Quantification of interaction and topological parameters of polyisoprene star polymers under good solvent conditions

Abstract

Mass fractal scaling, reflected in the mass fractal dimension d f , is independently impacted by topology, reflected in the connectivity dimension c, and by tortuosity, reflected in the minimum dimension d min . The mass fractal dimension is related to these other dimensions by d f = cd min . Branched fractal structures have a higher mass fractal dimension compared to linear structures due to a higher c, and extended structures have a lower dimension compared to convoluted self-avoiding and Gaussian walks due to a lower d min . It is found, in this work, that macromolecules in thermodynamic equilibrium display a fixed mass fractal dimension d f under good solvent conditions, regardless of chain topology. These equilibrium structures accommodate changes in chain topology such as branching c by a decrease in chain tortuosity d min . Symmetric star polymers are used to understand the structure of complex macromolecular topologies. A recently published hybrid Unified scattering function accounts for interarm correlations in symmetric star polymers along with polymer-solvent interaction for chains of arbitrary scaling dimension. Dilute solutions of linear, three-arm and six-arm polyisoprene stars are studied under good solvent conditions in deuterated p-xylene. Reduced chain tortuosity can be viewed as steric straightening of the arms. Steric effects for star topologies are quantified, and it is found that steric straightening of arms is more significant for lower-molecular-weight arms. The observation of constant d f is explained through a modification of Flory-Krigbaum theory for branched polymers.

SANS Study on Critical Polymer Clusters of Tetra-Functional Polymers

“…The estimated fractal dimension for prepolymers from the Figure was 1.80 ± 0.02 according to the general scattering theory of polymer chains ( I /φ ∼ q – D s ). , The estimated fractal dimension is close to the theoretical value for the linear polymer chains in good solvent in dilute state ( D s = 1.67). This similarity of the fractal dimension of star polymer chains and linear polymer chains in good solvents has been reported by Rai et al …”

“…18,20 The estimated fractal dimension is close to the theoretical value for the linear polymer chains in good solvent in dilute state (D s = 1.67). This similarity of the fractal dimension of star polymer chains and linear polymer chains in good solvents has been reported by Rai et al 25 To investigate the structure and the size distribution of the critical clusters, we diluted the as-prepared critical clusters with the same buffer used to synthesize these clusters, and carried out the same SANS experiments on those dilutions.…”

Structural determination of Enzyme-Graphene Nanocomposite Sensor Material

“…The choice of the number of the levels used for the data interpretation depends on the features in the SANS curve. Owing to the presence of three distinct bend/hump in the SANS curve (at q ~ 0.004, 0.02 and 0.07 Å −1 ), the GOx dimer system is fitted with a three level Unified Fit, as: 2,18,44,46–49 where, , , and erf is the error function. The subscripts c , a and G indicate different levels of GOx organizations namely the clusters, aggregates and GOx dimer levels, respectively.…”

“…The ability of differentiating and effectively outlining the thermodynamics and topologies in fractal and hierarchical structure using Unified Fit on SANS is well investigated 18,43,49 .…”

Star polymers as unit cells for coarse-graining cross-linked networks

“…The body of work investigating low branched SPs remains rather scarce. A few authors made important remarks that properties of low branched SPs could differ from those of highly branched [10][11][12]. Thus, when f ≤ 10 the monomer density around the central bead is no longer described by the blob model, and the Yukawa-type repulsion is not observed [10,13].…”