Abstract
Proton NMR spin-lattice relaxation time (T1) and dielectric relaxation time (τ0) have been used to correlate the experimental and calculated values of T1 for Poly (propylene glycol) at 300 K. Also, the contributions of dielectric relaxation time (τ0) of each constituent group of PPG-425 to the effective dielectric relaxation time due to the whole chain of the polymer have been calculated using NMR spin–lattice relaxation time. The H1 NMR data and dielectric data of Poly (propylene glycol) HO [CH(CH3)CH2O]nH with number average molecular weight 425 (n = 7) g mol−1have been used to understand the conformation and basic mechanism of relaxation in polymer in its pure liquid state. Conformational analysis using Hartree-Fock formalism was performed for the polymer of n = 7 and the average bond distances obtained from the computation were used to assign NMR relaxation times to specific subgroups. Free energy and enthalpy of activation associated with methyl and other groups in the chain of PPG molecules have been calculated. BPP (Bloembergen Purcell Pound) model gives better correlation for molecular tumbling motion for PPG-425 in pure liquid state than Kubo & Tomita equation.
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