Microwave dielectric relaxation study of poly(propylene glycol) in dilute solution

Microwave dielectric relaxation and molecular dynamics in binary mixtures of poly(propylene glycol) 2000 and poly(ethylene glycol)s of varying molecular weight in dilute solution

“…Its value depends on the overall size of the molecules. For macromolecules, a low value of τ o for higher molecular weight polymers in comparison with their oligomers confirmed that there is large coiling in the molecular chain 6–10. In liquid–liquid binary mixtures of PPG–PEGs, we observed symmetrical variations in the value of τ o in benzene solutions (see Table 2 for the τ o values).…”

“…These linear slopes are used for the determination of the average relaxation time τ o and distribution parameter α. The values of these slopes of polymer mixtures, together with the values of linear slopes of individual molecules of PPG 2000 and PEGs in benzene and carbon tetrachloride,6, 7, 10 can be used to study the distribution of the dielectric constant and loss, and may also be used for theoretical modelling. Values of τ o and α were calculated by Higasi's single frequency measurement equations35 proposed for dilute solutions where ω is the angular frequency and A = a″ (a o − a ∝ ), B = (a o − a′) (a′ − a ∝ ) − a″ 2 and C = (a′ − a ∝ ) 2 + a″ 2 .…”

“…The calculated values of τ o , α, τ 1 and τ 2 of various binary mixture of PPG + PEGs in benzene and carbon tetrachloride are reported in Table 2. Earlier6, 7, 10 observed values of τ o , α, τ 1 and τ 2 of individual solutes (ie polymer mixture constituents) in benzene and carbon tetrachloride are also recorded in Table 2 for comparison and discussion of molecular bynamics in binary mixtures.…”

“…These dielectric relaxation studies are very interesting and confirm that molecular conformation becomes more complicated with increasing chain length in these flexible self‐associating molecules. At the same time, we investigated the microwave dielectric behaviour of poly(propylene glycol)10 of average molecular weight 2000 g mol −1 in different non‐polar solvents so as to understand the effect of solvent environment on molecular dynamics. More recently Leon et al 11 also measured the low frequency dielectric relaxation of propylene glycol (PG) and oligomers having different numbers of repeat units ( n = 2, 3 and 69) and established a relationship between the primary and secondary dielectric relaxation processes at temperatures above the glass transition temperature, T g .…”

Integrating Microwave‐Assisted Synthesis and Solid‐Supported Reagents

“…For example, if a polymer resin is introduced into a system, greater dielectric loss is observed. This has been extensively investigated only for systems containing soluble polymers [80][81][82][83][84][85][86][87][88][89][90] , but the concept can be extrapolated to other resin environments as well. The origin of microwave heating lies with the ability of the electric field to induce a polarisation of charges within the heated sample.…”