Polymers, spectroscopic determination

Non-reacted vinyl groups of these crosslinked polymers may be expressed by the residual unsaturation (RU). The RU is a measure for both the reactivity of the monomer and the structure of the crosslinked polymer. The RU may be determined by spectroscopic or chemical methods. For the spectroscopic determination a model compound of low molar mass is required as a reference for the standardization [217, 231, 254]. For the chemical determination a reagent of low molar mass is added to the pendant vinyl groups. Then the RU is obtained either by elemental analysis or by back-titration of the non-reacted reagent [231, 283-285]. 

Spectroscopic Determination of the Low-Frequency Dynamics of Biological Polymers and Cells... 

The purpose of this paper is the presentation of a brief overview of recent literature in which new models of electronic states in polymers and molecular solids have been proposed (, 2, 5-16). Since localized (e.g., molecular-ion) states seem prevalent in these materials, I indicate in Sec. II the physical phenomena which lead to localization. Sec. Ill is devoted to the description of a model which permits the quantitative analysis of the localized-extended character of electronic states and to the indication of the results of spectroscopic determinations of the parameters in this model for various classes of polymeric and molecular materials. I conclude with the mention in Sec. IV of an important practical application of these concepts and models The contact charge exchange properties of insulating polymers ( 7, 17, 18, 19). 

Once chain initiation is complete, the monomer consumption rate is determined only by the chain propagation step. With the less efficient lithium alkyl initiators in hexane or cyclohexane, rather large amounts of monomer are needed to complete chain initiation. The appearance of a first order decay in monomer concentration, invariably obtained in these experiments, is not a very sensitive indication of the complete absence of initiator. Analysis of trial samples for hydrolysis products of lithium alkyls or spectroscopic determination that the polymer anion concentration has reached a plateau are preferable. A seeding technique is often used [32, 59] where the real initiator is a pre-formed active polymer... 

Using liquid/liquid phase separation by thenoyltrifluoracetone, TTA, in benzene, the authors studied the speciation of Zr in the concentration range 10 to 0.1 M in 2 M perchloric acid solution as well as in 1 M HCIO4/I M LiC104 solutions. TTA is known to selectively extract free tetravalent ions such as Zr or the tetravalent actinide ions. Polymer formation by Zr in the aqueous phase is reflected quantitatively as a decrease in the distribution coefficient. The experiments were conducted very carefully spectroscopic determination of species in the benzene phase, correction for TTA loss of the benzene phase, consideration for complexation of Zr by TTA in the aqueous phase, recrystallisation of starting solids, consideration of impurities in the test, assurance that equilibrium has been reached and discussion of errors related to the variation of proton activity in the aqueous phase due to the extraction reaction. 

Characterization. Polymer composition was determined by a variety of classical analytical techniques that included elemental analysis and NMR. The carboxyl content of the polymers was determined by potentiometric titration following conversion to the acid form with an ion-exchange column. Analysis of the sodium content in the polymers gave carboxyl values within a few percent of those found by the titration technique. The number of hydrophobic groups in the polymers in this study was too low to allow quantification by conventional analytical techniques. The levels cited in this chapter refer to amounts added to the reactor and complete incorporation into the polymer was assumed. A recent study (8) using a UV spectroscopic technique on model hydrophobic monomers indicated that this was a fairly good assumption. 

Bokobza, L. Rapoport, O., Filled Elastomers Mid- and Near-IR Spectroscopic Determination of Rubber Dimensions in Composite in Unstretched State and Under Uniaxial Extension. J. Appl. Polym. Sci. 2003,87,1204-1208. 

DMF, and benzyl alcohol. These studies demonstrated the importance of the conformational structure of a conducting polymer in determining the bulk properties such as conductivity and crystallinity in the solid state. Next I will focus on only the UV-vis-NlR spectroscopic method. This technique has a unique place in studying the conformations of conjugated polymers, since the overlaps between tt electrons, hence the electronic absorptions, are very sensitive to the conformational structures of the polymer backbones. 

As an alternative to wet ehemical routes of analysis, this monograph deals mainly with the direct deformulation of solid polymer/additive compounds. In Chapter 1 in-polymer spectroscopic analysis of additives by means of UV/VIS, FTIR, near-IR, Raman, fluorescence spectroseopy, high-resolution solid-state NMR, ESR, Mossbauer and dielectrie resonance spectroscopy is considered with a wide coverage of experimental data. Chapter 2 deals mainly with thermal extraction (as opposed to solvent extraction) of additives and volatiles from polymerie material by means of (hyphenated) thermal analysis, pyrolysis and thermal desorption techniques. Use and applieations of various laser-based techniques (ablation, spectroscopy, desorption/ionisation and pyrolysis) to polymer/additive analysis are described in Chapter 3 and are critically evaluated. Chapter 4 gives particular emphasis to the determination of additives on polymeric surfaces. The classical methods of... 

Grunnet-Jepsen, A., Wright, D., Smith, B., Bratcher, M.S., DeClue, M.S., Siegel, J.S., and Moerner, W.E. (1998) Spectroscopic determination of trap density in Cco-sensitized photorefractive polymers. Chem. Phys. Lett., 291, 553-561. 

In an attempt to overcome the difficulty of interference effects by other polymer additives in the ultraviolet spectroscopic determination of phenolic antioxidants, Wexler makes use of the bathochromic shift exhibited by phenols on changing from a neutral or acidic medium to an alkaline one. This shift is due to the change of absorbing species... 

The grafting of nucleic acid base derivatives with a hydroxyl group onto poly(ethyleneimine) polymer backbone was also carried out by the activated ester method. Since the reactivity of the lactone is low, the direct reaction of the lactone derivative with poly(ethyleneimine) was not effective. Therefore, the lactone derivatives were at first hydrolyzed to the 3-hydroxybutyric acid derivatives, followed by condensation with poly(ethyleneimine) using the activated ester method. The grafting reaction was carried out in N,N-dimethylformamide, where a small amount of 4-pyrrolidinopyridine was added as an effective catalyst. Nucleic acid base contents of the polymers were determined by UV spectroscope of hydrolyzed samples. A quantitative calculations were made by using the corresponding carboxyethyl derivatives as standards. The nucleic acid base units (unit mol%) on the polymer are tabulated in Table 1. 

Table 5.1 Interference by other Polymer Additives in the Ultraviolet Spectroscopic Determination of Uvitex OB in Foodstuff Extractants ...

Meszlenyi, G., M. Sipos, E. Juhdsz, M. Lelkes, IR spectroscopic determination of the average composition of derivatives of ethylene oxide-propylene oxide block polymers, Acta Chim. Hung., 1990,127,495 99. 

The techniques used in the work have generally been spectroscopic visible-uv for quantitative determinations of species concentrations and infrared-Raman for structural aspects of the polymer. Although the former has often been used in the study of plutonium systems, there has been considerably less usage made of the latter in the actinide hydrolysis mechanisms. 

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