Polystyrene prepared with AIBN

The number of initiator fragments could also be determined by 2H NMR analysis of polystyrene prepared with AIBN-<712.42 The value (1.65) is consistent with those obtained by other methods,42,43,70 and suggests that the disproportionation is not of negligible importance in the radical polymerization of styrene. 

The number of initiator fragments per polymer molecule was calculated to be 1.59, indicating that there are two types of polymer molecules which contain one and two initiator fragments, respectively. Analysis of the polystyrene prepared with 2H- and 13C-labelled AIBN also showed that the polystyrene molecule contained 1.6542 and 1.7-1.843 initiator fragments, respectively (cf. Section 3.2.1). 

Finally, the lithiation of a soluble chloromethylated polystyrene 16 (prepared by AIBN-indnced copolymerization of styrene and 4-chloromethylstyrene in a 3 1 molar ratio) with lithinm and a catalytic amonnt of DTBB (10%) in THF at —78 °C gave the expected... 

Undeuterated polystyrene (Mn = 18 400) prepared in bulk with AIBN at 60°C showed small NMR peaks at 1.01 and 1.18 ppm (Fig. 6B), which were assigned by Johns et al. to the methyl protons of initiator fragments.44 The number of initiator fragments per chain was calculated to be 1.52. From the polystyrene, lower (Mn = 7760) and higher (Mn = 41 300) molecular weight portions were fractionated using GPC. Analysis of the fractions revealed that the former had 1.44 initiator fragments per chain and the latter 1.77. This shows that the... 

Pseudo-IPN s (PDIPN s) Two types of pseudo-IPN s were prepared, one from crosslinked PPO (CPPO)/linear polystyrene (LPS) (PDIPN-1) and the other from a linear PPO (LPPO)/crosslinked polystyrene (CPS (PDIPN-2). The former PDIPN s were prepared from a mixture of PPO solution with ethylene diamine (crosslinking agent) and styrene monomer with AIBN. 1.4 g. of ethylene diamine was added to 40 g. of PPO. The mixture of PPO solution and styrene... 

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

By far the most studied PolyHIPE system is the styrene/divinylbenzene (DVB) material. This was the main subject of Barby and Haq s patent to Unilever in 1982 [128], HIPEs of an aqueous phase in a mixture of styrene, DVB and nonionic surfactant were prepared. Both water-soluble (e.g. potassium persulphate) and oil-soluble (2,2 -azo-bis-isobutyronitrile, AIBN) initiators were employed, and polymerisation was carried out by heating the emulsion in a sealed plastic container, typically for 24 hours at 50°C. This yielded a solid, crosslinked, monolithic polymer material, with the aqueous dispersed phase retained inside the porous microstructure. On exhaustive extraction of the material in a Soxhlet with a lower alcohol, followed by drying in vacuo, a low-density polystyrene foam was produced, with a permanent, macroporous, open-cellular structure of very high porosity (Fig. 11). 

Two of the polystyrene samples were benzoyl peroxide-initiated commercial materials one of these had been on the shelf for over twenty years. The poly (n-butyl methacrylate) and the poly (vinyl chloride) were also commercial materials. The poly (methyl methacrylate) and the third polystyrene sample were prepared under nitrogen from freshly distilled monomers by bulk initiation with azobisisobutyronitrile (AIBN). Each of the above samples was purified by two reprecipitations from tetrahydrofuran solution with methanol and dried in vacuum at 65 °C. for at least 24 hours. The poly (ethylene terephthalate) was a sample of 5-mil Mylar Type A sheet which had been cleaned by detergent washing and water rinsing, followed by vacuum-drying at room temperature for 16 hours. 

Initiation reactions are usually started by an active free radical such as peroxide (-0-0-), e.g. benzoyl peroxide is a good inititator for the free radical addition polymerisation of styrene to produce polystyrene AICI3 is an initiator for the cationic addition polymerisation of isobutylene to form isobutyl synthetic rubber or azobisiso-butyronitrile compounds (-N=N-) (abbreviated to AIBN). Propagation reactions are the continuing process and, eventually, lead to the termination stage that occurs by combination or disproportionation. This usually occurs when the free radicals combine with themselves and signals the end of the polymerisation process. All polymers formed by this process are thermoplastics. Table 4.1 is a list of common polymers prepared by the addition process. 

NMP is based on the concept of a dynamic equilibration between dormant alkoxyamines and propagating radicals as shown in eqn [55].The choice of the persistent radical is cmcial for controlled polymerization. While styrene can be easily moderated by 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO), other monomers required the development of nitroxides that contain hydrogen atoms at the a-C. There are two different initiation methods for NMP. Conventional radical initiators (i.e., AIBN, BPO) in conjunction with a persistent radical were initially used to prepare polymers by NMP, but these systems were limited in the choice of monomer. Functionality could be incorporated via a functionalized initiator or a functionalized persistent radical. For example, Baumert and Mulhaupt prepared carboxylic acid-terminated polystyrene, poly(styrene-co-acrylonitrile), and polystyrene-b-poly (styrene-co-acrylonitrile) by the use of the functionalized initiator 4,4 -azobis(4-cyanopentanecarboxylic acid). The polymerization was controlled by the addition of 2,2,6,6-tetramethyl-l-piperidyloxyl radical, and polymers with... 

Miaowave irradiation was successfully used to prepare nanocomposites of polystyrene silica (PS/SNs) with diffaent contents of inorganic nanofilfets by in situ bulk radical copolymerization of styrene with methacryloxypropyl silica nanopartides (MPSNs). Unda optimized condition, 33% of grafting could be achieved with 98% convasion of styrene. In a typical experiment, MPSNs were mixed with styrene and a certain amount of AIBN with ultrasonic vibrations for 30 min. Then the mixture was irradiated in a miaowave oven (700 W) for lOmin with a diffaent power." ... 

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