To produce an impact toughened grade of 'Victrex' Polyethersulphone by blending with (A-B)n type Polyethersulphone/Poly(dimethylsiloxane ) [P.E.S./P.D.M.S.] block copolymers. A number of novel (A-B)n type P.E.S./P.D.M.S. block copolymers of varying block molecular weights have been synthesised and characterised. These have been melt blended with pure 4800P grade P.E.S. to yield a series of 'impact modified' P.E.S./P.E.S.-co-P.D.M.S. blends. Standard Izod and Tensile test pieces have been injection moulded from these blends, and these test pieces used in a study of the physical, chemical and mechanical properties of the blends. The melt shear viscosity of P.E.S. has been found to be substantially reduced by the presence of P.E.S./P.D.M.S. copolymers. This is believed due, at least in part, to the migration of the P.O.M.S. bearing copolymer to the surface of the blend during processing. Improvements in sharp notch impact strength of up to 43% have been observed in P.E.S./P.E.S.-co-P.D.M.S. blends containing as little as 2.5% copolymerised P.O.M.S. These improvements have been achieved at the expense of more modest reductions (no more than 24%) in tensile strengths. Examination of impact fracture surfaces has revealed that the copolymers promote localised plastic deformation in sharply notched P.E.S., the copolymer particles themselves undergoing cavitation during crack propagation. It has also been shown, however, that the copolymers suppress the gross plastic deformation usually observed in unnotched or bluntly notched P.E.S. The additive particles promote crack initiation in such specimens, and although they also facilitate localised plastic deformation, the overall result is usually a decrease in P.E.S. impact strength. Significantly, blends containing P.E.S. and P.E.S./P.O.M.S. copolymers do not appear to perform any better under impact than simple physical blends of P.E.S. and linear P.D.M.S. This is believed to be due to migration of the P.D.M.S. domains to the surface of the P.E.S./P.D.M.S. copolymers. Once at the surface, they inhibit the formation of the desired adhesive bond between the P.E.S. matrix and the P.E.S. domains in the copolymer. The presence of the copolymers does not appear to have any significant effect on the mechanical performance of P.E.S. as tested after immersion in a range of organic and inorganic reagents at room temperature.

No description available.

Free-radical solution polymerization techniques have been used to prepare carboxyl-terminated poly(methyl methacrylate) and poly(2- ethyl hexyl acrylate) homopolymers. The molar masses of these prepolymers were readily controlled and they were found to be approximately monofunctional with respect to carboxy I groups. These carboxyl-terminated prepolymers were converted to methacrylate-terminated macromonomers via acyl chlorideterminated intermediates. The macromonomer functionalities obtained by this procedure were high, typically 0.90-1.05 methacrylate groups per molecule on average. The prepolymers and macromonomers were characterized using End-group analysis (EGA). Infra-red spectroscopy (IR), 1H Nuclear Magnetic Resonance spectroscopy (lH NMR) and Gel-permeation Chromatography (GPC). Polystyrene-graft-poly(methyl methacrylate) and polystyrene-graft-poly(2-ethyl hexyl acrylate) copolymers were prepared by the free-radical solution copolymerization of macromonomers (M2) with styrene (M1). A dual detector GPC method was used to estimate macromonomer conversions. Unreacted macromonomer and styrene were removed and the purified graft copolymers were characterized by Thin-layer Chromatography (TLC) , GPC, IR and 1H NMR. It was shown that efficient grafting had occurred by copolymerization of the macromonomer end-group and that ungrafted polystyrene backbone was not produced. The graft copolymer chemical compositions and physical architectures were controlled by changing the comonomer feed composition or the macromonomer molar mass. Reactivity ratios (r1) were determined by the Jaacks, Finnemann-Ross and Kelen-TUdos methods. It was shown that the reactivities of the methacrylate-terminated macromonomers were approximately similar to conventional methacrylates and independent of the macromonomer molar mass or composition within the limits investigated. The polystyrene-graft-poly(2-ethyl hexyl acrylate) copolymers have been used as stabilizers in the free-radical non-aqueous dispersion polymerization of methyl methacrylate in aliphatic hydrocarbons. The poly(methyl methacrylate) particles were characterized by Transmission Electron Microscopy (TEM) in order to determine their size, shape and state of aggregation. Ultraviolet spectroscopy (UV) was used to determine the graft copolymer content of the particles, from which an estimate of surface coverage was made. The effects of varying the polymerization method, and both the composition and concentration of stabilizers used, were studied. The average particle size, particle size distribution and the state of aggregation were found to be dependent upon these parameters.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed Feb. 8, 2010). Additional advisors: J. Barry Andrews, Kathryn Brannon, Derrick R. Dean, Gregg M. Janowski, Mark L. Weaver. Includes bibliographical references (p. 158-161).