Self-assembly of Symmetrical Poly(oxyalkylene)-diamidoacid Copolymers

• Main Authors: Chi-He Stephen Wang, 王棋禾
• Other Authors: Jiang-Jen Lin
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/59499717571007086944

碩士 === 國立中興大學 === 化學工程學系 === 93 === The study involves the preparation of sodium salts of poly(oxypropylene)-trimellitic amidoacid copolymers (POP-amidoacid), the interface property, self-assembly, morphological changes in molecular self-assembly, and molecular manipulation. 1. Sodium salts of poly(oxypropylene)-trimellitic amidoacid copolymers (POP-amidoacid), prepared from the reaction of POP-diamines and trimellitic anhydride, were found to self-assemble into orderly molecular bundles. The POP-amidoacid has a symmetrical structure consisting of a hydrophobic POP middle block (2000 g/mole) and four symmetrical carboxyl end groups. By dissolving in water and evaporating on a polyether sulfone film, the POP-amidoacid molecules self-assembled into a unique array with average dimensions of 7-13 nm in width, 2-5 nm in height, and 20-50 nm in length, observed by atomic force microscope. Varied morphologies were also observed when varying the pH, solvents, evaporating rate, concentration, and substrate surface. Unlike the common surfactants of single head-to-tail structure and the naturally occurring phospholipids of one-head and two-tails, the synthesized POP-derivative is a symmetrical structure of four hydrophilic heads and one long hydrophobic block. Through the complementary noncovalent bonding forces, the molecules tend to align into molecular bundles or loops as the primary structure. The formation of different morphologies is controlled by the intermolecular forces including hydrogen bonding, aromatic π-π stacking, ionic charge, and hydrophobic interaction, in a concerted manner. 2. Changes in molecular self-assemblies from poly(oxypropylene)-trimellitic amidoacids or imidoacids have been investigated by using dynamic mode atomic force microscopy (DFM). Imidoacids were prepared from a ring-closure of amidoacids at high temperature. Through DFM continuous scanning, different self-assembled morphologies from amidoacid and imidoacid were observed. Besides the multiplicity of carboxyl functionalities, the backbone variety (oxypropylene vs. oxyethylene) and molecular weight (2000 g/mol vs. 400 g/mol) are important factors affecting the self-assemblies on polyether sulfone surface. These copolymers were found to be amphiphiles demonstrating an ability of lowering interfacial tension at the toluene/water interface. Their surfactancy and self-assembling properties are attributed to the complimentary forces in the structures.