Synthesis of network polymers by means of ring-opening addition reaction of a tri-aziridine and dicarboxylic acid compounds

Polyethylenimine (PEI) is widely used in various products. Development of PEI network polymers would expand the application of the PEI. Ring-opening homo-polymerization of tri-aziridine compounds yielded the PEI-based hard network polymers derived from high dense crosslinking structure. Introduction of the flexible unit in the polymer network should be effective to control the mechanical properties of the resulting network polymers. In the present study, ring-opening addition reactions between a tri-aziridine, 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] (3AZ), and alpha,omega-dicarboxylic acid, RCAn (HOOC-(CH2)n-COOH): succinic acid (RCA2), adipic acid (RCA4), dodecanedioic acid (RCA10), or alpha,omega-dicarboxylic acid with ether linkage, ECAm (HOOC-(CH2OCH2)m-COOH); diglycolic acid (ECA1), 3,6,9-triocaundecanedionic acid (ECA3), poly(ethylene glycol) bis(carboxymethyl) ether (ECA4) were conducted to yield the polymers with controlled network struc-ture. The reactions at room temperature in N,N-dimethylformamide successfully yielded gels. Young's modulus of the gel decreased with increasing in the chain length of the dicarboxylic acid used. The reaction of 3AZ with RCA4 in acetone or ethanol (EtOH) induced phase separation and produced porous polymers. The reactions with oxalic acid (RCA0), glutaric acid (RCA3), suberic acid (RCA6), ECA1, ECA3, or ECA4 in EtOH also yielded the porous polymers. The morphology in the porous polymers was formed by connected particles. The Young's modulus of the porous polymer also decreased with increasing in the chain length of the dicarboxylic acid used. The resulting porous polymers absorbed various solvents, such as acetone, water, dichloromethane, and chlo-roform. Hydrophobicity and hydrophilicity of the porous polymers can be controlled by the molecular structure of the dicarboxylic acid in the polymer networks.

Automated summary

In this study, PEI-based hard network polymers with controlled structure were successfully prepared by the ring-opening homo-polymerization of tri-aziridine compounds and dicarboxylic acids. The mechanical properties of the resulting polymers were influenced by reaction temperature and chain length of the dicarboxylic acid. The porous polymers obtained exhibited the ability to absorb various solvents, and the porosity could be controlled by the molecular structure of the dicarboxylic acid.