Dielectric studies of chain dynamics in homogeneous semi-interpenetrating polymer networks

Molecular dynamics in polyester- or polyether-urethane networks based on different diisocyanates

“…The g-relaxation is assigned to the movements of the (CH 2 ) x sequences in the soft segments of PU chains [14][15][16]. For this reason the g-relaxation activation energy is similar in all the systems based on the same macrodiol because in these materials such sequences are identical.…”

“…The secondary b-relaxation can be most probably attributed to the local motions of the polar urethane groups, as proposed by several authors [2,[15][16][17]. It is, however, not clear why this relaxation is not visible in the systems based on both the macrodiol Terathane Ò 650 and the diisocyanate H 12 MDI.…”

Molecular dynamics of linear and hyperbranched polyurethanes and their blends

“…The low-temperature secondary relaxation process (b) is associated with the local motion of the (CH 2 ) 4 sequences of PTMO [34]. The second local relaxation (b 0 ), which is located between two primary processes, is most probably connected with the local movements of the segments including urethane groups [36,37].…”

Dielectric Analysis (DEA)

“…6.6.5.1. These mechanisms exhibit a spectrum of activation energies and relaxation strength strongly dependent on the packing density and the interchain interactions (Georgoussis et al 2000b ). Since the mid -1990s, in particular, the molecular dynamics and phase morphology of thermoplastic linear/low -branched polyurethanes have been studied in detail by TSC and DEA, for their utilization in specialized technological and biomedical applications (Fr ü bing et al 2002 ;Charnetskaya et al 2003 ;Okrasa et al 2005 ;Kalogeras et al 2005b ).…”

“…Since the mid -1990s, in particular, the molecular dynamics and phase morphology of thermoplastic linear/low -branched polyurethanes have been studied in detail by TSC and DEA, for their utilization in specialized technological and biomedical applications (Fr ü bing et al 2002 ;Charnetskaya et al 2003 ;Okrasa et al 2005 ;Kalogeras et al 2005b ). Modifi cation in the packing density and the morphology of the polyurethane DIELECTRIC ANALYSIS OF THERMOPLASTICS (Georgoussis et al 2000b ). 6.23 a.…”