How we can interpret the T₁ dispersion of MC, HPMC and HPC polymers above glass temperature?

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• 作者：Adam Rachocki ; Joanna Kowalczuk ; Jadwiga Tritt-Goc
• 关键词：Polymer chain dynamics ; Field-cycling NMR relaxometry ; Tube/reptation model
• 刊名：Solid State Nuclear Magnetic Resonance
• 出版年：2006
• 出版时间：October 2006
• 年：2006
• 卷：30
• 期：3-4
• 页码：192-197
• 全文大小：274 K

文摘

The chain dynamics in methyl cellulose (MC), hydroxypropylmethyl cellulose (HPMC) and hydroxypropyl cellulose (HPC) were studied with the aid of field-cycling NMR relaxometry technique in the temperature range from 300 to 480 K that is above the glass transition, but below thermal degradation. The frequency dependence of proton spin-lattice relaxation time was determined between 24 kHz and 40 MHz for selected temperatures. The experimental spin-lattice relaxation dispersion data were fitted with the power law relations of T₁∝ω^γ predicted by the tube/reptation model. The exponent's values found from the fitting procedure for MC, HPMC and HPC almost exactly match the ones predicted in tube/reptation model for limit II (γ=0.75) and in MC also for limit III (γ=0.50). Remarkably, this finding concerns the polymers in networks formed of the same polymer species.