Macromolecules, 37 (2), 429 -436, 2004. 10.1021/ma035402g S0024-9297(03)05402-0
Web Release Date: December 17, 2003

Copyright © 2003 American Chemical Society

Investigating the Crystalline Structure of Poly(vinylidene fluoride) (PVDF) in PVDF/Silica Binary and PVDF/Poly(methyl methacrylate)/Silica Ternary Hybrid Composites Using FTIR and Solid-State 19F MAS NMR Spectroscopy

Jin-Woo Park, Yun-Ah Seo, Il Kim, and Chang-Sik Ha*

Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, Korea

Keitaro Aimi and Shinji Ando

Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-Ku, Tokyo 152-8552, Japan

Received September 19, 2003

Revised Manuscript Received November 12, 2003

Abstract:

We investigated the crystalline structures of poly(vinylidene fluoride) (PVDF) in PVDF/silica (SiO2) binary and PVDF/poly(methyl methacrylate) (PMMA)/SiO2 ternary hybrid composite films using infrared (IR) analysis and solid-state, high-speed magic-angle-spinning (MAS) 19F NMR spectroscopy. These hybrid films were prepared by sol-gel processes. We used three different blending sequences to prepare the ternary hybrid composite films: (1) The "Type 1" hybrid was prepared from a one-pot mixture of PVDF, PMMA, and tetraethoxysilane (TEOS), the silica precursor, in dimethylacetamide (DMAc). (2) The "Type 2" hybrid composite was prepared by first forming a PVDF/silica hybrid and then mixing it with PMMA. (3) The "Type 3" hybrid composite was prepared by mixing a preformed PMMA/silica hybrid with PVDF. The crystallinity of the PVDF/SiO2 hybrid composite films decreased upon increasing the silica content. By using the different methods to prepare the PVDF/PMMA/SiO2 ternary hybrid composite films, we were able to assign the -phase of PVDF crystals in the solid-state 19F MAS NMR spectrum, which shows seven resonances that are attributable to an amorphous domain (-88 ppm), crystalline domains (-101.3, -93.7, -84.2, and -79.6 ppm), and regioirregular structures (-112.4 and -110.4 ppm). 19F MAS NMR spectra of the Type 2 and Type 3 PVDF/PMMA/SiO2 hybrid composite films show two new resonances, assignable to the -phase at lower (-101.3 ppm) and higher (-84.2 ppm) frequencies, which show long 19F spin-lattice relaxation times in the rotating frame (T1F) and chemical shifts that are significantly different from those of - and -phases of the PVDF crystals. The disappearance of the -phase of PVDF crystals in the Type 2 and Type 3 hybrid composite films can be explained by the large silica particles in the PVDF/PMMA matrix hindering crystallization of PVDF. Solid-state 19F spin-lock NMR spectroscopy experiments also indicate significant differences exist between the values of T1F of the crystalline and amorphous domains depending on the method of hybrid preparation.

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