Characterisation of double hydrophilic block copolymers

Abstract

Block copolymers enable combining the properties of multiple polymers into a single material. A particularly innovative means of combining properties is through Double Hydrophilic Block Copolymers (DHBCs) which contain "smart" polymers. DHBCs are diblock copolymers where both blocks are water soluble. Smart polymers have the ability to respond to changes in their environment, examples of them are the pH responsive poly(acrylic acid) - PAA - and the thermoresponsive poly(N-isopropylacrylamide) - PNIPAM. Therefore smart block copolymers have numerous potential applications in drug delivery, removable coatings, controlled mineralisation and many others. However, the current means of characterising DHBCs suffers from many limitations resulting in their applications being significantly hindered. The chemical structure of block copolymers is described by a number of distributions including distributions of molar masses, of branching architectures, of compositions and of end groups. These distributions and the purity of the block copolymer influence the properties of the resulting material. Currently smart polymers are mainly characterised in terms of their molar mass using size exclusion chromatography (SEC). However, cationic DHBCs such as poly(acrylamido-N-propyltrimethylammonium chloride-b-NIPAM) - P(APTAC-b-NIPAM) - cannot be characterised by SEC due to strong adsorption onto the stationary phase. Furthermore even when SEC takes places with a quantitative recovery, the separation is by hydrodynamic volume and cannot alone yield all information regarding the chemical structure. This work involved the development of a means to assess the purity and composition of DHBCs, namely diblock copolymers, using free solution capillary electrophoresis (CE), also known as capillary zone electrophoresis, thus enabling the characterisation of DHBCs including cationic ones. Charged oligomers (

Date of Award	2014
Original language	English