Combined FTIR and Dielectric Investigation of Poly(vinyl acetate) Adsorbed on Silica Particles

Abstract

Samples with different amounts of poly(vinyl acetate) adsorbed on silica particles were prepared in order to study their interfacial interactions and dynamics. The interface of adsorbed polymers to a substrate plays an important role in many applications such as polymer nanocomposites, thin films, and coatings. Characterization of such interfaces is thus of high importance since they were found to differ from bulk properties. Thermogravimetric analysis (TGA) is applied to analyze the amounts of polymer adsorbed on silica particles. Broadband dielectric spectroscopy (BDS) is employed in a broad frequency (10–1–106 Hz) and temperature range (178–423 K) in order to probe the polymer/silica interface. Two relaxation processes can be identified for the composites: one corresponding to the bulklike polymer and a second one related to polymer chains close to the silica surface. For the latter the dynamic glass transition is shifted to higher temperature due to reduced mobility. This effect is investigated in dependence on the polymer content. Further investigations are done to obtain information about bound and free carbonyl fractions of poly(vinyl acetate) using Fourier transform infrared spectroscopy (FTIR) measurements.

Calorimetric evidence for a mobile surface layer in ultrathin polymeric films: poly(2-vinyl pyridine)

“…A similar result was reported for poly(vinyl acetate) filled with silica nanoparticles. 49 These results are in contradiction to an investigation of P2VP films spin coated on a highly doped Si wafer by broadband dielectric spectroscopy 50 where the dynamic glass transition was found to be independent of the film thickness. Also semi-isolated P2VP chains adsorbed on a doped Si wafer seem to resemble bulk like dynamics.…”

Reduced-mobility layers with high internal mobility in poly(ethylene oxide)–silica nanocomposites

“…URL: www.physik.uni-halle.de/nmr system and the same method. [12][13][14] In this context DSC, 10,16,19 dielectric spectroscopy, 23,24 NMR spectroscopy, 13,18,20,21 and static 22 as well as dynamic 9,11,12,14,15 neutron scattering techniques have been used. Apart from purely structural (=density) information obtained by static scattering, 22 most other techniques are sensitive to dynamic properties.…”

Unexpected Molecular Weight Effect in Polymer Nanocomposites

“…To verify this hypothesis, we performed detailed studies on model PNCs [15,21] using small angle X-ray scattering (SAXS), broadband dielectric spectroscopy (BDS), temperature modulated differential scanning calorimetry (TMDSC), and mass density measurements. Details of the measurements are presented in the Supplementary Materials (SM) [33].…”

“…Adding silica nanoparticles to PVAc leads to several changes in the dielectric spectra (Fig.1) [15,[21][22][23]: (i) the α-relaxation peak (segmental dynamics) shifts slightly to lower frequency, broadens and decreases in amplitude; (ii) an additional contribution appears on the low-frequency side (α'-peak); (iii) the Maxwell-Wagner-Sillar's (MWS) polarization process appears at even lower frequency; and (iv) the conductivity changes. The α'-process, corresponding to the segmental dynamics in the interfacial layer [21,23] which was not resolved in previous studies [15,[21][22][23], is now clearly visible especially in the derivative spectra, ε' der (ω) = -π/2*∂ε'(ω)/∂ln(ω) (Fig.S2 in SM [33]), and the relaxation time distribution analysis (Fig.1b) (for details of this analysis see Ref. [41] and SM [33]).…”

“…To the best of our knowledge, this is the first clear demonstration of the interfacial layer dynamics as a well-resolved relaxation process in PNCs. The dielectric spectra of PNCs are often analyzed as the summation of the Havriliak-Negami functions (HN-fitting) of the bulk segmental peak (α-peak) and of the interfacial peak (α'-peak) [21,23] as shown in Fig.1a. We recently realized this approach ignores the heterogeneous nature of nanocomposites and is not accurate [41].…”