Styrene - acrylonitrile copolymers Characterization

Glockner, G., van den Berg, J. H. M., Meijerink, N. L., Scholte, T. G. Characterization of copolymers chromatographic cross-fractionation analysis of styrene-acrylonitrile copolymers , in Kleintjens, L., Lemstra, P. (ed) Integration of Fundamental Polymer Science and Technology , Elsevier Applied Science Publ., Barking, UK (1986), p. 85... 

Figure 12.8 Microcolumn size exclusion chromatogram of a styrene-acrylonitrile copolymer sample fractions transferred to the pyrolysis system are indicated 1-6. Conditions fused-silica column (50 cm X 250 xm i.d.) packed with Zorbax PSM-1000 (7 j.m dty, eluent, THF flow rate, 2.0 xL/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 permission from the American Chemical Society.

The development of SAN was triggered by the idea of building a polar comonomer into polystyrene to improve its resistance to chemicals and to stress cracking. The relatively polar acrylonitrile presented itself as a suitable comonomer in this case. Styrene-acrylonitrile copolymers are further characterized by high rigidity and thermal shock resistance. Two parameters substantially determine the properties of SAN molecular weight and the proportion of acrylonitrile. 

Vukovic R and Gnjatovic V (1970) Characterization of styrene-acrylonitrile copolymer by pyrolysis gas chromatography. J Polym Sci, Part A-l 8 139-46. 

Mori S (1996) Characterization of styrene-acrylonitrile copolymers by size exclusion chromatography/stepwise gradient elution-liquid precipitation chromatography. Int J Polym Anal Charact 2 185-92. 

Errors in variables methods are particularly suited for parameter estimation of copolymerization models not only because they provide a better estimation in general but also, because it is relatively easy to incorporate error structures due to the different techniques used in measuring copolymer properties (i.e. spectroscopy, chromatography, calorimetry etc.). The error structure for a variety of characterization techniques has already been identified and used in conjunction with EVM for the estimation of the reactivity ratios for styrene acrylonitrile copolymers (12). 

Refractive index and specific refractive index increments - (k = dn/dc) of polymers in solution have been studied extensively in connection with light scattering measurements and size exclusion chromatography applications to polymer characterization for which refractometers are used as standard concentration detectors. Contrary to the observations made in the infrared region (12), refractive index increments have been shown to be a function of the molecular weight of the polymers (2) and, in some cases, of the copolymer composition (17). Therefore, the assumptions of linearity and additivity (Eq. 1 to 4) have to be verified for each particular polymer system. In the case of styrene/acrylonitrile copolymers, there is an additional uncertainty due to the... 

The polymerization of vinyl monomers in liquid and supercritical CO2 has been studied extensively. Patents were issued in 1968 to the Sumitomo Chemical Company [81] and in 1970 to Fukui et al. [82] for the preparation of homopolymers of polystyrene, poly(vinyl chloride), poly(acrylonitrile) (PAN), poly-(acrylic acid) (PAA), and poly(vinyl acetate) (PVAc), as well as the random copolymers PS-co-PMMA and PVC-co-PVAc. Additionally, a patent was issued in 1995 to Bayer AG [83] for the preparation of styrene/acrylonitrile copolymers in SCCO2. In 1986, the BASF Corporation was issued a Canadian patent for the precipitation polymerization of 2-hydroxyethylacrylate and various N-vinylcarboxamides in compressed carbon dioxide [84]. In 1988, Terry et al. attempted to homopolymerize ethylene, 1-octene, and 1-decene in SCCO2 for the purpose of increasing the viscosity of CO2 for enhanced oil recovery [85]. These reactions utilized free-radical initiation with benzoyl peroxide and r-butylperoctoate at 71 °C and 100-130 bar for 24-48 h. Although the resulting polymers were not well characterized, they were found to be relatively... 

The styrene-acrylonitrile copolymers and block copolymers were characterized by selective solvent fractionation, NMR, pyrolysis gas chromatography, and differential scanning calorimetry. 

Plastics can be divided according to their character into amorphous and crystalline. Crystallization is never complete and the so-called crystalline polymers are virtually semicrystalline ones. Examples of amorphous plastics are polystyrene, acrylonitrile-butadiene—styrene copolymers, styrene—acrylonitrile copolymers, polymethylmethacrylate, poly(vinyl chloride), cellulose acetates, phenylene oxide-based resins, polycarbonates, etc. Amorphous polymers are characterized by their glass transition temperature, semicrystalline polymers by both melting and glass transition temperatures. 

Bourbigot, S. VanderHart, D.L. Gilman, J.W. Bellayer, S. Stretz, H. Paul, D.R. Solid state NMR characterization and flammability of styrene-acrylonitrile copolymer montmorillonite nanocomposite. Polymer 2004, 45, 7627-7638. 

Cortes et al have described an on-line coupled microcolumn size exclusion chromatographic - pyrolysis - gas chromatographic system for the characterization of styrene-acrylonitrile copolymers. 

Hoffman [64] studied monodisperse suspensions of polyvinyl chloride and styrene-acrylonitrile copolymer particles of diameter 0.4 to 1.25 pm using both rheological and structural characterization techniques as shown in Figure 2.1. The shear viscosities showed striking viscosity increases at critical shear rates. Structurally, the suspensions at low shear rates were found to exhibit a hexagonal crystalline lattice. At a critical shear rate, this lattice structure broke up into less-oriented arrays with a jump increase in shear viscosity. 

An appropriate formalism for Mark-Houwink-Sakurada (M-H-S) equations for copolymers and higher multispecies polymers has been developed, with specific equations for copolymers and terpolymers created by addition across single double bonds in the respective monomers. These relate intrinsic viscosity to both polymer MW and composition. Experimentally determined intrinsic viscosities were obtained for poly(styrene-acrylonitrile) in three solvents, DMF, THF, and MEK, and for poly(styrene-maleic anhydride-methyl methacrylate) in MEK as a function of MW and composition, where SEC/LALLS was used for MW characterization. Results demonstrate both the validity of the generalized equations for these systems and the limitations of the specific (numerical) expressions in particular solvents. 

The chlorinated alkanes have proven useful for solubilizing lower molecular weight polymers and oligomers. As detailed in the alkane and alcohol chapters, dichloro-methane (DCM) has been used in conjunction with methanol and heptane gradients for the characterization of polystyrenes [272] and styrene/ethyl methacrylate copolymers [649] and with heptane for co-poly (styrene/acrylonitrile) materials [244, 527]. 

Mes and coworkers compared TDA, DLS, HDC, and SEC and showed that all four methods can be used effectively to determine diffusion coefficients of systems with low polydispersities by measuring a series of styrene acrylonitrile (SAN) copolymers. Although these are polymeric systems, it is possible to apply the findings to supramolecular ensembles. The characterization of samples of low polydispersity was achieved best with TDA and DLS, since they both allow the rapid and absolute determination of the diffusion coefficient. However, TDA has the disadvantage that it is subject to interference due to the presence of low-molecular-mass chromophoric compounds. DLS, on the other hand, is influenced much more by the polydispersity of the sample than TDA. Furthermore, the use of DLS enables direct measurements of the Z-average diffusion coefficient of a polydisperse sample but requires a relatively large amount of the sample and is concentration dependent. Unlike TDA, DLS is especially suited for the analysis of high-molecular-mass systems, such as supramolecular systems, and is not disturbed by the presence of low-molecular-mass impurities. 

When the polymer was prepared by the suspension polymerization technique, the product was crosslinked beads of unusually uniform size (see Fig. 16 for SEM picture of the beads) with hydrophobic surface characteristics. This shows that cardanyl acrylate/methacry-late can be used as comonomers-cum-cross-linking agents in vinyl polymerizations. This further gives rise to more opportunities to prepare polymer supports for synthesis particularly for experiments in solid-state peptide synthesis. Polymer supports based on activated acrylates have recently been reported to be useful in supported organic reactions, metal ion separation, etc. [198,199]. Copolymers are expected to give better performance and, hence, coplymers of CA and CM A with methyl methacrylate (MMA), styrene (St), and acrylonitrile (AN) were prepared and characterized [196,197]. 

The backbone of acrylonitrile-styrene copolymers containing more than 60% AN is characterized by ... 

In a patent dated 1965 Stowe35) laid the basis for the copolymerization of PEO macromonomer with comonomers such as acrylonitrile. It was searched for an increased wettability of polyacrylonitrile films or fibers by a permanent surface modification. ro-Styryl poly(oxyethylene) macromonomers readily copolymerize with acrylonitrile in water emulsions. They can also be copolymerized with styrene-sulfonates in the presence of poly(vinylpyrrolidone). The presence of small amounts of such copolymers in polyacrylonitrile fibers was shown to increase their wettability and their receptivity to dyes and to make them more resistant to electric loading (antistatic fibers). No characterization data on the copolymers formed have been reported. 

This chapter discusses the dynamic mechanical properties of polystyrene, styrene copolymers, rubber-modified polystyrene and rubber-modified styrene copolymers. In polystyrene, the experimental relaxation spectrum and its probable molecular origins are reviewed further the effects on the relaxations caused by polymer structure (e.g. tacticity, molecular weight, substituents and crosslinking) and additives (e.g. plasticizers, antioxidants, UV stabilizers, flame retardants and colorants) are assessed. The main relaxation behaviour of styrene copolymers is presented and some of the effects of random copolymerization on secondary mechanical relaxation processes are illustrated on styrene-co-acrylonitrile and styrene-co-methacrylic acid. Finally, in rubber-modified polystyrene and styrene copolymers, it is shown how dynamic mechanical spectroscopy can help in the characterization of rubber phase morphology through the analysis of its main relaxation loss peak. 

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