Polyion complex fiber and capsule formed by self-assembly of chitosan and poly(alpha,L-glutamic acid) at solution interfaces

Different characteristic surface structures such as spherical capsules, reg ularly spaced droplets and fibers are formed by electrostatic polysaccharid e interaction between chitosan and poly(alpha ,L-glutamic acid) via polyion complex (PIC) formation. Spherical droplet-like PIC capsules of varying di ameters form in solutions. Some dyes absorb on the surface of the capsules, while other dyes and benzoic acid derivatives penetrate into the capsules. The PIC fiber can be prepared by reactive-spinning at the solution interfa ce, followed by gravity and by removing water in ethanol. The tensile stren gth of the fiber is 11.2 kg . mm(-2) (1.48 g . denier(-1)) and the knotting strength is 2.15 kg . mm(-2) (0.30 g . d(-1)). By reaction with an organic cross-linking agent, ethylene glycol diglycidyl ether (EGDE), the tensile strength of the fiber can be increased to 18.1 kg . mm-2 (3.14 g . d(-1)), and by reacting with hexamethylene diisocyanate (HMDI), the knotting streng th of the fiber can be increased to 7.58 kg . mm(-2) (0.89 g . d(-1)). The interaction energies (work of absorption, W-abs) of PLG and chitosan in aqu eous solution were estimated by a surface chemical approach, and a relation ship between the W-abs values and the tensile strengths of the PIC fibers a nd the W-abs indicated that the higher W-abs system gives the higher tensil e strength. The PIC fiber can be dyed by four different dyeing procedures s uch as direct and vat dyeings. When the cross-linked PIC fiber was incubate d in an aqueous solution in the presence of endocrine disruptor related com pounds such as dibenzofuran and biphenyl, these compounds were accumulated onto and/or into the fibers.