Synthesis and Associating Properties of Poly(ethoxyethyl glycidyl ether)/Poly(propylene oxide) Triblock Copolymers

• Published in: Macromolecules 2004-02, Vol.37 (3), p.1000-1008
• Main Authors: Dimitrov, Philip, Rangelov, Stanislav, Dworak, Andrzej, Tsvetanov, Christo B
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma0354039

A number of ABA and BAB triblock copolymers of ethoxyethyl glycidyl ether (EEGE) and propylene oxide (PO) were prepared by sequential anionic polymerization. The copolymers were characterized by nuclear magnetic resonance and gel permeation chromatography. The total number-average molecular weights were in the range 1000−9000, whereas the degrees of polymerization of the PPO and PEEGE blocks varied from 2 to 34 and from 3 to 17, respectively. The copolymers were comprised of blocks with different lower critical solution temperatures (LCSTs) in aqueous media. Their self-association in aqueous environment was studied by cloud point (CP) measurements, dye solubilization, light scattering, 1H nuclear magnetic resonance, and scanning electron microscopy. Although the behavior of the copolymers was found to depend on their architecture, the PO/EEGE ratio, and the degrees of polymerization of the different blocks, the role of the PEEGE blocks was decisive:  it is PEEGE that determines the LCST properties of the copolymers as well as their CP and critical micelle concentration values. The copolymers form nanosized particles as revealed by light scattering. The aggregates exhibit different temperature behavior depending on the copolymer architecture. The aggregates of the copolymers of a normal, i.e., ABA, architecture were found to undergo a secondary aggregation at certain temperatures, whereas those of the BAB copolymers gradually increased in size with increasing temperature. The difference is attributed to the different arrangement of the chains in the corona regions, directly affecting the continuity and thickness of the corona.