Effects of the architecture and environment on polymeric molecular assemblies of novel amphiphilic diblock copolynorbornenes with narrow polydispersity via living ring-opening metathesis polymerization

Abstract

Diblock copolymers of 5-(methylphthalimide)bicyclo[2.2.1]hept-2-ene (NBMPI) and 1,5-cyclooctadiene were synthesized by living ring-opening metathesis polymerization with a well-defined catalyst {RuCl2(CHPh)[P(C 6H11)3]2}. Unhydrogenated diblock copolymers showed two glass transitions due to poly(NBMPI) and polybutadiene segments, such as two glass-transition temperatures at -86.5 and 115.3°C for polyla and -87.2 and 115.3°C for poly1b. However, only one melting temperature could be observed for hydrogenated copolymers, such as 119.8°C for poly2a and 121.7°C for poly2b. The unhydrogenated diblock copolymer with the longer poly(NBMPI) chain (polyla; temperature at 10% mass loss = 400°C) exhibited better thermal stability than the one with the shorter poly(NBMPI) chain (poly1b; temperature at 10% mass loss = 385°C). Two kinds of hydrogenated diblock copolymers, poly2a and poly2b, exhibited relatively poor solubility but better thermal stability than unhydrogenated diblock copolymers because of the polyethylene segments. Poly[(hydrochloride quaternized 2-norbornene-5-methyleneamine)-b-butadiene]-l (poly3a) was obtained after the hydrolysis and quaternization of polyla. Dynamic light scattering measurements indicated that the hydrodynamic diameters of the cationic copolymer (poly3a) in water (hydrodynamic diameter = 1580 nm without salt), methanol/water (4/96 v/v; hydrodynamic diameter= 1500 nm without salt), and tetrahydrofuran/water (4/96 v/v; hydrodynamic diameter= 1200 nm without salt) decreased with increasing salt (NaCl) concentration. The effect of temperature on the hydrodynamic diameter of hydrophobically modified poly3a was also studied. The inflection point of the hydrodynamic diameter of poly3a was observed at various polymer concentrations around 30°C. The critical micelle concentration of hydrophobically modified poly3a was observed at 0.018 g dL-1. © 2006 Wiley Periodicals, Inc.