Dynamics of poly(vinyl butyral) studied using dielectric spectroscopy and ¹H NMR relaxometry

Abstract

Dielectric Spectroscopy (DS) and H Fast Field-Cycling (FFC) NMR relaxometry were applied for understanding the dynamic behavior of the amorphous ter-polymer poly(vinyl butyral) (PVB) across the glass transition temperature (T = 70 °C by Differential Scanning Calorimetry). Above T, main chain segmental motions (α relaxation) were detected and characterized using both DS and FFC NMR relaxometry. The correlation times extracted by the analysis of DS and FFC NMR relaxometry data agreed within a factor of three and showed a Vogel-Fulcher-Tammann temperature dependence, with an associated T of 69 °C and a fragility of 155 for PVB glass. Below T, a secondary process (β relaxation) was revealed by DS, and was ascribed to reorientations of the vinyl alcohol dipoles due to local twisting motions with an associated activation barrier of 11 kcal mol. The β process was also found to contribute to H NMR relaxation above T.

Unravelling Main- and Side-Chain Motions in Polymers with NMR Spectroscopy and Relaxometry: The Case of Polyvinyl Butyral

“…An estimate of the correlation time for the motion governing relaxation in the observed frequency range can be obtained by the relationship at the maximum of R 1 , ωτ≅1; a value of τ of ~3∙10 −7 s is determined. This value is in agreement with that previously determined for commercial PVB at the same temperature [ 21 ].…”

“…If we compare these results with our previous findings on commercial PVB [ 21 ], we can state that the estimated value for the correlation time of the main-chain motion agrees with that determined for the α-relaxation by DS measurements. On the other hand, the correlation time of the side-chain motion at 115 °C is much longer than that associated to the β-relaxation as extrapolated at the same temperature from DS data.…”

“…In spite of the large number of technological applications, only a few studies were reported concerning the dynamics of PVB [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Recently, PVB dynamics was investigated by some of us over broad frequency and temperature ranges by DS and 1 H field-cycling (FC) NMR relaxometry, focusing on a commercial sample [ 21 ]. DS allowed the α-relaxation to be characterized.…”

PVB/ATO Nanocomposites for Glass Coating Applications: Effects of Nanoparticles on the PVB Matrix

“…This technique is sensitive to motions characterized by frequencies ranging from 10 kHz to tens of MHz. In a previous study on pure PVB [54], FFC NMR relaxometry allowed different motional processes to be identified above T g : segmental dynamics with characteristic frequencies of 10 5 -10 6 Hz and faster local motions with frequencies higher than 10 7 Hz. In the present work, the NMRD curves were acquired on the PVB-ATO composites in the temperature range between 90 and 120 • C; representative curves are shown in Figure 9.…”

Butyralization of poly(vinyl alcohol) under supercritical carbon dioxide for a humidity-resistant adhesive to glass substrates

“…PVB is accepted as an adhesive for lamination of glass and as a high-barrier layer towards moisture permeation in device sealing. [9][10][11][12][13][14][15] The adhesive properties are attributed to the polar hydroxyl groups of vinyl alcohol units and flexible moieties of butyral side chains. The moisture-sealing property is provided from the hydrophobicity of butyl side chains of PVB.…”