Polystyrene, uses

Sheeting materials are utilized in a wide variety of appHcations (17). About 30% of the sheet market is foamed sheet, mostly all polystyrene, used for... 

Because of the chain-stiffening effect of the benzene ring the TgS of commercial materials are in the range 90-100°C and isotactic polymers have similar values (approx. 100°C). A consequence of this Tg value plus the amorphous nature of the polymer is that we have a material that is hard and transparent at room temperature. Isotactic polystyrenes have been known since 1955 but have not been of commercial importance. Syndiotactic polystyrene using metallocene catalysis has recently become of commercial interest. Both stereoregular polymers are crystalline with values of 230°C and 270°C for the isotactic and syndiotactic materials respectively. They are also somewhat brittle (see Section 16.3). 

Polystyrene produced by free-radical polymerisation techniques is part syndio-tactic and part atactic in structure and therefore amorphous. In 1955 Natta and his co-workers reported the preparation of substantially isotactic polystyrene using aluminium alkyl-titanium halide catalyst complexes. Similar systems were also patented by Ziegler at about the same time. The use of n-butyl-lithium as a catalyst has been described. Whereas at room temperature atactic polymers are produced, polymerisation at -30°C leads to isotactic polymer, with a narrow molecular weight distribution. 

Applications of radiation grafting in the coating industry for improving adhesion and other properties has been an active field. For instance, grafting of styrene onto polyester fibers was found to improve the interfa-cial adhesion between grafted chopped polyester fibers and polystyrene used as a matrix [139]. 

Polysaccharide. 974, 1000-1001 synthesis of, 1001-1002 Polystyrene, uses of, 242 Polytetrafluoroethylene, uses of, 242 Polyunsaturated fatty acid, 1061... 

To run the residence time distribution experiments under conditions which would simulate the conditions occurring during chemical reaction, solutions of 15 weight percent and 30 percent polystyrene in benzene as well as pure benzene were used as the fluid medium. The polystyrene used in the RTD experiment was prepared in a batch reactor and had a number average degree of polymerization of 320 and a polydispersity index, DI, of 1.17. 

Degradation of polystyrene using natural clay catalysts... 

Table II. Percent Recoveries of Polystyrene Using SLS and NaCl...

Figure 9 Scaling relationship between root-mean-square radius and molecular weight for polystyrene using GPC/MALLS. (From Wyatt, P. Hicks, D. L., Jackson, C., and Wyatt, G. K., Am. Lab., 20, 108,1988. With permission.)...

Stafford, C.M., Russell, T.P, and McCarthy T.J., Expansion of polystyrene using supercritical carbon dioxide, effects of molecular weight, polydispersity, and low molecular weight components, Macromolecules, 32, 7610, 1999. 

There are many different ways of making polystyrene using the suspension process. Most producers use a batch process, although there are no technical reasons why a continuous process could not work.10 For this study a batch... 

For the hydrosilylation reaction various rhodium, platinum, and cobalt catalysts were employed. For the further chain extension the OH-functionalities were deprotected by KCN in methanol. The final step involved the enzymatic polymerization from the maltoheptaose-modified polystyrene using a-D-glucose-l-phosphalc dipotassium salt dihydrate in a citrate buffer (pH = 6.2) and potato phosphorylase (Scheme 59). The characterization of the block copolymers was problematic in the case of high amylose contents, due to the insolubility of the copolymers in THF. 

Fig. 55. Gel-permeation chromatogram(GPC) of a microgel sample of Mw = 10X106 g/mol obtained in the anionic polymerization of EDMA in toluene. Microgel concentration = 1 g/L solvent = butyl acetate elution temperature = 70 °C is the weight-average molar mass of linear polystyrene used for comparison. [Reproduced from Ref. 256 with permission, Huthig Wepf Publ., Zug, Switzerland].

Some of the most remarkable achievements include microencapsulation in polystyrenes such as entrapped 0s04 for olefin hydroxylation (exploiting the interaction between n-electrons of benzene rings of the polystyrenes used as polymer backbones and the vacant orbitals of the catalysts) 5 polyurea-entrapped palladium (PdEnCat)6 for a multiplicity of C C forming reactions and the use of carboxylic acid-functionalized polymer (FibreCat).7 In general, however, metal leaching cannot be avoided. The PdEnCat catalyst, for instance, leaches some 4% of palladium per catalytic reaction run. 

B. Fragneaud, K. Masenelli-Varlot, A. Gonzalez-Montiel, M. Terrones, J.Y. Cavaille, Efficient coating of N-doped carbon nanotubes with polystyrene using atomic transfer radical polymerization., Chemical Physics Letters, vol. 419, pp. 567-573, 2006. 

There are many methods to test low-temperature behaviour and the possibility to use a thermoplastic at low temperature depends on the service conditions. Some grades can be used at -200°C or less if there are no impacts. Some other thermoplastics can be brittle at ambient temperature like the polystyrene used for yoghurt packaging. 

The limitation of Dole s experiments was that the ions of the electrosprayed high-molecular weight polystyrene used in his group could not be detected by mass spectrometry. [42-44] It took years of work and lasted until the ending 1980s for the Fenn group to fully realize that analytes of 100-2000 u molecular weight can be readily analyzed with a quadrupole analyzer attached to a properly constructed ESI ion source. [2,6,45]... 

For the synthesis of perfectly dendronized sohd-phase polymers (Fig. 7.4) various dendritic structures were prepared based on amide connections [6]. For example, the naturally occurring amino acid lysine was used as a building block in creating a dendritic scaffold [33]. The synthesis of symmetrical tri-branching den-drimers on aminomethyl polystyrene macrobeads was also described in literature [34]. Recently, aryl ether dendrimers were prepared on hydroxymethyl polystyrene using a Mitsunobu reaction with 3,5-bis(acetoxymethyl)phenol [35]. 

I 3 Catalytic Properties of Single Site Catalysts Prepared via Surface Organometallic Chemistry Table 3.4 Characteristics of the polystyrenes used. 

Polystyrene is presently the overwhelming choice as the polymer support [Frechet and Farrall, 1977 Frechet et al., 1988 Messing, 1974]. The polystyrene used is a crosslinked polymer prepared by copolymerization of styrene with divinylbenzene (DVB). (The divinyl-benzene is usually the commercially available mixture containing the meta and para isomers... 

Combine your results to obtain a value for the shear stress at the capillary wall, and use that value to estimate the extrudate swell, D/Dq for polystyrene using Figure 7.56. What effect does molecular weight have on die swell at these shear levels ... 

To give an impression of the nature of useful experimental results, some flow birefringence measurements which were obtained on a solution of polystyrene in methyl 4-bromo-phenyl carbinol, are reproduced in Figs. 1.2 and 1.3. The concentration of the solution was 2 wt. percents, measuring temperatures are indicated in the figures. The special polystyrene used was a well-known sample of anionically polymerized polystyrene, viz. S 111, provided by the courtesy of Dow Chem. Corp. Its molecular weight is 224,000. The indicated solvent is, at 18 °C, a 0-solvent and possesses practically the same refractive index as polystyrene itself (32). The measurement results are kindly provided by Daum from his still unpublished work. 

Table 4.1. Molecular weights of anionic polystyrenes used for Fig. 4.4...

Almost all electrophilic substitutions known to proceed in solution with isopropylbenzene can also be performed with polystyrene, using solvents such as nitrobenzene, carbon disulfide, or carbon tetrachloride. These substitutions include bromination [42], nitration [43,44], sulfonylation, Friedel-Crafts acylations [45 49], and alkylations... 

Figure 16.9. Synthesis of oligonucleotides on non-cross-linked polystyrene using nucleoside 5 -phos-phates [91],...

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