Synthesis of amphiphilic heteroarm star block copolymers and effect of their architecture on micellar properties.

摘要

Amphiphilic A1A2, A₂B and A ₃B₃ heteroarm star block copolymers, and (AB)₃ star block copolymer have been synthesized using living cationic polymerization techniques. These block copolymers consist of polyisobutylene (A) as a hydrophobic block and poly(methyl vinyl ether); (B) as a hydrophilic block. The effect of architecture on their micellar properties in aqueous system has been investigated.; 1. A1A2B and A₂B heteroarm star block copolymers. Furan functionalized polyisobutylene (2-PIB-Fu) has been employed as a polymeric capping agent to prepare amphiphilic A 1A2B and A₂B heteroarm star block copolymers (A = polyisobutylene, B = poly(methyl vinyl ether)). The superscripts denote molecular weight asymmetry. Total molecular weight and composition have been kept constant.; 2. Effect of architecture on the micellar properties of AB, A 1A2B and A₂B. The influence of architecture on aqueous micellar properties of amphiphilic AB, A1A 2B and A₂B block copolymers were investigated in the temperature range of 20–30°C by fluorescence spectroscopy, and static and dynamic light scattering (SLS and DLS). The critical micelle concentration (CMC) measured at 23°C increased in the order A₂B A1A 2B AB.; 3. Amphiphilic A₃B₃ heteroarm star block copolymers. Furan functionalized polyisobutylene (2-PIB-Fu) and a multi-functional initiator tricumylchloride (TriCumCl) have been employed to prepare amphiphilic A₃B₃ poly (isobutylene3- star-methyl vinyl ether₃) heteroarm star block copolymer. Quantitative addition of 2-PIB-Fu to TriCumCl was obtained in conjunction with TiCl₄ as Lewis acid in hexanes/CH₂Cl₂ 40/60 v/v at −80°C in the presence of proton trap.; 4. Effect of architecture on the micellar properties of AB, A₂B₂, A₃B₃ and (AB) ₃. The influence of architecture on micellization of amphiphilic block copolymers AB, A₂B₂, A₃B₃ and (AB)₃ (A = polysiobutylene (PIB), B = poly(methyl vinyl ether) (PMeVE)) was investigated in water, which is a selective solvent for PMeVE. The critical micelle concentration (CMC) measured by fluorescence spectroscopy at 23°C increased in the order AB = (AB)₃ A₂B ₂ A₃B₃. The hydrodynamic radii (R_h) and aggregation numbers (N_agg) of micelles were determined using static and dynamic light scattering (SLS and DLS) in the temperature range of 20–30°C. (Abstract shortened by UMI.)