Contents 4 Polymer solutions

At first glance, the contents of Chap. 9 read like a catchall for unrelated topics. In it we examine the intrinsic viscosity of polymer solutions, the diffusion coefficient, the sedimentation coefficient, sedimentation equilibrium, and gel permeation chromatography. While all of these techniques can be related in one way or another to the molecular weight of the polymer, the more fundamental unifying principle which connects these topics is their common dependence on the spatial extension of the molecules. The radius of gyration is the parameter of interest in this context, and the intrinsic viscosity in particular can be interpreted to give a value for this important quantity. The experimental techniques discussed in Chap. 9 have been used extensively in the study of biopolymers. 

Alkaline (and also acidic) ester hydrolysis of /3-poly(L-malate) is accompanied by side reactions leading to the formation of fumarate, maleate and/or racemiza-tion, especially at elevated temperatures. The above assays thus underestimate the polymer contents due to the formation of small amounts of 2-4% fumarate (unpublished results). This fraction of fumarate increases for the hydrolysis of more concentrated polymer solutions. 

A portion of each solution was retained for analysis of carb-oxylate content at zero time. Samples of the polymer solutions were weighed into glass jars, the pH adjusted to 8.5 and the jars were sealed with tightly fitting screw caps. The jars were placed in thermostatted ovens at 90°, 108°, and 120°C. After the appropriate time, the jars were removed, cooled and weighed to ensure no loss of contents, prior to analysis for hydrolysis. 

Solutions containing 0.15 g/dL polymer and between 0 and 0.342 molar sodium chloride or between 0 and 2.49 x 10 molar calcium chloride show declines in viscosity as salt content increases. Solution viscosity of nonionic copolymers declines, at most,... 

An aqueous colloid/emulsion of rubber particles can be up to 65% solids content generally low viscosity compared to polymer solutions. Only rubbers produced by emulsion polymerisation or natural rubber can be found in this form. 

Precipitation of the catalyst can be effected by treating the polymer solution with acid/base and/or oxidants. Poloso and Murray [95] proposed a method to recycle the nickel octanoate ((CH3(CH2)6C02)2Ni)/triethylaluminum((C2H5)3Al) catalyst from a styrene-butadiene polymer solution. The polymer solution containing the catalysts was refluxed with 4 wt.% glacial acetic acid (relative to polymer) for 4 h, followed by treatment with 1.4 wt.% anhydrous ammonia. The solution was then filtered through a diatomaceous earth. The nickel content in the polymer was decreased from 310 ppm to 5.6 ppm. 

Adsorption is commonly used for catalyst removal/recovery. The process involves treating the polymer solution with suitable materials which adsorb the catalyst residue and are then removed by filtration. Panster et al. [105] proposed a method involving adsorbers made from organosiloxane copolycondensates to recover rhodium and ruthenium catalysts from solutions of HNBR. These authors claimed that the residual rhodium could be reduced to less than 5 ppm, based on the HNBR content which had a hydrogenation conversion of over... 

Contents K. Osaki Viscoelastic Properties of Dilute Polymer Solutions. W.L. Carrick The Mechanism of Olefin Polymerization by Ziegler-Natta Catalysts. C. Tosi,... 

Figure 9.15 presents an example of the in vivo measurements of the oxygen content in the arterial blood of dogs over a period of 10 h. The dots represent the batch gas analysis performed with a Nova Biomedical blood gas analyzer. The solid lines represent the analyses monitored by the instrument. Blood oxygen measurements were obtained continuously (not shown in the figure) about every 3 sec. Two different polymer solutions are shown. The measurements performed by the instrument are not affected by the presence of unmetabolized clots and/or anesthetics in the blood stream. Additionally, no deterioration of the signal was found after 10-h periods. 

The influence of salt content in the polymer solution, and particularly monovalent salts used to neutralise the polymer, were also studied. 

When the leuconitrile content was 1.0 mole %, the 1 mass % aqueous polymer solution showed Tc at 29.2 °C. Upon UV irradiation, the polymer did not show any more clear phase separation. The transmittance decreased gradually with increasing temperature above 36 °C. The absence of the phase separation behavior indicates that the hydrophobic interaction of the main chain is not strong enough to overcome the hydrophilidty of the photogenerated triphenyl-methyl cations and the polymer chain cannot shrink any further even at a higher temperature. 

Craft Copolymers with Low Backbone-Polymer Content. The procedure for preparing this kind of graft copolymer is based on the dissolution of the backbone polymer in the monomer, dispersion of this solution in water, and polymerization by means of an organic peroxide. It applies only to soluble backbone polymers, such as most EPR s. As the handling of a too-viscous vinyl chloride/backbone polymer solution is impractical, this procedure is normally used for preparing end products of the type VC/backbone polymer (95-5) or (90-10). 

As viscosity increases with decreasing volatile content, the flash tank becomes inefficient as bubbles are entrapped and redissolved upon discharge. The falling-strand devolatilizer, shown schematically in Fig. 8.2, was developed to answer this problem, and represents an improvement over the ordinary flash tank. Here the polymer solution is pumped at high superheat into thin strands that fall gravitationally into the vacuum tank. Free of hydrostatic or shear-induced pressure fields, the bubbles nucleate, grow, coalesce, and rupture so that the volatiles are released before they get trapped in the melt of the cachepot. 

The monograph contains the fundamentals of the theory and reflects the modern situation in understanding the relaxation behaviour of a polymer solutions and melts. The contents of the monograph can be related to the fields of molecular physics, fluid mechanics, polymer physics and materials science. I have tried to present topics in a self-contained way that makes the monograph a suitable reference book for professional researchers. I hope that the book will also prove to be useful to graduate students of above mentioned specialities who have some background in physics and mathematics. It would provide material for a one or two semester graduate-level course in polymer dynamics. 

The long decay time (T2 ) of the other component is typical of semi-diluted polymer solutions. The T2 value continuously increases with an increasing solvent content. This... 

As dimerization competes with polymerization, dimer formation very slightly reduces polymer yield. The toxicity and the smell of VCH are much more relevant. VCH is removed from the rubber solution together with residual monomer and solvent prior to the isolation of the rubber from the polymer solution. As VCH has a higher boiling point than BD and hexane an efficient stripping process has to be used in order to reduce VCH contents to environmentally friendly levels. 

With higher quantities of volatile components from viscous media, such as polymer melts or polymer solutions, the resulting large quantity of gas or vapor is difficult to remove. Apart from achieving a specific residual amount of solvent, the safe removal of the resulting large quantities of gas or vapor also introduce certain operating limits, particularly for media with a volatile component content of more than 5 to 10%. 

Characterization. The NMR spectra were recorded on a Bruker DRX 500 spectrometer (500 MHz). The solvent (acetone- ) was used as an internal reference. UV-VIS spectra were recorded on UV-VIS Perkin Elmer Lambda 19 spectrometer. For the estimation of photo cross-linker content at a wavelength of 305 nm, 1 mol% of polymer solution in water was used. 

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