Relation between polyisocyanate side-chain structure and properties

Copolymers of 2-butylhexyl isocyanate and (R)-(+)-2,6-dimethylheptyl isocyanate, 3-butylheptyl isocyanate and (R)-(+)-2,6-dimethylheptyl isocyanate were synthesized. Optical activities of the copolymers of 3-butylheptyl isocyanate and (R)-(+)-2,6-dimethylheptyl isocyanate were similar to that of copolymers of n-hexyl isocyanate and (R)-(+)-2,6-dimethylheptyl isocyanate. The copolymer synthesized from 2-butylhexyl isocyanate and minute proportions of (R)-(+)-2,6-dimethylheptyl isocyanate showed an optical activity easily measurable whereas copolymers of n-hexyl isocyanate with such small proportions of the chiral comonomer, have no observable optical activity. This extreme chiral amplification of the 2-butylhexyl isocyanate system is due to the high thermodynamic helical reversal energy estimated as at least 5 kcal/mol using statistical physical methods based on experimental data generated in this thesis. Terpolymers of achiral 2-butylhexyl isocyanate and nearly enantiomeric mixtures of (R) and (S)-2,6-dimethylheptyl isocyanate were also synthesized. Surprisingly, dilution of these nearly racemic chiral side groups with the achiral groups, even up to 99% made no difference to the helical sense excess. This startling experimental finding has been shown to be consistent with an extension of the statistical physical analysis, which also predicts the limits to this effect.; A water-soluble polyisocyanate, poly(3-(2-(2-methoxyethoxy)ethoxy) propyl isocyanate) (PDEGIC), has been synthesized by incorporation of oligooxyethylene side chains to the helical backbone. PDEGIC dissolves both in water and in a wide variety of organic solvents. It exhibits unusual behavior in both its viscosity and its optical activity properties as a function of solvent compared to poly(alkyl isocyanates). An optically active copolymer was made containing DEGIC with the chiral monomer, (R)-(+)-2,6-dimethylheptyl isocyanate using an organometallic initiator. It shows an inexplicable slow transformation to insoluble morphologies in the solid state, which can be reversed by mild heating and can be blocked by copolymerization with small amounts of n-hexyl isocyanate, which still allows water solubility. The ionic conductivity of the material is very high and may even lead to practical applications. In water solution the material depolymerizes which, according to our detailed study occurs by a base catalyzed mechanism. The polarity present in the side chain of PDEGIC allowed the formation of thermodynamically stable molecular composites with random copolymers of styrene and 4-hydroxy styrene (PHS-9) and also copolymers of styrene and 4-vinylphenyldiphenyl silanol. A fluorinated analog of PDEGIC was synthesized which in a preliminary experiment showed solubility in supercritical carbon dioxide.; An attempt was made to couple the slowly interconverting enantiomeric twist states of pendant atropisomeric binaphthyl and biphenyl groups to the fast interconverting left and right handed helical sense regions of the polyisocyanate backbone. Many different kinds of copolymers and terpolymers were synthesized in which atropisomeric groups containing binaphthalene and biphenyl moieties were incorporated. Unfortunately none of these copolymer and terpolymer system showed the time dependent optical activity characteristics we were looking for. Nevertheless, in some of the synthetic systems we could see evidence of coupling between the atropisomeric chirality and the polyisocyanate backbone helical sense via degradation to the isocyanurate trimers. In these trimers the excess twist sense of the atropisomeric group was maintained long enough to be detected.