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 ZnI2 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 ZnI2, which is attributed to the fact that part of the ZnI2 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 PMVE36‐b‐PIBVE54 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 PMVE36‐b‐PIBVE54 block copolymer at 20 °C.magnified image50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE36‐b‐PIBVE54 block copolymer at 20 °C.

A range of hydrophilic poly(methyl vinyl ether) (PMVE) polymers was synthesized by living cationic polymerization of methyl vinyl ether (MVE), having different hydrophilic or hydrophobic chain-end functionalities. The dissimilar end-groups were either introduced by end-capping of the growing polymer chain with LiBH 4 , methanol, and water or by functional initiation with 2-bromo-(3,3-diethoxy-propyl)-2-methylpropanoate. The synthesized PMVEs were characterized by 1 H NMR, size exclusion chromatography, and matrix-assisted laser desorption ionization time of flight, displaying a narrow polydispersity. Modulated temperature DSC was applied to study the influence of the nature of the end-groups on the solubility behavior of PMVE in water. Terminalmodification with a hydroxyl function improves the solubility, whereas a Br-containing end-group causes the polymer to be insoluble in water at room temperature; however, the special type III lower critical solution temperature demixing behavior being maintained. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: [461][462][463][464][465][466][467][468][469] 2006

Summary: The colloidal stability of the aqueous dispersions of hydrophobic organic pigments, CuPc and carbon black, stabilized by a wide range of polymer structures based on alkyl vinyl ethers was studied. It was shown that, unlike the homopolymers and the random copolymers, the amphiphilic AB, ABA and BAB block copolymers of MVE with IBVE or ODVE show stabilizing activities that depend on their hydrophilic/hydrophobic balance and polymer architecture. After optimization, the colloidal stabilization is competitive with commercial PEO‐PPO block copolymers (Pluronic®). It was found that the sedimentation of the dispersions was much faster at a higher temperature, above the LCST of the PMVE‐blocks. The loss of the stabilizing activity of the block copolymers correlates with an increase of the hydrophobicity of the treated pigment surface. These properties enable the creation of colloidal dispersions with stabilities that can be tuned as a function of temperature.

The static structure factor and associated dynamics have been investigated in a series of block copolymers of poly(methyl vinyl ether) (PMVE) and poly(isobutyl vinyl ether) (PiBVE) using x-ray scattering and dielectric spectroscopy (DS). The origin of the dynamic arrest at the glass temperature (T(g)) of PiBVE has been explored by temperature- and pressure-dependent DS and pressure-volume-temperature measurements. Both temperature and volume are responsible for the segmental dynamics but temperature has a stronger effect. The copolymers display a minimal dynamic asymmetry (Delta T(g) approximately 7 K), nevertheless, are spatially and dynamically heterogeneous. Increasing pressure, unlike temperature, enhances the dynamic heterogeneity. This effect originates from the distinctly different pressure sensitivities of the homopolymers and can be traced back to differences in local packing.

Thermo-sensitive nanosized structures have been prepared in water from poly(methyl vinyl ether)-blockpoly(isobutyl vinyl ether) (PMVE-b-PIBVE) block copolymers. The composition and the architecture (diblock and triblock architectures) of the PMVE-b-PIBVE copolymers have been varied. The investigated copolymers had an asymmetric composition with a major PMVE block. While the PIBVE blocks are hydrophobic, the PMVE blocks are hydrophilic at room temperature and become hydrophobic above their demixing temperature (around 36 °C) as a result of the lower critical solution temperature (LCST) behavior. At room temperature, the amphiphilic copolymers aggregate in water above a critical micelle concentration, which has been experimentally measured by hydrophobic dye solubilization. The hydrodynamic diameter of the structures formed above the cmc has been measured by dynamic light scattering (DLS) while their morphology has been studied by transmission electron microscopy (TEM). 1 H NMR measurements in D 2 O at room temperature reveal that the aggregates contain PIBVE insoluble regions surrounded by solvated PMVE chains. These investigations have shown that polydisperse spherical micelles are formed for asymmetric PMVE-b-PIBVE copolymers containing at least 9 IBVE units. For copolymers containing less IBVE units, loose aggregates are formed.Finally, the thermo-responsive, reversible properties of these structures have been investigated. Above the cloud point of the copolymers, the loose aggregates precipitate while the micelles form large spherical structures.