Organic microcrystals ranging from several tens nm to µm in size of several chromophores were successfully prepared by simply dispersing ethanol solutions of compounds into stirred water, i.e. by a reprecipitation method. The size of microcrystals was found to depend on concentration of ethanol solutions, dispersing conditions, temperature and so on.

Ion Binding to Poly(oxyethylene) in Methanol latter for the p-nitroperbenzoic acid results could be appreciable. Effect of Brownian Motion of the LigandWhen the target area is smaller than the mean free path of the ligand, the diffusion-controlled rate constant cannot be deduced from a simple diffusion equation.36 However, the mean free path, L, calculated from the following equation36 is only 0.07 Á for p-nitroperbenzoic acid, where M is molecular weight and R is gas constant: L D( §iY Therefore, the effect of Brownian motion is almost negligible for the horseradish peroxidase-ligand system. Publication costs assisted by Tohoku UniversityThe binding of alkali metal cation with poly(oxyethylene) was studied by means of conductometry in methanol. Apparent binding constants, KA, were determined by assuming the existence of discrete binding sites distributed every a monomer units along the polymer chain. KA increased in the order Li < Na < K < Cs < Rb. For large anions, such as thiocyanate or perchlorate, the formation of an ion pair complex was indicated. KA and a increased rapidly with decreasing salt concentration. This result was interpreted by the increased electrostatic repulsion between bound ions. The linear relationship between a1/2 and Cs"1/2 conforms to the Gaussian distribution of the segment between charges as well as to the partial retention of crystalline conformation of the poly-(oxyethylene)-ion complex.Publication costs assisted by the National Science Foundation and the Petroleum Research Fund Two recent theories for ionic mobility, the Hubbard-Onsager theory which is based on a continuum model and the Wolynes theory which is based on a stochastic model, are critically tested by comparison with conductance data. Both theories predict finite mobilities as the ionic size decreases and thus can successfully account for many of the observed features of conductance data. The models upon which the theories are based are described in detail and the current state of ionic mobility theory is discussed.

A statistical model for the cooperative thermochromic transition of polysilanes is proposed. The basic assumption of this treatment is that the origin of the thermochromism is the conformational transition between two ordered states, i.e., all-trans and helix structures. We have calculated the partition function of a single polysilane chain by assuming that the total conformational energy of the chain can be described by a simple sum of the nearest-neighbor interaction energies and the energies of trans, gauche(+), and gauche(-) structures. A comparison of the theoretical results with the experimental intensity of absorption maxima has enabled us to estimate the free energy of stabilization of the ordered sequences. The calculation suggests that the transition-type thermochromism is observable only when the conformational stabilization energies of the ordered sequences are large.