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High-resolution solid-state NMR study of isotactic polypropylenes

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Author(s): O. Fricova | M. Uhrinova | V. Hronsky | M. Kovalakova | D. Olcak | I. Chodak | J. Spevacek

Journal: eXPRESS Polymer Letters
ISSN 1788-618X

Volume: 6;
Issue: 3;
Start page: 204;
Date: 2012;
Original page

Keywords: Material testing | metallocene isotactic polyprop | Ziegler - Natta isotactic poly | solid state NMR | segmental motion

ABSTRACT
The high-resolution solid-state 13C NMR spectra were recorded for metallocene (m) and Ziegler-Natta (ZN) isotactic polypropylenes (iPP) in pelletized form using cross polarization (CP) and magic angle spinning (MAS) techniques within the temperature range of 20–160°C. Besides the CP MAS experiments also the MAS 13C NMR spectra (without CP), MAS 1H NMR spectra and rotating frame spin-lattice relaxation times T1ρ (13C) were measured at elevated temperatures. With the rise of temperature the splitting of CH2, CH and CH3 signals into two components was detected in 13C NMR spectra and assigned to amorphous and crystalline phases. The temperature dependences of chemical shifts and integral intensities obtained from the deconvoluted spectra provided information on the main chain and CH3 groups motions in amorphous and crystalline regions of studied samples. While T1ρ (13C) values show that the rate of segmental motion in amorphous regions in m-iPP and ZN-iPP is virtually the same, larger linewidths in 13C and 1H NMR spectra indicate somewhat larger restraints of the motion in amorphous regions of ZN-iPP.
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