Macroporous polymers and Janus particles prepared via redox-initiated polymerisation of emulsion templates at room temperature

Althubeiti, Khaled

Abstract

The main focus of this thesis is on the preparation of macroporous polymers and Janus particles using emulsion templates. Benzoyl peroxide – dimethyl-p-toluidine (BPO-DMPT) redox-initiation couple is used to polymerise the oil phase of water-in-oil (w/o) or oil-in-water (o/w) emulsion templates at room temperature and produce macroporous polymeric materials or Janus particles, respectively.
The preparation of macroporous polymers via emulsion templating usually uses water-in-oil emulsions. The polymerisation of the oil phase is initiated either by a thermo-initiator at elevated temperature (60-80 oC) or a photo-initiator by irradiating relatively thin transparent samples with UV light. Both approaches suffer from low energy efficiency and require tedious sample preparation (removal of inhibitors, inert atmosphere). Those drawbacks are addressed by us in Chapter 3 of the thesis, where the polymerisation of w/o emulsion templates with a BPO-DMPT redox-initiation system at room temperature is investigated. The morphology and mechanical properties of the porous materials obtained are compared to those synthesised from emulsion templates using the traditional thermo-initiated polymerisation in Chapter 4. It is demonstrated for the first time that MMA-based emulsion templates can be polymerised using BPO-DMPT redox-initiation to produce open cell macroporous polymeric materials at room temperature without the need of any complicated steps of preparation typical for other methods. The method developed by us is simpler, faster and cheaper in comparison to the existing methods. It allows for the preparation of materials with up to 93 % porosity and better mechanical properties than those produced with the thermo-initiation method.
The preparation of Janus particles in large quantities is still one of the most challenging problems in the field. Most of the preparation methods reported suffer from limited yields or Janus functionalities which could be achieved. The use of particle-stabilised (Pickering) emulsions of paraffin wax-in-water has been used with some success for making Janus particles in large amounts, but the paraffin wax has caused problems with the poor particle adhesion and the limited conditions for chemical modification. In Chapter 5, we use our knowledge for redox-initiated polymerisation of methacrylates gained in the macroporous polymer study to develop efficient and reliable procedures for the preparation of Janus particles using polymerised o/w Pickering emulsions. The feasibility of this approach is demonstrated by small-scale experiments conducted using high speed homogenisation in the emulsion preparation. The possibility of scaling up the process to achieve larger yields of Janus particles is also demonstrated. Janus particles with hydroxyl-amine functionalities have been produced and their Janus character revealed by zeta-potential measurement in comparison to bare and fully aminated silica particles.

Citation

Althubeiti, K. (2018). Macroporous polymers and Janus particles prepared via redox-initiated polymerisation of emulsion templates at room temperature. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4224075

• Thesis Type: Thesis
• Deposit Date: Mar 24, 2022
• Publicly Available Date: Feb 24, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4224075
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Mar 1, 2018