Preparation and Characterization of Four-Branched Star Polystyrene

Abstract

A method is described for the preparation of well-defined four-star polystyrenes involving coupling of polystyryllithium with l,2-bis(methyldichlorosilyl)ethane. Nine samples were prepared over a 30-fold range of molecular weight.Osmotic and light-scattering techniques were used to measure number-and weight-average molecular weights where possible. Intrinsic viscosity and sedimentation coefficients were measured in cyclohexane at 35 and 50°and in toluene at 35°. The ratio g' ([z?](branched)/[T7](linear)) was found to be 0.76 under 6 conditions and slightly lower in better solvents. The value falls between theoretical estimates. The corresponding ratio of sedimentation coefficients (/z) was found to be 0.93-0.94 compared with a theoretical value of 0.89.

Spherical polymer brushes under good solvent conditions: Molecular dynamics results compared to density functional theory

“…However the effect of a spherical geometry of the substrate on the brush structure has been considered mostly for the extremely high curvature regime. It is indeed well known that when the radius of the central nanoparticle gets smaller than the typical size of the free macromolecule in solution, a crossover to the behavior of star polymers [34][35][36][37][38][39][40][41] is expected. The intermediate curvature regime, where the size of the core is comparable to the full molecule extension, has received somewhat less attention.…”

Scaling Theory and Computer Simulation of Star Polymers in Good Solvents

“…The experimental studies of star polymers have stimulated theoretical studies to be more closely tied up with the experiments. For example, the virial coefficients [40][41][42], relaxation times [43,44] and hydrodynamic effects [45][46][47][48] have been more recently investigated with a powerful tool of computer simulations and some of their results have been successfully compared with the experiments [31][32][33][34][35][36][37]49,50] (for a recent review, see [51]). The effect of walls or other confining geometries has also found interest [52][53][54] in connection , for example, with surface critical phenomena (see [55] for a review).…”

“…In the past two decades, the great progress in the synthesis of highly qualified monodisperse polymer networks [31][32][33][34][35][36][37][38] has stimulated many experimental and theoretical studies of star polymers. More recently, star polymers with a huge number of arms has also been synthesized in a controlled fashion [39].…”

Effects of Chain Ends and Three-Segment Interactions on Second and Third Virial Coefficients of Four-Arm Star Polystyrenes

“…15 This prediction, contradictory to the behavior of experimental A 2 for star polymers, at least, with f 4, prompted us to examine the end effects on A 2 of four-arm star PS as was done for linear PS. We note that the previously investigated star polystyrene samples, anionically synthesized with butyllithium, [16][17][18][19][20] had a butyl group at each arm end.In the present work, we prepared three and two low molar mass samples of four-arm star polystyrenes with a benzyl group (4SPS-Bz) and a butyl group (4SPS-Bu) at each arm end, respectively, and determined their A 2 and A 3 (the third virial coefficient) in cyclohexane at  by light scattering. Our interest in A 3 was to see whether the third coefficients for the two star polymers increase with lowering M w as was found for linear polystyrenes by Mizuno et al…”

“…15 This prediction, contradictory to the behavior of experimental A 2 for star polymers, at least, with f 4, prompted us to examine the end effects on A 2 of four-arm star PS as was done for linear PS. We note that the previously investigated star polystyrene samples, anionically synthesized with butyllithium, [16][17][18][19][20] had a butyl group at each arm end.…”