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

Silvia Pizzanelli; Daniele Prevosto; Massimiliano Labardi; Tommaso Guazzini; Simona Bronco; Claudia Forte; Lucia Calucci

doi:10.1039/c7cp02595e

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

Phys Chem Chem Phys. 2017 Dec 6;19(47):31804-31812. doi: 10.1039/c7cp02595e.

Authors

Silvia Pizzanelli¹, Daniele Prevosto², Massimiliano Labardi², Tommaso Guazzini², Simona Bronco², Claudia Forte¹, Lucia Calucci¹

Affiliations

¹ CNR-ICCOM, Istituto di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle Ricerche-CNR, Via G. Moruzzi, 1, 56124 Pisa, Italy. silvia.pizzanelli@pi.iccom.cnr.it.
² CNR-IPCF, Istituto per Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche-CNR, Via G. Moruzzi, 1, 56124 Pisa, Italy.

PMID: 29171606
DOI: 10.1039/c7cp02595e

Abstract

Dielectric Spectroscopy (DS) and ¹H 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_g = 70 °C by Differential Scanning Calorimetry). Above T_g, 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_g of 69 °C and a fragility of 155 for PVB glass. Below T_g, 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^-1. The β process was also found to contribute to ¹H NMR relaxation above T_g.