Simple-liquid dynamics emerging in the mechanical shear spectra of poly(propylene glycol)

Gainaru, C.; Hecksher, Tina; Fan, Fei; Xing, Kunyue; Cetinkaya, Burak; Olsen, Niels Boye; Dyre, Jeppe C.; Sokolov, Alexei P.; Böhmer, Roland

doi:10.1007/s00396-017-4206-6

Cited by 2 publications

(2 citation statements)

References 36 publications

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“…Polypropylene glycol (PPG) is a common glass-forming polymer that has been studied by different techniques such as dielectric spectroscopy, − calorimetry, nuclear magnetic resonance (NMR), mechanical experiments, − neutron scattering, and various light scattering methods. − It is known that the glass transition temperature ( T g ) of PPG with hydroxyl groups at both chain-ends is almost independent of molecular weight . On the contrary, Engberg et al found that the structural relaxation dynamics of methyl-terminated PPG exhibits a pronounced molecular weight dependence.…”

Section: Introductionmentioning

confidence: 99%

The Role of Chain-End Association Lifetime in Segmental and Chain Dynamics of Telechelic Polymers

et al. 2018

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Broadband dielectric spectroscopy, differential scanning calorimetry, and rheology were employed to study the impact of hydrogen (H)-bonding end-groups on segmental and chain dynamics of telechelic polypropylene glycol (PPG) and poly(dimethylsiloxane) (PDMS). Polymer chains with three types of H-bonding end-groups possessing different interaction strengths and a non-H-bonding end-group as reference were compared. The glass transition temperature (T g ) of H-bonding PPG systems with low molecular weight increases compared to the reference, and the T g difference varies with chain-end interaction strength. In contrast, their shear viscosities (for T g -scaled temperature, i.e., when the shift in T g is accounted for) are similar to that one of the reference. This is in strong contrast to the behavior of telechelic PDMS with the same set of endgroups, where the T g increase of all H-bonding systems is independent of H-bond strengths, while shear viscosity increases significantly only for the strongest H-bonding end-groups. These observations are explained by the difference in lifetime of the end-group associations relative to segmental and chain relaxation times.

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Section: Introductionmentioning

confidence: 99%

The Role of Chain-End Association Lifetime in Segmental and Chain Dynamics of Telechelic Polymers

et al. 2018

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“…Poly(propylene oxide) (PPO) is a poly(alkyl ether) showing similarity but with lower polarity than PEO and has been largely studied by different techniques in the past decades. ,− It is a so-called “type A” polymer that features an electrical dipole moment formed along the backbone chain contour, so that it is possible to study the segmental relaxation and the normal modes easily via dielectric spectroscopy. ,− The segmental motion responsible for the α-relaxation is regarded as local and should cover only few repeating units, but the so-called normal mode process is highly cooperative and involves the whole polymer chain . While in the past the association of heterocomplementary bifunctional PPO, bearing also either DAT or THY as end groups, was studied by small-angle neutron scattering (SANS), the dynamics of such supramolecular polymers has not been addressed in any detail, in particular, the segmental and association dynamics.…”

Section: Introductionmentioning

confidence: 99%

Influence of Polymer Polarity and Association Strength on the Properties of Poly(alkyl ether)-Based Supramolecular Melts

et al. 2022

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The present work focuses on the impact of polymer polarity and hydrogen-bonding (H-bonding) end groups association strength on the structure and dynamics of poly(alkyl ether)-based supramolecular model polymers studied by means of small angle scattering (SAS), rheology, dielectric relaxation spectroscopy (DRS), and differential scanning calorimetry (DSC). These consist of poly-(propylene oxide) (PPO) or poly(ethylene oxide) (PEO) backbone that selfassembly in the bulk via hydrogen bonding (H-bonding). Diaminotriazine (DAT) and thymine-1-acetic acid (THY) as well as 2-ureido-4[1H]-pyrimidinone (UPY) are the H-bonding end groups of choice. Both PPO and PEO bearing either DAT or THY as end groups associate into linear chains, but PPO-THY/DAT forms longer chains in comparison with PEO-THY/DAT. The lower polarity of the backbone results in stronger associations for the same end groups. However, the temperature dependence of the association/dissociation lifetimes for this H-bonding type is independent of the different main chain polarity as these breaking times do not exceed the rouse chain dynamics as expected within the Cates model. PPO-UPY forms a transient network characterized by the interplay between small transient bonds controlled by the characteristic times of association/dissociation between pairs of UPY groups involving probably just two ends, revealed by the similar dielectric spectra with PPO backbone, and a more stable bond type of associate that forms phase separated UPY clusters. The latter are responsible for the physical cross-links in the network and result in the rubbery-like plateau of the rheological spectra. PPO-UPY has similar structure to PEO-UPY, as validated by small angle scattering, but the UPY detachment times in the clusters are longer for PEO-UPY than for PPO-UPY, though the activation energies are very close and match the typical energy barrier specifically imposed by the hydrogen bonds. Moreover, while the segmental relaxation times and the glass transition temperature (T g ) of PPO-UPY is similar to PPO, PEO-UPY has the highest T g value and a much slower segmental relaxation as compared to PEO and PPO based supramolecular polymers. This seems to indicate that the Hbonding association dynamics of the UPY groups is strongly influenced by the main chain polarity that play a fundamental role in defining the time scale of the association process.

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Simple-liquid dynamics emerging in the mechanical shear spectra of poly(propylene glycol)

Cited by 2 publications

References 36 publications

The Role of Chain-End Association Lifetime in Segmental and Chain Dynamics of Telechelic Polymers

The Role of Chain-End Association Lifetime in Segmental and Chain Dynamics of Telechelic Polymers

Influence of Polymer Polarity and Association Strength on the Properties of Poly(alkyl ether)-Based Supramolecular Melts

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