Grafting purification, graft copolymer

Wenz and colleagues at Bayer Polymers Inc. describe the use of Raman spectroscopy to determine the reaction end point for the emulsion production of ABS graft copolymer [197]. Early termination reduces product yield and results in an extra product purification step termination too late reduces product quality. 

When isolation and purification of a graft copolymer is accomplished, we should undertake to determine the chemical structure of the graft copolymer. 

Summary. Solubility, H NMR, DTA, and GPC all support the conclusion that pure graft copolymer is obtained by the present method of synthesis. The only purification necessary is removal of the silver salts. Properties of the neoprene-g-PTHF copolymers depend on composition and branch length and generally lie between those of the backbone and branch. 

The synthesis and purification of polystyrene methacryloyl macromonomers (PS-MA) in the molecular weight range Mn= 1000-2000 g mol 1 by living anionic polymerization of styrene (S), termination with ethylene oxide (EO), and subsequent reaction with methacrylic chloride has already been described in detail elsewhere [180] (see also Scheme 16). In this context it has to be emphasized that the hydroxyethyl-terminated PS-MA macromonomer precursor (PS-OH) as obtained after purification of the crude PS-OH by silica column chromatography (cyclohexane/dichloromethane 1/1 v/v) and as charged in the PS-MA synthesis still contains up to about 15 wt-% of non-functionalized polystyrene (PS-H). This PS-H impurity of the PS-MA macromonomer does not interfere with the PS-MA synthesis and the subsequent TBA/PS-MA copolymerization and is easily and conveniently removed from the resulting PTBA-g-PS graft copolymer (see below). 

The composition of the PAA-g-PS graft copolymer reaction product and its purification, especially as far as the removal of unreacted PS-MA macromonomer by silica column chromatography is concerned, and the successful selective cleavage of the ferf-butyl ester under acidic conditions to render the graft copolyelectrolyte PAA-g-PS were analyzed by XH NMR spectroscopy and SEC. Figure 8a shows the SEC curves of the polystyrene macromonomer (PS-MA), the crude poly (ferf-butyl acrylate-gra/f-styrene) (PTBA-g-PS) and the PTBA-g-PS the polymethylacrylate (PMA) originates from esterification of the poly (acrylic acid) (PAA) obtained after complete saponification of the graft copolymer and represents the backbone. The XH NMR spectra of PSMA, PTBA-g-PS and of the final reaction product PAA-g-PS are shown in Fig. 8b. 

Modification of natural polysaccharides through various graft copolymerization techniques is discussed in this chapter. Characterization of graft copolymers using different techniques like FT-IR, C-NMR, SEM, XRD, TGA, DTA and DTG along with their physical, chemical and mechanical properties are discussed as a function of different reaction conditions of their synthesis. Applications for modified polysaccharides include drug delivery devices, controlled release of fungicides, selective water absorption from oil-water emulsions and purification of water. 

Purification of the Graft Copolymer by the Solvent Extraction Method... 

The synthesis of core-shell magnetic nanoparticles from polyacrylic acid (PAA) graft copolymers containing side chains of PEO and PPO (Fig. 5) was demonstrated by Hatton et al. [102]. Using a mixture of the polymers at a temperature of 180°C, amine-terminated PEO and PPO were coupled onto the PAA via amidation. Super-paramagnetic polymer-coated nanoparticles were synthesized by the hydrolysis and condensation of Fe(II) and Fe(III) chloride salts in the presence of PPO- or PEO-modified PAA copolymers. The extraction of organic compounds from aqueous media towards the copolymer shell of hydrophobic PPO segments can be applied in the field of water purification. 

The purification of grafted copolymers is generally performed by fractional precipitation of the reaction mixture in a pair of solvent and non-solvent of the... 

The authors show that the addition of grafted copolymer affects the strength at break, and, in a lesser proportion, the elongation at break. As previously mentioned, the copolymer purification after synthesis is irrelevant for the performance, and, actually, the best performance is reached with non-purified copolymers. SEM micrographs (Photographs 1,2,3, and 4) show evident improvement in the phases dispersion and a decrease of the nodules size by a factor 5 for compatibilized blends. 

Graft Copolymers. The hydrosilation technique described above for difunctional PDMS macroinitiators is also suitable for pendant functional polymers. For example, commercially available poly(dimethylsiloxane-5rar-vinylmethylsiloxane) was reacted with 2-(4-chloromethylphenyl)ethyldimethylsilane in a hydrosilation analogous to the top reaction shown in Scheme 3 to yield PDMS containing pendant benzyl chloride moieties. ATRP of styrene proceeded with first order kinetic consumption of monomer. An increase in molecular weight was observed from M = 6600 to 14,800. Unlike the triblock copolymers, here the polydispersity increased from 1.8 to 2.1 due to an inconsistent number of initiating sites per PDMS chain. Again, the product was isolated as a soluble white powder after purification 34). 

Cellulose either substituted with quaternary ammonium groups or grafted with polyacrylic acid has been used for ion-exchange chromatography, particularly in the purification of textile effluents. Graft copolymers of acrylic acid and a quaternary ammonium derivative of cellulose (obtained by condensation of cellulose with epoxypropyltriethylammonium chloride) were prepared quaternary ammonium derivatives of cellulose can also be obtained in one step by heating cellulose with epichlorohydrin and an amine. The... 

---