Novel hydrophobic macromonomers for potential amphiphilic block copolymers

Abstract

Oligomers of 2-methyl nylon3 (2mN3) and 3-methyl nylon3 (3mN3) were synthesized by base-catalyzed hydrogen transfer polymerization (HTP) of methacrylamide and crotonamide, respectively. The detailed structural analyses of 2mN3 and 3mN3 were performed using MALDI-MS, 1H-NMR, elemental analysis and several end-group analyses to ascertain polymerization mechanism and exact chemical structures of final products. The structural analyses revealed that (1) base-catalyzed HTP of methacrylamide and crotonamide follows the sequence of: hydrogen abstraction from amide group of monomer by basic catalyst (NatBuO), addition of monomeric units to the anionic center, intramolecular hydrogen migration and finally, termination by hydrogen transfer from protonated catalyst (tBuOH) to anionic end-group, (2) both oligomeric products have olefinic chain-ends resulting from the initiation mechanism. The specific behavior of basic catalyst leads to the formation of olefinic chain-ends that are apt to possible end-group functionalization. Since the functional end-groups of a well-defined macromonomer are of importance in terms of chain extension, grafting, chemical modification, click chemistry, monolayer surface modification, etc., it was aimed to create more reactive functional end-groups by epoxylation and bromination. Disappearance of the signals belonging to the olefinic protons in 1H-NMR spectra of modified oligomers and existence of bromine and epoxy adducts in MALDI MS spectra of the modified oligomers were attributed to end-group modification as intended. Hence, four novel macromonomers of polyamidic backbone with functional chain-ends were synthesized successfully.