Polystyrene irradiated

G. Geuskens, D. Baeyens Volant, G. Delaunois, Q. Lu Vinh, W. Piret, and C. David, Photo oxidation of Polymers II. The Sensitized Decomposition of Hydroperoxides as the Main Path for Initiation of the Photo oxidation of Polystyrene Irradiated at 253.7 nm, Eur. Polym. J., 14, 299 303 (1978). 

It is known that polystyrene irradiated at 45"C, for example, has G(x) = 0.04 and G(s) — 0.02 (20,29,30) which are similar values to those found in this study. Increasing the temperature during irradiation, favored the disproportionation reaction of chain scission radicals relative to recombination reactions and thereby increased main chain scission yields (20) (Figure 7). 

Figure 5. Contact angle changes with various liquids on a film of polystyrene irradiated in air...

Figure 9. Carbonyl-stretching region in polystyrene irradiated 5 hours in air at 30°C. FMIR spectra...

Figure 10. Relation between the relative carbonyl absorbance for polystyrene irradiated 5 hours and the water contact angle on a film irradiated 2 hours...

These free radicals produced in polystyrene irradiated with UV light should be compared with cyclohexadienyl type radicals produced after irradiation with ionizing radiation (89). 

The H2 yield from polystyrene irradiated with y-rays is two orders of magnitude less than that in polyethylene. The H2 yields increase with increasing LET for all the polymers shown in Fig. 2, but the increase is not linear. There is a considerably greater increase for polystyrene than polyethylene. A 5 MeV helium ion, a-particle, gives a G-value for H2 of 4.6 molecules/100 eV from polyethylene and 0.15 molecule/100 eV from polystyrene [11], The large increase in H2 yield for polystyrene suggests that this material is not as radiation inert as typically thought. The use of yields determined with y-rays for heavy ion radiolysis would clearly underestimate the production of H2 in transuranic waste materials. More experiments coupled with sophisticated models are required to predict H2 yields in other unexamined polymers and in complex mixtures. 

Radical pairs were detected recently by Wilske and Heusinger [140] in polystyrene irradiated at 77°K. If the polystyrene samples are warmed up,... 

A saturation effect for radical concentration has been reported for some polymers. It occurs at about 7 Mrad for PMMA irradiated at room temperature [207]. This effect, however, probably depends on the purity of the sample since it could not be reproduced in our laboratory. A very important decrease in the net rate of radical formation in polyvinyl chloride at the same dose (7 Mrad) has been measured [208]. In polystyrene irradiated at room temperature, three different radicals formed [209]. They were shown to saturate at different doses (Fig. 3.1). The first break in the curve corresponds to the saturation of... 

YIELD OF CROSSLINKING OF POLYVINYLPYRIDINE (PVP) AND POLYSTYRENE IRRADIATED AT ROOM TEMPERATURE [340]... 

TABLE 1 Chemical Yield of Different Molecules Emitted from Polyethylene and Polystyrene Irradiated with 100-keV He and 200-keV Ar Ion Beams... 

Keywords Reciprocity UV intensity Weathering Acceleration Correlation ORWET Polystyrene Irradiance Temperature Ultra-Accelerated Weathering System UA EMMA Exposure Exhapolation ASTM G90 Color Outdoor Static Dynamic Hypervolume... 

Fig. 10.107. Contact angle 6) changes with various liquids on a film of polystyrene irradiated in air [667]. (Reprinted with permission from [667]. Copyright (1968) American Chemical Society.)...

Materials are being developed to exhibit both photochromic and photographic behaviors one such system is based on a substituted indolinospiro-hen opyrene embedded in a polystyrene matrix (26). This system acts as a photochromic system at low exposure in the uv range and at high exposure it functions as a photographic system. The image can be devisualized by heat and can be restored many times with uv irradiation. 

PL can be used as a sensitive probe of oxidative photodegradation in polymers. After exposure to UV irradiation, materials such as polystyrene, polyethylene, polypropylene, and PTFE exhibit PL emission characteristic of oxidation products in these hosts. The effectiveness of stabilizer additives can be monitored by their effect on PL efficiency. 

Susceptibility to radiation damage must be considered seriously if reference samples are to be calibrated for use in place of absolute systems. For the measurement of absolute C He, H) cross sections, films of polystyrene (CH) (which is relatively radiation hard) have been used successfiiUy, the RBS determination of carbon providing implied quantitation for the hydrogen present in the film. For a durable laboratory reference sample, however, there is much to recommend a known ion-implanted dose of H deep within Si or SiC, where the loss of hydrogen under room temperature irradiation will be neghgible. 

The Pictet-Spengler reaction has been carried out on various solid support materials " and with microwave irradiation activation.Diverse structural analogues of (-)-Saframycin A have been prepared by carrying out the Pictet-Spengler isoquinoline synthesis on substrates attached to a polystyrene support. Amine 20 was condensed with aldehyde 21 followed by cyclization to give predominantly the cis isomer tetrahydroisoquinoline 22 which was further elaborated to (-)-Saframycin A analogues. 

The quantum yield of polymerization is 6.72 and for photoinitiation < / = 2.85 x 10 . The polystyrene produced with this initiator shows photosensitivity when irradiated with UV light (A = 280 nm). This polymer, which carries two photosensitive end groups of - SC(S) N(CH3)2, behaves as a telechelic polymer and it is useful for production of ABA block copolymer. 

Figure 4 Changes in (a) carbonyl index and (b) hydroxyl index versus irradiation time for polystyrene films. O-con-trol -2,4-DHBP -2H-4MBP -2H-4BB X-DHBP-F A-HMBP-F and D-HBBP-F.

Figure 7 Optical density (280 nm) versus irradiation time (hours) for polystyrene films -2,4-DHB -2H-4BB -DHBP-F A-2H-4MB A-HMBP-F and B-HBBP-F.

Furthermore, photochemically induced homolytical bond cleavage can also be applied when the prepolymer itself does not contain suitable chromophoric groups [113-115]. Upon thermolysis of ACPA in the presence of styrene, a carboxyl-terminated polystyrene is formed. This styrene-based prepolymer was reacted with lead tetraacetate and irradiated with UV light yielding free radicals capable of initiating the polymerization of a second monomer (Scheme 33) [113]. 

A one-pot synthesis of thiohydantoins has been developed using microwave heating [72]. A small subset of p-substituted benzaldehydes, prepared in situ from p-bromobenzaldehyde by microwave-assisted Suzuki or Negishi reactions, was reacted in one pot by reductive amination followed by cyclization with a thioisocyanate catalyzed by polystyrene-bound dimethyl-aminopyridine (PS-DMAP) or triethylamine, all carried out under microwave irradiation, to give the thiohydantoin products in up to 68% isolated yield (Scheme 16). 

Rapid loading of cross-linked PS Wang resin (4-(benzyloxy)benzyl alcohol PS) with a selection of /3-ketoesters was shown to reach completion within 1-10 min if microwave irradiation at 170 °C was employed. The conventional thermal method for acetoacetylation of hydroxymethyl-functionalized polystyrene resins takes several hours therefore, microwave heating allowed for... 

Hlasta and Deng have developed a two-step solid-phase method for the decoration of azoles at C-2 [188]. First, imidazole was loaded onto a polystyrene-bound carbamyl chloride via a benzaldehyde bridge (Fig. 40). The 2-substi-tuted imidazole was efficiently cleaved in good yields in the presence of various nucleophiles (i.e., water, alcohols, and amines), trifluoroacetic acid, and boron trifluoride under microwave irradiation in a closed vessel at 120 °C for 5 min. 

It has to be noted that the temperatures up to 220 °C involved in the transformations on polystyrene-based support do not affect the resin stabihty. The controlled microwave irradiation appeared to be very effective in speeding up the linking of 2(lH)-pyrazinones to an appropriate resin as well as in accelerating the rate of subsequent solid-phase Diels-Alder reaction and the following cleavage of a resulting pyridinone from the sohd support. 

The yield of cross-linking depends on the microstructure of polybutadiene and purity of the polymer as well as on whether it is irradiated in air or in vacuum. The cross-link yield, G(X), has been calculated to be lowest for trans and highest for vinyl isomer [339]. The introduction of styrene into the butadiene chain leads to a greater reduction in the yield of cross-linking, than the physical blends of polybutadiene and polystyrene [340]. This is due to the intra- and probably also intermolecular energy transfer from the butadiene to the styrene constituent and to the radiation stability of the latter unit. 

Figure 10.7 The phase diagram (a) and the glass transition temperatures (b) of a PSC/PVME mixture obtained, respectively, by light scattering and differential scanning calorimetry (DSC). Irradiation experiments were performed in the miscible region at 127 C indicated by (X) in the figure of trans-cinnamic acid-labeled polystyrene/poly(vinyl methyl ether) blends.

Fe(6-Mepy)2(py)tren] (004)2 Doped in PSS. Magnetic susceptibilities measured for a microcrystalline sample of the complex produce a magnetic moment value = 0.36 pg at 10 K and 0.61 pg at 150 K, followed by a gradual increase to Peff = 2.80 pe at 311 K [138]. Thus 26% of the complexes are in the HS state at 300 K if a magnetic moment of 5.1 Pe is assumed for the pure HS compound. On the other hand, the complex doped into a polystyrene sulfonate (PSS) film does not provide any evidence for a thermal population of the HS state up to 340 K as demonstrated by variable-temperature UV-VIS and Mossbauer spectra. In fact, all the complexes doped into the PSS film are in the LS state at temperatures below 340 K. However, if irradiated by a single pulse of a Q-switched Nd/YAG laser (532 mp), the complex is excited from the LS ground state to the HS J2 states via an intermediate MLCT state and the metal states. The subsequent back relaxation from the excited T2 state to the... 

UV light in a second step. In later work reported by Tazuke, Kimura et al. (6-8) successful photograftings on the polymer surface of thin films (polyethylene, polypropylene and polystyrene) were achieved with various monomers. In this work, grafting was induced by UV irradiation through the film which was in contact with a solution containing initiator and monomer. The method is slow and - in addition to surface grafting - large amounts of homopolymer are formed. 

Pt-catalyzed hydration of various aliphatic and aromatic alkynes under phase transfer conditions in (CH2C1)2/H20 in the presence of Aliquat 336 led to either a Markovnikov product, mixtures of two ketones, or ketones with the carbonyl group positioned away from the bulky side.72 In the absence of the phase transfer reagent, Aliquat 336, hardly any reaction took place. Recently, a hydrophobic, low-loading and alkylated polystyrene-supported sulfonic acid (LL-ALPS-SO3H) has also been developed for the hydration of terminal alkynes in pure water, leading to ketones as the product.73 Under microwave irradiation, the hydration of terminal arylalkynes was reported to proceed in superheated water (200°C) without any catalysts.74... 

Polyethylene and polystyrene are examples of plastics subject to environmental stress cracking. Crack resistance tests have shown that surfactants, alcohols, organic acids, vegetable and mineral oils, and ethers provide an active environment for stress cracking of polyethylene. Table 6 lists typical sterile devices and plastic materials used to fabricate them, while Tables 7-9 list the potential effects of sterilization processes on polymeric materials. The effect of gamma irradiation on elastomeric closures has been studied by the Parenteral Drug Association [15]. 

Repeating unit of polymer chain including solvation Mn of samples not irradiated based on GPC in NMP with polystyrene standards, or by NMR end-group analysis if so indicated Measured net G value after cesium-137 irradiation corrected relative to Fricke dosimeter... 

Pol VG, Grisaru H, Gedanken A (2005) Coating noble metal nanocrystals (Ag, Au, Pd and Pt) on polystyrene spheres via ultrasound irradiation. Langmuir 21 3635-3640... 

---