Block Copolymers of Vinyl Ethers as Thermo‐Responsive Colloidal Stabilizers of Organic Pigments in Aqueous Media

Abstract

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.

Comparative Study of the Solid–Liquid Interface Behavior of Amphiphilic Block and Block‐Like Copolymers

“…[8,29] This is ascribed to the fact that THF, used as a polymer solvent in the present study, is known to cause THF swollen micelles in water which in turn facilitate the transport and deposition of the polymer to the pigment surface.…”

“…Using this procedure, the precipitation of the PiBA-PAA copolymers is prevented. [8] Dispersion of pigment was first achieved by means of a laboratory stirrer (700 rpm for 10 min). When ultrasonic treatment was applied, the system was subsequently treated with ultrasound for 2 min with a Branson Sonifier B-12 ultrasonic generator with an actual power of 1.5 W Á cm À2 .…”

Functionalized Thermo‐Responsive Poly(vinyl ether) by Living Cationic Random Copolymerization of Methyl Vinyl Ether and 2‐Chloroethyl Vinyl Ether

“…[2] Because of the living character of the cationic polymerization procedure, more complex polymer structures become easily available. For example, we demonstrated earlier that block copolymers containing segments based on methyl vinyl ether (MVE) and hydrophobic isobutyl vinyl ether (IBVE) units exhibit a highly thermo-responsive behaviour, [3,4] even though it was almost not existing for the random copolymers. [5] The behaviour of vinyl ether-based copolymers in water can be modified in different ways.…”

Association behavior of thermo-responsive block copolymers based on poly(vinyl ethers)

“…This interest is motivated by the potential utilization of these materials for a number of technological applications, such as stimuli-controlled release of drugs [1], stimuli-controlled stabilization of emulsions [2] and [3], thermo-adjustable colloidal stabilization of organic pigments [4], etc. In water, the commonly applied stimuli are pH, ionic strength and temperature.…”

“…Above the LCST, the emulsifying properties were considerably reduced or even disappeared. Second, the block copolymers show thermo-adjustable stabilizing activities towards hydrophobic pigment particles such as copper phthalocyanine and carbon black [4]. A detailed study of the micellization behavior of this new class of thermo-responsive surfactants as a function of the copolymer composition, polymer architecture (triblock versus diblock) and temperature is, therefore, needed, which is the purpose of the present paper.…”