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Block Copolymers of Methyl Vinyl Ether and Isobutyl Vinyl Ether With Thermo‐Adjustable Amphiphilic Properties
Author(s) -
Verdonck Beatrice,
Goethals Eric J.,
Du Prez Filip E.
Publication year - 2003
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200350069
Subject(s) - living cationic polymerization , copolymer , vinyl ether , amphiphile , lower critical solution temperature , polymer chemistry , chemistry , cationic polymerization , cloud point , organic chemistry , aqueous solution , polymer
The thermo‐adjustable hydrophilic/hydrophobic properties of AB, ABA and BAB block copolymers in which A is poly(methyl vinyl ether) (PMVE) and B is poly(isobutyl vinyl ether) (PIBVE) have been investigated. The block copolymers were prepared by “living” cationic polymerization using sequential addition of monomers. The polymerizations were carried out with the system acetal/trimethylsilyl iodide as initiator and ZnI 2 as activator. The initiating system based on diethoxyethane leads to AB block copolymers whereas the initiating system based on tetramethoxypropane leads to ABA or BAB triblock copolymers. Well‐defined block copolymers of different composition with controlled molecular weights up to approx. 10 000 have been prepared. When IBVE is added to living PMVE, PIBVE‐blocks form only in the presence of an additional amount of ZnI 2 , which is attributed to the fact that part of the ZnI 2 is inactive because of complex formation with PMVE. At room temperature, the combination of hydrophilic (PMVE) and hydrophobic (PIBVE) segments provides the copolymers with surfactant properties. Above the lower critical solution temperature (LCST) of PMVE, situated around 36 °C, the PMVE‐blocks become hydrophobic and the amphiphilic nature of the block copolymers is lost. The corresponding changes in hydrophilic/hydrophobic balance have been evaluated by investigation of the emulsifying properties of the block copolymers for water/decane mixtures as a function of the temperature. Below the LCST, the block copolymers have emulsifying properties similar to or better than those of the commercial PEO‐PPO block copolymers (Pluronic®). Either oil‐in‐water or water‐in‐oil emulsions can be obtained, depending on the polymer architecture and the water/decane volume ratio. The emulsifying properties are strongly reduced or completely lost above 40 °C. Emulsions obtained with a PMVE 36 ‐ b ‐PIBVE 54 block copolymer for a water/decane (v/v) ratio of 85/15 remained stable for more than six months.50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE 36 ‐ b ‐PIBVE 54 block copolymer at 20 °C.