pH-Responsive Non-Ionic Diblock Copolymers: Ionization of Carboxylic Acid End-Groups Induces an Order-Order Morphological Transition

Autor: Lovett, JR, Warren, NJ, Ratcliffe, LPD, Kocik, MK, Armes, SP
Rok vydání: 2014
Předmět:
Zdroj: Angewandte Chemie (International Ed. in English)
ResearcherID
ISSN: 0044-8249
1433-7851
DOI: 10.1002/ange.201409799
Popis: A carboxylic acid based reversible additionfragmentation transfer (RAFT) agent is used to prepare gels composed of worm-like diblock copolymers using two non-ionic monomers, glycerol monomethacrylate (GMA) and 2-hydroxypropyl methacrylate (HPMA). Ionization of the carboxylic acid end-group on the PGMA stabilizer block induces a worm-to-sphere transition, which in turn causes immediate degelation. This morphological transition is fully reversible as determined by TEM and rheology studies and occurs because of a subtle change in the packing parameter for the copolymer chains. A control experiment where the methyl ester derivative of the RAFT agent is used to prepare the same diblock copolymer confirms that no pH-responsive behavior occurs in this case. This end-group ionization approach is important for the design of new pH-responsive copolymer nano-objects as, unlike polyacids or polybases, only a minimal amount of added base (or acid) is required to drive the morphological transition.
Databáze: OpenAIRE
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