Adhesiveness of AcrySof to a collagen film.

PURPOSE: To measure the adhesiveness of the AcrySof intraocular lens (IOL) to a collagen film to ascertain its capacity to adhere to the lens capsule. SETTING: Haibara General Hospital, Haibara, and Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan. METHODS: Each of five AcrySof IOLs was attached to a collagen film, slightly pressed in intraocular irrigating solution, and then pulled up and off the film with a DuNouy's surface balance. The force recorded by the surface balance at the moment it detached from the film was defined as the lens' adhesiveness. A control experiment was performed using five conventional poly(methyl methacrylate) (PMMA) IOLs. RESULTS: Mean adhesiveness was 2.76 gram-weight (gw) +/- 0.55 (SD) for AcrySof and 0.81 +/- 0.20 gw for PMMA. The difference was statistically significant (P < .0001, t-test). CONCLUSION: AcrySof may have a strong tendency to adhere to the lens capsule, contributing to posterior and anterior capsule clarity and preventing lens decentration in vivo.

The release of monovalent counterions by addition of divalent countemons to aqueous solutions of maleic acid copolymer.

Divalent cation binding and the release of monovalent cations accompanying the cation binding were experimentally studied by ion-selective electrode methods in aqueous solutions of copolymer of maleic acid and ethyl vinyl ether. It was found that in the process of Ca2+ addition, all the Ca2+ added was bound to polyions and the initially condensed Na+ was released in proportion to the concentration of the added Ca2+ up to the critical concentration of added Ca2+ at which the condensation of Ca2+ ceases. Values of the structural charge density parameter xi(s), were determined from the end-points of condensation of Ca2+. The process of Na+ release by adding Ca2+ was analyzed on the basis of the counterion condensation theory by using these xi(s) values. In addition, the relationship between the activity coefficient gamma-- of Ca2+ and degree of neutralization alpha in salt-free solutions was obtained from the Manning theory. Agreement between the calculated and experimental values was excellent in both cases.

Dielectric dispersion of alternating copolymers of maleic acid.

Dielectric dispersions of three kinds of copolymers of maleic acid, poly (maleic acid-co-methyl vinyl ether) (PMAMVE), poly(maleic add-co-ethyl vinyl ether) (PMAEVE) and poly (maleic acid-co-styrene) (PMAST), were measured by use of a pseudorandom noise dielectric spectrometer. A large dielectric increment was observed in the low frequency region (10-20 Hz), and was explained in terms of our theory of ion fluctuation. When these copolymers were neutralized with mixtures of NaOH and Ca(OH)2 by changing their ratio, enhancement of the static dielectric increment was observed in the intermediate ratios of both ion species. This phenomenon was analyzed by modifying our. theory of ion fluctuation to the case of alternating copolymers. Quantitative agreement with experimental results was obtained by using values of parameters representing binding energies and mutual repulsion, which are chosen to fit the calculated degree of ion binding to the experimental data on activities of Na+ and Ca2+ ions. At large fractions of divalent ions, the increment, relaxation time and specific viscosity were found to decrease sharply due to chelation by divalent ions.

The development of an equation for the potentiometric titration of linear polyelectrolytes using a site model.

An equation for the potentiometric titration of linear polyelectrolytes is derived by considering neighbor interactions of ionizable groups and the association equilibria between ionized groups and counterions. The first, second, ... and lth neighbor interactions are directly introduced into the equation, and additional neighbor interactions together with interactions between the ionizable groups and simple salt ions are taken into account as perturbed electrostatic potentials. It is observed that the approximation which includes the second or third neighbor interaction is sufficient for description of the potentiometric titration. Good agreement between predictions of the present theory and experiment is obtained for isotactic and syndiotactic poly(acrylic acids).