Syntheses, Specific Interactions, and pH-Sensitive Micellization Behavior of Poly [vinylphenol-b-2-(dimethylamino)ethyl methacrylate] Diblock Copolymers

Abstract

We have used anionic polymerization to prepare a series of poly [vinylphenol-b-2(dimethylamino)ethyl methacrylate] (PVPh-b-PDMAEMA) block copolymers. These block copolymers are miscible, with strong specific interactions occurring between the OH groups of the PVPh segments and the tertiary ammonium groups of the PDMAEMA segments. These PVPh-b-PDMAEMA diblock copolymers exhibit higher glass transition temperatures than do the corresponding PVPh/partially protonated PDMAEMA blends obtained from DMSO solution, which we suspect exist in the form of separate coils. The blocks of the PVPh-b-PDMAEMA diblock copolymers interact strongly, resulting in polymer complex aggregation similar to the behavior of PVPh/partially protonated PDMAEMA blend complexes obtained from methanol solution. The spin-lattice relaxation times in the rotating frame, determined through solid state NMR spectroscopic analysis, provided clear evidence that the polymer complex aggregates formed from the diblock copolymers have shorter values of TV, than do the corresponding separated coils in the miscible blends. In addition, these PVPh-b-PDMAEMA diblock copolymers exhibit a novel type of pH sensitivity: at low pH, compact spherical micelles are formed possessing PDMAEMA coronas and PVPh cores; at medium pH, vesicles are observed, consisting of partially protonated hydrophilic PDMAEMA shells and hydrophobic PVPh cores; at high pH, the spherical micelles that formed comprised ionized PVPh coronas and deprotonated hydrated-PDMAEMA cores, i.e., phase inversion of the micelles formed at pH 2.