Concentration dependence of the viscoelastic properties of polystyrene‐tricresyl phosphate solutions

Abstract

Based on creep and creep‐recovery measurements, the viscoelastic functions [J(t), Jr(t), J′(ω), J″(ω), G′(ω), G″(ω), and L(lnτ)] are presented for solutions of a narrow molecular‐weight‐distribution polystyrene in tri‐m‐tolyl phosphate in the concentration range of 1% to 100% polymer. For concentrations of 25% polymer and above, two maxima are exhibited by the retardation spectrum, L(lnτ). In the neighborhood of each of the maxima the retardation spectra of the more concentrated solutions can be superimposed by translations along both the logL and logτ axes. Reflecting the increasing width of the rubbery plateau with increasing polymer concentration, the dependence of the concentration time‐scale shift factors is greater for the terminal region of response. The response of the solvent is seen at the lower concentrations and it is a less sensitive function of the concentration than that of the polystyrene. This behavior is associated with the previously reported observation of two glass‐transition temperatures in the middle concentration range. For the higher concentrations, both the steady‐state and rubbery‐plateau compliances are inversely proportional to the square of the concentration.

Dynamics in glass-forming mixtures: Comparison of behavior of polymeric and non-polymeric components

“…Similar observations were made earlier in the Ref. [29] but not widely understood because that prevailing view has been the miscible systems must show a single T g . For glass-forming mixtures involving polymers, self-concentration provides a natural explanation for miscible systems that show more than one T g .…”

Extraordinary elevation of the glass transition temperature of thin polymer films grafted to silicon oxide substrates

“…The PS-OH in our samples is likely to be highly entangled since the M W we have used is 100 kg/ mol, well above the molecular weight of entanglement of PS, M e Ϸ17.7 kg/mol. 48,49 For PHS, however, our data indicate that chain entanglement is unlikely to be an important factor in determining the thickness dependence of T g because: ͑1͒ the thickness of the grafted layer after a Soxhlet extraction in THF is within 10% of the thickness after the PGMEA wash, indicating that there is little entangled but ungrafted polymer in the residual layer, and ͑2͒ the molecular weights of the two samples of PHS we have studied are 10 kg/mol and 20 kg/mol, below the M e of PHS. 50,51 In terms of our previous work demonstrating the effect of interfacial energy on the T g of supported films, chains grafted to the substrate could be viewed as constituting a very high-energy interface.…”

Anomalous viscoelastic properties of polymers: Experiments and explanations

“…This property of the spectrum of response is called thermorheological simplicity. This assumption turns out to be incorrect as I and my collaborators found by experiments over the last three decades [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and have been repeatedly confirmed by others in other polymers [22][23][24][25][26][27][28][29][30][31][32]. For a review see Ref.…”