Preparation of Polystyrene

Styrene is one of those monomers that lends itself to polymerization by free-radical, cationic, anionic, and coordination mechanisms. This is due to several reasons. One is resonance stabilization of the reactive polystyryl species in the transition state that lowers the activation energy of the propagation reaction. Another is the low polarity of the monomer. This facilitates attack by free radicals, differently charged ions, and metal complexes. In addition, no side reactions that occur in ionic polymerizations of monomers with functional groups,are possible. Styrene pol erizes in the dark by a free-radical mechanism more slowly than it does in the presence of light. Also, styrene formed in the dark is reported to have a greater amount of syndiotactic placement. The amount of branching in the polymer prepared by a free-radical mechanism increases with temperature. This 

The following information has evolved about the free-radical polymerization of styrene  

Styrene polymerizes thermally. This is discussed in Chapter 2. 

Oxygen retards polymerizations of styrene. At higher temperatures, however, the rate is accelerated due to peroxide formation. 

The rate of styrene polymerizations in bulk is initially, at low conversions, first order with respect to monomer concentrations. In solution, however, it is second order with respect to monomer. 

Purpose To demonstrate the synthesis of polystyrene by free-radical polymerization under different conditions. 

The free-radical initiator ferf-butyl peroxybenzoate is a safe material to use in this experiment because it decomposes at a moderate rate when heated. Nonetheless, do not heat this catalyst excessively when performing the polymerization. 

Preparation Sign in at www.cengage.com/login to answer Pre-Lab Exercises, access videos, and read the MSDSs for the chemicals used or produced in this procedure. Review Sections 2.9, 2.17, 2.19, 2.21, and 2.22. 

Apparatus A separatory funnel, small soft-glass test tube, 25-mL round-bottom flask, microburner, apparatus for magnetic stirring, heating under reflux, and flameless heating. 

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Benzene was prepared from coal tar by August W von Hofmann m 1845 Coal tar remained the primary source for the industrial production of benzene for many years until petroleum based technologies became competitive about 1950 Current production IS about 6 million tons per year m the United States A substantial portion of this ben zene is converted to styrene for use m the preparation of polystyrene plastics and films... 

Emulsion Polymerisation It is a very good process which is used for the preparation of polystyrene. Emulsion polymerisation which is mainly used in the production of polystyrene latex used in water-based surface coating. 

The preparation of polystyrene-supported selenosulfonates and their application for the synthesis of acetylenic sulfones have been reported by Huang et al. (Scheme 3.3) [126],... 

Uses Preparation of polystyrene, styrene oxide, ethylbenzene, ethylcyclohexane, benzoic acid, synthetic rubber, resins, protective coatings, and insulators. 

Using a typical poly (vinyl chloride) (PVC)-based membrane with different ionophores - Zn-bis(2,4,4-trimethylpen-tyl) dithiophosphinic acid complex [450], protoporphyrin IX dimethyl ester [451], porphyrin derivative [452] and hemato-porphyrin IX [453], tetra(2-aminophenyl) porphyrin [454], cryptands [455, 456], 12-crown-4 [457], benzo-substituted macro-cyclic diamide [458], 5,6,14,15-dibenzo-l, 4-dioxa-8,l 2, diazacyclopentadecane-5,14-diene [459], and (A-[(ethyl-l-pyrrolidinyl-2 -methyl) ] methoxy-2-sulfamoyl-5 -benza-mide [460] - the sensors for zinc ions were prepared and investigated. The armed macrocycle, 5,7,7,12,14,14-hexamethyl-1,4,8,11 -tetraazacyclo tetradeca-4,11 -diene dihydrogen perchlorate was used for the preparation of polystyrene-based Zn(II)-sensitive electrode [461]. 

Preparation of Polystyrene by a Free Radical Polymerization Process... 

In 1838 Regnault [15] reported that vinylidene chloride could be polymerized. In 1839 Simon [16] and then Blyth and Hofmann (1845) [17] reported the preparation of polystyrene. These were followed by the polymerization of vinyl chloride (1872) [18], isoprene (1879) [19], methacrylic acid (1880) [20], methylacrylate (1880) [21], butadiene (1911) [22], vinyl acetate (1917) [23], vinyl chloroacetate [23], and ethylene (1933) [24]. Klatte and Rollett [23] reported that benzoyl peroxide is a catalyst for the polymerization of vinyl acetate and vinyl chloroacetate. 

To study the effect of the BG on threading process, triphenylmethyl-based azo compounds were designed as BG initiators for the preparation of polystyrene rotaxane 32 [67-69]. The BG fragments were shown to end up at both chain ends of the polystyrene since termination occurs nearly exclusively by combination. However, the threading efficiencies did not increase with 29 as cyclic and increased very little in other instances relative to those without BG. 

Figure 4.3. Preparation of polystyrene-bound organometallic compounds by transmetallation and direct lithiation [16,25,26,29],...

Figure 9.1. Strategies for the preparation of polystyrene-bound organoselenium compounds [1,2],...

Polymer-linked MWCNT nanocomposites were prepared by reversible addition fragmentation chain transfer (RAFT). The RAFT reagent was successfully grafted on to the surface of MWCNTs and PS chains were grafted from MWCNTs via RAFT polymerization [192], By covalently linking acyl chloride functions of functionalized MWCNTs with living polystyryllithium, Huang et al. succeeded in the preparation of polystyrene-functionalized MWCNTs (Scheme 1.32) [193],... 

Scheme 1.32 Covalently linking of MWCNT-acyl chlorides with living polystyryllithium for the preparation of polystyrene-functionalized MWCNTs.

Generally only solvent cleaning and abrasion are necessary for surface preparation of polystyrene parts. Methanol and isopropanol are acceptable solvents for solvent cleaning of polystyrene. For maximum bond strength the substrates can be etched with sodium dichromate-sulfuric acid solution at elevated temperature. Table 16.14 shows the results of a study on the durability of joints formed between polystyrene and aluminum with different types of adhesives exposed to different environments. 

For the preparation of polystyrene latexes, the compositions listed in Table 11 were employed. The molecular weight and conversion after 24 h of... 

Preparation of Polystyrene-g-Dibenzo-18-Crown-6-Ether-g-(Nanotube-g-Guanidine)... 

Preparation of Polystyrene-g-(Benzyl-Ethyl-Sulfonaniide)Octafluoro-Butane-l-Sulfonic acid... 

Preparation of (Polystyrene-b-((Polyethylene-co-Butylene)-g-(Diethyleneglycol Succinate)-b-Styrene)... 

Preparation of Polystyrene-Supported Trimethylammonium o-Methyl-1-(2-Hydroxyl-Cyclohexyl)-Carborane Zirconium Chloride... 

In order to synthesize polyfpropylene imine) dendrimers onto polystyrene via the divergent method, well-defined primary amine functionalized polystyrene had to be prepared as the core molecule. The anionic polymerization technique was chosen for the preparation of polystyrene (PS), because of the possibility of control over molecular weight and end group functionalization. An indirect amination procedure was developed [50], In this procedure a standard quantitative end-cap reaction with CO2 is used and a spacer is created between polystyrene and the primary amine function. The obtained polystyrene-COOH (PS-COOH), with Af around 3kgmol and values around 1.05, could be quantitatively reduced to the... 

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