Layers of Distinct Mobility in Densely Grafted Dendrimer Arborescent Polymer Hybrids

Kardasis, Panagiotis; Kalafatakis, Nikolaos; Gauthier, Mario; Vlassopoulos, Dimitris; Floudas, G.

doi:10.1103/physrevlett.126.207802

Cited by 8 publications

(8 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Under these conditions, monomeric iso-friction conditions are guaranteed for comparison among particles with different degrees of polymerization (or silica contents). Moreover, we note that the combination of high grafting densities and topology, which is responsible for the “dry” and “wet” layer conformations of GNPs and stars, gives rise to regimes of distinct local mobility. − In the present work, we focus on large-scale dynamics associated with the response of grafted arms and of the entire nanoparticle. The results indicate rich relaxation dynamics with both polymeric and colloidal contributions observable in the same rheological spectrum and occurring at different time (and length) scales.…”

Section: Resultsmentioning

confidence: 70%

Universal Polymeric-to-Colloidal Transition in Melts of Hairy Nanoparticles

et al. 2021

Self Cite

View full text Add to dashboard Cite

Two different classes of hairy self-suspended nanoparticles in the melt state, polymer-grafted nanoparticles (GNPs) and star polymers, are shown to display universal dynamic behavior across a broad range of parameter space. Linear viscoelastic measurements on well-characterized silica-poly(methyl acrylate) GNPs with a fixed core radius (R core) and grafting density (or number of arms f) but varying arm degree of polymerization (N arm) show two distinctly different regimes of response. The colloidal Regime I with a small N arm (large core volume fraction) is characterized by predominant low-frequency solidlike colloidal plateau and ultraslow relaxation, while the polymeric Regime II with a large N arm (small core volume fractions) has a response dominated by the starlike relaxation of partially interpenetrated arms. The transition between the two regimes is marked by a crossover where both polymeric and colloidal modes are discerned albeit without a distinct colloidal plateau. Similarly, polybutadiene multiarm stars also exhibit the colloidal response of Regime I at very large f and small N arm. The star arm retraction model and a simple scaling model of nanoparticle escape from the cage of neighbors by overcoming a hopping potential barrier due to their elastic deformation quantitatively describe the linear response of the polymeric and colloidal regimes, respectively, in all these cases. The dynamic behavior of hairy nanoparticles of different chemistry and molecular characteristics, investigated here and reported in the literature, can be mapped onto a universal dynamic diagram of f/[R core 3/ν0)1/4] as a function of (N armν0 f)/(R core 3), where ν0 is the monomeric volume. In this diagram, the two regimes are separated by a line where the hopping potential ΔU hop is equal to the thermal energy, k B T. ΔU hop can be expressed as a function of the overcrowding parameter x (i.e., the ratio of f to the maximum number of unperturbed chains with N arm that can fill the volume occupied by the polymeric corona); hence, this crossing is shown to occur when x = 1. For x > 1, we have colloidal Regime I with an overcrowded volume, stretched arms, and ΔU hop > k B T, while polymeric Regime II is linked to x < 1. This single-material parameter x can provide the needed design principle to tailor the dynamics of this class of soft materials across a wide range of applications from membranes for gas separation to energy storage.

show abstract

Section: Resultsmentioning

confidence: 70%

Universal Polymeric-to-Colloidal Transition in Melts of Hairy Nanoparticles

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…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%

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

et al. 2022

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…Figure a depicts four characteristic time scales. Three are equilibrium processes, segmental relaxation, followed by the longest normal mode and by the soft-colloidal mode of the multiarm star polymer. − The latter is associated with the cooperative reorganization of the star and involves rotational and translational motions. Representative fits for the segmental, longest NM, and slower processes are shown in Figure S5, and the respective times are discussed in Figure S6.…”

Section: Results and Discussionmentioning

confidence: 99%

Ultraslow Adsorption of Star cis-1,4-Polyisoprenes by In Situ Imbibition in Nanopores

Kardasis,

Sakellariou,

Floudas

2023

Macromolecules

Self Cite

View full text Add to dashboard Cite

Using in situ nanodielectric spectroscopy, we report the imbibition kinetics of star cis-1,4-polyisoprenes in alumina nanopores as a function of chain architecture (linear vs multiarm stars), pore size, molar mass, and temperature. We demonstrate that the imbibition kinetics of star cis-1,4-polyisoprenes proceeds via a slow adsorption mechanism, about 2 orders of magnitude slower than in linear polyisoprenes. Such ultraslow time scales (∼106 s) have not been reported for any polymer at temperatures well above T g. We have explored the different imbibition kinetics of linear and star topologies in separating the components of a homogeneous blend composed of linear/star chains.

show abstract

Layers of Distinct Mobility in Densely Grafted Dendrimer Arborescent Polymer Hybrids

Cited by 8 publications

References 35 publications

Universal Polymeric-to-Colloidal Transition in Melts of Hairy Nanoparticles

Universal Polymeric-to-Colloidal Transition in Melts of Hairy Nanoparticles

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

Ultraslow Adsorption of Star cis-1,4-Polyisoprenes by In Situ Imbibition in Nanopores

Contact Info

Product

Resources

About