Polystyrene polymer synthesis

Puskas, J.E. Biomacromolecular engineering Design, S3mthesis and characterization. One-pot synthesis of block copolymers of arborescent polyisobutylene and polystyrene, Polym. Adv. TechnoL, 7, 1, 2006. 

In a process related to RAFT, BASF workers have shown that 1,1-diphenylethylene will control the molecular weight of PMMA and polystyrene, and permit block polymer synthesis [92]. They propose that radical chain ends add to the diphenylethylene to form a stable diphenylalkyl radical that does not add more monomer but can reverse to diphenylethylene and the same radical chain end for addition of more monomer. The diphenylalkyl radical cap has the additional possibility of forming a reversible dimer (Scheme 35). 

An excellent example where a capsid virus has been given a new supramolecular application can be found in the work of Nolte who took an icosahedral capsid virus, cowpea chloritic mottle virus (CCMV) and used it as a nanoreactor for polymer synthesis [30], Natural CCMV spontaneously assembles in acidic aqueous solution and disassembles in basic solution. The capsid contains pores open at pH 5 to release RNA into the host. Once the RNA leaves, the empty capsule is left. The Nolte group was able to assemble the subunits around polystyrene sulfonate with a mass of 9.9 kDa but the resulting structure had a different morphology to the natural system. Indeed, capsules formed around polymers with masses between 2 and 85 kDa but not around those with masses above 100 kDa. This raised the question of the potential for polymers to form within a capsid but to test the possibility a mixture of botanical, biological and chemical approaches was needed. 

Although a large variety of reactions were successfully transferred to the solid phase there are only a few examples of free radical reactions on solid phase [173,174]. The free allyl radical transfer was achieved when the carbohydrate auxiliary was linked to a noncross-linked polystyrene polymer (NCPS) [175]. The use of NCPS instead of cross-linked supports has several advantages, including complete solubility in many organic solvents [176]. The polymer 269 was obtained in a radical polymerization of two equivalents of styrene and one equivalent /7-chloromethylstyrene. The protected D-xylose 270 was covalently linked to the support by a Williamson synthesis generating compound 271 (Scheme 10.88). 

FUNCTIONALIZATION OF POLYSTYRENE. II SYNTHESIS OF CHELATING POLYMERS BY ALKYLATION OF 4-AMINOMETHYLPOLYSTYRENE... 

M. Stern. M. Fridkin and A. Warshawsky. Functionalization of polystyrene. HI. Synthesi.s of polymeric thiol reagents. J. Polym. Sci.. Polym. Chem. Fd.. 20 (19X2) 1469. 

Photolytic cleavage at the anomeric center of glycosides as an analytical or preparative tool does not have a very extensive literature. It has, however, been found useful in the solid-phase synthesis of oligosaccharides. Thus the synthesis by Nicolaou and coworkers of the phytoelicitor heptasaccharide of Phytophthora megasperma (Section V) depends on detachment of the protected heptasaccharide from the support by photolytic cleavage of a 4-nitrophenoxy link to the polystyrene polymer. 

Preparation of the resin Polystyrene-divinylbenzene (1%) copolymer 21 (Fluka) was washed [71] to removed shorter polystyrene components and remaining monomers and reagents with each of the following solutions at 60-80°C for 30-60 min NaOH (1 N), HCl (1 N), NaOH (2 N)-dioxane (1 2), HCl (2 N)-dioxane (1 20, water, dimethyl formamide (DMF). The resin was then washed at room temperature with HCl (2 N) in methanol, water, methanol, methanol-dichloromethane (1 3), and methanol-dichlo-romethane (1 10) and the resin was dried at 50-70°C under reduced pressure. The washed polystyrene resin (13 g) was suspended under nitrogen in anhydrous cyclohexane (80 mL) in a 250-mL polymer synthesis flask. Tetra-methylethylenediamine (TMEDA, 20 mL, 132.5 mmol) and n-butyllithium (2.0 M in cyclohexane, 80 mL, 160 mmol) were successively added and the mixture was stirred at 65°C for 4 h. The dark burgundy-colored resin was filtered under nitrogen and washed with anhydrous cyclohexane (2 X 100... 

Of particular relevance to this chapter is the use of CO2 in polymer synthesis, in the manufacture of polymethylmethacrylate and polystyrene (Xerox) and for the production of fluoropolymers (DuPont). One of the main drivers for the latter was the phasing out of the chlorofluorocarbons (CFCs) used in the original process. The main advantage to this application is not necessarily the avoidance of the use of CFCs (although this is important), but the superior polymer processing properties made possible by the relative volatility of CO2 and its ease of removal. 

The production and applications of polymers have gradually developed, gaining ground in many fields. The main classes of polymers, namely polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene and polyethylene terephthalate are produced in millions of tonnes annually [1]. There are many methods of polymer synthesis free-radical polymerisation (bulk, solution, emulsion and suspension), condensation polymerisation, ethoxylation, polymer compounding and formulations involving solvents, fillers, pigments and so on. Besides the high volume consumption of these common plastics, the demand for polymers with specific end-use properties has increased. 

An important feature of polymer synthesis by the active ester method is that displacement of the polymer-bound activating 0eaving) groups can be readily monitored by IR qiectroscopy of the polymer. Tl% IR spectrum generally shows the disappearance of the phenyl ester carbonyl at about 1760 cm, and the appearance of a new carbonyl absorption at 1620-80 cm (amide) and/or 1720-30 cm (ester), together with other characteristic absorptions due to A and A. In some cases, a relatively weak polystyrene band at ca. 1607 cm is also observed. A typical illustration is provided by Fig. IS, showing the amino-lysis of the activated polymer with 6-tert.-butoxycarbonylaminohexylamine, followed by reaction with dimethylamine (see the first entry in Table 7). 

A novel approach to peptide synthesis has been the use of a chloromethylated polystyrene polymer as an insoluble but porous solid phase on which the coupling reactions are carried out. Attachment to the polymer, constitutes protection of the carboxyl group (as a modified benzyl ester), and the peptide is lengthened from its amino-end by successive carbodiimide couplings. The method has been applied to the synthesis of a tetrapeptide, but incomplete reactions lead to the accumulation of by products. Further development of this interesting method is awaited. 

These losses contribute to heat buildup in the tire and consequent loss in properties such as strength and tear resistance. Since the losses increase with temperature below 100 C the rate of heat generation also increases with temperature, a very unstable situation for tires. This situation also dooms the use of polystyrene-b-polyisoprene-b-polystyrene polymers with low end-block concentrations. In terms of other physical properties, there is no compelling reason to believe that vulcanized block copolymers would be Inferior to other tire rubbers. What limits their consideration here is most likely the higher cost of the block copolymer synthesis. 

---