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Synthesis and solution properties of block polyampholyte

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Title: Synthesis and solution properties of block polyampholyte
Author(s): Meriläinen, Kati
Contributor: University of Helsinki, Faculty of Science, none
Discipline: none
Degree program: Master's Programme in Materials Research
Specialisation: Polymer Materials Chemistry
Language: English
Acceptance year: 2020
In this thesis, synthesis and solution properties of the polyampholyte poly(acrylic acid)-b-poly[(vinylbenzyl)trimethylammonium chloride], PAA-PVBTMA-Cl, were investigated in aqueous solutions. First, the diblock copolymer was synthesized via RAFT polymerization where poly(acrylic acid), PAA was used as a chain transfer agent (CTA). In addition, the homopolymer poly[(vinylbenzyl)trimethylammonium chloride], PVBTMA-Cl, was synthesized via RAFT polymerization to compare the solution properties with the block copolymer. Molar masses of the polymers were determined using several methods such as NMR, UV-Vis spectroscopy and SEC. The experimental molar masses were close to theoretical values and block ratio in diblock copolymer from NMR was 30% of AA and 70% of VBTMA-Cl. Furthermore, the solution properties of the polyampholyte were studied under external stimuli such as pH and temperature. UCST type of behaviour was observed for aqueous PAA-PVBTMA-Cl solutions when the hydrophobic trifluoromethanesulfonate (OTf) anion was introduced. In addition, self-assembly of the diblock copolymer was confirmed by zeta potential measurements in different pH conditions. The expected reverse of the micelle structure with changing pH was not observed. However, aqueous PAA-PVBTMA-Cl showed UCST behaviour and micellization induced by the hydrophobic counterion.

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