Elemental analysis monomer composition

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. 

Table I summarizes conditions for the synthesis of two series of PDMAAm-1 -PIBs. The samples are identified by a code consisting of a letter and two numbers the letter (A) denotes the hydrophilic monomer DMAAm, whereas the two numbers indicate the Mn of the starting MA-PIB-MA (divided by 1,000) and the weight percent of PIB in the network (determined by elemental analysis). For example, A-4-26 denotes an amphiphilic network prepared with DMAAm as the hydrophilic moiety, containing a Mn=4,000 MA-PIB-MA, whose composition is 26% PIB.

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 Samples were withdrawn from the reaction mixture at various time intervals and the polymer was precipitated in an excess of acetone.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 ... 

Polymer complex Reagent mole ratio monomer halogen Polymer composition (elemental analysis) Conductivity cr(S cm1) Deconvoluted halogen spectra" XPS surface stoichiometry N halogen ratio Nls spectra components (B.E. > 401 eV)... 

Conversions in pentane proceed in an nonuniform manner at high temperatures. In addition to unidentified products exhibiting different 31P NMR AX patterns, as well as the main product dichlorophosphane and another unknown substance, which exhibits a 31P NMR shift of + 301 ppm, one obtains a red compound, of which elemental analysis and the molecular mass point to the trimer phosphathioketene. The number of isomer compounds of this composition is limited by the 31P NMR spectrum. The A2X system, of which the X triplet is split into a double doublet if detected in solution in chloroform, indicates two acyclic PC double bonds and one phosphorus atom as a ring member (117). A possible explanation is given in Fig. 22. This could be in agreement with the addition of a monomer to the dimer, forming the six-membered ring compound with the proposed structure. 

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. 

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 =...

An elemental analysis of a MIP ascertains that the composition of the polymer is the expected one. Comparison of the analytically determined amounts of the elements with the theoretical values gives an indication of the outcome of the polymerization. An estimation of the success of the removal of the template can also be obtained by elemental analysis if the template contains elements not present in the monomers. Other characterization methods that give information on the composition of a polymer include FTIR and NMR. 

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. 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. 

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). 

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. 

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 average particle size as well as the particle size distribution of the prepared lattices was investigated under reaction state concentration using a novel dynamic light scattering method. Table 1 summarizes relevant data of the prepared products. Furthermore, the composition of the monomer feed as well as the composition of the polymer is given in Table 1. The polymer composition has been calculated from elemental analysis data. 

The copolymers of acrylamide with sodium-3-acrylamido-3-methylbutanoate (NaAMB), as well as the homopolymer of NaAMB, were prepared in aqueous solution at 30 C using 0.1 mole percent potassium persulfate as the initiator. The feed ratio of AM NaAMB was varied from 95 5 to 25 75, and the total monomer concentration was held constant at 0.456 M. Following reaction, the polymers were purified by precipitation in acetone, dialysis, and lyophilization. Conversions were determined gravimetricallv and compositions were determined using elemental analysis and NMR. ... 

The proposed structure for the DVE-MA copolymer is supported by (1) the elemental analysis for the copolymer obtained at high conversion is consistent (2) the IR spectrum is essentially devoid of residual double bond absorption and contains characteristic absorption bands for cyclic anhydride and six-membered cyclic ether structures (3) the copolymer composition of 1 2 molar ratio of DVE to MA is consistent with the known reactivity ratios of these types of monomers and (4) the presence of the cyclic ether group has been confirmed by chemical evidence which involved cleavage by hydriodic acid and incorporation of iodine into the polymer. Similar but not such extensive evidence has been obtained for the other copolymers reported [9]. 

Copolymer resin (p-CAF) was synthesized by the condensation of p-cresol and adipamide with formaldehyde in the presence of hydrochloric acid as catalyst and using varied molar ratios of reacting monomers. A composition of the copolymers has been determined on the basis of their elemental analysis. The number average molecular weight of resins was determined by conductometric titration in non-aqueous medium. The copolymer resins were characterized by viscometric measurements in dimethylsulphoxide (DMSO), UV-visible absorption spectra in non-aqueous medium, infrared (IR) spectra, and nuclear magnetic resonance (NMR) spectra. The morphology of the copolymers was studied by scanning electron microscopy (SEM). 

Run Starting monomer/ polymer ratio (wt/wt) Element analysis Yield of PPy, PAn or poly(3Mth) (%) Blend composition cr (S cm )... 

Neoh and co-workers [110] investigated the simultaneous chemical copolymerization and oxidation of pyrrole and A-methylpyrrole by bromine and iodine. By varying the monomer feed ratio, they could in effect control the copolymer composition. Based on elemental analysis of the copolymers, they determined that ri = 1.13 and r2 = 0.35 for pyrrole and 1-methylpyrrole, respectively. In the copolymerization induced by bromine, the electrical conductivity, thermal stability and Br content of the doped copolymer decreased with increasing concentration of A/-methylpyrrole in the copolymer. When iodine was included in the charge, the halogen content of the copolymers did not vary substantially, but the electrical conductivity and thermal stability of the doped copolymer also decreased with an increase in the fraction of A/-methylpyrrole in the copolymer. 

Because the results of elemental analysis of the doped A/-methyl- and A/-phenylpyrrole copolymers with pyrrole do not accurately measure copolymer composition, Reynolds and others [5,6] prepared poly(pyrrole-co-A/-(3-bromophenyl)pyrrole tosylate). CV indicates that this comonomer has an oxidation potential of 1.7 V versus SCE, confirming its similar electrochemical behaviour to A/-phenylpyrrole. Elemental analysis of the copolymer prepared from a monomer feed of 95 moI% A-(3-bromophenyl)pyrrole contains only 9.3 mole% N-(3-bromopenyl)pyrrole units, based on the results of its elemental analysis. This means that only 30% of the pyrrole monomer used is inserted into the copolymer, and it is therefore difficult to prepare pyrrole/A/-phenylpyrrole copolymers of uniform composition containing more than 10% phenyl-substituted monomers. 

The chemical composition, including ionic character of the component monomers, can be determined using various standard chemical and instrumental analysis procedures such as GC-pyrolysis, IR and NMR spectroscopy, as well as elemental analysis techniques. 

Brar and Sunita [58] described a method for the analysis of acrylonitrile-butyl acrylate (A/B) copolymers of different monomer compositions. Copolymer compositions were determined by elemental analyses and comonomers reactivity ratios were determined using a non-linear least squares errors-in-variables model. Terminal and penultimate reactivity ratios were calculated using the observed distribution determined from C( H)-NMR spectra. The triad sequence distribution was used to calculate diad concentrations, conditional probability parameters, number-average sequence lengths and block character of the copolymers. The observed triad sequence concentrations determined from C( H)-NMR spectra agreed well with those calculated from reactivity ratios. 

The polymers and monomers were characterized for chemical composition and purity (NMR, FT-IR, elemental analysis), thermal analysis (DSC), melt rheology (melt stability and viscosity), molecular weight (inherent viscosity), crystallinity (XRD). Baseline and in-vitro mechanical properties (Instron stress/strain) were determined on molded and extruded samples. 

A three compartment electrolytic cell with two fritted disk separators was used. An auxiliary platinum electrode was placed in each of the two end compartments while an aluminium strip, to which a surface treatment based on chromic acid etching had been applied, was placed in the middle compartment. Ihe monomer solution contained methacrylic acid (0.436 M) and -methylenebisacrylamide (0.145 M) in water. The pH of the above solution was adjusted to desired values by adding either sulfuric acid or aqueous sodium hydroxide. The monomer solution (400 mi) was placed in the middle compartment while two end compartments contained water adjusted to the same pH as the monomer solution. While bubbling nitrogen through the monomers solution, the electrolysis was conducted at 10 vdts for 6 hours such that the cathodic reaction would occur in the center compartment. The polymer coating obtained on the aluminium cathode was washed with fresh water, dried in vacuum oven at room temperature, and weighed. The copolymer was then scraped off from aluminium and its composition determined by elemental analysis. 

No copolymer was generated when the initiator concentration was below 0.06 mole/liter or the reaction temperature below 55°C. Holding the total monomer feed constant and varying the monomer feed ratio systematically, a series of low conversion copolymers were prepared. The copolymer compositions, as shown by elemental analysis, was independent of monomer feed composition and the molar ratio of the two monomers in the copolymer was essentially unity. The number average molecular weights for the series varied from 2 250 to 3 165, with the 3 165 value found for the equimolar feed case. 

Composite materials were received by treating MCC or DAC, water-soluble monomeric guanidine derivatives (Table 6.1), with subsequent polymerization. Quantity of the monomer/polymer zwitterionic quaternary ammonium eations aerylate and diallyl guanidine derivatives were included in MCC or DAC determined by nitrogen content using elemental analysis. 

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