Ring-Opening Metathesis Block Copolymerization of Amino Acid Functionalized Norbornene Monomers. Effects of Solvent and pH on Micelle Formation

Amino acid derived norbornene monomers having unprotected carboxy ( 1 ) and amino groups ( 2 ) and 7-oxanorbornene having ester groups ( 3 ) were block copolymerized using the Grubbs ruthenium complexes. In the combination of 1 and 2, block copolymers with number-average molecular weights ranging from 43 000 to 95 000 were obtained in good yields. Poly( 1 ) 75 - block -poly( 2 ) 25 was soluble in 0.5 M NaOH(aq) but insoluble in 0.1 M HCl, while poly( 1 ) 25 - block -poly( 2 ) 75 was soluble in 0.1 M HCl but insoluble in 0.5 M NaOH(aq). Thus, the block compositions remarkably affected the solubility of the copolymers in acidic and basic media. On the other hand, poly( 2 ) 62 - block -poly( 3 ) 38 was soluble in H 2 O but insoluble in CH 2 Cl 2 and CHCl 3, while poly( 2 ) 38 - block -poly( 3 ) 62 was soluble in CH 2 Cl 2 and CHCl 3 but insoluble in H 2 O. In this monomer combination, the block compositions significantly affected the solubility of the copolymers in organic and aqueous media. 1 H NMR spectroscopic, turbidity, and dynamic light scattering measurements revealed that poly( 1 ) 50 - block -poly( 2 ) 50 formed micelles with a diameter around 130 nm in 0.5 M NaOH(aq). In a similar manner, it was revealed that poly( 2 ) 62 - block -poly( 3 ) 38 and poly( 2 ) 38 - block -poly( 3 ) 62 formed micelles with a diameter around 80 nm in H 2 O and reverse micelles with a diameter around 45 nm in CH 2 Cl 2, respectively.