Comparison of surface mechanical properties among linear and star polystyrenes: Surface softening and stiffening at different temperatures

Viscoelastic modeling of nanoindentation experiments: A multicurve method

“…Similar results for the viscoelastic response of a PDMS have been reported by Houston . Later Karim and McKenna applied the particle embedment method and found the surface modulus to be softer than the macroscopic glassy modulus for a neat epoxy, an epoxy/POSS composite system and for polystyrene films at least for the materials far below their glass transition temperatures ( T g ) . Forrest et al also observed softening behavior for polystyrene using similar experiments.…”

“…10 Later Karim and McKenna 11 applied the particle embedment method and found the surface modulus to be softer than the macroscopic glassy modulus for a neat epoxy, an epoxy/POSS composite system and for polystyrene films at least for the materials far below their glass transition temperatures (T g ). 12,13 Forrest et al 14,15 also observed softening behavior for polystyrene using similar experiments. VanLandingham et al 16,17 performed step loading and step indentation depth experiments and found that the viscoelastic properties obtained were consistent with macroscopic mechanical measurements.…”

Local Glass Transition Temperature Tg(z) Profile in Polystyrene next to Polybutadiene with and without Plasticization Effects

“…Over two decades of study on such so-called confined systems have demonstrated that interfaces perturb the local properties not only at the interface, but that the disturbance propagates into the material away from the interface for some distance. [8][9][10][17][18][19][20][21][22][23][24][25] Different types of material properties, glass transition temperature (T g ), [17,[26][27][28] modulus, [13,[29][30][31][32] viscous flow, [33][34][35][36] and physical aging, [18,19,37] have all been reported to change near interfaces and in thin films. Additives distance z ≈ 225-250 nm before bulk PS T g is recovered, while rubbery PS next to glassy polysulfone (PSF) or poly(methyl methacrylate) (PMMA), or rubbery PnBMA next to glassy PS, requires z ≈ 100-125 nm before T g bulk is recovered.…”

Highly efficient synthesis and characterization of multiarm and miktoarm star-long-branched polymers via click chemistry

“…3c and 4c) indicated the formation of 3-arm to 12-arm star polymers. Such higher efficiency is attributed to the below reasons: (1) high-capping rate in anionic polymerization and 100% esterication efficiency; (2) controlling molar ratio as 1 : 1 between azido group in linear polymer chain-end and alkynyl group in cores; (3) controlling concentration of single-arm polymer within appropriate range. These curves kept the same monomodal and symmetric elution peak with small narrow PDI (#1.04) as PB-N 3 and PS-N 3 except residual small amount of single-arm linear polymer.…”

“…[1][2][3][4] As the simplest branched structure, star polymers have different behaviors and properties in solution, bulk and melt from their linear counterparts. [1][2][3][4] As the simplest branched structure, star polymers have different behaviors and properties in solution, bulk and melt from their linear counterparts.…”