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Milan, for supplying some samples and many useful suggestions and to Dr. M. Dell'Eva and Mr. A. Tealdi for valuable help. This investigation was supported by the Italian Research Council through its "Chimica Fine e Secondaria" project.

The titration behavior of ethylene-maleic anhydride, propylene-maleic anhydride, isobutylene-maleic anhydride, 2-methylpentene-l-maleic anhydride, and styrene-maleic anhydride copolymers was investigated. The carboxyl groups of each copolymer are characterized by two intrinsic pA's, one of which is increased and the other decreased on increasing the number of carbon atoms on the alkyl side chain of the olefin comonomer.The phenomenon is attributed to an alteration of the effective dielectric constant and its consequent effect on chargedipole and charge-charge interactions. The titration behavior of the corresponding polycations having dimethylaminopropylmaleimide as comonomer was also investigated. The interaction of the polyanion copolymers with poly-n-lysine and poly-n-ornithine was investigated by determining the conditions for formation of a coprecipitate. The alkyl side chain of the polyanion influences complex formation through the effect it has on the ionization of the carboxyl groups as well as through hydrophobic interactions. The two effects are not, in general, additive.A series of poly electrolytes corresponding to different R substituents was used. The variation of the alkyl or aromatic substituent affords a method for investigating in a systematic manner the role of steric hindrance on the ionization of titratable groups. The results obtained can possibly be applied to the titration of more complex systems {i.e., the proteins).Besides the titration behavior of these copolymers, we present here some results pertaining to their interaction with model polypeptides in an attempt to investigate the forces involved in the formation of insoluble complexes between the copolymers and the proteins.The variation of alkyl and aromatic substituents on the polymer chain backbone also represents a potential variation in the so-called6 hydrophobic bonding. This bond is now regarded as a major parameter in the stabilization of the tertiary structure of proteins and possibly contributes to the forces responsible for the formation of a copolymer-protein complex. Experimental SectionMaleic anhydride copolymers were kindly supplied by Dr. J. E. Fields and Dr. J. H. Johnson of the Monsanto Co. They were described as essentially 1:1 copolymers and were prepared by free radical catalyzed solventnonsolvent techniques which traditionally yield relatively narrow molecular weight distributions {i.e.,(1) Thesis submitted by Miss R. Parodi as a partial requirement for the doctoral degree in chemistry.

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