A series of homopolyimides and copolyimides was synthesized by the solution condensation of biphenyltetracarboxylic dianhydride (BPDA) isomers and various diamines followed by chemical imidization. These polyimides had intermediate to high molecular weights with inherent viscosities of 0.34–1.01 dL/g for homopolyimides and 0.48–1.02 dL/g for copolyimides. Thermogravimetric analysis indicated that the aromatic polyimides were stable up to 500°C, and the 5% weight loss temperatures were recorded in the range of 506–597°C in an air atmosphere and in the range of 517–601°C in a nitrogen atmosphere, depending on the diamines used. The glass transition temperatures of aromatic homopolyimides were above 271°C, while the glass transition temperatures of the copolyimides increased with an increase in the 2, 2′, 3, 3′‐BPDA‐component. The effects of the chemical structure of the polymer chain on the solubility were investigated. It was found that the solubility of BPDA‐based polyimides could be improved by the introduction of flexible units, nonlinear and non‐coplanar units, and copolymerization. The polyimides with nonlinear and non‐coplanar units derived from 2, 2′, 3, 3′‐BPDA appeared to have prominently enhanced solubility in polar aprotic solvents and polychlorocarbons when compared with the homopolyimide derived from 3, 3′, 4, 4′‐BPDA.
Research has been focused on the development of molecularly imprinted polymers using a chitosan derivative as the precursor. An O-acyl chitosan was synthesized by the selective protection of amino groups of chitosan in MeSO3H and was cross-linked with glutaraldehyde in the presence/ absence of template molecule, cholesterol. The effect of the degree of the acyl substitution on the selection of precursor was investigated, regarding the solubility of chitosan derivative, interaction between the precursor and imprinted molecule, and degree of the cross-linking of precursor. The rebinding experiments indicated the significant recognition for cholesterol with imprinted polymer as compared with non-imprinted polymer. It was found that a good binding capacity of the imprinted polymer towards cholesterol could be achieved in a less-polar solvent. And the O-acyl chitosan-based molecularly imprinted polymer obtained displayed good recognition selectivity for cholesterol in comparison to similarly strctural analogue, cholesterol acetate.
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