Solvent effect polymer degradation

Moussa, T., Tiu, C., and Sridhar, T., Effect of solvent on polymer degradation in turbulent flow, J. Non-Newtonian Fluid Mech. 45 261 (1993). 

Structure and mechanism in photochemical reactions. The reactions of geminal radical pairs created in bulk polymers are presented by Chesta and Weiss in Chapter 13. Of the many possible chemical reactions for such pairs, they are organized here by polymer and reaction type, and the authors provide solid rationalizations for the observed product yields in terms of cage versus escape processes. Chapter 14 contains a summary of the editor s own work on acrylic polymer degradation in solution. Forbes and Lebedeva show TREPR spectra and simulations for many main-chain acrylic polymer radicals that cannot be observed by steady-state EPR methods. A discussion of conformational dynamics and solvent effects is also included. 

Somewhat similar measurements could be based on solid disruption [18], polymer degradation [7], or accelerated dissolution. These well-known mechanical effects of ultrasound also derive from cavitation. Thus one might measure the rate of particle size reduction under sonication of some standard solid dispersed in a given fluid. Alternatively one could measure the rate of dissolution of a standard solid in a solvent, or the reduction in molecular weight of polymer chains. Here again the initial particle size and surface conditions, together with pressure and temperature, should be carefully monitored. 

The existence of UCST is typically attributed to the energy differences between polymer and solvent and of LCST to the so-called free-volume effects, which are dne to the differences in size and free-volume between polymer and solvent. Free-volume effects are small for nonpolymeric solutions and are discussed in conjunction with free-volume-based activity coefficient models in Section 16.4. The LCST was first discovered by Freeman and Rowlinson only about 40 years ago, but is now considered to be a universal phenomenon of polymer-solvent systems at high temperatures. In some cases, it is not observed if the polymer degrades before reaching the LCST. 

Degradation in the presence of solvents has also been applied to the conversion of other styrenic polymers, such as poly(p-methylstyrene) and poly(styrene-allyl alcohol).64,65 Figure 4.11 shows the temperature dependence of the conversion of poly(p-methylstyrene) when using phenol, 1-methyl-naphthalene and tetralin as solvents. In this case, tetralin leads to the greatest degradation below 370 °C, whereas the order is reversed above that temperature. These results indicate that the effect of the solvent in the degradation of styrenic polymers is strongly influenced by the temperature. 

Effect of polymer molecular structure Effect of molecular weight and its distribution Effect of concentration Solvent quality Mechanical degradation... 

Slagowski et al. (33) demonstrated the feasibility of HFIP as the SEC eluant for several polytetramethylene terephthalate polymers. Because polystyrene is not soluble in HFIP, no MW values were reported. In the same year Drott (7) used HFIP as SEC solvent for both nylons and polyesters. A polyelectrolyte effect had been observed for nylons but it was not a problem for polyesters. Drott also indicated that no polymer degradation occurred in HFIP by comparing the intrinsic viscosities of the initial and recovered PET samples. The direct calibration method was used by trial-and-error adjustment of the coefficients of a cubic polynomial until intrinsic viscosities of the samples calculated from SEC data (using the Mark-Houwink equation) agreed with experimentally measured values. 

Sikorska Wanda, Adamus Grazyna, Dobrzynski Piotr, et al. Forensic engineering of advanced polymeric materials—Part II The effect of the solvent-free non-woven fabrics formation method on the release rate of lactic and glycolic acids from the tin-free poly(lactide-co-glycolide) nonwovens. Polym. Degrad. Stabil. 110 (2014) 518-528. 

Table 2 Summary of Some Representative Studies on Effects of Solvent Types on Polymer Degradation... 

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