Copolymers elemental analysis, composition

Elemental analysis Gross composition of polymers and copolymers, yielding the percent composition of each element C, H, N, O, S, and so on. (a)... 

The copolymer composition equation relates the r s to either the ratio [Eq. (7.15)] or the mole fraction [Eq. (7.18)] of the monomers in the feedstock and repeat units in the copolymer. To use this equation to evaluate rj and V2, the composition of a copolymer resulting from a feedstock of known composition must be measured. The composition of the feedstock itself must be known also, but we assume this poses no problems. The copolymer specimen must be obtained by proper sampling procedures, and purified of extraneous materials. Remember that monomers, initiators, and possibly solvents are involved in these reactions also, even though we have been focusing attention on the copolymer alone. The proportions of the two kinds of repeat unit in the copolymer is then determined by either chemical or physical methods. Elemental analysis has been the chemical method most widely used, although analysis for functional groups is also employed. 

Recently, Kroeze et al. prepared polymeric iniferter 34 including poly(BD) segments in the main chain [152]. They successfully synthesized poly(BD)-block-poly(SAN), which was characterized by gel permeation chromatography, elemental analysis, thermogravimetric analysis, NMR, dynamic mechanical thermal analysis, and transmission electron microscopy. By varying the polymerization time and iniferter concentration, the composition and the sequence length were controlled. The analysis confirmed the chain microphase separation in the multiblock copolymers. 

R values were calculated from elemental analysis for carbon, hydrogen, and chlorine. It can be seen again that temperature has a very marked effect on composition. Even at 100°, however, about 16 mol% sulfur dioxide is present. There was also produced a small quantity (1 to 10% of the amount of copolymer) of the cyclic addition product, 3-chloro-2,5-dihydrothiophene-l,1-dioxide, m.p. 99-100°. 

The copolymers obtained for the P(DMA)-itat-(HPA) (Scheme 9) library revealed relatively low PDI values below 1.3 and increasing Mn,opc values with increasing HPA content, as listed in Tables. It should be noted that a poly(methyl methacrylate) (PMMA) calibration was used for the calculation of the Mn pc values and this causes an overestimation for HPA containing polymers. The copolymer compositions were calculated from the H NMR spectra however, this method was not suitable for reliable conversion determination since the DMA-C//3 groups overlap in the NMR spectra not only with the HPA-O// group but also with broad backbone signals, which obstruct any reliable integration. Therefore, elemental analysis was used as an alternative method for the calculation of the molecular composition of the copolymers. 

Quantitative analysis of copolymers is relatively simple if one of the comonomers contains a readily determinable element or functional group. However, C,H elemental analyses are only of value when the difference between the carbon or hydrogen content of the two comonomers is sufficiently large. If the composition cannot be determined by elemental analysis or chemical means, the problem can be solved usually either by spectroscopic methods, for example, by UV measurements (e.g., styrene copolymers), by IR measurements (e.g., olefin copolymers), and by NMR measurements, or by gas chromatographic methods combined with mass spectroscopy after thermal or chemical decomposition of the samples. 

Average copolymer compositions of SAN samples were determined by elemental analysis, yielding weight percent acrylonitrile in the polymer. Compositions of S/MA and S/MA/MM were determined by sequential hydrolysis and pyridine titration to obtain maleic anhydride content and by infrared analysis for methyl methacrylate content. 

Table II compares compositional analysis results by Reman spectroscopy with elemental analysis (C,H,N) for various mixtures of P(M-CN) copolymers the agreement between the two methods is quite good and the results are consistent with published (, 3, 13.) reactivity ratios for this system. Because of the limited range of composition of the available samples of this copolymer, reactivity ratios were not calculated.

In the pmr data for the terpolymer, overlap between the CH3 absorption of the oxime ester and the backbone absorption is greater than in the copolymer pointed out in Figure k. Thus, while the agreement between the Raman and pmr data for the terpolymer is not very good, (lT-32 difference), it is completely within the experimental error of the pmr data. This large error and the fact that pmr can only distinguish two of the components of the terpolymer demonstrate that it is unsuited for compositional analysis of this system. Based on the agreement with published reactivity ratios and with the elemental analysis of the P(M-CN) copolymer, it is assumed that the Raman data are more accurate. 

The compositions of copolymers of methacrylates or aldehydes were determined by 1H NMR spectroscopy or elemental analysis. 

The terpolymerization of CPT-SO2 and acrylonitrile is shown in Table II. It was necessary to accelerate the polymerization by adding azobisisobutyronitrile (AIBN) as initiator. The nature of the propagating species may not be different with a different initiator. Polymerization ceased at a low conversion at 40 °C in toluene. The terpolymer composition calculated from elemental analysis of C, H, N, and S showed an equimolar ratio of CPT and S02. The terpolymers are white powders, soluble in DMF, can be cast into transparent film different from the CPT-SO2 copolymer, and showed melting temperature without decompo-... 

Procedures. A standard recipe for the latex preparation is shown below (St + M2) 20 g, (water + buffer) 160 g, and initiator 5 mmole/1. The weight fraction of M2 in monomer charge (f) was varied from 0.01 to 0.50. Polymerizations were carried out at 55°C or 70°C and pH 2.5 or 9.0 under nitrogen. Samples were withdrawn from the reaction mixture at various time intervals and the polymer was precipitated in an excess of acetone. The conversion and polymer composition were determined by gravimetric means and by elemental analysis, respectively. The M2 fraction in instantaneously-formed copolymer ( Fi ) was calculated from eq. 1 ... 

The concentration of the siloxane introduced into the copolymer is most easily determined by proton NMR for soluble systems, as briefly referred to in Sect. 3.1. This was demonstrated by Summers et al. [45] and Arnold and coworkers [46-50], as well as Rogers et al. [52]. Others have routinely conducted these experiments to establish the copolymer composition. Infrared spectroscopy has been particularly useful for demonstrating the transformation of the amic acid, which is often an intermediate for the final imide form. The assignments have been noted in many of the polyimide reviews referred to earlier [1-8]. In addition, it is useful to conduct an elemental analysis for silicon as complementary proof of copolymer composition. Solid-state NMR can be used even for intractable polyimide systems to provide a good estimate of the copolymer composition. 

Copolymer Analysis. Even though the overall copolymer composition can be determined by residual monomer analysis, it still is necessary to have reliable quantitative techniques for copolymer composition measurements on the actual copolymer, mainly because concentration detectors for SEC or HPLC are sensitive to composition and because the conversion histories are not always available. Some of the techniques used to determine copolymer composition are melt viscometry (46), chemical analysis, elemental analysis, infrared spectroscopy (IR), Nuclear Magnetic Resonance (NMR), ultra-violet spectroscopy (UV), etc. Melt viscometry, chemical and elemental analysis are general techniques that can be applied to almost any polymer. The spectroscopic techniques can be applied depending on the ability of the functional groups present to absorb at specific wavelengths. 

Copolymer compositions were determined by a high resolution nuclear magnetic resonance spectrometer (180 HMz). Copolymers of methyl methacrylate and styrene were dissolved in deuterated chloroform for the analysis. Deuterated pyridine was the solvent for the methyl methacrylate - methacrylic acid copolymers. Elemental analysis was also used in copolymer composition analysis to complement the NMR data. 

Figure 1. Monomer—copolymer composition relationship for the plasma-initiated copolymerization of methyl methacrylate with styrene. Plasma-initiated polymerization (%) NMR, (x) elemental analysis. Thermal polymerization (O) NMR, (Aj elemental analysis, (—) theoretical curve, tmma = 0.46 =...

Synthesis was carried out of the copolymers of 4-vinylpyridine (4VP), styrene (St) and divinylbenzene (DVB) with varied compositions, P(4VP-St-DVB), by suspensionpolymerisationusing 2,2 -azobisisobutyronitrile (AIBN) as an initiator. Preparation of the insoluble (crosslinked) pyridinium-type polymers in benzyl-pyridinium bromide form, which possess various macromolecular chain compositions, was performed by the reaction of eachP(4VP-St-DVB) with benzyl bromide (BzBr), respectively. By using different halohydrocarbon RX in the quatemisation of P(4VP-St-DVB), the insoluble pyridinium-type polymers with various pyridinium group stractures were obtained. FTIR was nsed to identify the stractures of P(4VP-St-DVB) and its quatemised product Q-P(4VP-St-DVB). The 4VP content in each copolymer P(4VP-St-DVB) was measured by non-aqueous titration and the pyridinium group content (Cq) in each Q-P(4 VP-St-DVB) sample was determined by means of the back titration manner in argentometiy and/or the elemental analysis method, respectively. Also, the particle structure... 

The compositional analysis of a copolymer can be achieved by several methods other than NMR spectroscopy, such as elemental analysis, infrared and ultraviolet spectroscopies, and pyrolysis-gas chromatography. However, NMR spectroscopy has several advantages it does not need calibration if the operation conditions are properly set, and it can distinguish impurities easily. Quantitative aspects of compositional analysis by H and 13C NMR have been discussed for styrene-MMA copolymer12 and vinylidene chloride-acrylonitrile copolymer,13 respectively. 

Table 3 shows the results of compositional analysis for radically prepared copolymer of MMA and styrene.14 H and 13C NMR analyses and elemental analysis gave consistent results as seen in the table, indicating good accuracy for all these analyses. 

Table I summarizes some of the data obtained in this study. Copolymer composition has been evaluated by elemental analysis (15) and confirmed by NMR spectroscopy. Random copolymers show an alternation tendency expressed by the product r2 of 0.218-0.252 (15).

Analytical Procedures. The purity of all copolymers, i.e. absence of monomers, was checked by thin layer chromatography (TLC). Composition of the DHA -co-4VP copolymers was determined from elemental analysis data obtained by Micro-Analysis, Inc., Wilmington, Del. Compositions of the DHA-co-NVP copolymers were determined by non-aqueous titration, using 0.1N perchloric acid and gentian violet indicator in glacial acetic acid (11). Isocyanate was determined as reported previously (12). 

Characterization of Block Copolymers. The copolymers were characterized by velocity ultracentrifugation, osmotic pressure, and ordinary element analysis in order to determine the molecular weight monodispersity of the copolymers and the degree of contamination with the corresponding homopolymers, the number average molecular weight (Mn), and the fractional compositions of the block copolymers, respectively. 

Copolymer Characterization. Copolymer compositions were determined by elemental analysis and thermal gravimetric analysis. A Perkin-Elmer TGS-2 ther-mogravimetric analyzer, programmed from ambient to 800 C in N2 and air, was used. Spectroscopic analysis of the copolymers was not as useful as elemental analysis and thermal gravimetric analysis measurements for analyzing these copolymers. Viscometric measurements were made in a solution of water and NaCl with a Contraves low-shear viscometer. 

Comonomer Composition. Comonomer composition in each copolymer was calculated on the basis of the results obtained from elemental analysis (C%), assuming that the composition of the copolymer was (C6Hio02)x(C2H3R)i x, where R=P(0)(0H)2, P(0)(0CH3)2, COOH. Each comonomer composition is represented by ester mol% (x) and is listed in Table 1. The ester mol% is less than 50% for all the 1 1 comonomer feed ratio, similar to the results Bailey et al. obtained for the copolymerizations of MDO with other vinyl monomers (70). 

Elemental analysis (EA) is a convenient method for determination of copolymer and blend composition if one homopolymer contains an element not present in the second one. For example, EA can be properly used to quantify nitrogen in copolymers containing acrylonitrile units and oxygen in polymeric surfactants such as poly(oxy-alkylene). Therefore, for a binary system, every element can be balanced according to the following equation ... 

Analysis of Polymers. The repeat unit structure of a synthetic polymer usually is known from the method of synthesis. Compositions of copolymers often are determined by elemental analysis when one monomer contains an element not present in the other monomer. Soluble polymers are often characterized by their molecular weights and molecular weight distribution, but insolubility prevents such characterization of cross-linked polymers. 

Copolymer composition can be obtained using nuclear magnetic resonance spectroscopy (NMR), IR spectroscopy, high-performance liquid chromatography (HPLC), elemental analysis or in some cases by titration of specific groups (see Section 11.2.3). 

Analysis of plastics is a complex task and involves preliminary tests, determination of nonmetallic and metallic elements, analysis of functional groups and double bonds, molecular weight determinations, chemical compositional analysis, sequence length distribution in copolymers, determination of tacti-city and branching in polymers, and analysis of additives. Because of the great variety in structures in commercially produced plastics, the number of methods that can be applied for their analysis is considerable. 

In order to calculate a copolymerization reactivity ratio, it is first necessary to determine the composition of the copolymer or of the unconverted monomer mixture (or both). Elemental analysis, spectroscopic methods (IR, UV, NMR), refractive index determination, or turbidimetric titration can be suitable for determining the copolymer composition. 

Copolymers are composed of at least two types of monomer unit. Although it can be expected that the composition of copolymers fits well with the composition of the different monomers used during copolymer synthesis, there are different reasons inherent to polymerisation reactions that can explain why the composition of the copolymer can differ from the initial composition of the copolymerisation medium (see Section 3.8). For this reason, the composition of copolymers needs to be determined in the routine characterisation of such a type of polymer. The most widely used methods for this are those based on the elemental analysis or on spectral analysis of the copolymer. 

The principle of elemental analysis is to determine the percentage of each type of atom included in a compound. The composition of the copolymer is then... 

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