Anionic polystyrene, oxidized

Figure 11. Dielectric loss of oxidized anionic polystyrene (L5 hr at 254 nm in 400 torr 02)jit low temperatures (f = 2.4 X 104 Hz) Mn = 10s...

Liu et al. developed a simple method to fabricate polystyrene (PS) nanotube templates to mimic a soft environment for capturing breast cancer cells from whole blood. First, PS was dissolved in a solvent, forming a solution. Then, anionic aluminum oxide (AAO) was made to have intimate contact with such solution. Through capillary forces, the solution was absorbed into the nanopores of AAO. After complete evaporation of the solvent, all components solidified. Then, AAO was etched off with NaOH, leaving a template covered by PS nanotubes. As shown in Figure 16.5B, such soft structure was... 

Photolysis of oxidative products (hydroperoxide groups, chain peroxides and ketonic groups) formed during the preparation of polystyrene. If hydroperoxides are present (Fig. 3.51) the oxidation rates are increased, and degradation can also be induced in the anionic polystyrene. 

The uncatalyzed thermal oxidation of atactic polystyrene has been studied extensively, including main chain deuterated derivatives. Such studies are usually conducted around 475 K over the course of hours. However, in preliminary infrared studies with cast films of anionic polystyrene (molecular weight 4,(X)0) on a AgQ plate, carbonyl bonds were first detected after 10 minutes heating in air at 403 Oxidation is an exothermic reaction. We have not located a measured heat of oxidation. However, comparisons with the heats of combustion for ethylbenzene and acetophenone in the Handbook of Chemistry and Physics indicate a liberation of 102 kcal/mol for the oxidation of ethylbenzene to acetophenone. The course of oxidation of polystyrene is a complex chain reaction but we will assume a net heat of liberation of = 100 kcal/mol to hold. 

Anionic polymerization of ethylene oxide by living carbanions of polystyrene was first carried out by Szwarc295. A limited number of methods have been reported in the preparation of A-B and A-B-A copolymers in which B was polystyrene and A was poly(oxyethylene)296-298. The actual procedure was to allow ethylene oxide to polymerize in a vacuum system at 70 °C with the polystyrene anion initiated with cumyl potassium in THF299. The yields of pure block copolymers are usually limited to about 80% because homopolymers are formed300. ... 

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

Polystyrene/polyethylene oxide dendrimers were prepared by ATRP using tri- and tetra (bromomethyl) benzene as the initiators [207]. Each bromine end-group of the resulting stars was transformed first to two - OH groups and subsequently to potassium alcholate, as shown in Scheme 114. These - OK sites served to initiate the anionic polymerization of EO. The synthesized dendritic copolymers were found to display monomodal and narrow molecular weight distribution. 

Imanaka—heterogenization of Rh complexes. In 1991, Imanaka and coworkers124 reported the heterogenization of Rh complexes by binding them to aminated polymers. As discussed previously, these findings led to fruitful research by Ford, Pardey, and others. The isolated polymer-bound Rh carbonyl anion complex was found to be reusable for reactions such as water-gas shift and reduction of nitro compounds. The polymer-bound Rh complexes were characterized by infrared spectroscopy. Water-gas shift activity (80 mol H2 per mol Rh6(CO)i6 in 24 hours) was recorded using the Rh complexes at 100 °C with 0.92 atm of CO, 2.16 ml H20, 0.05 mmol Rh6(CO)16, aminated polystyrene, 5.0 mmol of N, 5.56 ml ethoxyethanol and reduction of nitro-compounds (e.g., aliphatic nitro compounds to nitriles, oximes to nitriles, hydroxylamines to nitriles, and N-oxides to amines) occurred at 40 °C. 

It has been shown recently (10) that such block structures could be tailored precisely by the general method summarized hereabove. It is indeed possible to convert the hydroxyl end-group of a vinyl polymer PA (f.i. polystyrene, or polybutadiene obtained by anionic polymerization terminated with ethylene oxide),into an aluminum alcoholate structure since it is well known that CL polymerizes in a perfectly "living" manner by ring-opening insertion into the Al-0 bond (11), the following reaction sequence provides a direct access to the desired copolymers, with an accurate control of the molecular parameters of the two blocks ... 

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