Polystyrene grafting

The relative U.S. production of styrene homopolymer and copolymer resins is also noteworthy (103) (Fig. 6). The impact polystyrene (graft and polymer blend) copolymers are produced in nearly the same quantities as styrene homopolymers. The ABS resins are synthesized in lesser, yet significant, quantities. 

The isolation of product is usually possible after evaporation of the solvent and extraction with hexane, ether, or toluene. Supported versions, for example on polystyrene grafted with PPh2 groups, have proved unsatisfactory because the rate of deactivation is greatly enhanced under these conditions [37]. Asymmetric versions exist, but the ee-values tend to be lower than in the Rh series [38]. With acid to neutralize the basic N lone pair, imine reduction is fast. Should it be necessary to remove the catalyst from solutions in order to isolate a strictly metal-free product, a resin containing a thiol group should prove satisfactory. A thiol group in the substrate deactivates the catalyst, however. 

FIGURE 5.10 Synthesis of a polyethyleneglycol-polystyrene graft polymer by etherification of Merrifield resin using potassium tetra(oxyethylene) oxide, followed by extension of the chain by reaction of the potassium salt, which is present as the crown ether.21 In several TentaGel resins, the connecting bond is an ethyl ether that is more acid-stable than the benzyl ether. 

E Bayer, M Dengler. B Hemmasi. Peptide synthesis on the new polyoxyethylene-polystyrene graft copolymer, synthesis of insulin B21.30. btt J Pept Prot Res 25, 178, 1985. 

S Zalpsky, JL Chang, F Albericio, G Barany. Preparation and applications of polyethylene glycol-polystyrene graft resin supports for solid-phase peptide synthesis. Reactive Polymers 22, 243, 1994. 

The Acid Effect. The possible mechanistic role of hydrogen atoms in the current radiation grafting work becomes even more significant when acid is used as an additive to enhance the copolymerisation. At the concentrations utilised, acid should not affect essentially the physical properties of the system such as precipitation of the polystyrene grafted chains or the swelling of the polyethylene. Instead the acid effect may be attributed to the radiation chemical properties of the system. Thus Baxendale and Mellows (15) showed that the addition of acid to methanol increased G(H2) considerably. The precursors of this additional hydrogen were considered to be H atoms from thermalised electron capture reactions, typified in Equation 5. 

A graft copolymer in which the polybutadiene backbone has a degree of polymerization (DP) of 1 700 and the polystyrene grafts have an unknown DP polybutadiene-grq/i-polystyrene (1 700 a DP)... 

In the presence of a dissolved polymer, the radical polymerization of a monomer by thermal decomposition of an initiator results in a mixture of homopolymerization and graft polymerization [Brydon et al., 1973, 1974 Ludwico and Rosen, 1975, 1976 Pham et al., 2000 Russell, 2002], Polymer radicals (XXX), formed by chain transfer between the propagating radical and polymer, initiate graft polymerization of styrene. The product (XXXI) consists of polystyrene grafts on the 1,4-poly-1,3-butadiene backbone. Polymer radicals are also formed... 

Fig. 10. Scanning electron microscopy microphotographies of the surface of different polystyrene-grafted polyvinylidene difluoride (PVDF) surfaces the grafting was performed upon irradiation with Argon ions with various fluences or absorbed doses, (a) PVDF-gAr-PS (V = 2.5%), D=3.72 kGy, (=1.1x10 ions/cm (b) PVDF-gAr-PS (V= 19%), D= 3.72 kGy,...

Fig. 4 A Atomic force microscope (AFM) images, projected at 30° for viewing, of non-treated dithiocarbamated polymer film surface (a) and the PST(polystyrene)-grafted surface by UV irradiation through the lattice-patterned projection mask for 5 (fc), 10 (c), and 20 min (d). B Relationship between the average thickness of the PST-grafted layers and UV irradiation time...

The new synthetic approach being adopted for the preparation of the lignin-polystyrene graft copolymer involved three steps. 

Figure 7. Intrinsic Viscosity of polystyrene graft as a function of dose rate. Solid Line Represents Homopolymer.

A polyethylene glycol-polystyrene graft copolymer palladium catalyst has been used in allylic substitution reactions of allyl acetates with various nucleophiles in aqueous media.58 Another polymer-bound palladium catalyst 40 was developed and used in a Heck coupling of allylic alcohols with hypervalent iodonium salts to afford the substituted allylic alcohols as the sole products under mild conditions with high catalytic efficiency.59 The same polymer-bound palladium catalyst has also been used for Suzuki cross-coupling reactions.60... 

Berg, R. H. Almdal, K. Pedersen, W. B. Holm, A. Tam, J. P Merrifield, R. B. Long-Chain Polystyrene-Grafted Polyethylene Film Matrix A New Support for Solid-Phase Peptide Synthesis, J. Am. Chem. Soc. 1989, 777, 8024. 

It appears (Table 11) that the reinforcing ability exhibited by a HAF carbon black in polybutadiene or EPR is much lower after its surface has been previously modified by grafting of polystyrene M). Such results cannot, however, be associated with the elastomer s incompatibility towards the polystyrene grafts since poly-isoprene-grafted carbon blacks yield similar conclusions 65). 

NMR spectra is improved when the mobility of support-bound molecules increases. Hence, gel-phase NMR of PEG-polystyrene graft supports, for instance, will generally give better spectra than if normal cross-linked polystyrene is used as the support. Gel-phase H NMR spectra, even if recorded on well-solvated and flexible supports, are, however, too poorly resolved to be of use for the characterization of support-bound intermediates. 

Linear polystyrene can be generated on insoluble polymers by /-irradiation of the latter in a solution of styrene [110]. Polystyrene grafted onto polytetrafluoroethylene [111-116], polyethylene [2,110,117], or polypropylene [15] can be functionalized in the same way as cross-linked polystyrene, and loadings of up to 1.0 mmol/g can be attained. These supports, which are also available as crown-shaped pins (Multipin, 2-3 mm diameter, 8-10 pmol per crown), have been used for the synthesis of peptides [2,110,111,118], oligonucleotides [112-115,117,119], and small molecules [120-122]. 

Poly(ethylene glycol)-Polystyrene Graft Polymers... 

Figure 2.4. Preparation of PEG-polystyrene graft supports [5,12,51,62,131]. Ar 4-(N02)C6H4 L linker X OH, NH2.

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