We synthesized methoxy poly(ethylene glycol)-b-poly(α,l-glutamic acid) (mPEGGA) diblock copolymer by ring-opening polymerization of N-carboxy anhydride of γ-benzyl-l-glutamate (NCA) using amino-terminated methoxy polyethylene glycol (mPEG) as macroinitiator. Polyelectrolyte complexation between mPEGGA as neutral-block-polyanion and chitosan (CS) as polycation has been scrutinized in aqueous solution as well as in the solid state. Water-soluble polyelectrolyte complexes (PEC) can be formed only under nonstoichiometric condition while phase separation is observed when approaching 1:1 molar mixing ratio in spite of the existence of hydrophilic mPEG block. This is likely due to mismatch in chain length between polyanion block of the copolymer and the polycation or hydrogen bonding between the components. Hydrodynamic size of primary or soluble PEC is determined to be about 200 nm, which is larger than those reported in some literatures. The increase in polyion chain length of the copolymer leads to the increase in the hydrodynamic size of the water-soluble PEC. Formation of spherical micelles by the mPEGGA/CS complex at nonstoichiometirc condition has been confirmed by the scanning electron microscopy observation and transmission electron microscopy observations. The homopolymer CS experiences attractive interaction with both mPEGA and PGA blocks within the copolymer. Competition of hydrogen bonding and electrostatic force in the system or hydrophilic mPEG segments weakens the electrostatic interaction between the oppositely charged polyions. The existence of hydrogen bonding restrains the mobility of mPEG chains of the copolymer and completely prohibits crystallization of mPEG segments. In vitro culture of human fibroblasts indicates that mPEGGA/CS-based materials have potential in biomedical application, especially in tissue engineering.

The polymeric films have been prepared based on blends of chitosan with two cellulose ethers—hydroxypropylmethylcellulose and methylcellulose by casting from acetic acid solutions. The films were transparent and brittle in a dry state but an immersion of the samples in deionized water for over 24 h leads to their disintegration or partial dissolution. The miscibility of the polymers in the blends has been assessed by infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis. It was shown that although weak hydrogen bonding exists between the polymer functional groups the blends are not fully miscible in a dry state.