Enhancing the molecular cooperativity of polyvinyl butyral using liquid additives. Issue 4 (21st November 2017)

• Record Type: Journal Article
• Authors: Carini, Giovanni; Carini, Giuseppe; D'Angelo, Giovanna; Federico, Mauro; Marco, Gaetano Di; Bartolotta, Antonino
• Is Part Of: Journal of polymer science. Volume 56:Issue 4(2018)
• Page Start: 340
• Page End: 346
• Publication Date: 2017-11-21
• Subjects: activation entropy -- dielectric relaxations -- mechanical relaxations -- polyvinyl butyral; 547
• DOI: 10.1002/polb.24547
• Languages: English
• ISSNs: 0887-6266

Abstract

ABSTRACT: The specific role of acetonitrile and methoxypropionitrile, as accelerators of the relaxation dynamics of polyvinyl butyral (PVB), was investigated in polymer/additive mixtures with a saturation liquid content. The aim was to improve the ionic mobility of PVB‐based solid electrolytes to be used in solid dye‐sensitized solar cells. Mechanical and dielectric relaxation measurements between 120 K and 380 K revealed that the α‐relaxation observed above 330 K in dry‐PVB is shifted quite below room temperature in PVB/additives. Both the additives cause a growing intermolecular cooperativity, the sub‐glass β‐relaxation exhibiting a strength enhanced by a factor 3 and a frequency factor which increases from 10 15 s −1 to 10 21 s −1 . This discloses an activation entropy as high as 165.7 J/K mol in comparison to 40.8 J/K mol in dry‐PVB. It is suggested the existence of cooperative transitions, mainly driven by bridges formed through additive molecules, which influence both short‐ and long‐scale segmental motions and also favor the ion dynamics in PVB/additive/electrolyte systems. The room temperature ionic conductivity σ rt exhibits large changes from 6.4*10 −14 S/m in dry PVB, through 1.5*10 −8 S/m in PVB/LiI, to 2.45*10 −5 S/m in PVB/MPN/LiI. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2018, 56, 340–346 Abstract : Addition of acetonitrile (ACN) and methoxypropionitrile (MPN) to polyvinyl butyral (PVB) accelerates the relaxation dynamics of the host polymer. The α‐relaxation observed above 330 K in PVB is shifted quite below room temperature in PVB/additives. Both the additives cause a growing intermolecular cooperativity of subglass β‐relaxation with an activation entropy as high as 165.7 J/K mol in comparison to 40.8 J/K mol in pure PVB.