Characterization, polymer

The composition of the copolymers was checked by chemical analysis (ratio of the sulfur and nitrogen contents). As this method is not very accurate the results were confirmed by proton NMR spectroscopy. In all cases the copolymer composition is very close to the corresponding monomer mixture in the reaction bath. The ionic monomer ratio ranges between 0 and 11.5% (Table 9.1). Taking into account the usual difficulties to determine the molecular weight of water soluble copolymers several ways of determination were used. 

As previously we determined a relation between the intrinsic viscosity [fy] and the mean molecular weight (in weight, M ) for cationic copolymers of acrylamide with similar structure [19], we assumed that, at least in the range of low ionic compositions, the same relation holds and the measurements of intrinsic viscosity leads to according to the relation  

The absolute value of was also established by light scattering thanks to a FICA 42 000 apparatus equipped with a laser He-Ne source. Mean values of molecular weight and additionally of distribution were obtained by gel permeation chromatography (Water ALC 201 equipment with Shodex OH-pak columns). The eluent was lithium nitrate (with 400 ppm of sodium azide as bactericide). Our apparatus was equipped with three detectors a refractometer, a light scattering detector (chromatix CX 100) and a viscometric detector developed in the Laboratory [20-21]. 

The results are shown in Table 9.1. The determined by the three techniques are in reasonable agreement. In all cases the molecular weight distribution is very large. We can mention that we found two samples - one anionic P(AM-AMPS) 4%, the other cationic P(AM-MSA) 4% - with practically similar elution patterns in gel permeation chromatography. 

Here Pj is the concentration of the polymer with chain length j— the same symbol is also used for representing the polymer species Pp w is the molecular weight of the repeating unit in me chain. 

A factor in addition to the residence time distribution and temperature distribution that affects the molecular weight distribution is the type of the chemical reaction (e.g., step or addition polymerization). 

Two major polymerization mechanisms are considered chain growth and step growth. In addition, polymerization can be homopolymerization—a single monomer is used—and copolymerization usually with two monomers with complementary functional groups. 

The complete analysis of a commercial polymer provides an interesting challenge since the materials are rarely, if ever, pure components so the identification and quantitative evaluation of the base polymer is part of a much wider investigation. In order to enhance the processing or physical properties of the materials, many additives are deliberately introduced. Typically, these might include antioxidants, antistatic agents, pigments, fire retardants, plastisizers and many more (see Table 2.1). 

It is not uncommon for there to be as many as 20 or more additives in one polymer, all present in relatively small amounts, but nevertheless essential to ensure that the performance of the base polymer is acceptable for a particular end use. Many products are blends of two or more polymers or comprise two or more materials combined in a strategic way. For example, packaging materials commonly have a sandwich structure of three or four different polymers polymer composites are an important class of engineering materials containing substantial amounts of particulate or fibrous reinforcing agents. 

Naturally occurring polymers or macromolecular materials such as cellulose (wood, cotton and paper), keratins (wool and hair) and rubber (Havea brasiliensis - essentially cis-polyisoprene) present their own range of analytical problems. The very process of isolating these materials for analysis can impose changes at a molecular level which can be difficult to quantify. 

The main analytical or characterization concerns here are not those of natural products or additives, reinforcing agents, or residuals in synthetic 

Molecular weight Molecular weight distribution Copolymer composition Copolymer composition distribution Chain branching Crosslinking 

Another interesting development in the field of synthetic polymer charaeteriza-tion is the emergence of ambient-pressure desorption ionization techrriques such as desorption electrospray ionization mass spectrometry (DESI-MS) and many 

In general, there are two distinctively different classes of polymerization (a) addition or chain growth polymerization and (b) condensation or step growth polymerization. In the former, the polymers are synthesized by the addition of one unsaturated unit to another, resulting in the loss of multiple bonds. Some examples of addition polymers are (a) poly(ethylene), (b) poly(vinyl chloride), (c) poly(methyl methacrylate), and (d) poly(butadiene). The polymerization is initiated by a free radical, which is generated from one of several easily decomposed compounds. Examples of free radical initiators include (a) benzoyl peroxide, (b) di-tert-butyl peroxide, and (c) azobiisobutyronitrile. 

Other macromolecules are formed by condensing their monomers to form a repeat functional group (e.g., esters, amides, ethers) interspersed by alkyl chains, aromatic rings, or combinations of both. These condensations are characterized frequently, although not always by the loss of some by product (e.g., water, alcohol). The methods of formation of these polymers are far more varied than those of addition polymers. Examples of condensation polymers are (a) poly(esters), (b) poly(urethanes), (c) poly (carbonate), and (d) polyphenylene oxide). 

In polymers that exhibit tacticity, the extent of the stereoregularity determines the crystallinity and the physical properties of the polymers. The placement of the monomer units in the polymer is controlled first by the steric and electronic characteristics of the monomer. However, the presence or absence of tacticity, as well as the type of tacticity, is controlled by the catalyst employed in the polymerization reaction. Some common polymers, which can be prepared in specific configuration, include poly(olefins), poly(styrene), poly(methyl methacrylate), and poly(butadiene). 

5 is Chevron LDPE 5422, a low-density poly (ethylene). The number of branches per 1000 carbon atoms may be calculated (Table 13.1) [26,27]. 

It is possible to calculate the number average molecular weight, Mn, using carbon-13 NMR (Table 13.2) [26,29,30], These data compare well with those obtained from gel permeation chromatography (GPC). 

It was prepared from 0.55 mL (511.5 mg, 5.0mmol) phenylacetylene, 29.0mg (0.05 mmol) TaBrsin 5.0mL toluene by the procedure similar to that used in the polymerization. The product was piuified by silica chromatography using hexane as eluent. White powdery 15 was obtained in 85% yield. 1,3,5- and 1,2,4-isomers of 15 were separated by recrystaUizations from ethanol and a 1 1 mixture of ethanol/ hexane, respectively. The molar ratio of 1,3,5- to 1,2,4- was 1.0 2.0. 

CPs designed for biomedical applications generally require good electrical conductivity, physicochemical and mechanical stability, and biocompatibility to effectively interact with biological system. A wide range of analytical techniques to characterize the feasibility of conducting polymers as biomaterials are summarized here. 

Optical transmittances of the hybrid membranes are shown in Table 8.1. The hybrid membranes have high homogeneity and silica particles are finely dispersed in the HBPIs 

Coefficients of thermal expansion (CTEs) from 100 to 150°C of the hybrid membranes are listed in Table 8.1. The CTE of the TMOS system greatly decreases with increasing silica content, indicating the enhancement of thermal mechanical stability of the HBPIs by the formation of robust three-dimensional Si-O-Si network. In contrast, the CTE of 

Anne-Marie M. Baker and Joey Mead, Thermoplastics, in Handbook of Plastics Elastomers and Composites, Charles A. Harper, ed., McGraw-Hill, New York, N.Y., USA, 2002. 

Carl C. Wamser, Portland State University, Chemistry Department, Portland, Ore., USA, 2000. 

Polymerization Chemistry, Tangram Technology Ltd., Hitchin, Hertfordshire, UK, 2000. 

University of Southern Mississippi, Department of Polymer Science, Hattiesburg, Miss., USA, 2004. 

Polyanion 7 is, to our knowledge, the first reported organometallic polyanion. The material is highly water soluble it could be dissolved to concentrations exceeding 100 mg/mL. It must be noted that the solubility of the polyanion, which is a weak polyelectrolyte, decreases below pH 6 In conclusion, a universal route to functionalized polyferrocenylsilanes, using nucleophilic substitution reactions, enabled us to produce water-soluble polyferrocenylsilane polycations and polyanions. 

Polymers 5 and 7 were furthermore studied by viscometry in ultrapure water, in the absence of salt. As an example, values of the reduced viscosity, T[sp/C of 7 are plotted against polymer concentration C. For both polymers, the reduced viscosity increased strongly with decreasing polymer concentrations, exhibiting a pronounced concave-upward relationship (Psp is the specific viscosity) (see Fig. 2). This behavior is typical of polyelectrolytes.  

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Light scattering teclmiques play an important role in polymer characterization. In very dilute solution, where tire polymer chains are isolated from one anotlier, tire inverse of tire scattering function S (q) can be expressed in tire limit of vanishing scattering vector > 0 as 1121... 

Atactic polymer (Section 7 15) Polymer characterized by ran dom stereochemistry at its chirality centers An atactic polymer unlike an isotactic or a syndiotactic polymer is not a stereoregular polymer... 

We can now drop the superscript > on the T in the numerator, recognizing that it is merely the temperature at which we are evaluating AG for the process c 1 for a crystal characterized by r and 1 and a polymer characterized by AHy, T , and 7. When the value of this AG is zero, we have the actual melting point of the crystal of finite dimension Tj . That is. 

Figure 7.10 Nuclear magnetic resonance spectra of three poly(methyl methacrylate samples. Curves are labeled according to the preominant tacticity of samples. [From D. W. McCall and W. P. Slichter, in Newer Methods of Polymer Characterization, B. Ke (Ed.), Interscience, New York, 1964, used with permission.]...

SOME PROPERTIES OF POLYMER SOLUTIONS AND THEIR RELATION TO POLYMER CHARACTERIZATION... 

The phenomena we discuss, phase separation and osmotic pressure, are developed with particular attention to their applications in polymer characterization. Phase separation can be used to fractionate poly disperse polymer specimens into samples in which the molecular weight distribution is more narrow. Osmostic pressure experiments can be used to provide absolute values for the number average molecular weight of a polymer. Alternative methods for both fractionation and molecular weight determination exist, but the methods discussed in this chapter occupy a place of prominence among the alternatives, both historically and in contemporary practice. 

Since the development of a method for polymer characterization has been spread over several sections and since the literature contains several variations in the manner data is displayed, a summary of some pertinent definitions and relationships will be helpful at this point ... 

In addition, the intercept obtained by extrapolating this asymptote back to sin (0/2) = 0 equals (2M )". Note that both Mand are number averages when this asymptotic limit is used. This is illustrated schematically in Fig. 10.15 and indicates that even more information pertaining to polymer characterization can be extracted from an analysis of the curvature in Zimm plots. 

Analytical investigations may be undertaken to identify the presence of an ABS polymer, characterize the polymer, or identify nonpolymeric ingredients. Fourier transform infrared (ftir) spectroscopy is the method of choice to identify the presence of an ABS polymer and determine the acrylonitrile—butadiene—styrene ratio of the composite polymer (89,90). Confirmation of the presence of mbber domains is achieved by electron microscopy. Comparison with available physical property data serves to increase confidence in the identification or indicate the presence of unexpected stmctural features. Identification of ABS via pyrolysis gas chromatography (91) and dsc ((92) has also been reported. 

Over a period of about 50 years, the science of polymer chemistry has developed a comprehensive means of polymer characterization techniques. In the case of PE, these parameters include the composition, molecular weight, and compositional distribution. The composition of ethylene copolymers is usually measured by C-nmr, H-nmr, or in techniques. 

Core technical competencies may be composed of a number of core or key technologies. The competencies in turn can support product families, platforms, or core products, which then support individual products. These products may ultimately be found in a number of forms or shapes. For example, a key technology such as polymer characterization may support a competency in polymer synthesis and architecture, which in turn supports the platform of fluoropolymers and the product family of Teflon (DuPont) fluoropolymer resins that can be found as films, fibers, or in other forms. 

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. 

PSS SEC/SEC columns cover the full range of applications for polymer characterization. They comprise columns for all types of separations, eluents, and tasks. 

Applications polymer characterization, preparative-scale fractionations, sample preparation, ultraquick separations, separations with highest efficiency... 

Data in this chapter have been processed with CPCwin (Colloid and Polymer Characterization for Windows A.H group, Austria e-mail anton.huber kfuni), a software package that has been developed to handle SEC data. The... 

Figure 12.8 Mia ocolumn size exclusion chromatogram of a styrene-aaylonitrile copolymer sample fractions ti ansfeired to the pyrolysis system are indicated 1-6. Conditions fused-silica column (50 cm X 250 p.m i.d.) packed with Zorbax PSM-1000 (7p.m 4f) eluent, THF flow rate, 2.0 p.L/min detector, Jasco Uvidec V at 220 nm injection size, 20 nL. Reprinted from Analytical Chemistry, 61, H. J. Cortes et al, Multidimensional chromatography using on-line microcolumn liquid chromatography and pyrolysis gas chromatography for polymer characterization , pp. 961 -965, copyright 1989, with peimission from the American Chemical Society.

Figure 12.9 Typical pyrolysis chromatogram of fraction from a styrene-acTylonitiile copolymer sample obtained from a miciocolumn SEC system 1, acrylonitrile 2, styrene. Conditions 5 % Phenylmetliylsilicone (0.33 p.m df) column (50 m X 0.2 mm i.d.) oven temperature, 50 to 240 °C at 10 °C/min carrier, gas, helium at 60 cm/s flame-ionization detection at 320 °C make-up gas, nitrogen at a rate of 20 mL/min. P indicates tlie point at which pyrolysis was made. Reprinted from Analytical Chemistry, 61, H. J. Cortes et ai, Multidimensional cliromatography using on-line microcolumn liquid cliromatography and pyrolysis gas cliromatography for polymer characterization , pp. 961-965, copyright 1989, with permission from tlie American Chemical Society.

H. J. Goites, G. L. Jewett, G. D. Pfeiffer, S. Martin and G. Smith, Multidimensional cliromatography using on-line microcolumn liquid cliromatography and pyrolysis gas cliromatography for polymer characterization . Awn/. Chem. 61 961-965 (1989). 

E. Schroder et al., Polymer Characterization, Hanser Publisher, New York (1989). 

These include cold drawn, high pressure oriented chain-extended, solid slate extruded, die-drawn, and injection moulded polymers. Correlation of hardness to macroscopic properties is also examined. In summary, microhardness is shown to be a useful complementary technique of polymer characterization providing information on microscopic mechanical properties. 

It is however necessary to prove carefully in each case whether the system is suited for anionic polymerizations, whether no side reactions are involved, whether initiation is fast and quantitative, whether the synthesis conditions are adequate. Accurate polymer characterization is required to check the efficiency of the preparation method. Although anionic polymerizations are extremely efficient and useful in macromolecu-lar engineering, they are no panacea and have to be applied with circumspection and much care. 

Magonov, S. and Chemoff, D.A., Atomic force microscopy, in Comprehensive Desk Reference of Polymer Characterization and Analysis, Brady, R.F., Jr. (Ed.), Oxford University Press, New York, 2003, Chapter 19. 

Vol. 113. Modern Methods of Polymer Characterization. Edited by Howard G. Barth and Jimmy W. Mays... 

In the past three decades, industrial polymerization research and development aimed at controlling average polymer properties such as molecular weight averages, melt flow index and copolymer composition. These properties were modeled using either first principle models or empirical models represented by differential equations or statistical model equations. However, recent advances in polymerization chemistry, polymerization catalysis, polymer characterization techniques, and computational tools are making the molecular level design and control of polymer microstructure a reality. 

Hamielec, A.E., Computer Applications Modeling of Polymer Reactor Systems , Proceedings - Polymer Characterization Conference, Cleveland State University. Division of Continuing Mucation, Qeveland, Ohio, April 30 - May 1, 1974. 

The accuracy of the polymer characterization is evaluated and the polyiterization products of trimer obtained from different sources are characterized and compared. 

Klumperman, B. and Philipsen, H.J.A., Gradient polymer elution chromatography as a versatile tool in polymer characterization, LC-GC 17(2), 118, 1999. 

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