In this study, we develop a completely green process that could generate a recycled and value added product of polystyrene (PS), such as micro- and nanosized particles, from waste expanded PS (EPS). The process uses the eco-friendly solvent, d-limonene for dissolving waste EPS. We show the first time use of water as a nonsolvent for the recovery of micro- and nanosized PS particles based on an emulsification–diffusion method. Water forms a low boiling azeotrope with d-limonene and reduces the operating temperatures significantly. Poly­(vinyl alcohol) (PVA), a water-soluble polymer, is used for stabilizing the oil–water emulsion and to control the particle size. The obtained particles were characterized using scanning electron microscopy, FTIR and dynamic light scattering techniques. Effect of PS and PVA concentrations, stirring speed and oil to water (o/w) ratio on the yield and particle size were investigated. The spent solvent was recovered using a distillation process that was carried out along with the emulsification–diffusion, making the process more efficient and sustainable.

Three subjects in polymer and soft matter physics are outlined in the present article. The first relates to concepts of an ideal glass transition. We describe work on ultra-stable glass, either a 20-million-year-old amber or a vapor deposited amorphous fluoropolymer, which examines the temperature dependence of the dynamics in a window between a low fictive temperature and the glass transition temperature. From this "finesse" of the problem of the geological time scales in sub-glass temperature systems strong evidence that the divergence of the relaxation times at finite temperature from WLF-types of extrapolation is not correct. The second topic is polymer nonlinear viscoelasticity as it relates to dynamic heterogeneity. We show results from mechanical hole burning experiments that suggest that dynamic heterogeneity arises from the nature of specific relaxation mechanisms rather than heterogeneous changes in, for example, the fictive temperature. Included is a discussion of large amplitude oscillatory shear testing and how it relates to characterization of nonlinear viscoelastic materials. The last topic addressed is the rheology of circular macromolecules. Here, we take a historical perspective and describe important new results from several laboratories that seem inconsistent. New works from our own studies on circular DNA are also discussed.

Nonlinear mechanics of soft materials such as polymer melts or polymer solutions are frequently investigated by Large Amplitude Oscillatory Shear (LAOS) spectroscopy tests. Less work has been reported on the characterization of the nonlinear viscoelastic properties of glassy polymers within a similar framework. In the present work, we use an extension of LAOS, i.e., mechanical spectral hole burning (MSHB), to investigate the nonlinear dynamics of an amorphous polymer in the deep glassy state. MSHB was developed as an analog to non-resonant spectral hole burning developed by Schiener et al. [Science 274(5288), 752–754 (1996)], who attributed the presence of holes to dynamic heterogeneity. On the other hand, Qin et al. [J. Polym. Sci., Part B: Polym. Phys. 47(20), 2047–2062 (2009)] in work on polymer solutions of tailored heterogeneity have attributed the presence of holes to the type of dynamics (Rouse, rubbery, etc.) rather than to a specific spatial heterogeneity. Here, we have performed MSHB experiments on poly(methyl methacrylate) in the deep glassy state (at ambient temperature, which is near to the β-relaxation) to investigate the presence and origin of holes, if any. The effects of pump frequency and pump amplitude were investigated, and we find that vertical holes could be burned successfully for frequencies from 0.0098 Hz to 0.0728 Hz and for pump amplitudes from 2% to 9% strain. On the other hand, horizontal holes were incomplete at high pump amplitude and low frequency, where higher spectral modification is observed. The results are interpreted as being related to the dynamic heterogeneity corresponding to the β-relaxation rather than to the hysteresis energy absorbed in the large deformation pump.

Mechanical spectral hole burning (MSHB) has been used to investigate the nonlinear dynamics in polymers, ranging from melts, solutions, block co-polymers, and glasses. MSHB was developed as an analog to the dielectric spectral hole burning method, which is not readily applicable in polymers due to weak dielectric response. While similar holes were observed in both mechanical and dielectric hole burning, the interpretations were different. In the latter case, it has been argued that the holes are related to dynamic heterogeneity as related to an increase in the local temperature of molecular sub-ensembles (spatial heterogeneity), while in the former case, the holes have been related to the type of dynamics (rubbery, Rouse, etc.). Recent work from our laboratories used MSHB to investigate glassy poly(methyl methacrylate) and showed evidence of hole burning and supported the hypothesis that the origin of holes was related to dynamic heterogeneity as evidenced by the holes being developed near the strong β-relaxation in PMMA. In this work, MSHB is used to study polycarbonate, which has a weak β-relaxation, and the results are compared with those observed in PMMA. We observe that the polycarbonate exhibits weak holes and the nature of the holes with a change in pump amplitude and frequency is different than observed in PMMA. These results support the hypothesis that the hole burning observed in amorphous polymers below the glass transition temperature is related to the strength of the β-transition, which, in turn, is related to molecular level heterogeneity in the material dynamics.

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