Organic−inorganic interpenetrating polymer networks were synthesized with an SiO2 phase made by sol−gel chemistry and the organic phase made from poly(2-hydroxyethyl acrylate). The resultant morphologies were characterized by small-angle scattering and electron microscopy. When the vinyl polymerization is more rapid than the sol−gel reaction, gross phase separation occurs giving a heterogeneous structure. For comparable rates of the two polymerizations, the specimens have a dendritic morphology on the scale of 0.5 μm. The more rapid formation of the silica phase relative to the organic network produces rigid and optically transparent materials, with a finely divided structure as seen by transmission electron microscopy. The glass content of these materials is about 0.15 g/g and the sizes of the SiO2-rich domains are 100 Å or less. Addition of tetrakis(2-(acryloxy)ethoxy)silane was also studied and found to promote phase mixing between the organic and inorganic phases.

BILBY is a recently constructed and commissioned time-of-flight small-angle neutron scattering instrument, operated by the Australian Centre for Neutron Scattering at the Australian Nuclear Science and Technology Organisation (ANSTO). BILBY provides a wide accessible q range (q ' 1.0 Â 10 À3 Å À1 to $1.8 Å À1 ) and variable wavelength resolution (Á/ ' 3-30%) to complement the other small-angle and ultra-small-angle neutron scattering capabilities available at ANSTO. Since its construction, BILBY has been used to study samples from a wide range of scientific disciplines, including biology, chemistry, physics and materials science. This article describes the BILBY design and components, and shows data collected from a number of reference samples.

Rheological and small-angle X-ray scattering (SAXS) measurements on a polystyrenepolyisoprene-polystyrene block copolymer indicate that high-strain, high-stress unidirectional shear flow in the microphase-separated regime produces a well-oriented, microdomain structure with cylindrical microdomains. Experiments in low-stress, high-strain flow produced little orientation. The material studied is a high molecular weight copolymer with 24 vol % polystyrene and a cylindrical microdomain morphology as indicated by SAXS. Flow above the microphase-separation temperature (2'~s~) determined by linearviscoelastic measurements resulted in no microdomain orientation. The linear-viscoelastic results show that materials sheared near T~T do not recover to a well-microphase-separated morphology after high-strain shear flow. A flow mechanism for microphase-separated block copolymers proposed previously is compatible with the results obtained here. IntroductionIn the first paper of this series2 t h e effect of unidirectional shear flow on a polystyrene-polybutadienepolystyrene block copolymer, SBS81, was investigated. That polymer showed evidence of microphase separation at all temperatures studied, indicating that the microphaseseparation temperature, TMST, is much greater than 220 "C. This study concerns a second polymer of comparable molecular weight and polystyrene (PS) volume fraction, which contains a different centerblock, polystyrenepolyisoprene-polystyrene (SIS65). In linear-viscoelastic

A simple kinematic model for rotational jump diffusion of a normal alkane about its long axis (circular random walk model) is developed. Inelastic neutron scattering data obtained on the Fermi chopper time-of-flight instrument at the National Bureau of Standards reactor using an incident neutron wavelength of 2.47 A (/),,1..11.. = 3.8%) are compared with the predictions of the model. Data taken below the temperature of the "rotator" phase transition in n -nonadecane (295 OK) show no quasielastic scattering due to diffusive motions. Data taken in n -nonadecane in its disordered solid phase show quasielastic scattering consistent with the circular random walk model. Estimates for values of the model parameters of 3.5 psec. for T, and N ;::: 8 are obtained.

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