A new family of random co-poly(ester amides)s (co-PEAs) having reactive pendant functional carboxylic acid groups were synthesized by co-polycondensation of di-p-toluenesulfonic acid salts of bis-(L-alpha-amino acid (L-leucine and/or L-phenylalanine)) alpha,omega-alkylene diesters with active diesters of dicarboxylic acids using di-p-toluenesulfonic acid salt of L-lysine benzyl ester as a co-monomer. The lateral benzyl ester groups in the L-lysine segment of co-PEAs were subsequently transformed into free COOH groups by catalytic hydrogenolysis using Pd black as a catalyst. The co-PEA-based polyacids obtained, as well as the original co-PEA having lateral benzyl ester groups were characterized by standard methods. In vitro biodegradation studies in the presence of hydrolases like alpha-chymotrypsin and lipase showed significant enzymatic-catalyzed biodegradation of these co-PEAs. These co-PEA-based polyacids were used for covalent attachment of iminoxyl radicals (4-amino-TEMPO) and in vitro biodegradation of 4-aminoTEMPO attached polymer was studied along with releasing kinetic of iminoxyl radical.
High-resolution NMR spectra of 13C-iodomethane dissolved in thermotropic and lyotropic liquid crystalline
solvents have been used to measure 1H−H and 13C−1H dipolar couplings. The ratio of these two couplings,
which is a function of the H−C−H bond angle in 13C-iodomethane, is, in general, different from that expected
from the known molecular structure; solvent−solute interactions in liquid crystalline solutions are responsible
for this difference. In thermotropic liquid crystalline solutions, the apparent bond angle deviation (Δθa) increases
with decreasing molecular ordering. In contrast, in lyotropic liquid crystals, no significant spectral aberration
has been observed. These results indicate a fundamental physicochemical difference between the intermolecular
interactions that prevail in thermotropic and lyotropic liquid crystals.
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