Dielectric relaxation measurements of a series of oligo(propylene glycol) dimethyl ethers, CH3-O-[CH2-CH(CH3)-O]N-CH3, including samples with the number of PG units N = 1, 2, 3, 7, 17, 34, and 69, were made by Mattsson et al. [Phys. Rev. Lett. 94, 165701 (2005)] at ambient pressure. The objective of the study was to relate the change of properties of the glass transition dynamics to the number of monomer units N in the chain. Not examined in the previous publication is how the change of the width of the frequency dispersion of the α-relaxation with N is related to the observed change in the α-β bifurcation characterized by the ratio, τ(α)(T(g))/τ(β)(T(g)). In this paper, the frequency dispersion of the dimer, trimer, and heptamer are fitted by the Fourier transform of the Kohlrausch stretched exponential function, φ(t) = exp[-(t/τ(α))(1-n)]. Determined from experimental data, both τ(α)(T(g))/τ(β)(T(g)) and n increase with N. More interestingly, we find τ(α)(T(g))/τ(β)(T(g)) has approximately the same value as [τ(α)(T(g))/t(c)](n) with t(c) = 2 ps, in accordance with the prediction of the Coupling Model of approximate relation between τ(α) and τ(β) given by τ(β) ≈ (t(c))(n)(τ(α))(1-n). Considered also are previously unpublished dielectric loss spectra of the heptamer taken at different combinations of T and P with τ(α)(T,P) fixed by Roland et al. [Phys. Rev. B 77, 012201 (2008)]. The dielectric loss data show not only the α-loss peaks superpose but also the high frequency flank including the barely resolved JG β-relaxation superposes approximately. This is again consistent with the approximate relation between τ(α) and τ(β) from the Coupling Model because n is unchanged on varying P and T with τ(α)(T,P) kept constant, and t(c) is a constant. The additional advance made herein has the benefit of enhancing the impact of the earlier experimental studies of the oligo(propylene glycol) dimethyl ethers on current understanding of the dynamics of glass transition.
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http://dx.doi.org/10.1063/1.4854115 | DOI Listing |
Polymers (Basel)
December 2022
Research Laboratory "New Polymeric Materials", Nizhny Novgorod State Technical University n.a. R.E. Alekseev, 24 Minin Street, Nizhny Novgorod 603950, Russia.
The properties of polymer brushes based on three macromonomers were investigated in aqueous and organic solutions. Methacrylic monomers with different compositions of the oligo(oxyalkylene) substituents and arrangements of the oligo(ethylene glycol) and oligo(propylene glycol) blocks were used for the synthesis of polymers. There were methoxy [oligo(ethylene glycol)-block-oligo(propylene glycol)] methacrylate, methoxy [oligo(propylene glycol)-block-oligo(ethylene glycol)] methacrylate, and methoxy oligo(propylene glycol) methacrylate.
View Article and Find Full Text PDFPolymers (Basel)
August 2021
Institute of Macromolecular Compounds of the Russian Academy of Sciences, Bolshoy Prospekt 31, 199004 Saint Petersburg, Russia.
Polymethacrylic molecular brushes with oligo(ethylene glycol)-block-oligo(propylene glycol) side chains were investigated by static and dynamic light scattering and viscometry. The solvents used were acetonitrile, tetrahydrofuran, chloroform, and water. The grafted copolymers were molecularly dispersed and dissolved in tetrahydrofuran and acetonitrile.
View Article and Find Full Text PDFJ Chem Phys
December 2013
Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, Italy.
Dielectric relaxation measurements of a series of oligo(propylene glycol) dimethyl ethers, CH3-O-[CH2-CH(CH3)-O]N-CH3, including samples with the number of PG units N = 1, 2, 3, 7, 17, 34, and 69, were made by Mattsson et al. [Phys. Rev.
View Article and Find Full Text PDFJ Appl Biomater Funct Mater
September 2013
Center for Biomaterial Development and Berlin-Brandenburg Centre for Regenerative Therapies, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow, Germany.
Background: Triblock copolymers from hydrophilic oligo(ethylene glycol) segment A and oligo(propylene glycol) segment B, providing an ABA structure (OEG-OPG-OEG triblock), are known to be biocompatible and are used as self-solidifying gels in drug depots. A complete removal of these depots would be helpful in cases of undesired side effects of a drug, but this remains a challenge as they liquefy below their transition temperature. Therefore we describe the synthesis of covalently cross-linked hydrogel networks.
View Article and Find Full Text PDFJ Appl Biomater Funct Mater
September 2013
Center for Biomaterial Development and Berlin-Brandenburg Centre for Regenerative Therapies, Institute of Polymer Research, Helmholtz-Zentrum Geesthacht, Teltow, Germany.
Purpose: The formation of photoresponsive hydrogels were reported by irradiation of star-shaped poly(ethylene glycol)s with terminal cinnamylidene acetic acid (CAA) groups, which are capable of a photoinduced [2+2] cycloaddition. In this study we explored whether oligo(ethylene glycol)s and oligo(propylene glycol)s of varying molecular architecture (linear or star-shaped) or molecular weights could be functionalized with CAA as terminal groups by esterification or by amide formation.
Methods: Oligo(ethylene glycol) (OEG) and oligo(propylene glycol) (OPG) with varying molecular architecture (linear, star-shaped) and weight average molecular weights between 1000 and 5000 g.
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