Elongational behavior of sphere-forming triblock copolymers is examined using a series of sample having almost the same molecular weight but different bridge fractions prepared by mixing polystyrene-b-polyisoprene-b-polystyrene (SIS) and the cyclic-SI. A polystyrene-b-polyisoprene-b-poly(2-vinylpyridine) sample was also used as a 100% bridged reference. The lattice deformation examined by SAXS can be well expressed by affine deformation, independent of the bridge fraction. Macroscopic stress and the orientation function of I segments examined by IR dichroism can be also approximately expressed by affine deformation, where magnitudes are proportional to the bridge fraction. In the stress-strain curves, small shoulders were observed at low strains. The presence of the shoulder can be explained by restoring force of the lattice, the magnitude of which depends on the regularity of the microdomain lattice. It is found that the restoring force linearly depends on the bridge fraction of the middle block chains in bulk states, in contrast to the results reported for solvent-containing systems.

ABSTRACT:Flow-induced structure of lamellar forming poly(styrene-d 8 -block-isoprene)s (DI) solutions under steady shear flow are examined by small angle neutron scattering and compared with those of poly(styrene-d 8 -block-2-vinylpyridine)s (DP) solutions based on the experimentally determined interaction parameters, ðNÞ eff . For DI solutions, it is observed that parallel and perpendicular alignments of lamellae coexist at low shear rates and the latter become dominant at high shear rates in the quiescent ordered states and disordered states very close to the quiescent order-disorder transition (ODT). At still lower concentration C below the quiescent ODT, flow-induced ordering with perpendicular alignment is observed. For DP solutions, coexistence of parallel and perpendicular alignments are only observed at low shear rates for relatively high C above the ODT, while only perpendicular alignment was observed at lower C near the ODT. It is concluded that the degree of perpendicular alignment (ratio of sector averaged intensities) is primarily determined by ðNÞ eff and reduced shear rates. In addition, concentration and shear rate regions in which parallel alignment coexists become narrower for the DP diblock copolymers consist of components with almost the same viscosities. [DOI 10.1295/polymj.37.900] KEY WORDS Poly(styrene-block-isoprene)s / Poly(styrene-block-2-vinylpyridine)s / FlowInduced Structure / Order Disorder Transition / Lamellar Structure / Small Angle Neutron Scattering / Flow effects on the structure of diblock copolymers near the order-disorder transition (ODT) have been extensively studied especially for those assume lamellae structure. It was reported that the lamellar domains in the ordered states are oriented to a particular direction under oscillatory and steady shear flows, but the direction depends on samples and experimental conditions. [1][2][3][4][5][6][7] Under ''reciprocating steady shear'' (with large amplitude, typically 500%), 3 and steady shear flows, 6,7 so-called parallel and perpendicular orientations as illustrated in Figure 1 coexist. Here, the normals of lamellae are parallel to the shear flow, shear gradient, and vorticity direction in the transverse, parallel, and perpendicular alignments, respectively. Roughly speaking, the latter is more favored near the ODT and at the same condition the former is dominant at low shear rates, while the latter is dominant at high shear rates in the quiescent ordered states. In addition, flow-induced ordering and alignment of the structure are also reported even in the disordered states. These observations are qualitatively explained by a theory proposed by Fredrickson,8 in which the fluctuation effects and the difference in the viscosities of the component polymers in the diblock copolymers are taken into account.When lamellae structure is well aligned, the viscoelastic properties of block copolymers are dominated Figure 1. Schematic illustrations of the transverse, parallel, and perpendicular alignments of lamellae under shear flow. Th...

The role of intraocular pressure (IOP) on axial elongation was studied by the following three experiments. 1) Thickness of the sciera in the lid-sutured-myopia of three monkeys was examined by light microscopy. The sciera of the experimental eye in the posterior pole was thinner than that of the control eye, but no differences were found in the equatorial and limbal parts of the sciera.2) By increasing IOP, the scierai wall extensibility in 8 normal, enucleated rabbit eyes was measured by placing the foil strain gauges on the sciera. Extensibility of the sciera in the posterior pole showed a different response from that at the equator and in the limbus.3) IOPs of the 184 human myopic eyes were measured by a Mackay-Marg tonometer in various postures. IOP elevations in high myopia and postural variations of IOP were obtained.From these experiments, it was suggested that IOP seemed to be one of the main factors in increasing the axis to the posterior pole.

Ocular complications of chronic active Epstein-Barr virus infection (CAEBV) have rarely been reported. We describe a 7-year-old girl with CAEBV with associated uveitis. The patient was first observed to have recurrent fever and hepatos-plenomegaly in August 1991. She presented with left facial nerve palsy in June 1993. Ocular examination showed right iridocyclitis. Both optic disks were swollen, and the retinal vessels were dilated. Antibody titers to EBV were markedly elevated. Treatment with topical steroids, systemic interleukin-2 and splenectomy dramatically relieved all her symptoms, including the ocular ones.