And of polystyrene

The theory of radiation-induced grafting has received extensive treatment. The direct effect of ionizing radiation in material is to produce active radical sites. A material s sensitivity to radiation ionization is reflected in its G value, which represents the number of radicals in a specific type (e.g., peroxy or allyl) produced in the material per 100 eV of energy absorbed. For example, the G value of poly(vinyl chloride) is 10-15, of PE is 6-8, and of polystyrene is 1.5-3. Regarding monomers, the G value of methyl methacrylate is 11.5, of acrylonitrile is 5.6, and of styrene is >0.69. 

Fig. 17. Electrostatic domain of polymer-Co(III) complex (a) and of polystyrene sulfonate) (b)...

Further cycloadditions used to prepare cycloalkenes on insoluble supports include the cyclopropanation of resin-bound alkynes and of polystyrene [165] (Figure 5.18). The latter reaction has been used to introduce tags onto polystyrene beads, which enable the recognition of a certain bead in compound libraries produced using the mix-and-split method (Section 1.2 [165-167]). The structure of polystyrene tagged in this way has not, however, been rigorously determined. 

A similar procedure was used for the heparinization of block copolymers composed of the poly-adduct of N,N -dimethyl-ethylenediamine and 1,4-bisacryloylpiperidine as a central block and of polystyrene as the end blocks 82). To enhance the stability of the material, heparin was crosslinked with glutaric dialdehyde. The resultant HCP sustained a 6 month implantation into the dog s vena cava. 

The degradation reactions of polymers have been widely reviewed 525). In the absence of air, thermal reactions are the important degradation route. They may involve reactions of functional groups on the chain without chain scission, typified for example by the dehydrochlorination of PVC, or reactions involving chain scission, often followed by depropagation and chain-transfer reactions to yield complex mixtures of products. This latter route would be typical of the degradation of poly(methyl methacrylate), which depolymerizes smoothly to its monomer, and of polystyrene, which produces a wide range of tarry products. 

With copolymers an analogous situation is met as with blends Here also the components may be molecularly compatible or not. When the copolymer is random , i.e. the building blocks are arranged in a random sequence, then the copolymer is, as a matter of fact, homogeneous on a molecular scale, even if the components are incompatible. An example is SBR, a copolymer of styrene and butadiene. It shows a single glass transition at about -65 °C, which is roughly in accordance with the styrene content (23%) and the Tg s of polybutadiene (-95 °C) and of polystyrene (90 °C). 

Figure 1 KBr transmission spectrum of polystyrene resin (lower curve) and of polystyrene resin loaded with adipinic acid monoamide (upper curve). The carbonyl bands of the acid (at 1720 cm-1) and of the amide (at 1650 cm-1) are clearly seen in the overlay plot. The spectra were obtained, in the 4000-400 cm 1 range with 32 scans at 2 cnr1 resolution, by means of a Bruker IFS 66 spectrophotometer.

Isotactic polystyrene was epimerized to various extents by reaction with KOtBu in hexamethylphosphor-amide solution at 100°. The 13C-NMR spectra of the epimerized samples and of polystyrene in 9 1 trichlorobenzene nitrobenzene-d6 solution at 150° were recorded and analyzed using stereosequence distributions that were calculated for the samples by Monte Carlo simulation of the epimerization process. 

Example 5.24 Preparation of Foamable Polystyrene and of Polystyrene Foam... 

The peeling force, for a pressure-sensitive tape, is expended (dissipated) in the elongation of the filaments.(1A local temperature rise is observed in peeling(i 3) it has been attributed to the plastic and elastic deformation that occurs when these filaments are drawn.(D A large, transient temperature rise has been observed in the fracture of PMMA and of polystyrene. See the review of the thermal effects on pp. 136-139 in Doll.d )... 

Friedman and Porter [ 14] studied bidisperse blends of PDMS and of polystyrene and concluded that 77o depends uniquely on the weight average molecular weight and no other moment . Other studies of polystyrene have led to the same conclusion, although various values of a have been reported, e.g., a= 3.7 [15], a= 3.4 [16], and a= 3.6 [17]. The last dted study involved blend components with molecular weights up to 400,000. 

---