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The ultrasonic degradation of poly (styrene-co-methyl methacrylate) (SMMA), poly (styrene-co-ethyl methacrylate) (SEMA) and poly (styrene-co-butyl methacrylate) (SBMA) copolymers of different compositions was studied. The copolymers were synthesized and NMR spectroscopy was used to determine the composition, and the glass transition temperatures were determined by DSC. The reactivity ratios were determined by the Kelen-Tudos method and it indicated that the copolymers were random. The effect of solvent, temperature and copolymer composition on the ultrasonic degradation rate of these copolymers was investigated. A model based on continuous distribution kinetics was employed to study the degradation kinetics. The degradation rate coefficients of the copolymers decreased with an increase in the styrene content in the copolymer. At any particular copolymer composition the rate of degradation follows the order: SBMA>SEMA>SMMA. Thermogravimetric analysis (TGA) of the copolymers was carried in order to assess their thermal stability. The same order of degradation was observed for the thermal degradation of the copolymers as that observed for ultrasonic degradation., ((c) 2010 Elsevier B.V. All rights reserved.)

Nanocomposites with multi-walled carbon nanotubes (MWNT) and polystyrene (PS) were synthesized via an in-situ bulk sonochemical polymerization under the application of ultrasonication to open pi-bonds in the MWNT, thus enhancing the PS polymerization. Sonication of vinyl monomers such as styrene leads to radical initiation of polymerization. Various characteristics such as morphology, thermal property of the synthesized PS in the presence of the MWNT in the PS/MWNT composites were examined by SEM, TEM, thermogravimetric analysis, respectively. Their rheological properties were also investigated using a stress-controlled rotational rheometer under small amplitude oscillation and steady transient shear in their melt state.

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation.

Rapid, efficient and selective alkene epoxidation and alkane hydroxylation with sodium periodate catalyzed by Mn (TPyP) supported on chloromethylated polystyrene, [Mn(TPyP)-CMP], under ultrasonic irradiation were reported. This catalytic system showed high selectivity in epoxidation of stilbenes and R-(+)-limonene and exhibits a particular ability to epoxidize linear alkenes such as 1-heptene. This supported catalyst can catalyze the oxidation of very inert saturated hydrocarbons as well as alkylbenzene derivatives with NaIO4 under ultrasonic irradiation. Under mild reaction conditions, this catalyst was consecutive reused five times without detectable catalyst leaching and gave over 95% epoxide yield in the epoxidation of styrene.

In this work, a route for the synthesis of inorganic/polymer core/shell composite nanoparticles was proposed, which can be called the antisolvent-ultrasound method. Compressed CO2 was used as antisolvent to precipitate the polymer from its solution dispersed with inorganic nanoparticles, during which ultrasonic irradiation was used to induce the coating of precipitated polymers on the surfaces of the inorganic nanoparticles. TiO2/polystyrene (PS) core/shell nanocomposites have been successfully prepared using this method. The transmission electronic micrographs (TEM) of the obtained nanocomposites show that the TiO2 nanoparticles are coated by the PS shells, of which the thickness can be tuned by the pressure of CO2. The phase structure, absorption properties, and thermal stability of the composite were characterized by X-ray diffraction (XRD), UV-vis spectra, and thermogravimetry, respectively. The results of X-ray photoelectron spectra (XPS) indicate the formation of a strong interaction between PS and TiO2 nanoparticles in the resultant products. This method has some potential advantages for applications and may be easily applied to the preparation of a range of inorganic/polymer core/shell composite nanoparticles.

We detail here studies into the nature of mechanochemical degradation of macromolecules, effected by means of ultrasonic (US) irradiation. Specifically, we have investigated the effect of long-chain branching (LCB), in the star configuration, on the degradation mechanism of polystyrene dissolved in DMAc/LiCl. The information obtained from size-exclusion chromatography with triple detection (refractometry, viscometry, multi-angle light scattering) shows that the degradation mechanism of stars is radically different from that of linear polymers. Whereas in the latter, from a macromolecular standpoint, it is merely necessary for the molar mass to be greater than some limiting value (M(lim)), in the former both molar mass and structural factors affect ultrasonic degradation. We have examined the effects of arm number and of arm molar mass on star degradation, and propose the concept of a spanning molar mass (M(span) approximately 2M(arm)) such that, even in the event that M(arm)M(lim). This mechanism has been extended to other types of architecture (e.g., H-branched, dendritic), where it is proposed that a continuous path must exist with M(path)>M(lim) for degradation to occur. Examination of the different radii afforded by viscometric and light-scattering detection gives insight into the solution thermodynamics and conformation of the stars with differing arm number and molar mass and of the effects of insonation on macromolecular structure.