Polymer capillary interactions

Dilute Polymer Solutions. The measurement of dilute solution viscosities of polymers is widely used for polymer characterization. Very low concentrations reduce intermolecular interactions and allow measurement of polymer—solvent interactions. These measurements ate usually made in capillary viscometers, some of which have provisions for direct dilution of the polymer solution. The key viscosity parameter for polymer characterization is the limiting viscosity number or intrinsic viscosity, [Tj]. It is calculated by extrapolation of the viscosity number (reduced viscosity) or the logarithmic viscosity number (inherent viscosity) to zero concentration. 

There are several ways to reduce or suppress the electroosmotic flow in capillaries. These methods involve either eliminating the zeta potential across the solution-solid interface or increasing the viscosity at this interface. One approach is to coat the capillary wall, physically, with a polymer such as methylcellulose or linear polyacrylamide. Because of the difficulty in deactivating the capillary surface reproducibly, however, alternative methods employing dynamic reduction of solute-capillary interactions have been developed. Dynamic reduction of these interactions include the addition of chemical reagents such as methylhydroxyethylcellulose, S-benzylthiouro-nium chloride, and Triton X-100. 

Lichtenthaler, R. N. Liu, D. D. Prausnitz, J. M., "Polymer-Solvent Interactions from Gas-Liquid Chromatography with Capillary Columns," Macromolecules, 7, 565 (1974a). 

Moreover, Shi and his group reported electrochemical deposition of PPy microcontainers onto soap bubbles associated with O2 gas released from the electrolysis of H2O in an aqueous solution of /3-naphthalenesulfonic acid (/3-NSA), camphorsulfonic acid (CSA), or poly(styrene sulfonic acid) (PSSA), which act both the surfactant and dopant [79-81]. Morphologies such as bowls, cups, and bottles could be controlled by electrochemical conditions (Figure 11.6). However, the microcontainers were randomly located on the electrode surface, which limited further applications, Shi and coworkers reported a linear arrangement of PPy microcontainers by self-assembly with gas bubbles acting as templates on a silicon electrode surface patterned by photolithography [82]. They found that capillary interactions between the gas bubbles and the polymer photoresist walls led the microcontainers to be arranged linearly. 

POLYMER-SURFACTANT INTERACTION AND ITS EFFECT ON THE MOBILIZATION OF CAPILLARY-TRAPPED OIL... 

Fig. 4. Fluorescence anisotropy of the enantiomers of binaphthyl phosphate in the presence of a micelle polymer. Capillary electrophoresis measurements confirmed the enantiomer with the greatest interaction also had the greatest anisotropy value (inset). Reproduced with permission from Ref. [28]. Copyright 2001, Am. Chem. Soc.

There are several methods of buffer and capillary surface modification used to prevent electrostatic interactions. Two modes have been examined mn buffer with pH >10 in the uncoated capillary and anionic polymer coating capillary, developed in lAI. 

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