Effect of Star Architecture on the Dynamics of 1,4-<i>cis</i>-Polyisoprene under Nanometer Confinement

Kardasis, Panagiotis; Oikonomopoulos, Angelos; Σακελλαρίου, Γεώργιος; Steinhart, Martin; Floudas, George

doi:10.1021/acs.macromol.1c02212

Cited by 8 publications

(19 citation statements)

References 69 publications

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“…This effect for star polymers can be discussed with respect to a recent investigation of star PIs under confinement within the same pores (following long annealing). It was shown that star-shaped polymers with a large number of arms, present a higher affinity for adsorption in comparison to linear polymers and hence are more strongly affected by the confinement . Chain adsorption affected the dielectric strength of the chain modes that are unable to fluctuate.…”

Section: Resultsmentioning

confidence: 99%

“…The missing dielectric strength of the stars (blue arrow in Figure b) reflects the fraction of adsorbed arms on the AAO walls. It has been employed earlier by us to obtain an estimate of the thickness of the interfacial layer and further, to suggest some possible arm configurations next to the pores …”

Section: Resultsmentioning

confidence: 99%

“…Instead, stars relax through the arm retraction mechanism, e.g., by withdrawing an arm down the tube toward its branching point and by relaxing to a new tube. − The process has a relaxation time that increases exponentially with the arm molar mass. In addition, a slower dielectric process was found in the vicinity of the soft-colloidal process identified earlier by rheology. − Confinement was found to strongly affect the star dynamics because PI stars were more strongly affected by adsorption than linear chains . The reduced dielectric strength of the chain modes was employed as a measure of the thickness of the interfacial layer.…”

Section: Introductionmentioning

confidence: 84%

“…Therefore, overall stars consist of 72.5% 1,4- cis configurations. The synthesis of the star-shaped polyisoprenes is reported elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…Recently, we investigated the effect of chain topology (in a series of cis -1,4-polyisoprene stars with functionality, f ) on the polymer dynamics within nanoporous alumina by dielectric spectroscopy . In comparison to linear polymers, the reptation mechanism in the stars is suppressed due to the branching point functionality.…”

Section: Introductionmentioning

confidence: 99%

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Non-equilibrium Effects of Polymer Dynamics under Nanometer Confinement: Effects of Architecture and Molar Mass

et al. 2022

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The non-equilibrium dynamics of linear and star-shaped cis-1,4 polyisoprenes confined within nanoporous alumina is explored as a function of pore size, d, molar mass, and functionality (f = 2, 6, and 64). Two thermal protocols are tested: one resembling a quasi-static process (I) and another involving fast cooling followed by annealing (II). Although both protocols give identical equilibrium times, it is through protocol I that it is easier to extract the equilibrium times, t eq, by the linear relationships of the characteristic peak frequencies with time and rate, respectively, as log(fmax) = C 1 – k log(t) and log(fmax) = C 2 + λ log(β). Both thermal protocols establish the existence of a critical temperature (at T c, where k → 0 and λ → 0) below which non-equilibrium effects set-in. The critical temperature depends on the degree of confinement, 2R g/d, and on molecular architecture. Strikingly, establishing equilibrium dynamics at all temperatures above the bulk, T g, requires 2R g/d ∼ 0.02, i.e., pore diameters that are much larger than the chain dimensions. This reflects non-equilibrium configurations of the adsorbed layer that extent away from the pore walls. The equilibrium times depend strongly on temperature, pore size, and functionality. In general, star-shaped polymers require longer times to reach equilibrium because of the higher tendency for adsorption. Both thermal protocols produced an increasing dielectric strength for the segmental and chain modes. The increase was beyond any densification, suggesting enhanced orientation correlations of subchain dipoles.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 84%

“…Therefore, overall stars consist of 72.5% 1,4- cis configurations. The synthesis of the star-shaped polyisoprenes is reported elsewhere …”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Non-equilibrium Effects of Polymer Dynamics under Nanometer Confinement: Effects of Architecture and Molar Mass

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Molecular Dynamics and Viscoelastic Properties of the Biobased 1,4-Polymyrcene

et al. 2022

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We report the synthesis and dynamics of a series of polymyrcene homopolymers, all with identical microstructures (95% 1,4-units and 5% of 3,4units), the latter by dielectric spectroscopy and rheology. Polymyrcene belongs to an important class of bio-based polymers (polyterpenes) with known members, the cis-1,4-polyisoprene and the cis-1,4-polyfarnesene. Polyterpenes constitute a class of type-A polymers where by architectural design, one can control the thickness of chains and henceforth the segmental and chain dynamics. The dielectric, rheology, and thermodynamic results showed a lower glass temperature in cis-1,4polymyrcene as compared to cis-1,4-polyisoprene. A weak dependence of the segmental and longest normal mode on pressure revealed the dominant effect of the backbone. Furthermore, comparing polymyrcene with available literature data of polyisoprene and polyfarnesene, we report the effect of chain thickening on the viscoelastic properties. The plateau modulus, G N 0 , decreased, the entanglement molar mass increased (from 5 kg•mol −1 in cis-1,4polyisoprene to 22 kg•mol −1 in cis-1,4-polymyrcene), and the packing length, p, increased (from 3.1 Å in cis-1,4-polyisoprene to 4.7 Å in cis-1,4-polymyrcene) as anticipated by chain thickening. The plateau modulus, G N 0 , followed the proposed empirical relation: G N 0 = 0.00226k B T/p 3 , further reflecting the proportionality between the tube diameter and the packing length.

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Cyclic Topologies in Linear α,ω-Dihydroxy Polyisoprenes by Dielectric Spectroscopy

et al. 2022

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A series of mono- and di-functionalized polyisoprenes (PIs) bearing hydroxyl (OH−) end-group(s) with different molar masses ranging from 2 to 30 kg mol–1 were synthesized and studied by a combination of temperature- and pressure-dependent dielectric spectroscopy and rheology. In the di-functionalized PIs, the −OH end-group interactions result in a mixture of linear and cyclic configurations (up to 45% cyclic configurations for the lower molar masses). The formation of cyclic topologies due to increased H-bonding interactions restricted the backbone mobility and increased the glass temperature, T g, especially for the lower molar masses. Moreover, an additional process (termed α*) was evidenced in the dielectric spectroscopy in the range between the segmental process and the global chain relaxation. It followed a Vogel–Fulcher–Tammann temperature dependence, freezing at a temperature in the vicinity of the liquid-to-glass temperature, being independent of molar mass. Its molecular origin was identified by employing the pressure sensitivity of the characteristic relaxation times and the pressure dependence of T g. It reflects the relaxation of segments in the vicinity of the H-bonded groups. Overall, this study provided information on the impact of weakly associating polar end-groups (hydroxyl) on the molecular dynamics of type-A polymers. Furthermore, it suggested promising routes for designing polymers with a higher concentration (>50%) of cyclic topologies, for example, by employing (i) short chains with (ii) strongly associating end groups (stronger than the hydroxyl end-groups).

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Effect of Star Architecture on the Dynamics of 1,4-cis-Polyisoprene under Nanometer Confinement

Cited by 8 publications

References 69 publications

Non-equilibrium Effects of Polymer Dynamics under Nanometer Confinement: Effects of Architecture and Molar Mass

Non-equilibrium Effects of Polymer Dynamics under Nanometer Confinement: Effects of Architecture and Molar Mass

Molecular Dynamics and Viscoelastic Properties of the Biobased 1,4-Polymyrcene

Cyclic Topologies in Linear α,ω-Dihydroxy Polyisoprenes by Dielectric Spectroscopy

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