SynopsisThe binding of acid azo dyes having phenolic hydroxyl groups such as orange I (I), orange I1 (111, chrome violet (III), 4-hydroxyazobenzene-4'-sulfonate (IV), and 2,4dihydroxyazobenzene-4-sulfonate (V) by polyethylenimine was studied by equilibrium dialysis and spectroscopic methods. The results obtained indicate that dyes (111) and (V) with two OH groups are bound much more strongly than dyes (I), (ID, and (IV) with one OH group. Also polyethylenimine is far superior to any other polymers which have been examined, including bovine serum albumin, polyvinylpyrrolidone, and poly-L-lysine, in its ability to form complexes with these dyes (111) and (V). The OH groups involved participate preferentially in complex formation with polyethylenimine. The unusual affinity of polyethylenimine for the dyes carrying OH groups is discussed.hydroxyazobenzene-4'-sulfonate (V). These dyes, in particular dyes (111) and (V), were found to exhibit very remarkable binding properties toward un-

2‐Hydroxyethyl methacrylate (HEMA)‐N‐vinyl‐2‐pyrrolidone (VPy) copolymers of various compositions have been prepared. The copolymers obtained were examined for their ability to bind a homologous series of methyl orange derivatives, methyl orange, ethyl orange, propyl orange, and butyl orange, at 5, 15, 25, and 35°C, respectively, in an aqueous solution. The first binding constants and the thermodynamic parameters that accompanied the binding were evaluated. The binding ability of the copolymer for the small cosolute was enhanced with an increase of the HEMA content in the copolymer. Moreover, a bell‐shaped curve appeared in the binding of butyl orange by the copolymers having higher HEMA residues when the first binding constant was plotted as a function of temperature, whereas no such phenomenon was detected for the copolymers with less HEMA content or for the less hydrophobic dye, methyl orange, ethyl orange, or propyl orange. This peculiar temperature dependence of the first binding constant shows that the enthalpy of the binding varies from a positive (unfavorable) value below ca. 15°C to a negative (favorable) one above this temperature. This behavior can be accounted for in terms of more hydrophobic effects involved in the binding process.

SynopsisThree structural modifications of poly(y-benzyl L-glutamate) (PBLG), forms A, B, and C, were prepared by varying the casting solvents and casting temperature. From x-ray analysis, infrared absorption spectroscopy, differential scanning calorimetry, and viscoelastic measurements, it is concluded that form A of PBLG is characterized by intramolecular stacking between the benzene rings in the side chain, form B exhibits intermolecular stacking, and form C has no stacking. The transition which corresponds to the breakdown of stacking of form A at 135OC is irreversible, while that of form B at llO°C is reversible. The degree of stacking is larger for form A than for form B.These structural features of the side chain region reflect the permeation and sorption behavior of carbon dioxide. Breakdown of stacking between benzene rings causes an abrupt increase in permeability in both form A and form B, and the permeation behavior for form A is not reversible, as is suggested from the irreversibility of the transition. The larger the degree of stacking, the lower is the amount of sorption. Although stacking is considered to affect the sorption site (solubility) and molecular motion, its influence on solubility is more evident in the temperature range up to about 5OOC.

Powdered Nylon 66 was prepared as a model of amorphous polymers. The resultant powder polyamide was composed of only amorphous regions. The extent of uptake of the acid azo dyes, a homologous series of methyl orange derivatives, by the polymer was measured in an aqueous solution. The first binding constants and the thermodynamic parameters in the course of the binding were evaluated. The thermodynamic behaviors obtained are very similar to those of crosslinked polyvinylpyrrolidone. The favorable free energy of the binding is accompanied by an entropy gain and an exothermic enthalpy change. The shorter the alkyl chain of the dyes, the more negative is the enthalpy change and, hence, the smaller is the entropy change. The thermodynamic data for butyl orange showed that the binding process is athermal and is wholly an entropic effect. The binding of the dyes to the matrix is entropically favorable as a result of the operation of the hydrophobic effect. In addition, an electrostatic force is operative between the sulfonate group on the dyes and the terminal amino groups on the polyamide.

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